JPH08181661A - Radio signal transmitter - Google Patents

Abstract

PURPOSE: To eliminate deterioration in transmission quality due to nonlinearity in electro/optic converter and photoelectric converter with respect to radio signal transmitter using an optical transmission line. CONSTITUTION: Transmission signal processing circuits 341 , 491 of a radio central station 221 and a radio base station 231 convert an analog radio modulation signal from a modulator 311 or a low noise amplifier 47 into a digital radio modulation signal. An electro/optic converter 35 converts the digital radio modulation signal being an electric signal into an optical signal. A photoelectric converter 37 converts the optical signal received via an optical transmission line into a digital radio modulation signal being an electric signal. Reception signal processing circuits 381 , 441 of the radio central station 221 and the radio base station 231 convert th digital radio modulation signal from the photoelectric converter 37 into an analog radio modulation signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio signal transmission device, and more particularly to a radio signal transmission device for transmitting a modulated radio signal using an optical transmission line. In the wireless signal transmission device, it is necessary to improve the deterioration of transmission quality caused by the non-linearity of the electric / optical converter and the optical / electrical converter.

[0002]

2. Description of the Related Art PHS (Personal Handy)
Optical SCM (S) used for phone system
In a wireless signal transmission apparatus applying the ub Carrier Multiplex) transmission method, wireless modulators and wireless demodulators are centrally arranged in a wireless central station, and an optical transmission line is provided between wireless base stations scattered at remote locations. , And wirelessly modulated signals are transmitted.

FIG. 16 is a schematic block diagram of a conventional radio signal transmission apparatus. Wireless modulator 1 of wireless central station 122
25 modulates a carrier wave with the data transmitted from the exchange 120 to generate a radio frequency modulated signal having a radio frequency.
The electro-optical converter 126 converts the wireless modulation signal into an optical signal. The converted optical signal is transmitted to the wireless base station 123 at a remote place by an optical transmission line such as an optical fiber.

Optical / electrical converter 127 of radio base station 123
Receives the optical signal transmitted from the electrical / optical converter 126 of the wireless central station 122 and converts it into an electrical signal. This electric signal is amplified by the power amplifier 131 and then radiated from the antenna 133. The radio modulated signal received from the antenna 133 is amplified by the low noise amplifier 132,
It is supplied to the electrical / optical converter 126. Electric / optical converter 1
26 converts the radio modulation signal supplied from the low noise amplifier 132 into an optical signal. The converted optical signal is transmitted to the wireless central station 122 via the optical transmission line.

An optical / electrical converter 127 of the radio base station 122.
Receives an optical signal transmitted from the electrical / optical converter 126 of the wireless base station 123 and converts the optical signal into an electrical signal. This electric signal is demodulated by the wireless demodulator 128 into data and then transmitted to the exchange 120.

As described above, the wireless modulator 125 and the wireless demodulator 128 are centrally arranged in the wireless central station 122 to facilitate maintenance of the wireless modulator 125 and the wireless demodulator 128.

[0007]

In the radio signal transmission apparatus of FIG. 16, the radio modulation signal is an analog signal,
The electro-optical converter 126 converts the analog voltage of the wireless modulation signal into light intensity by using light intensity modulation. Further, the optical / electrical converter 127 converts the intensity of light into an analog voltage of a wireless modulation signal.

The electrical / optical converter 126 has poor linearity between the input electrical signal and the output optical signal, and is likely to generate non-linear distortion due to intermodulation. Similarly, the optical / electrical converter 127
Has poor linearity between the input optical signal and the output electrical signal,
Intermodulation distortion is likely to occur. Therefore, there is a problem that the transmission quality of the signal deteriorates due to the intermodulation distortion caused by the non-linearity of the electrical / optical converter 126 and the optical / electrical converter 127.

Particularly, in the application such as the SCM system, in which a plurality of wireless carrier waves are set up within a certain wireless frequency band and each wireless modulated signal is collectively subjected to electrical / optical conversion and optical / electrical conversion, this intermodulation is performed. Distortion becomes a problem. In particular,
In the case of transmission from the wireless base station 123 to the wireless central station 122, since there is no correlation in the power between these multiple wireless carriers, the intermodulation distortion between strong waves seriously affects weak waves.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a radio signal transmission apparatus which does not cause deterioration of transmission quality due to non-linearity of an electric / optical converter and an optical / electrical converter. To aim.

[0011]

According to a first aspect of the present invention, there is provided a wireless signal transmission device for transmitting a wireless modulation signal in a predetermined band as an optical signal through an optical transmission line, and a transmitting side for transmitting the optical signal to the optical transmission line. The apparatus has analog / digital conversion means for converting an analog modulation signal corresponding to a wireless modulation signal into a digital modulation signal, and an electric / optical converter for converting the digital modulation signal which is an electric signal into an optical signal, A receiving side device that receives an optical signal from the optical transmission line includes an optical / electrical converter that converts the received optical signal into a digital modulation signal that is an electrical signal, and a digital / electrical converter that converts the digital modulation signal into an analog modulation signal. And an analog conversion means.

According to a second aspect of the present invention, in the radio signal transmission apparatus according to the first aspect, the transmission side device converts the radio modulation signal in a predetermined band into an intermediate frequency modulation signal having a frequency lower than an original frequency, It has a first frequency conversion means for supplying to the analog / digital conversion means, the receiving side device,
The intermediate frequency modulation signal supplied from the digital / analog conversion means is converted into a radio modulation signal having an original frequency, and second frequency conversion means is provided.

According to a third aspect of the present invention, in the radio signal transmission apparatus according to the first aspect, the transmission side device has a plurality of radio modulation signals whose bands are dispersed within a predetermined radio frequency band, and has a frequency higher than that of the radio modulation signals. A third intermediate frequency modulation signal having a continuous low frequency band, synthesized and synthesized, and supplied as a synthesized intermediate frequency modulation signal to the analog / digital conversion means.
The frequency conversion means, and the receiving side device disperses a plurality of intermediate frequency modulation signals separated from the combined intermediate frequency modulation signal supplied from the digital / analog conversion means within the predetermined radio frequency band. And a fourth frequency converting means for converting into a plurality of wireless modulation signals.

According to a fourth aspect of the present invention, in a radio signal transmission device for transmitting a radio modulated signal in a predetermined band as an optical signal through an optical transmission line, the transmission side device for transmitting the optical signal to the optical transmission line has a predetermined radio frequency. Fifth frequency conversion means for converting a plurality of wireless modulation signals whose bands are dispersed within a band into a plurality of intermediate frequency modulation signals whose frequencies are lower than those of the wireless modulation signals and whose bands are continuous, and the plurality of analog signals which are analog signals. The optical / optical converter includes an analog / digital converter that individually converts the intermediate frequency modulated signal into a digital intermediate frequency modulated signal, and an electric / optical converter that converts the digital intermediate frequency modulated signal that is an electrical signal into an optical signal. A receiving side device that receives an optical signal from a transmission line includes an optical / electrical converter that converts the received optical signal into a digital intermediate frequency modulated signal that is an electric signal, and the optical signal. A digital / analog converting means for converting a plurality of digital intermediate frequency modulated signal supplied from the electrical converter into separate analog intermediate frequency modulated signal,
A sixth frequency conversion means for converting the plurality of intermediate frequency modulation signals supplied from the digital / analog conversion means into a plurality of radio modulation signals having a band dispersed within the predetermined radio frequency band. .

According to a fifth aspect of the present invention, there is provided a radio signal transmission device for transmitting a radio modulation signal in a predetermined band as an optical signal through an optical transmission line between a radio base station transmitting and receiving radio waves via an antenna and a radio central station. In the wireless centralized station, a transmitting side device that transmits an optical signal to an optical transmission line corresponds to a plurality of wireless modulation signals whose bands are dispersed within a predetermined wireless frequency band based on data to be transmitted, A modulation means for generating a plurality of intermediate frequency modulation signals having a frequency lower than that of the modulation signal and having a continuous band; and an analog / digital conversion means for individually converting the plurality of intermediate frequency modulation signals into digital intermediate frequency modulation signals; An optical / electrical converter for converting the digital intermediate frequency modulated signal, which is a signal, into an optical signal, and receiving the optical signal from an optical transmission line in the wireless base station. The side device individually converts the received optical signal into a digital intermediate frequency modulated signal which is an electric signal, and a plurality of digital intermediate frequency modulated signals supplied from the optical / electrical converter, which are individually converted into analog signals. Digital / analog conversion means for converting into an intermediate frequency modulation signal, and the plurality of intermediate frequency modulation signals supplied from the digital / analog conversion means into a plurality of wireless modulation signals whose bands are dispersed within the predetermined wireless frequency band. And a sixth frequency converting means for converting, wherein a transmitting side device for transmitting an optical signal to an optical transmission line in the wireless base station, a plurality of wireless modulated signals whose bands are dispersed within a predetermined wireless frequency band. Fifth frequency conversion means for converting into a plurality of intermediate frequency modulation signals whose frequencies are lower than that of the modulation signal and which are continuous in band, and supplied from the fifth frequency conversion means An analog / digital conversion means for individually converting the plurality of intermediate frequency modulated signals into digital intermediate frequency modulated signals, and an electric / optical converter for converting the digital intermediate frequency modulated signals which are electric signals into optical signals. In the wireless centralized station, a receiving side device that receives an optical signal from an optical transmission line includes an optical / electrical converter that converts the received optical signal into a digital intermediate frequency modulated signal that is an electric signal, and the optical / electrical conversion device. A digital / digital converter for individually converting a plurality of digital intermediate frequency modulation signals supplied from a converter into analog intermediate frequency modulation signals.
An analog conversion means and a demodulation means for individually demodulating the plurality of intermediate frequency modulated signals supplied from the digital / analog conversion means to generate demodulated data are configured.

According to a sixth aspect of the present invention, there is provided a radio signal transmission device for transmitting a radio modulation signal of a predetermined band as an optical signal through an optical transmission line between a radio base station transmitting and receiving radio waves via an antenna and a radio central station. A transmitting side device for transmitting an optical signal to an optical transmission line in the wireless central station, has a plurality of wireless modulated signals whose bands are dispersed within a predetermined wireless frequency band and whose frequency is lower than that of the wireless modulated signal and which has a continuous band. Third intermediate frequency conversion means for converting the intermediate frequency modulated signal into a digital intermediate frequency modulated signal, and a third frequency conversion means for generating a combined intermediate frequency modulated signal by combining the plurality of intermediate frequency modulated signals, and an analog for converting the combined intermediate frequency signal into a digital intermediate frequency modulated signal. / Digital conversion means and an electric / optical converter for converting the digital intermediate frequency modulated signal, which is an electric signal, into an optical signal, and an optical / optical converter is provided in the radio base station. Receiving device for receiving an optical signal from the transmission line comprises an optical / electrical converter for converting the digital intermediate frequency modulated signal is an electrical signal the optical signal received, said optical /
Digital / analog conversion means for converting the digital intermediate frequency modulation signal supplied from the electric converter into a composite intermediate frequency signal, and a plurality of intermediate frequency modulations separated from the composite intermediate frequency modulation signal supplied from the digital / analog conversion means Fourth frequency conversion means for converting a signal into a plurality of radio modulation signals whose bands are dispersed within the predetermined radio frequency band, and a transmission side device for transmitting an optical signal to an optical transmission line in the radio base station. Are detecting means for respectively detecting a plurality of radio modulated signals whose bands are dispersed within a predetermined radio frequency band to generate a baseband signal; and analog / digital converting means for individually converting the baseband signal into a digital signal. An electric / optical device for converting a digital signal, which is an electric signal supplied from the analog / digital converting means, into an optical signal A receiving side device having a converter and receiving an optical signal from an optical transmission line in the wireless centralized station includes an optical / electrical converter for converting the received optical signal into a digital signal which is an electric signal, and the optical / electrical converter. Demodulation means for generating demodulated data having a correct phase relationship for each of a plurality of digital signals corresponding to respective baseband signals supplied from the electric converter.

According to a seventh aspect of the present invention, there is provided a radio signal transmission device for transmitting a radio modulated signal of a predetermined band as an optical signal through an optical transmission line between a radio base station which transmits and receives radio waves through an antenna and a radio central station. In the wireless centralized station, a transmission side device that transmits an optical signal to an optical transmission line corresponds to a plurality of wireless modulation signals whose bands are dispersed within a predetermined wireless frequency band, and has a lower frequency than the wireless modulation signal. Modulation means for generating a plurality of intermediate frequency modulation signals having continuous bands, analog / digital conversion means for individually converting the plurality of intermediate frequency modulation signals into digital intermediate frequency modulation signals, and the digital intermediate frequency as an electric signal An electric / optical converter that converts a modulated signal into an optical signal, and a receiving side device that receives an optical signal from an optical transmission line in the wireless base station is An optical / electrical converter for converting the digital intermediate frequency modulated signal is an electrical signal to issue, the light /
Digital / analog conversion means for individually converting a plurality of digital intermediate frequency modulation signals supplied from an electric converter into analog intermediate frequency modulation signals, and the plurality of intermediate frequency modulation signals supplied from the digital / analog conversion means And a sixth frequency conversion means for converting into a plurality of radio modulated signals whose bands are dispersed within the predetermined radio frequency band, and the sending side device for sending an optical signal to an optical transmission line in the wireless base station is Detecting means for respectively detecting a plurality of radio modulated signals whose bands are dispersed within a predetermined radio frequency band to generate a baseband signal; and analog / digital converting means for individually converting the baseband signal into a digital signal, Electric / optical converter for converting a digital signal, which is an electric signal supplied from the analog / digital converting means, into an optical signal It has the radio toll receiving apparatus for receiving an optical signal from the optical transmission line in converts the received optical signal into a digital signal which is an electrical signal light /
A structure having an electric converter and demodulation means for generating demodulated data having a correct phase relationship with respect to each of a plurality of digital signals corresponding to respective baseband signals supplied from the optical / electrical converter; To do.

[0018]

According to the present invention, the analog modulation signal corresponding to the radio modulation signal is converted into a binary digital modulation signal and then converted into an optical signal by the electric / optical converter for optical transmission. Transmit the line. In the optical / electrical converter, the digital optical signal transmitted through the optical transmission line is converted into a digital modulated signal which is an electric signal, and the digital modulated signal is converted into an original analog modulated signal.

As described above, since the optical / electrical converter and the electric / optical converter handle binary digital signals, the intermodulation distortion caused by the non-linearity of the optical / electrical converter and the electric / optical converter is caused. This can be neglected, and the wireless modulation signal can be transmitted without distortion. According to the second aspect of the present invention, the wireless modulation signal is converted into an intermediate frequency modulation signal having a frequency lower than that of the wireless modulation signal, the intermediate frequency modulation signal is converted into a digital modulation signal, and then converted into an optical signal to be transmitted through an optical transmission line. To transmit. Therefore, the sampling frequency of the analog / digital conversion means and the digital / analog conversion means can be significantly reduced.

According to the third aspect of the present invention, when the original radio modulation signal is converted into a low frequency intermediate frequency modulation signal,
A plurality of radio modulation signals dispersed within a predetermined radio frequency band are arranged in a continuous band. Therefore, the maximum frequency of the composite intermediate frequency modulation signal can be made lower than that in the case of converting each modulation signal in the dispersed state to the intermediate frequency, and the sampling frequency of the analog / digital conversion means and the digital / analog conversion can be reduced. It is possible to further lower.

According to the inventions of claims 4 and 5, the intermediate frequency modulation signals are individually converted into intermediate frequency modulation signals corresponding to a plurality of wireless modulation signals dispersed in a predetermined wireless frequency band, and each intermediate frequency modulation signal is individually converted. To convert to a digital intermediate frequency modulation signal.
Therefore, the bands of the intermediate frequency modulated signals may overlap or may be set to the same band. For this reason, the maximum frequency of the intermediate frequency modulated signal can be further lowered as compared with the case of generating the synthetic intermediate frequency modulated signal, and the sampling frequency of the analog / digital conversion means and the digital / analog conversion can be further lowered. And

In the fifth aspect of the present invention, in the wireless centralized station, the modulating means directly generates the intermediate frequency modulated signal, and the demodulating means directly demodulates the intermediate frequency modulated signal. For this reason, the wireless centralized station does not need a frequency conversion means, and the configuration can be simplified.

According to the sixth and seventh aspects of the present invention, in the wireless central station, the intermediate frequency modulation signal corresponding to the wireless modulation signal is set to 2
The value is converted into a digital intermediate frequency modulation signal, and then converted into an optical signal by an electric / optical converter and transmitted through an optical transmission line.
The optical / electrical converter of the radio base station converts the digital optical signal transmitted through the optical transmission line into a digital intermediate frequency modulated signal which is an electric signal, and converts the digital intermediate frequency modulated signal into an analog intermediate frequency modulated signal. After that, it is converted to the original radio modulated signal.

In the radio base station, a baseband signal is generated by the detection means of the radio base station, the baseband signal is converted into a binary digital signal, and then converted into an optical signal by an electric / optical converter to generate an optical signal. Transmit the transmission line. In the optical / electrical converter of the wireless centralized station, the digital optical signal transmitted through the optical transmission line is converted into a digital signal which is an electric signal, and demodulation means generates demodulated data based on the digital signal.

As described above, since the optical / electrical converter and the electric / optical converter handle binary digital signals, the intermodulation distortion caused by the non-linearity of the optical / electrical converter and the electric / optical converter is caused. This can be neglected, and the wireless modulation signal can be transmitted without distortion. Further, in the transmission from the wireless central station to the wireless base station, an intermediate frequency modulated signal having a frequency lower than that of the wireless modulated signal is subjected to analog / digital conversion and digital / digital conversion.
Since the analog conversion is performed, the sampling frequency of the analog / digital conversion means and the digital / analog conversion means can be significantly reduced.

Further, since the baseband signal is a signal having a frequency significantly lower than that of the intermediate frequency modulated signal, the analog / digital converting means of the radio base station has a more analog / digital conversion than the intermediate frequency modulated signal. Further, it is possible to lower the sampling frequency.

[0027]

FIG. 1 is a block diagram of a wireless central station 22 in a wireless signal transmission apparatus to which each embodiment of the present invention is applied.
FIG. 2 shows a configuration diagram of the radio base station 23. Wireless central station 2
2 is connected to the exchange 20 and is also connected to eight radio base stations 23 (23 _{# 1} to 23 _{# 8} ). Here, the subscripts # 1 to # 8 are for identifying the eight radio base stations 23. The wireless central station 22 generates a wireless modulation signal or an intermediate frequency modulation signal in accordance with the data for each wireless base station 23 transmitted from the exchange 20, converts it into an optical signal, and transmits it to the corresponding wireless base station 23 by an optical transmission line. Send out. Also, after converting the optical signal received from the wireless base station 23 into an electrical signal, the wireless modulated signal or the intermediate frequency modulated signal is demodulated, and the demodulated data is transmitted to the exchange 20.

In the wireless central station 22, the input / output switch 2 is used as a sending side device for receiving data from the exchange 20 and sending an optical signal to the wireless base station 23 through the optical transmission line.
6, baseband processing circuit 29 (29 _{$ 1 to} 29 _{$ 8} ), modulator 31 (31 _{$ 1 to} 31 _{$ 8} ), transmission distributor 27, transmission signal processing circuit 34 (34 _{# 1 to} 34 _{# 8} ), electrical / optical conversion The container 35 (35 _{# 1 to} 35 _{# 8} ).

In the wireless central station 22, the receiving side device for receiving the optical signal from the wireless base station 23 through the optical transmission line and transmitting the demodulated data to the exchange 20 is as follows.
Optical / electrical converter 37 (37 _{# 1 to} 37 _{# 8} ), reception signal processing circuit 38 (38 _{# 1 to} 38 _{# 8} ), reception distributor 28, demodulator 41 (41 _{$ 1 to} 41 _{$ 8} ), baseband processing Circuit 29
(29 _{$ 1 to} 29 _{$ 8} ) and an input / output switch 26.

Here, the subscripts # 1 to # 8 identify the eight radio base stations 23 and the transmission signal processing circuit 34 for processing the signals of each radio base station 23, the electrical / optical converter 35, and the optical / electrical converter. The converter 37 and the received signal processing circuit 38 are to be identified. The subscripts $ 1 to $ 8 are used to identify the eight sets of the baseband processing circuit 29, the modulation device 31, and the demodulation device 41 that correspond to the eight radio base stations 23.

Electric / optical converter 35_{# 1}And optical / electrical converter 3
7_{# 1}Is a wireless base station 23 through an optical transmission line._{# 1}Connected to
Have been. Similarly, the electrical / optical converter 35_{# 2}~ 35_{# 8}And light
/ Electric converter 37_{# 2}~ 37_{# 8}Each of the
Radio base station 23_{# 2}~ 23 _{# 8}It is connected to the.

Further, the wireless central station 22 includes the input / output switch 2
6, a transmission distributor 27, and a control device 25 for controlling switching of the reception distributor 28. The input / output switch 26 switches the connection between the lines * 1 to * 8 connected to the exchange 20 and the baseband processing circuits 29 _{$ 1 to} 29 _{$ 8} . The transmission distributor 27 switches between the modulators 31 _{$ 1 to} 31 _{$ 8} and the transmission signal processing circuits 34 _{# 1 to} 34 _{# 8} . Reception distributor 28
Are the reception signal processing circuits 38 _{# 1 to} 38 _{# 8} and the demodulation device 41 _{$ 1.
~} 41 Switch _{$ 8} connection.

The exchange 20 connects each of the lines * 1 to * 8,
The wireless base station 23 _{# 1} to 23 _{# 8} is set as a line for transmitting data. Further, control data for controlling switching of the input / output switch 26, the transmission distributor 27, and the reception distributor 28 is supplied to the control device 25.

The control device 25 switches between the input / output switch 26, the transmission distributor 27 and the reception distributor 28 according to the control data supplied from the exchange 20. This allows
Baseband processing circuits 29 _{$ 1 to} 29 _{$ 8} and modulators 31 _{$ 1 to} 3 for processing the respective signals of the radio base stations 23 _{# 1} to 23 _{# 8.}
1 _{$ 8} and demodulation devices 41 _{$ 1 to} 41 _{$ 8} are set.

FIG. 2 shows a radio base station 23 (23 _{# 1} to 2 _# 2).
3 _{# 8} ) is shown. In FIG. 2, the wireless base station 2
3 The case of _{# 1} is shown. Radio base station 23 (23 _# 1-2)
3 _{# 8} ) is an optical / electrical converter 37 and a received signal processing circuit 4
4, power amplifier 45, duplexer 46, low noise amplifier 4
7, a transmission signal processing circuit 49, an electric / optical converter 35, and an antenna 51.

In the wireless base station 23, the wireless central station 22
The receiving-side device that receives the optical signal from the receiver and generates the wireless modulation signal to be supplied to the antenna 51 includes an optical / electrical converter 37, a received signal processing circuit 44, and a power amplifier 45. Further, in the wireless base station 23, the transmission side device that generates an optical signal to be transmitted to the wireless centralized station 22 in response to the wireless modulated signal received by the antenna 51 is a low noise amplifier 47, a transmission signal processing circuit 49, and Electric / optical converter 35
Consists of

The optical / electrical converter 37 is connected via an optical transmission line.
Connected to the electrical / optical converter 35 of the wireless central station 22
The electrical / optical converter 35 is connected to the wireless transmission line via the optical transmission line.
It is connected to the optical / electrical converter 37 of the central office 22. Next
The general operation of the wireless signal transmission device shown in FIGS.
And the wireless base station 23_{# 1}The case will be described. here,
The line * 1 of the exchange 20 is the wireless base station 23_{# 1}Set for
The input / output switch 26 allows the line * 1 and baseband
Processing circuit 29 _{$ 1}Is connected and the transmission distributor 27
Adjustment device 31_{$ 1}And transmission signal processing circuit 34 _{# 1}Connected and received
Received signal processing circuit 38 by the signal distributor 27._{# 1}And demodulation equipment
Storage 41 _{$ 1}Are connected.

The data of the radio base station 23 _{# 1} transmitted from the exchange 20 through the line * ₁ is supplied to the baseband processing circuit 29 _{$ 1} via the input / output switch 26. The baseband processing circuit 29 _{$ 1} converts the data in the format for the exchange 20 into the data in the format for wireless modulation, and supplies the converted data to the modulator 31 _{$ 1} .

The modulator 31 _{$ 1} modulates the carrier wave with the data supplied from the baseband processing circuit 29 _{$ 1} ,
Generate a radio frequency or intermediate frequency modulated signal. As the modulation method, for example, 4-phase phase modulation is used. The modulated signal is supplied to the transmission signal processing circuit 34 _{# 1} via the transmission distributor 27.

The transmission signal processing circuit 34 _{# 1} converts an analog modulation signal into digital modulation data having a predetermined number of bits, as described in each of the embodiments described later. The digital modulation data is generated as a 1-bit bit stream (serial data). The electrical / optical converter 35 _{# 1} converts the digital modulation data supplied from the transmission signal processing circuit 34 _{# 1} into an optical signal. The digital modulation data is a 1-bit bit stream, and the converted optical signal is
It becomes an optical signal in which “0” and “1” of each bit are associated with different binary light intensities.

This converted optical signal is transmitted to the radio base station 23 _{# 1} located at a remote place by an optical transmission line such as an optical fiber. Optical / electrical converter 37 of radio base station 23 _{# 1}
Receives the optical signal transmitted from the electrical / optical converter 35 _{# 1} of the wireless centralized station 22 through the optical transmission line and converts it into an electrical signal. The converted electric signal is a reproduction of the digital modulation data generated by the transmission signal processing circuit 34 _{# 1} .

The reception signal processing circuit 44 converts the digital modulation data supplied from the optical / electrical converter 37 into an analog radio modulation signal, as described in each of the embodiments described later. This converted analog radio modulated signal is
That reproduces the analog modulated radio signal generated by the modulator 31 $ _1, or an analog modulated radio signal corresponding to the generated by the modulator 31 $ ₁ analog intermediate frequency modulated signal.

This analog radio modulated signal is amplified by the power amplifier 45, then supplied to the antenna 51 via the duplexer 46 and radiated from the antenna 51. The wireless modulated signal received by the antenna 51 is transmitted / received by the duplexer 4
It is supplied to the low noise amplifier 47 via 6, and after being amplified by the low noise amplifier 47, is supplied to the transmission signal processing circuit 49.

The transmission signal processing circuit 49 converts the analog radio modulation signal supplied from the low noise amplifier 47 into digital modulation data having a predetermined number of bits, as described in each of the embodiments described later. The digital modulation data is generated as a 1-bit bit stream.

The electric / optical converter 35 converts the digital modulation data supplied from the transmission signal processing circuit 49 into an optical signal. The digital modulation data is a 1-bit bit stream, and the converted optical signal is an optical signal in which "0" and "1" of each bit are associated with different binary light intensities.

The converted optical signal is transmitted to the optical / electrical converter 37 _{# 1} of the wireless centralized station 22 through an optical transmission line such as an optical fiber. The optical / electrical converter 37 _{# 1} of the wireless central station 22 receives the optical signal transmitted by the optical transmission line from the electric / optical converter 35 of the wireless base station 23 _{# 1} and converts it into an electrical signal. The converted electric signal is a reproduction of the digital modulation data generated by the transmission signal processing circuit 49.

The reception signal processing circuit 38 _{# 1} converts the digital modulation data supplied from the optical / electrical converter 37 _{# 1} into an analog modulation signal as described in each of the embodiments described later. This converted analog modulation signal corresponds to a reproduction of the analog wireless modulation signal generated by the low noise amplifier 47 in the wireless base station 23 _{# 1} , or an analog wireless modulation signal generated by the low noise amplifier 47. The intermediate frequency modulated signal. This analog modulated signal is supplied to the demodulator 41 _{$ 1} via the reception distributor 28.

The demodulator 41 _{$ 1} includes a received signal processing circuit 38.
Performs demodulation processing of the analog modulation signal supplied from _{# 1} ,
Generate demodulated data. The demodulated data is converted by the baseband processing circuit 29 _{$ 1} into data according to the format of the exchange, and then transmitted to the exchange 20 via the input / output switch 26 and the line * 1.

The operation of each of the blocks of the other radio base stations 23 _{# 2} to 23 _{# 8} and the radio central station 22 connected thereto is the same as that of the radio base station 23 _{# 1} . As described above, in each of the embodiments described later, the analog modulation signal is converted into binary digital modulation data, and then converted into an optical signal by the optical / electrical converter 35 to be transmitted through the optical transmission line.
The electric / optical converter 37 converts the digital optical signal transmitted through the optical transmission line into digital modulated data which is an electric signal, and converts the digital modulated data into the original analog modulated signal.

In this way, the optical / electrical converter 35 and the electric / electrical converter 35
Since the optical converter 37 handles binary digital signals,
Intermodulation distortion caused by the non-linearity of the electrical converter 35 and the electrical / optical converter 37 can be ignored, and the wireless modulation signal can be transmitted without distortion.

In the fifth embodiment described later, the radio base
Station 23_FiveThe wireless modulation signal received from the antenna 51 at
Generate a baseband signal and
A / D converted digital signal is used as an optical signal for wireless collection
Central station 22_FiveTo transmit. Wireless central station 22_FiveReceived signal processing
Logic circuit 38_FiveAnd demodulator 41_FiveThen, the wireless base station 23 _Five
The demodulation process directly from the transmitted digital signal.
To do.

By the way, when four carrier waves (carriers) are set up within a constant radio frequency band to transmit a radio modulation signal, D / U (De) for the required intermodulation distortion is generated.
The sier / Undesire) ratio is determined as follows. That is, it is considered that the three waves received at the maximum power have an effect on the one wave received at the minimum power, and when the received power fluctuation range is 70 dB, the converted amount of the two waves and the three waves is considered to be about 80 dB. D / U ratio is required.

In each of the embodiments of the present invention in which an analog modulated signal is converted into a digital signal and transmitted, the number of quantization bits of A / D conversion determines this D / U ratio, and it is about 80.
In the case of a D / U ratio of dB, a quantization bit number of 14 bits is required. In addition, the wireless base station 23 and the wireless central station 22
Can also be configured to use a diversity reception system. In this case, the wireless base station 23 generates an optical signal including the modulated signals of the two systems based on the modulated signals of the two systems received from the antennas of the two systems, and transmits the optical signal to the centralized wireless station 22. The wireless central station 22 selects, as effective data, data obtained by demodulating a modulated signal in a good reception state out of the two systems of modulated signals transmitted from the wireless base station 23.

FIG. 3 shows a radio signal transmission according to the first embodiment of the present invention.
The block diagram of a feeder is shown. In FIG. 3, the same as in FIGS.
The same reference numerals are given to one component, and the description will be omitted as appropriate.
It Note that in FIG. 3, one radio base station 23₁And this
Wireless central station 22 connected to₁Main part of device
(Modulator 31₁, Transmission signal processing circuit 34₁, Electricity / light
Converter 35) and the main part of the receiving side device (optical / electrical converter 3)
7. Received signal processing circuit 38 ₁, Demodulator 41₁)
I / O switch 26, transmission distributor 2
7, the reception distributor 28 and the like are omitted.

In each embodiment, the wireless base station 23 is set to 1
It is assumed that only the stations are provided, and the transmitting side device and the receiving side device of the wireless centralized station 22 connected thereto are also described as one set, and the subscripts # 1 to # 8 and $ 1 to $ 8 in the wireless centralized station 22 are added. I will not. Transmission of the wireless centralized station 22 ₁ signal processing circuit 34 ₁ and the transmission signal processing circuit 49 ₁ of the radio base station 23 ₁
Is an analog / digital conversion means, and
Digital converter (A / D converter) 55 ₁ and parallel /
It is composed of a serial converter 56. The reception signal processing circuit of the radio central station 22 ₁ 38 ₁ and the radio base station 23 ₁
The reception signal processing circuit 44 ₁ is a serial / parallel conversion means and is composed of a serial / parallel converter 57 and a digital / analog converter (D / A converter) 58 ₁ .

The modulator 31 ₁ is composed of one modulator 32. The modulator 32 generates an analog radio modulation signal according to the data from the baseband processing circuit 29. For example, four-phase phase modulation with a carrier wave of 800 MHz,
An analog radio modulation signal having a band of 20 MHz is generated.

The A / D converter 55 ₁ generates 14-bit parallel data by A / D converting the analog radio modulated signal. For example, the sampling frequency is about 1.6 GHz for an analog wireless modulation signal with a carrier wave of 800 MHz.
Flash operation (instantaneous detection) type A / D converter 55
_Set to ₁ .

The parallel / serial converter 56 is an A / D converter.
The 14-bit parallel data supplied from the converter 55 ₁ is converted into a bit stream (serial data),
Output as digital wireless modulation data. The electrical / optical converter 35 converts the digital wireless modulation data supplied from the transmission signal processing circuit 34 into an optical signal. The converted optical signal is “0” for each bit of the bit stream,
It becomes an optical signal (digital optical signal) in which "1" is associated with binary light intensity.

The converted digital optical signal is transmitted to the wireless base station 23 ₁ at a remote place through the optical transmission line. The optical / electrical converter 37 of the radio base station 23 ₁ receives the digital optical signal transmitted from the electric / optical converter 35 of the wireless central station 22 ₁ and converts it into an electric signal. The converted electric signal is a reproduction of the digital radio modulation data generated by the transmission signal processing circuit 34 ₁ .

The serial / parallel converter 57 of the reception signal processing circuit 44 ₁ converts the bit stream (serial data) supplied from the optical / electrical converter 37 into 14-bit parallel data. The specifications of the D / A converter 58 _{1 correspond to} the specifications of the A / D converter 55 ₁ . For example, like the A / D converter 55 _1, it is a 14-bit D / A converter with a sampling frequency of about 1.6 GHz.
Converts bit parallel data into an analog radio modulated signal. The converted analog wireless modulated signal is a reproduction of the analog wireless modulated signal generated by the modulator 31 ₁ .

This analog radio modulated signal is amplified by the power amplifier 45, then supplied to the antenna 51 via the duplexer 46 and radiated from the antenna 51. The wireless modulated signal received by the antenna 51 is transmitted / received by the duplexer 4
It is supplied to the low noise amplifier 47 via 6, and after being amplified by the low noise amplifier 47, it is supplied to the transmission signal processing circuit 49 ₁ . This wireless modulated signal is, for example, a carrier wave 800MH.
It is an analog radio-modulated signal with a band of 20 MHz that is quadrature phase-modulated by z.

A / D converter 5 of transmission signal processing circuit 49 ₁
5 ₁ generates 14-bit parallel data obtained by A / D converting the analog wireless modulation signal supplied from the low noise amplifier 47. The parallel / serial converter 56 is an A / D
The 14-bit parallel data supplied from the converter 55 _{1 is} converted into serial data (bit stream),
Output as digital wireless modulation data.

The electrical / optical converter 35 converts the digital radio modulation data supplied from the transmission signal processing circuit 49 ₁ into an optical signal. The converted optical signal becomes a digital optical signal in which "0" and "1" of each bit of the bit stream are associated with a binary optical intensity. The converted digital optical signal is transmitted to the wireless central station 22 ₁ through the optical transmission line.

Optical / electrical converter 37 of the wireless central station 22 _1.
Receives the digital optical signal transmitted from the electrical / optical converter 35 of the radio base station 23 ₁ and converts it into an electrical signal. The converted electric signal is transmitted to the transmission signal processing circuit 49.
It is a reproduction of the digital radio modulation data generated in ₁ .

The serial / parallel converter 57 of the reception signal processing circuit 38 ₁ converts the bit stream (serial data) supplied from the optical / electrical converter 37 into 14-bit parallel data. The D / A converter 58 ₁ is 1
4-bit parallel data is converted into an analog radio modulated signal. This converted analog radio modulated signal is
This is a reproduction of the analog radio modulation signal generated by the low noise amplifier 47. This analog radio modulated signal is supplied to the demodulation device 41 ₁ .

The demodulation device 41 ₁ is composed of one demodulator 42. The demodulator 42 demodulates the analog radio modulation signal supplied from the reception signal processing circuit 38 ₁ to generate demodulation data. For example, when the analog radio modulation signal is a signal that is phase-phase-modulated with a carrier wave of 800 MHz, the demodulator 42 performs synchronous detection using a local oscillation signal of 800 MHz having a phase difference of 90 °, and a two-sequence data string is obtained. Demodulate.

The demodulated data is sent to the baseband processing circuit 29.
The data is converted into data in the format of the exchange and then transmitted to the exchange 20. As described above, in the first embodiment, the transmission signal processing circuits 34 ₁ and 49 ₁ convert the analog radio modulation signal into a binary digital radio modulation signal (bit stream), and then the electrical / optical converter 35. Then, it is converted into a digital optical signal and transmitted through the optical transmission line. In the optical / electrical converter 37, the digital optical signal transmitted through the optical transmission line is converted into a digital radio modulated signal (bit stream) which is an electric signal, and this digital radio modulated signal is received signal processing circuit 44 ₁ , At 38 _{1, the} original analog radio modulated signal is converted.

As described above, since the electric / optical converter 35 and the optical / electrical converter 37 handle binary digital signals, they are caused by the non-linearity of the electric / optical converter 35 and the optical / electrical converter 37. Intermodulation distortion can be substantially ignored and the digital radio modulated signal can be transmitted without error.

Further, the distortion generated during the A / D conversion and the D / A conversion can be set to a negligible level by appropriately setting the number of quantization bits. Therefore, the wireless signal transmission apparatus of the first embodiment can transmit a wireless modulation signal without causing distortion, and is more susceptible to intermodulation distortion that occurs at the time of electrical / optical conversion and optical / electrical conversion, as compared with a conventional apparatus. As a result, the transmission quality of the wireless modulation signal can be greatly improved. In particular, it is effective when using the SCM transmission method in which a plurality of carrier waves are set up and transmitted within a constant radio frequency band.

Further, the electric / optical converter 35 and the optical / electrical converter 37 are not required to have the accuracy as high as that of the conventional device that handles analog signals, and thus can be constructed at a lower cost. FIG.
In the wireless signal transmission device of the second embodiment of the present invention,
Radio central station 22 ₂ and shows the transmission signal processing circuit 34 _2, 49 ₂ of the configuration diagram of a radio base station 23 _2, 5, wireless toll 22 ₂ and the radio base station 23 ₂ of the received signal processing circuit 38 _2,
4 shows a block diagram of 44 ₂ . 4 and 5, the same components as those in FIG. 3 are designated by the same reference numerals, and the description thereof will be appropriately omitted. The configuration of the second embodiment is the same except for the transmission signal processing circuits 34 ₂ and 49 ₂ and the reception signal processing circuits 38 ₂ and 44 ₂ .
This is the same as the first embodiment.

The transmission signal processing circuit 34 of the wireless central station 22 _2.
2 and the transmission signal processing circuit 49 ₂ of the radio base station 23 ₂ include a frequency converter 61 (first frequency conversion means), an A / D converter 55 ₂ and a parallel / serial converter 56 (analog / digital conversion means). Composed of. The frequency converter 61 converts the analog radio modulation signal into a low frequency intermediate frequency modulation signal (intermediate frequency modulation signal).

[0072] The reception signal of the radio central station 22 ₂ processing circuit 38 ₂ and the radio base station 23 ₂ of the received signal processing circuit 44 ₂
Is a serial / parallel converter 57 and a D / A converter 5
8 ₂ (digital / analog conversion means) and a frequency converter 62 (second frequency conversion means). The frequency converter 62 converts the intermediate frequency modulation signal (intermediate frequency modulation signal) converted by the frequency converter 61 into an original analog wireless modulation signal.

FIG. 6 is a block diagram showing an example of the frequency converter 61. The frequency converter 61 includes a local oscillator 65, a mixer 64, and a low pass filter 66. The mixer 64 is supplied with the analog radio modulation signal and the local oscillation signal and generates an intermediate frequency modulation signal having a frequency lower than that of the original analog radio modulation signal. Low pass filter 6
6 removes unnecessary band components and outputs only the frequency-converted intermediate frequency modulated signal.

For example, when the analog radio modulation signal has a carrier wave of 800 MHz and a band of 20 MHz, it can be converted into an intermediate frequency modulation signal of a center frequency of 20 MHz and a band of 20 MHz by appropriately setting the local oscillation signal. The A / D converter 55 ₂ converts the intermediate frequency modulated signal into an A / D signal.
Since it only needs to be converted, the analog radio modulated signal can be directly converted into A
The sampling frequency can be lowered as compared with the case of performing D / D conversion.

For example, in the frequency converter 61, the carrier wave 80
A modulated signal with a bandwidth of 20 MHz at 0 MHz and a center frequency of 2
When converting to an intermediate frequency modulation signal with a bandwidth of 20 MHz at 0 MHz, the maximum frequency is about 30 MHz, and the sampling frequency of the A / D converter 55 ₂ may be 60 MHz or higher, which is less than about 1.6 GHz of the first embodiment. Can be significantly lowered.

The parallel / serial converter 56 is an A / D converter.
The 14-bit parallel data supplied from the converter 55 ₂ is converted into a bit stream (serial data),
Output as digital intermediate frequency modulation data. Electricity/
The optical converter 35 converts the digital intermediate frequency modulation data supplied from the transmission signal processing circuits 34 ₂ and 49 ₂ into a binary digital optical signal.

The optical / electrical converter 37 of the wireless central station 22 ₂ or the wireless base station 23 ₂ receives the digital optical signal transmitted from the electrical / optical converter 35 of the wireless base station 23 ₂ or the wireless central station 22 _2. Then, it is converted into an electric signal. The converted electric signal is a reproduction of the digital intermediate frequency modulation data generated by the transmission signal processing circuits 34 ₂ and 49 ₂ .

The serial / parallel converter 57 converts the bit stream (serial data) supplied from the optical / electrical converter 37 into 14-bit parallel data. The specifications of the D / A converter 58 ₂ are A / D converter 55 ₂
It corresponds to the specifications of. For example, as with the A / D converter 55 ₂ , a sampling frequency of 60 MHz and a 14-bit D /
The A converter converts 14-bit parallel data into an analog intermediate frequency modulation signal. The converted analog intermediate frequency modulation signal is a reproduction of the analog intermediate frequency modulation signal generated by the frequency converter 61.

In this way, the D / A converter 58₂The sump
The ring frequency is also the A / D converter 55 ₂According to
Can be lowered to FIG. 7 shows the frequency converter 62.
The block diagram of an example is shown. The frequency converter 62 is a local oscillator.
68, mixer 67 and band pass filter 69
Is made. The mixer 67 outputs the intermediate frequency modulated signal and the local signal.
Signal to generate the original analog radio modulated signal
I do. The bandpass filter 69 removes unnecessary band components.
Then, only the original analog radio modulated signal is output.

For example, the frequency converter 61 causes the carrier wave 8
When the analog radio modulated signal of 00 MHz and the band of 20 MHz is converted into the intermediate frequency modulated signal of the center frequency of 20 MHz and the band of 20 MHz, the local oscillation signal of the local oscillator 68 is appropriately set to restore the original carrier wave 80.
It is possible to reproduce an analog radio modulation signal having a band of 20 MHz at 0 MHz.

As described above, in the second embodiment, since the intermediate frequency modulated signal is A / D converted and D / A converted, the sampling frequencies of the A / D converter 55 ₂ and the D / A converter 58 ₂ are changed. The A / D converter 55 ₂ and the D / A converter 58 ₂ with high accuracy can be easily constructed.

Further, since the operating frequencies of the electric / optical converter 35 and the optical / electrical converter 37 can be lowered, the electric / optical converter 35 and the optical / electrical converter 37 can be constructed at a lower cost. In the second embodiment, as in the first embodiment, the electrical / optical converter 35 and the optical / electrical converter 37 handle binary digital signals, so that the wireless modulated signal is transmitted without distortion. Therefore, it is possible to significantly improve the transmission quality of the wireless modulation signal as compared with the conventional device in which the electric / optical conversion and the intermodulation distortion generated during the optical / electrical conversion pose a problem. In particular, it is effective when using the SCM transmission method in which a plurality of carrier waves are set up and transmitted within a constant radio frequency band.

FIG. 8 shows a block diagram of the wireless central station 22 ₃ of the wireless signal transmission apparatus of the third embodiment of the present invention, and FIG. 9 shows a block diagram of the wireless base station 23 ₃ . 8 and 9,
The same components as those in FIGS. 1, 2 and 3 are designated by the same reference numerals, and description thereof will be omitted as appropriate. 8 and 9, main parts of one radio base station 23 ₃ (optical / electrical converter 37, reception signal processing circuit 44 ₃ , transmission signal processing circuit 49 ₃ , electricity / electrical converter 37).
The optical converter 35) and the wireless central station 2 connected to it
2 _{3 The} main parts of the transmission side device (modulation device 31 ₃ , transmission signal processing circuit 34 ₃ , electric / optical converter 35) and the main parts of the reception side device (optical / electrical converter 37, reception signal processing circuit 38 _3). , Demodulator 41 ₃ ), and the input / output switch 26, transmission distributor 27, reception distributor 28, etc. are omitted.

[0084] Modulation device ₃₁₃ of the radio central station 22 ₃ is constituted by the modulator 75a to 75d. In the third embodiment, carrier waves of four waves are set up within a constant radio frequency band to transmit a radio modulated signal. Therefore, the modulators 75a-
Each of 75d is a carrier wave having a different frequency within a constant radio frequency band, and performs modulation in accordance with data from the baseband processing circuit 29.

For example, the band 2 with the center frequency of 800 MHz
Four carrier waves are set up within 0 MHz, four-phase phase modulation is performed on each carrier, and four analog wireless modulation signals with an occupied band of 1.5 MHz are generated. The occupied band 1.5 MHz of the wireless modulation signal by each carrier wave is dispersed in the band of 20 MHz, and there is an unused band between the adjacent occupied band 1.5 MHz.

The transmission signal processing circuit 34 ₃ includes frequency converters 71a to 71d and a synthesizing circuit 73 (third frequency converting means), an A / D converter 55 ₃ and a parallel / serial converter 56 (analog / digital conversion). Means). The frequency converters 71a to 71d respectively include the modulator 7
The analog radio modulation signal supplied from 5a to 75d is an intermediate frequency modulation signal with a low frequency (intermediate frequency modulation signal).
Convert to.

The intermediate frequencies of the frequency converters 71a to 71d are set so that the bands of the intermediate frequency modulated signals converted by the frequency converters 71a to 71d are arranged in a continuous band. The frequency converters 71a to 71d can be configured similarly to the frequency converter 61 of FIG.

The synthesis circuit 73 includes frequency converters 71a to 71a.
The intermediate frequency modulation signals supplied from 1d are combined to obtain 4
A composite intermediate frequency modulation signal is output in a state where the intermediate frequency modulation signal by the wave carrier is arranged in a continuous band.
For example, in the modulator 31 ₃ , the center frequency is 800M
Occupied bandwidth 1.5M by setting 4 carrier waves within 20MHz band at 4Hz and performing 4 phase phase modulation on each carrier.
Consider the case of generating an analog radio modulated signal of Hz.

The frequency converters 71a to 71d are, for example,
Occupied bandwidth of each intermediate frequency modulation signal by carrier waves of 4 waves 1.5 MHz in 6 MHz band of 10 MHz to 16 MHz
The frequency conversion is performed so that are arranged continuously. In this case, the combining circuit 73 outputs a combined intermediate frequency modulation signal having a band of 10 MHz to 16 MHz. In this way, the band 6M narrower than the original band 20 MHz
A synthetic intermediate frequency modulated signal of Hz can be generated.

The A / D converter 55 ₃ A / D-converts the composite intermediate frequency modulation signal to generate 14-bit parallel data. The synthetic intermediate frequency modulation signal is a signal obtained by converting the original wireless modulation signal into a low frequency, and the sampling frequency can be significantly reduced as compared with the case of directly A / D converting the analog wireless modulation signal. Furthermore, during frequency conversion, the modulation signals of each carrier, which were dispersed in the original radio frequency band, are arranged in consecutive bands, so the maximum frequency can be lowered by that amount, and the sampling frequency can be further lowered. can do.

For example, band 2 with a center frequency of 800 MHz
If the 0 MHz radio modulation signal is converted as it is to an intermediate frequency modulation signal having a center frequency of 20 MHz and a band of 20 MHz, the maximum frequency is about 30 MHz and the required sampling frequency is 60 MHz or more. On the other hand, in the present embodiment, the modulation signal by the carrier waves of four waves dispersed in the band 20 MHz is converted into the intermediate frequency modulation signal,
It is continuously arranged in a 6 MHz band from 10 MHz to 16 MHz.

As a result, the maximum frequency of the synthetic intermediate frequency becomes 16 MHz, and the required sampling frequency is 32
The frequency may be set to MHz or higher, and the sampling frequency can be further lowered. Parallel / serial converter 56
Converts 14-bit parallel data supplied from the A / D converter 55 ₃ into a bit stream (serial data) and outputs it as digital intermediate frequency modulation data. The electrical / optical converter 35 converts the digital intermediate frequency modulation data supplied from the transmission signal processing circuit 34 ₃ into a binary digital optical signal. This digital optical signal is
It is transmitted to the radio base station 23 ₃ via the optical transmission line.

Optical / electrical converter 37 of the radio base station 23 _3.
Receives the digital optical signal transmitted from the electric / optical converter 35 of the wireless central station 22 ₃ and converts it into an electric signal. The converted electric signal is transmitted to the transmission signal processing circuit 34.
_This is a reproduction of the digital intermediate frequency modulation data generated in ₃ . The digital intermediate frequency modulation data is supplied to the reception signal processing circuit 44 ₃ .

Reception signal processing circuit 44 of radio base station 23 _3.
3 is a serial / parallel converter 57 and a D / A converter 58 ₃ (digital / analog conversion means), a demultiplexing circuit 74, frequency converters 78a to 78d, and a combining circuit 81.
(Fourth frequency conversion means).

The serial / parallel converter 57 is an optical / electrical converter.
Bit stream supplied from the air converter 37 (Syria
Data) to 14-bit parallel data
It D / A converter 58₃The specifications of A / D converter 55₃
It corresponds to the specifications of. For example, the A / D converter 55₃When
Similarly, with a sampling frequency of 32 MHz, 14-bit D /
It is an A converter that converts 14-bit parallel data to analog data.
Convert to a log intermediate frequency modulated signal. This is converted
The synthesized intermediate frequency modulated signal is transmitted to the radio base station 22. ₃The synthesis times
The synthetic intermediate frequency modulation signal generated in the path 73 is reproduced.
Of.

In this way, the D / A converter 58₃The sump
The ring frequency is also the A / D converter 55 ₃According to
Can be lowered to The demultiplexing circuit 74 carries four waves
The intermediate frequency modulated signal corresponding to the wave is placed in a continuous band.
Each intermediate frequency modulation signal from the synthesized intermediate frequency signal
Separated and supplied to each of the frequency converters 78a to 78d.
It

The frequency converters 78a to 78d convert the intermediate frequency modulation signal supplied from the demultiplexing circuit 74 into a radio modulation signal having the original carrier frequency. Frequency converter 78
The components a to 78d can be configured similarly to the frequency converter 62 of FIG.

For example, in the case where the analog radio modulation signal dispersed in the band 20 MHz at the center frequency 800 MHz by the frequency converters 71a to 71d is converted into the intermediate frequency modulation signal of 10 MHz to 16 MHz, the frequency converters 78a to 78d, respectively. By properly setting the local oscillation signal of, the original, center frequency 800MHz band 20M
Each analog radio modulated signal dispersed within Hz can be reproduced.

The synthesis circuit 81 includes frequency converters 71a-7a.
Dispersed within a fixed radio frequency band converted by 1d
Each analog wireless modulation signal is combined to the power amplifier 45.
Supply. Radio base station 23₃Transmission signal processing circuit 49₃
Is the demultiplexing circuit 82, the frequency converters 77a to 77d, and the combining circuit.
Composition circuit 73 (third frequency conversion means), A / D converter 5
5 ₃And parallel / serial converter 56 (analog / data
Digital conversion means).

The demultiplexing circuit 82 is supplied from the low noise amplifier 47 with an analog radio modulation signal in which radio modulation signals by four carrier waves are dispersed in a constant radio frequency band. The demultiplexing circuit 82 separates the radio modulation signal by each carrier wave and supplies it to the frequency converters 77a to 77d.

The functions of the frequency converters 77a to 77d are similar to those of the frequency converters 71a to 71d, and convert the analog radio modulation signal supplied from the demultiplexing circuit 82 into an intermediate frequency modulation signal of low frequency. The bands of the converted intermediate frequency modulation signals are arranged in continuous bands.

The synthesis circuit 73 includes frequency converters 77a to 77a.
4d by combining the intermediate frequency modulation signals supplied from 7d
A composite intermediate frequency modulation signal is output in a state where the intermediate frequency modulation signal by the wave carrier is arranged in a continuous band.
For example, in the case of an analog wireless modulation signal in which a wireless modulation signal having an occupied band of 1.5 MHz by four carrier waves is dispersed in a band 20 MHz with a center frequency of 800 MHz, the frequency converters 77a to 77d are, for example, 10 MHz to 1
Frequency conversion is performed so that the occupied band of 1.5 MHz of each intermediate frequency modulated signal by the four carrier waves is continuously arranged in the 6 MHz band of 6 MHz. The synthesizing circuit 73 is 10
A composite intermediate frequency modulation signal having a band of MHz to 16 MHz is output. In this way, the original band 20MHz
It is possible to generate a synthetic intermediate frequency modulation signal having a band of 6 MHz having a narrower band than the above.

A / D converter 55₃Is the synthetic intermediate frequency
14-bit parallel data after A / D conversion of key signal
To generate. A / D converter 55₃Is a transmission signal processing circuit
34 ₃A / D converter 55₃Modulation of each carrier as well as
Synthetic intermediate frequency modulated signal with signals arranged in continuous bands
A / D conversion is performed, so the sampling frequency is significantly reduced.
Can be done.

For example, band 2 with a center frequency of 800 MHz
When the modulation signal by the carrier wave of 4 waves dispersed in 0 MHz is converted into the intermediate frequency modulation signal and continuously arranged in the band of 6 MHz of 10 MHz to 16 MHz, the highest frequency of the synthetic intermediate frequency becomes 16 MHz, which is necessary. The sampling frequency may be 32 MHz or higher.

The parallel / serial converter 56 is an A / D converter.
The 14-bit parallel data supplied from the converter 55 _{3 is} converted into serial data (bit stream),
Output as digital intermediate frequency modulation data. Electricity/
The optical converter 35 converts the digital intermediate frequency modulation data supplied from the transmission signal processing circuit 49 ₃ into a binary digital optical signal. This digital optical signal is transmitted to the wireless central station 22 ₃ via the optical transmission line.

Optical / electrical converter 37 of wireless central station 22 _3.
Receives the digital optical signal transmitted from the electrical / optical converter 35 of the radio base station 23 ₃ and converts it into an electrical signal. The converted electric signal is transmitted to the transmission signal processing circuit 49.
_This is a reproduction of the digital intermediate frequency modulation data generated in ₃ . The digital intermediate frequency modulation data is supplied to the reception signal processing circuit 38 ₃ .

Received signal processing circuit 38 of wireless central station 22 _3.
3 is composed of a serial / parallel converter 57 and a D / A converter 58 ₃ (digital / analog conversion means), a demultiplexing circuit 74, and frequency converters 72a to 72d (fourth frequency conversion means). . Serial / parallel converter 5
Reference numeral 7 converts the bit stream (serial data) supplied from the optical / electrical converter 37 into 14-bit parallel data.

The specifications of the D / A converter 58 ₃ correspond to the specifications of the A / D converter 55 ₃ of the transmission signal processing circuit 49 ₃ . For example, like the A / D converter 55 _3, it is a 14-bit D / A converter with a sampling frequency of 32 MHz.
The 4-bit parallel data is converted into an analog synthetic intermediate frequency modulation signal. The converted combined intermediate frequency modulated signal is a reproduction of the combined intermediate frequency modulated signal generated by the combining circuit 73 of the transmission signal processing circuit 49 ₃ .

As described above, the sampling frequency of the D / A converter 58 ₃ can also be significantly lowered in accordance with the A / D converter 55 ₃ of the transmission signal processing circuit 49 ₃ . The demultiplexing circuit 74 separates each intermediate frequency modulated signal from the synthesized intermediate frequency signal arranged in the band where the intermediate frequency modulated signals corresponding to the four carrier waves are continuous, and the frequency converter 7
Supply to each of 2a to 72d.

The functions of the frequency converters 72a to 72d are similar to those of the frequency converters 78a to 78d.
The intermediate frequency modulation signal supplied from the device is converted into a wireless modulation signal with the original carrier frequency. For example, the frequency converters 77a to 77d provide a band 2 with a center frequency of 800 MHz.
Analog radio modulation signal dispersed within 0MHz is 10M
When converted to an intermediate frequency modulation signal of Hz to 16 MHz, the original center frequency 800 is set by appropriately setting the local oscillation signals of the frequency converters 72a to 72d.
It is possible to reproduce each analog radio modulated signal, which is dispersed in the band 20 MHz in MHz.

The demodulator 41 ₃ includes demodulators 76a to 76d.
Composed of. The demodulators 76a to 76d perform demodulation processing on each of the analog wireless modulation signals by the four-wave carrier waves supplied from the reception signal processing circuit 38 ₃ , and generate demodulation data. For example, each analog radio modulated signal has about 8
In the case of a 4-phase phase modulated signal with a carrier wave of 00 MHz,
Each of the demodulators 76a to 76d performs synchronous detection using a local oscillation signal of about 800 MHz having a phase difference of 90 °,
Demodulate two series of data strings.

The demodulated data is the baseband processing circuit 29.
The data is converted into data in the format of the exchange and then transmitted to the exchange 20. As described above, in the third embodiment, since the original radio modulation signal is converted into the composite intermediate frequency modulation signal of low frequency and then A / D converted, the A / D conversion is performed.
The sampling frequency of the converter 55 ₃ can be significantly reduced. Furthermore, during frequency conversion, the modulated signals of each carrier, which were dispersed in the original radio frequency band, are arranged in consecutive bands, so the maximum frequency of the composite intermediate frequency modulated signal can be lowered by that amount. The sampling frequency can be made lower than that in the second embodiment. Similarly, the sampling frequency of the D / A converter 58 ₃ can be significantly reduced.

As described above, in the third embodiment, the sampling frequencies of the A / D converter 55 ₃ and the D / A converter 58 ₃ can be significantly lowered, and the A / D converter 5 with high accuracy can be obtained.
5 ₃ and the D / A converter 58 ₃ can be easily constructed. Further, since the operating frequencies of the electric / optical converter 35 and the optical / electrical converter 37 can be lowered, the electric / optical converter 35 and the optical / electrical converter 37 can be constructed at a lower cost.

The third embodiment using the SCM transmission system in which a plurality of carrier waves are set up and transmitted within a constant radio frequency band is the same as the first embodiment, and the electrical / optical converter 35 and the optical / electrical converter are used. Since 37 handles binary digital signals, it is possible to transmit wirelessly modulated signals without causing distortion,
It is possible to significantly improve the transmission quality of the wireless modulation signal, as compared with the conventional device in which the electrical / optical conversion and the intermodulation distortion that occurs during the optical / electrical conversion poses a problem.

FIG. 10 is a block diagram of the wireless central station 22 ₄ of the wireless signal transmission apparatus according to the fourth embodiment of the present invention.
Shows a configuration diagram of the wireless base station 23 ₄ . 10 and 11
3, the same components as those in FIGS. 1, 2 and 3 are designated by the same reference numerals and the description thereof will be omitted as appropriate.

10 and 11, the main parts of one radio base station 23 ₄ (optical / electrical converter 37, received signal processing circuit 44 ₄ , transmission signal processing circuit 49 ₄ , electrical / optical converter 35) are shown. ) And the main part of the transmission side device of the wireless centralized station 22 ₄ connected to it (modulation device 31 ₄ , transmission signal processing circuit 3
4 ₄ , electric / optical converter 35) and a main part of the receiving side device (optical / optical)
Electric converter 37, received signal processing circuit 38 ₄ , demodulator 4
1 ₄₎ have indicated only the input and output switch 26,
The transmission distributor 27, the reception distributor 28, etc. are omitted.

[0117] modulator 31 ₄ radio central station 22 ₄ is constituted by the modulator 83a to 83d. In the fourth embodiment, carrier waves of four waves are set up within a fixed radio frequency band to transmit a radio modulation signal. The modulation unit 31 ₄ performs modulation at an intermediate frequency of a frequency lower than the radio frequency.

Each of the modulators 83a to 83d is an intermediate frequency signal corresponding to each radio carrier within a constant radio frequency band, modulates according to the data from the baseband processing circuit 29, and generates an intermediate frequency modulation signal. In the fourth embodiment, the intermediate frequency modulated signals corresponding to the four carrier waves are individually A / D converted and D / A converted, so that the bands of the intermediate frequency modulated signals may overlap. For example, the band of each intermediate frequency modulation signal may be set to the same band.

For example, the band 2 with the center frequency of 800 MHz
When four radio carriers are set up within 0 MHz, four-phase phase modulation is performed with intermediate frequency signals corresponding to the respective radio carriers to generate an analog intermediate frequency modulation signal having an occupied band of 1.5 MHz. Occupied bandwidth of each intermediate frequency modulation signal 1.5M
The Hz is arranged in the same band of 10 MHz to 11.5 MHz, for example.

[0120] The transmission signal processing circuit 34 ₄ is composed of an A / D converter 85a~85d and parallel / serial converter 86 (analog / digital converter). A / D
Each of the converters 85a to 85d includes a modulator 83a to 83d.
The intermediate frequency modulation signals corresponding to the respective carrier waves supplied from A / D are individually A / D converted to generate 14-bit parallel data.

The intermediate frequency modulation signal supplied to the A / D converters 85a to 85d is a signal modulated with an intermediate frequency signal of a low frequency corresponding to the wireless carrier frequency, and is an analog wireless modulated signal modulated with the wireless carrier. The sampling frequency can be significantly reduced as compared with the case of performing direct A / D conversion. In addition, the intermediate frequency modulation signals are individually A /
Because of the D conversion, the bands of the intermediate frequency modulated signals may overlap or may be set to the same band. Therefore, the maximum frequency of the intermediate frequency modulation signal can be further lowered and the sampling frequency can be further lowered, as compared with the third embodiment in which the synthetic intermediate frequency modulation signal is generated.

For example, band 2 with a center frequency of 800 MHz
If the 0 MHz radio modulation signal is converted as it is to an intermediate frequency modulation signal having a center frequency of 20 MHz and a band of 20 MHz, the maximum frequency is about 30 MHz and the required sampling frequency is 60 MHz or more. On the other hand, in the present embodiment, four systems of intermediate frequency modulated signals of 10 M are provided corresponding to four carrier waves dispersed in the band of 20 MHz.
It can be arranged in the same band from Hz to 11.5 MHz.

As a result, the maximum frequency of the intermediate frequency modulated signal becomes 11.5 MHz, and the required sampling frequency should be 23 MHz or higher, and the sampling frequency can be further lowered. The parallel / serial converter 86 multiplexes the 14-bit parallel data supplied from each of the A / D converters 85a to 85d into a bit stream (serial data) and outputs it as digital intermediate frequency modulation data.

As a method of multiplexing, for example, four systems of data from the A / D converters 85a to 85d are arranged in order of 14 bits, and identification bits (unique bits) are provided before and after the four systems of data. The electric / optical converter 35 is
The digital intermediate frequency modulation data supplied from the transmission signal processing circuit 34 ₄ is converted into a binary digital optical signal.
This digital optical signal is transmitted to the radio base station 23 ₄ via the optical transmission line.

Instead of the modulator 31 ₄ , a modulator that directly modulates four radio carriers to generate a radio modulated signal, and a frequency converter that individually converts each radio modulated signal into an intermediate frequency modulated signal. (Fifth frequency conversion means) may be used. The optical / electrical converter 37 of the wireless base station 23 ₄ is connected to the electrical / optical converter 35 of the wireless central station 22 _4.
The digital optical signal transmitted from the device is received and converted into an electrical signal. The converted electric signal is a reproduction of the digital intermediate frequency modulation data generated by the transmission signal processing circuit 34 ₄ . The digital intermediate frequency modulation data is supplied to the reception signal processing circuit 44 ₄ .

Reception signal processing circuit 44 of radio base station 23 _4.
4 is a serial / parallel converter 87 and D / A converters 88a to 88d (digital / analog conversion means),
It is composed of frequency converters 80a to 80d and a synthesizing circuit 81 (sixth frequency converting means).

The serial / parallel converter 87 separates the multiplexed bit stream (serial data) supplied from the optical / electrical converter 37 into four systems, and separates them into 14 systems.
Convert to bit parallel data. The data of each system can be identified by using the unique bit.

The specifications of the D / A converters 88a to 88d are A
This corresponds to the specifications of the / D converters 85a to 85d. For example, like the A / D converters 88a to 88d, it is a 14-bit D / A converter with a sampling frequency of 23 MHz.
The 4-bit parallel data is converted into an analog intermediate frequency modulation signal. This converted intermediate frequency modulated signal is
Is obtained by reproducing the intermediate frequency modulated signal generated by the modulator 83a~83d of modulator 31 _4.

As described above, the D / A converters 88a to 88d are provided.
Sampling frequency of A / D converters 85a to 85d
It can be significantly lowered to suit. The frequency converters 80a to 80d convert the intermediate frequency modulation signals supplied from the D / A converters 88a to 88d into the original wireless modulation signals by the four wireless carriers. Frequency converter 8
0a to 80d can be configured similarly to the frequency converter 62 of FIG. 7.

For example, when the modulator 31 ₄ generates an intermediate frequency modulated signal of 10 MHz to 11.5 MHz corresponding to four carrier waves having an intermediate frequency of 800 MHz and dispersed in a band of 20 MHz, the frequency converter 80a ~
By appropriately setting the respective local oscillation signals of 80d, it is possible to reproduce the analog wireless modulation signal by each carrier wave which is dispersed in the band 20 MHz at the center frequency of 800 MHz.

The synthesis circuit 81 includes frequency converters 80a-8a.
The analog radio modulated signals that have been converted by 0d and are dispersed within a fixed radio band are combined and supplied to the power amplifier 45. Transmission signal processing circuit 49 ₄ of the radio base station 23 ₄ includes a branching circuit 82 and the frequency converter 79A～79d (Fifth frequency conversion means), A / D converter 85a~85d and parallel / serial converter 86 (Analog / digital conversion means).

The demultiplexing circuit 82 is supplied from the low noise amplifier 47 with an analog radio modulation signal in which radio modulation signals of four radio carriers are dispersed within a constant radio frequency band. The demultiplexing circuit 82 separates the radio modulation signal by each carrier wave and supplies it to the frequency converters 79a to 79d.

The frequency converters 79a to 79d respectively convert the analog radio modulation signal supplied from the demultiplexing circuit 82 into an intermediate frequency modulation signal having a low frequency. The bands of the converted intermediate frequency modulation signals may overlap or may be the same band. For example, when the analog wireless modulation signal is a modulation signal with four carrier waves having a center frequency of 800 MHz and dispersed in a band of 20 MHz, an intermediate frequency modulation signal with an occupied band of 1.5 MHz is generated by an intermediate frequency corresponding to each carrier. To generate. The occupied bandwidth of the modulated signal at each intermediate frequency of 1.5 MHz is, for example, 10 MHz to 11.5 M.
They can be arranged in the same band of Hz.

Each of the A / D converters 85a to 85d individually A / D-converts the intermediate frequency modulation signal corresponding to each carrier wave supplied from the frequency converters 79a to 79d, to 14
Generates bit parallel data. A / D converter 85
The intermediate frequency modulation signal supplied to a to 85d is a modulation signal of a low frequency corresponding to the wireless modulation signal by the wireless carrier, compared to the case where the analog wireless modulation signal modulated by the wireless carrier is directly A / D converted. , The sampling frequency can be significantly reduced. Furthermore, since the intermediate frequency modulated signals are individually A / D converted, the bands of the intermediate frequency modulated signals may overlap or may be set to the same band.
Therefore, the maximum frequency of the intermediate frequency modulation signal can be further lowered and the sampling frequency can be further lowered, as compared with the third embodiment in which the synthetic intermediate frequency modulation signal is generated.

For example, the center frequency of 800 MHz and the band 2
If the 0 MHz wireless modulation signal is converted as it is to an intermediate frequency modulation signal with an intermediate frequency of 20 MHz and a band of 20 MHz, the maximum frequency is about 30 MHz and the required sampling frequency is 60 MHz or more. On the other hand, in the present embodiment, four systems of intermediate frequency modulated signals of 10 M are provided corresponding to four carrier waves dispersed in the band of 20 MHz.
It can be arranged in the same band from Hz to 11.5 MHz. Therefore, the maximum frequency of the intermediate frequency modulation signal is 1
1.5MHz, the required sampling frequency is 2
The frequency may be set to 3 MHz or more, and the sampling frequency can be further lowered.

Similar to the parallel / serial converter 86 of the transmission signal processing circuit 34 ₄ , the parallel / serial converter 8
Reference numeral 6 multiplexes 14-bit parallel data supplied from each of the A / D converters 85a to 85d, converts it into a bit stream (serial data), and outputs it as digital intermediate frequency modulation data.

[0137] Electrical / optical converter 35 converts the digital intermediate frequency modulated data supplied from the transmission signal processing circuit 49 ₄ into a digital optical signal 2 values. This digital optical signal is transmitted to the wireless central station 22 ₄ via the optical transmission line. The optical / electrical converter 37 of the wireless central station 22 ₄ receives the digital optical signal transmitted from the electric / optical converter 35 of the wireless base station 23 ₄ and converts it into an electric signal. The converted electric signal is obtained by reproducing the digital intermediate frequency modulated data generated by the transmission signal processing circuit 49 _4. The digital intermediate frequency modulation data is supplied to the reception signal processing circuit 38 ₄ .

Reception signal processing circuit 38 of the wireless central station 22 _4.
4 is composed of a serial / parallel converter 87 and D / A converters 88a to 88d (digital / analog conversion means). The serial / parallel converter 87 separates the multiplexed bit stream (serial data) supplied from the optical / electrical converter 37 into four systems and converts them into 14-bit parallel data. The data of each system can be identified by using the unique bit.

[0139] Specifications of the D / A converter 88a~88d correspond to the specifications of the transmission signal processing circuit 49 ₄ A / D converter 85 a - 85 d. For example, A / D converters 88a-8
Similar to 8d, it is a 14-bit D / A converter with a sampling frequency of 23 MHz and converts 14-bit parallel data into an analog intermediate frequency modulation signal. The converted intermediate frequency modulated signal is converted into frequency converters 79a to 79a.
It is a reproduction of the intermediate frequency modulation signal generated in d.

As described above, the D / A converters 88a to 88d are provided.
Also the sampling frequency, A of the transmission signal processing circuit 49 ₄
It can be significantly lowered according to the / D converters 85a to 85d. Demodulator 41 _4, demodulator 84a~84
d. Demodulator 84a~84d is supplied from the reception signal processing circuit 38 ₄ of the D / A converter 88 a to 88 d, performs the intermediate frequency modulated signal each of the demodulation process corresponding to the modulated radio signal by four-wave of the radio carrier, Generate demodulated data.

For example, each of the analog radio modulated signals is
In the case of a four-phase phase-modulated signal with a carrier of about 800 MHz, each of the demodulators 84a to 84d performs synchronous detection using a local oscillation signal of an intermediate frequency whose phase is different by 90 °,
Demodulate two series of data strings.

The demodulated data is the baseband processing circuit 29.
The data is converted into data in the format of the exchange and then transmitted to the exchange 20. It should be noted that instead of the demodulator 41 ₄ , a frequency converter (sixth frequency conversion means) for individually converting the four intermediate frequency modulation signals into the original radio modulation signal, and demodulation data is generated from this radio modulation signal. It may be configured to use a demodulation device that operates.

As described above, in the fourth embodiment, the intermediate frequency modulation signal having a frequency lower than the original radio modulation signal is A /
Since the D conversion is performed, the sampling frequency of the A / D converters 85a to 85d can be significantly reduced. Furthermore, since the intermediate frequency modulated signals are individually A / D converted by the A / D converters 85a to 85d, the bands of the intermediate frequency modulated signals may overlap or may be set to the same band. Therefore, the maximum frequency of the intermediate frequency modulation signal can be further lowered as compared with the third embodiment in which the synthetic intermediate frequency modulation signal is generated.
The sampling frequency can be further lowered.

Similarly, D / A converters 88a to 88d are also provided.
The sampling frequency of can be significantly reduced.
Thus, in the fourth embodiment, the A / D converters 85a-8a are provided.
5d and the sampling frequencies of the D / A converters 88a to 88d can be significantly lowered, and the highly accurate A / D converters 85a to 85d and the D / A converters 88a to 88d can be easily configured. .

Since the operating frequencies of the electric / optical converter 35 and the optical / electrical converter 37 can be lowered, the electric / optical converter 35 and the optical / electrical converter 37 can be constructed at a lower cost. In the fourth embodiment using the SCM transmission method in which a plurality of carrier waves are set up and transmitted within a constant radio frequency band, the electric / optical converter 35 and the optical / electric converter 37 are connected to each other as in the first embodiment. Since the digital signal of the value is handled, the wireless modulation signal can be transmitted without causing distortion,
It is possible to significantly improve the transmission quality of the wireless modulation signal, as compared with the conventional device in which the electrical / optical conversion and the intermodulation distortion that occurs during the optical / electrical conversion poses a problem.

FIG. 12 is a block diagram showing the essential parts (transmission signal processing circuit 49 ₅ and electro-optical converter 35) of the radio base station 23 ₅ of the radio signal transmission apparatus according to the fifth embodiment of the present invention. Thirteen
Shows a configuration diagram of main parts (optical / electrical converter 37, received signal processing circuit 38 ₅ , demodulator 41 ₅ ) of the wireless central station 22 ₅ . 12 and 13, the same components as those in FIGS. 1, 2 and 3 are designated by the same reference numerals, and the description thereof will be appropriately omitted.
12 and 13, one wireless base station 23 ₅ and one wireless central station 22 ₅ are connected, and the input / output switch 26, the transmission distributor 27, the reception distributor 28, etc. are omitted. .

The transmitting side device of the wireless central station 22 _{5 (} not shown) is similar to the fourth embodiment in that the modulating devices 31 ₄ ,
The transmission signal processing circuit 34 ₄ and the electrical / optical converter 35 are included. The receiving side device of the radio base station 23 ₅ , which is not shown, is the optical / electrical converter 3 as in the fourth embodiment.
7, a reception signal processing circuit 44 _{4 and the} like.

The transmitting side device of the wireless central station 22 ₅ and the receiving side device of the wireless base station 23 ₅ may have the same configuration as in the third embodiment. Transmission signal processing circuit 49 of the radio base station 22 _{5 5}
Is composed of a demultiplexing circuit 82, quasi-synchronous detection circuits 91a to 91d (detection means), A / D conversion circuits 92a to 92d, and a parallel / serial converter 93 (analog / digital conversion means).

In the fifth embodiment, four radio carriers are erected within a constant radio frequency band to transmit a radio modulated signal. The demultiplexing circuit 82 is supplied from the low noise amplifier 47 with an analog radio modulation signal in which radio modulation signals of four radio carriers are dispersed in a constant radio frequency band. The demultiplexing circuit 82 separates the radio modulation signal by each carrier wave and supplies it to the quasi-synchronous detection circuits 91a to 91d.

The quasi-synchronous detection circuits 91a to 91d detect the radio modulation signal using the local oscillation signal whose frequency is almost equal to that of the radio carrier. FIG. 14 shows a quasi-synchronous detection circuit 91a.
91d show the respective configuration diagrams. Quasi-synchronous detection circuit 91a-
91d is an amplifier 101, a distributor 102, a mixer 10
3, 104, local oscillator 105, 90 ° phase shifter 106,
It is composed of low-pass filters 107 and 108.

The radio modulated signal is sent to the amplifier 101 and the distributor 1.
It is supplied to the mixers 103 and 104 via 02.
The mixer 103 is supplied with a local oscillation signal from the local oscillator 105, and the mixer 104 is supplied with a local oscillation signal having a 90 ° phase difference from the local oscillation signal generated by the local oscillator 105. The frequency of the local oscillation signal generated by the local oscillator 105 is matched with the carrier frequency of the wireless modulation signal, but the phases are not necessarily matched.

From the mixers 103 and 104, 9
Baseband signals with different 0 ° phases are generated. The low-pass filters 107 and 108 output baseband signals from which unnecessary frequency components have been removed. However, since control is not performed so that the phase of the local oscillation signal exactly matches the phase of the carrier wave, the two series of baseband signals include an uncertain phase component. Uncertainty component of this phase is removed by demodulator 41 ₅ to be described later,
Correct data is demodulated.

The two series of baseband signals generated by the quasi-synchronous detection circuits 91a to 91d are A / D conversion circuits 92a.
~ 92d. A / D conversion circuits 92a to 92d
Each of the two A / D converters A / D converts two series of baseband signals supplied from the quasi-synchronous detection circuits 91a to 91d to convert 14-bit parallel data into two.
Generate a series.

The signals supplied to the A / D conversion circuits 92a to 92d are baseband signals, which are signals having a frequency significantly lower than that of the intermediate frequency modulation signal. Therefore, the sampling frequency can be further reduced as compared with the case of A / D converting the intermediate frequency modulation signal.

For example, the band 2 with the center frequency of 800 MHz
In the case where the radio modulation signal of the base band of 1.5 MHz by the four carrier waves is dispersed in the radio frequency band of 0 MHz, when the intermediate frequency modulation signal is A / D converted,
For example, in the fourth embodiment, the maximum frequency is 11.5 MHz and the required sampling frequency is 23 MHz or higher. On the other hand, the A / D conversion circuits 92a to 92a of the present embodiment
92d is a baseband signal with a bandwidth of 1.5 MHz A /
It suffices if D conversion is possible, and the required sampling frequency is 3
The frequency may be set to MHz or higher, and the sampling frequency can be significantly reduced.

The parallel / serial converter 93 is an A / D converter.
Two series 14 supplied from each of the conversion circuits 92a to 92d
Bit parallel data is multiplexed, converted into a bit stream (serial data), and output. As a multiplexing method, for example, a unique bit can be used as in the fourth embodiment.

The electrical / optical converter 35 is a transmission signal processing circuit.
49_FiveSupplied from the parallel / serial converter 93
Binary digitizer for bitstream (serial data)
Convert to optical signal. This digital optical signal is transmitted by optical
Wireless central station 22 via the track _FiveIs transmitted to

Optical / electrical converter 37 of wireless central station 22 _5.
Receives the digital optical signal transmitted from the electrical / optical converter 35 of the radio base station 23 ₅ and converts it into an electrical signal. The converted electric signal is transmitted to the transmission signal processing circuit 49.
It is a reproduction of the bitstream (serial data) generated in ₅ . This serial data is supplied to the reception signal processing circuit 38 ₅ .

Received signal processing circuit 38 of wireless central station 22 _5.
5 is composed of a serial / parallel converter 94. The serial / parallel converter 94 separates the multiplexed bit stream (serial data) supplied from the optical / electrical converter 37 into four systems and converts them into two series of 14-bit parallel data. The identification of the data of each line is
This can be done using the unique bit described above.

The data of 4 lines and 2 lines output from the serial / parallel converter 94 are converted into A / D conversion circuits 92a to 92a.
Data corresponding to the baseband signal generated in 92d is reproduced, and this data can be used as it is for demodulation processing. Therefore, in the reception signal processing circuit 38 ₅ , the D / A for generating the analog modulation signal is generated.
No converter required.

[0161] demodulator 41 _5, demodulator 95a~95d
Composed of. FIG. 15 shows a block diagram of each of the demodulators 95a to 95d. Each of the demodulators 95a to 95d includes sum-of-products circuits 111 and 112 and a rotation control circuit 113.
Data X and Y corresponding to two series of baseband signals are supplied from the serial / parallel converter 94 to the sum-of-products circuits 111 and 112, respectively.

The sum-of-products circuit 111 weights the data X and Y.
Sum of product data Z ₁To generate. Immediately
Chi, Z₁= A₁・ X + b₁・ Calculate and output Y 2.
Weighting coefficient a₁, B₁From the rotation control circuit 113
Given. Similarly, the sum-of-products circuit 112 uses the data X, Y
Sum of product data Z₂Generate
It That is, Z₂= A₂・ X + b₂・ Calculate and output Y
I do. Weighting coefficient a₂, B₂Is the rotation control circuit 11
Given from 3.

The rotation control circuit 113 includes a sum-of-products circuit 111,
Sum-of-products data Z generated from 112 ₁And Z₂Correlation of
Therefore, the uncertain component of the phase included in the data X and the data Y
To remove the coefficient a₁, B₁, A₂, B₂Decide
And supplies them to the sum-of-products circuits 111 and 112.

In this way, the two series of data Z ₁ and Z ₂ having the correct phase relationship are demodulated. The demodulated data is converted by the baseband processing circuit 29 into data according to the format of the exchange, and then transmitted to the exchange 20.

As described above, in the fifth embodiment, the quasi-coherent detection circuits 91a to 91d generate baseband signals, and the baseband signals are A / D conversion circuits 92a to 92d.
A / D conversion is performed by 2d. Since the baseband signal is a signal having a frequency significantly lower than that of the intermediate frequency modulation signal, the sampling frequency can be further reduced as compared with the case of A / D converting the intermediate frequency modulation signal.

As described above, in the fifth embodiment, the sampling frequencies of the A / D conversion circuits 92a to 92d can be significantly lowered, and the A / D conversion circuits 92a to 92d with high accuracy can be obtained.
2d can be configured easily and inexpensively. As a result, the total cost of the wireless signal transmission device can be reduced.

In the fifth embodiment in which a plurality of carrier waves are set up in a constant radio frequency band for transmission, the electrical / optical converter 35 and the optical / electrical converter 37 are binary, as in the first embodiment. Since it handles digital signals, wireless modulated signals can be transmitted without distortion, and electrical / optical conversion and optical / optical conversion can be performed.
It is possible to significantly improve the transmission quality of the wireless modulation signal as compared with the conventional device in which the intermodulation distortion that occurs during electrical conversion poses a problem.

[0168]

As described above, according to the inventions of claims 1 to 5, since the optical / electrical converter and the electric / optical converter handle binary digital signals, the optical / electrical converter and the electric / Intermodulation distortion due to the non-linearity of the optical converter can be ignored, and the wireless modulation signal can be transmitted without distortion. Therefore, it is possible to significantly improve the transmission quality of the wireless modulation signal as compared with the conventional device in which the electric / optical conversion and the intermodulation distortion generated at the time of the optical / electrical conversion pose a problem. S to establish and transmit the carrier wave of
This is effective when the CM transmission method is used.

According to the second aspect of the present invention, the radio modulation signal is converted into an intermediate frequency modulation signal having a frequency lower than that of the radio modulation signal, the intermediate frequency modulation signal is converted into a digital modulation signal, and then converted into an optical signal. Since the optical transmission line is transmitted via the optical transmission line, the sampling frequencies of the analog / digital conversion means and the digital / analog conversion means can be significantly reduced, and the highly accurate analog / digital conversion means and digital / analog conversion means can be easily provided. Can be configured.

According to the third aspect of the present invention, when the original radio modulation signal is converted into the composite intermediate frequency modulation signal of low frequency, a plurality of radio modulation signals dispersed within a predetermined radio frequency band are consecutively formed. Since it is arranged in the band, it is better than converting to the intermediate frequency while keeping each modulated signal dispersed.
The maximum frequency of the composite intermediate frequency modulation signal can be lowered, and the sampling frequency of the analog / digital conversion means and the digital / analog conversion can be further lowered. Therefore, the highly accurate analog / digital conversion means and digital / analog conversion means can be more easily configured.

According to the fourth and fifth aspects of the present invention, the intermediate frequency modulation signals corresponding to the plurality of wireless modulation signals dispersed in the predetermined wireless frequency band are individually converted into digital intermediate frequency modulation signals. The maximum frequency of the intermediate frequency modulated signal can be further lowered as compared with the case of generating the synthetic intermediate frequency modulated signal, and the sampling frequency of the analog / digital conversion means and the digital / analog conversion can be further lowered. Therefore, highly accurate analog /
The digital converting means and the digital / analog converting means can be more easily configured.

According to the invention of claim 5, in the wireless centralized station, the modulating means directly generates the intermediate frequency modulated signal, and the demodulating means directly demodulates the intermediate frequency modulated signal. The station does not need frequency conversion means,
The configuration can be simplified.

According to the inventions of claim 6 and claim 7,
Since the electrical converter and the electrical / optical converter handle binary digital signals, the intermodulation distortion caused by the non-linearity of the optical / electrical converter and the electrical / optical converter can be ignored, and the wireless modulation signal can be ignored. Can be transmitted without distortion. Therefore, it is possible to significantly improve the transmission quality of the wireless modulation signal as compared with the conventional device in which the electric / optical conversion and the intermodulation distortion generated at the time of the optical / electrical conversion pose a problem. This is effective when using the SCM transmission method in which the carrier wave is set up and transmitted.

In the transmission from the wireless central station to the wireless base station, the intermediate frequency modulated signal having a frequency lower than that of the wireless modulated signal is analog / digital converted and digital / analog converted. The sampling frequency of the analog conversion means can be significantly reduced.

Further, since the baseband signal is a signal having a frequency significantly lower than that of the intermediate frequency modulated signal, the analog / digital converting means of the radio base station is more likely than the case where the intermediate frequency modulated signal is analog / digital converted. Furthermore, the sampling frequency can be lowered, and the highly accurate analog / digital conversion means can be configured more easily and inexpensively. As a result, the total cost of the wireless signal transmission device can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a wireless central station in a wireless signal transmission device to which each embodiment is applied.

FIG. 2 is a configuration diagram of a wireless base station in a wireless signal transmission device to which each embodiment is applied.

FIG. 3 is a configuration diagram of a wireless signal transmission device according to a first embodiment.

FIG. 4 is a configuration diagram of a transmission signal processing circuit of a wireless central station and a wireless base station in a wireless signal transmission device of a second embodiment.

FIG. 5 is a configuration diagram of a received signal processing circuit of a wireless central station and a wireless base station in a wireless signal transmission device of a second embodiment.

6 is a block diagram of an example of the frequency converter in FIG.

7 is a configuration diagram of an example of the frequency converter in FIG.

FIG. 8 is a configuration diagram of a wireless central station of a wireless signal transmission device according to a third embodiment.

FIG. 9 is a configuration diagram of a radio base station of a radio signal transmission device according to a third embodiment.

FIG. 10 is a configuration diagram of a wireless central station of a wireless signal transmission device according to a fourth embodiment.

FIG. 11 is a configuration diagram of a wireless base station of a wireless signal transmission device according to a fourth embodiment.

FIG. 12 is a configuration diagram of a main part of a wireless base station of a wireless signal transmission device according to a fifth embodiment.

FIG. 13 is a configuration diagram of a main part of a wireless central station of a wireless signal transmission device according to a fifth embodiment.

FIG. 14 is a configuration diagram of a quasi-synchronous detection circuit.

15 is a configuration diagram of a demodulator in FIG.

FIG. 16 is a schematic configuration diagram of an example of a conventional radio signal transmission device.

[Explanation of symbols]

20 exchanges 22, 22 _{1 to} 22 ₅ wireless central stations 23 _{# 1} to 23 _{# 8} , 23 ₁ to 23 ₅ wireless base stations 25 control device 26 input / output switch 27 transmission distributor 28 reception distributor 29, 29 _{# 1} ~ 29 _{# 8} Baseband processing circuit 31 _{# 1 to} 31 _{# 8} , 31 _{1 to} 31 ₄ Modulator 32 Modulator 34 _{# 1 to} 34 _{# 8} , 34 _{1 to} 34 ₄ Transmission signal processing circuit 35, 35 _{# 1 to} 35 _{# 8} electrical / optical converter 37, 37 _# 1 to 37 _{# 8} optical / electrical converter 38 _# 1 to 38 _# 8, 38 ₁ to 38 ₅ receive signal processing circuit 41 _# 1 to 41 _# 8, 41 ₁ to 41 ₅ Demodulator 44, 44 _{1 to} 44 ₄ Received signal processing circuit 45 Power amplifier 46 Transmitter / receiver 47 Low noise amplifier 49, 49 ₁ to 49 ₅ Transmitted signal processing circuit 51 Antenna 55 _{1 to} 55 ₃ A / D converter 56 Parallel / serial converter 57 serial / parallel converter 58 ₁ 58 ₃ D / A converters 61 and 62 the frequency converter 64, 67 mixers 65, 68 a local oscillator 66 low-pass filter 69 band-pass filter 71 a to 71 d, 77a to 77d frequency converter 72a to 72d, 78a to 78d frequency converter 73 , 81 Combiner circuit 74, 82 Demultiplexer circuit 75a to 75d Modulator 76a to 76d Demodulator 79a to 79d, 80a to 80d Frequency converter 83a to 83d Modulator 84a to 84d Demodulator 85a to 85d A / D converter 86 Parallel / Serial converter 87 serial / parallel converter 88a to 88d D / A converter 91a to 91d quasi-synchronous detection circuit 92a to 92d A / D conversion circuit 93 parallel / serial converter 94 serial / parallel converter 95a to 95d demodulator 101 Amplifier 102 Distributor 103 , 104 mixer 105 local oscillator 106 90 ° phase shifter 107 low-pass filter 108 band-pass filter 111, 112 sum-of-products circuit 113 rotation control circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H04B 10/12 7/26

Claims (7)

[Claims] 1. In a wireless signal transmission device for transmitting a wireless modulation signal of a predetermined band as an optical signal through an optical transmission line, a transmission side device for transmitting the optical signal to the optical transmission line is an analog modulation corresponding to the wireless modulation signal. Receiving an analog / digital converting means for converting a signal into a digital modulated signal, and an electric / optical converter for converting the digital modulated signal which is an electric signal into an optical signal, and receiving the optical signal from the optical transmission line. The side device has an optical / electrical converter for converting the received optical signal into a digital modulation signal which is an electric signal, and a digital / analog conversion means for converting the digital modulation signal into an analog modulation signal. Radio signal transmission device. 2. The transmission side device converts a radio modulation signal in a predetermined band into an intermediate frequency modulation signal having a frequency lower than an original frequency, and supplies the first frequency conversion means to the analog / digital conversion means. The reception side device has second frequency conversion means for converting the intermediate frequency modulation signal supplied from the digital / analog conversion means into a radio modulation signal having an original frequency. The wireless signal transmission device described. 3. The transmission side device converts a plurality of radio modulated signals whose bands are dispersed within a predetermined radio frequency band into a plurality of intermediate frequency modulated signals whose frequencies are lower than those of the radio modulated signals and whose bands are continuous. It has a third frequency conversion means for synthesizing and supplying it to the analog / digital converting means as a synthetic intermediate frequency modulating signal, wherein the receiving-side device receives from the synthetic intermediate frequency modulating signal supplied from the digital / analog converting means. The radio signal transmission according to claim 1, further comprising fourth frequency conversion means for converting the plurality of separated intermediate frequency modulation signals into a plurality of radio modulation signals whose bands are dispersed within the predetermined radio frequency band. apparatus. 4. A wireless signal transmission device for transmitting a wirelessly modulated signal of a predetermined band as an optical signal through an optical transmission line, wherein a sending side device for sending an optical signal to the optical transmission line has a band within a predetermined wireless frequency band. Fifth frequency conversion means for converting a plurality of dispersed radio modulation signals into a plurality of intermediate frequency modulation signals having a frequency lower than that of the radio modulation signal and having a continuous band; and a plurality of intermediate frequency modulation signals which are analog signals. An analog / digital conversion means for individually converting into a digital intermediate frequency modulated signal, and an electric / optical converter for converting the digital intermediate frequency modulated signal which is an electric signal into an optical signal, and an optical signal from the optical transmission line The receiving side device for receiving the optical signal is an optical / electrical converter for converting the received optical signal into a digital intermediate frequency modulation signal which is an electric signal, and the optical / electrical converter. Digital-analog conversion means for individually converting the plurality of digital intermediate-frequency modulation signals supplied from an analog intermediate-frequency modulation signal, and the plurality of intermediate-frequency modulation signals supplied from the digital-analog conversion means, And a sixth frequency converting means for converting into a plurality of radio modulated signals whose bands are dispersed within a predetermined radio frequency band. 5. A radio signal transmission device for transmitting a radio modulated signal of a predetermined band as an optical signal through an optical transmission line between a radio base station transmitting and receiving radio waves via an antenna, and the radio central station. In the sending side, which sends an optical signal to the optical transmission line, the device on the basis of the data to be transmitted is compatible with a plurality of radio modulation signals whose bands are dispersed within a predetermined radio frequency band and has a frequency higher than that of the radio modulation signal. Modulating means for generating a plurality of intermediate frequency modulation signals having a low band and continuous, an analog / digital converting means for individually converting the plurality of intermediate frequency modulation signals into a digital intermediate frequency modulation signal, and the digital signal as an electric signal An electric / optical converter for converting the intermediate frequency modulated signal into an optical signal, and the receiving side device for receiving the optical signal from the optical transmission line in the wireless base station is An optical / electrical converter for converting the received optical signal into a digital intermediate frequency modulated signal which is an electric signal, and a plurality of digital intermediate frequency modulated signals supplied from the optical / electrical converter individually for analog intermediate frequency modulated signal And a digital / analog converting means for converting into a plurality of intermediate frequency modulation signals supplied from the digital / analog converting means into a plurality of radio modulated signals having a band dispersed within the predetermined radio frequency band. And a frequency conversion means of the transmitting device for transmitting an optical signal to an optical transmission line in the wireless base station, a plurality of wireless modulation signals whose band is dispersed within a predetermined wireless frequency band than the wireless modulation signal. Fifth frequency conversion means for converting into a plurality of intermediate frequency modulation signals of low frequency and continuous band, and the fifth frequency conversion means for supplying the fifth frequency conversion means. A number of intermediate frequency modulated signals are individually converted into digital intermediate frequency modulated signals, and an analog / digital converter means, and an electrical / optical converter for converting the digital intermediate frequency modulated signals which are electrical signals into optical signals, The receiving side device that receives an optical signal from an optical transmission line in the wireless centralized station includes an optical / electrical converter that converts the received optical signal into a digital intermediate frequency modulation signal that is an electric signal, and the optical / electrical converter Digital / analog conversion means for individually converting a plurality of supplied digital intermediate frequency modulated signals into analog intermediate frequency modulated signals, and individually demodulating the plurality of intermediate frequency modulated signals supplied from the digital / analog converting means And a demodulation means for generating demodulated data. 6. A radio signal transmission apparatus for transmitting a radio modulated signal of a predetermined band as an optical signal through an optical transmission line between a radio base station transmitting and receiving radio waves via an antenna, and the radio central station. In the transmitting side device for transmitting an optical signal to the optical transmission line, a plurality of radio frequency modulation signals whose bands are dispersed within a predetermined radio frequency band have a plurality of intermediate frequency modulation signals whose frequency is lower than that of the radio modulation signal and whose band is continuous. Frequency conversion means for converting the combined intermediate frequency signal into a digital intermediate frequency modulated signal, and third analog frequency conversion means for converting the combined intermediate frequency signal into a digital intermediate frequency modulated signal. An optical / electrical converter for converting the digital intermediate frequency modulated signal, which is an electric signal, into an optical signal, wherein an optical signal is transmitted from an optical transmission line in the wireless base station. The receiving side device for receiving the signal combines an optical / electrical converter for converting the received optical signal into a digital intermediate frequency modulated signal which is an electric signal, and a digital intermediate frequency modulated signal supplied from the optical / electrical converter. Digital / analog conversion means for converting to an intermediate frequency signal, and a plurality of intermediate frequency modulation signals separated from the combined intermediate frequency modulation signal supplied from the digital / analog conversion means, to disperse the band within the predetermined radio frequency band. A transmitting side device for transmitting an optical signal to an optical transmission line in the radio base station, the transmitting side device having a fourth frequency converting means for converting into a plurality of radio modulated signals; Detection means for detecting each of the radio modulated signals to generate a baseband signal, and an analog for individually converting the baseband signal into a digital signal And a digital conversion unit, and an electric / optical converter for converting a digital signal, which is an electric signal supplied from the analog / digital conversion unit, into an optical signal, wherein the wireless centralized station receives the optical signal from an optical transmission line. The receiving-side device includes an optical / electrical converter that converts a received optical signal into a digital signal that is an electric signal, and a plurality of digital signals that correspond to each baseband signal supplied from the optical / electrical converter. On the other hand, the wireless signal transmission device is provided with demodulation means for generating demodulated data having a correct phase relationship. 7. A radio signal transmission apparatus for transmitting a radio modulated signal of a predetermined band as an optical signal through an optical transmission line between a radio base station transmitting and receiving radio waves via an antenna, and the radio central station. In the transmission side device for transmitting an optical signal to the optical transmission line in, a plurality of radio modulation signals whose bands are dispersed within a predetermined radio frequency band are supported, and a plurality of radio frequency modulation signals whose frequencies are lower than those of the radio modulation signals and whose bands are continuous. Of the intermediate frequency modulated signal, an analog / digital converter for individually converting the plurality of intermediate frequency modulated signals into a digital intermediate frequency modulated signal, and an optical signal of the digital intermediate frequency modulated signal A receiving side device for receiving an optical signal from an optical transmission line in the radio base station, which has an electric / optical converter for converting the received optical signal into an electric signal. And an optical / electrical converter for converting into a digital intermediate frequency modulated signal, and a digital / analog converter for individually converting a plurality of digital intermediate frequency modulated signals supplied from the optical / electrical converter into analog intermediate frequency modulated signals Means, and sixth frequency conversion means for converting the plurality of intermediate frequency modulation signals supplied from the digital / analog conversion means into a plurality of radio modulation signals having a band dispersed within the predetermined radio frequency band. The transmitting side device for transmitting an optical signal to the optical transmission line in the wireless base station is a detection means for generating a baseband signal by detecting a plurality of wirelessly modulated signals whose bands are dispersed within a predetermined wireless frequency band. An analog / digital conversion means for individually converting the baseband signal into a digital signal, and the analog / digital conversion means. An electric / optical converter that converts a supplied digital signal that is an electric signal into an optical signal, and a receiving side device that receives an optical signal from an optical transmission line in the wireless centralized station, converts the received optical signal into an electric signal. Optical / electrical converter for converting into a digital signal which is a signal, and demodulated data having a correct phase relationship with respect to each of a plurality of digital signals corresponding to each baseband signal supplied from the optical / electrical converter And a demodulation unit for generating the signal.