JPH11205280A - Transmission device and reception device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set the frequency shift of local signals on reception device-sides arranged in respective repeating stations and a broadcasting place to be zero and to prevent the occurrence of swing in local oscillation frequencies in the respective repeater stations at the time of constructing a network for ground digital broadcasting by an SFN(single frequency network) system. SOLUTION: A pilot signal is overlapped on the upper side (or lower side) of a spectrum constituting an OFDM(orthogonal frequency division/multiplex) signal so that it becomes the frequency which is slightly detached from the spectrum of the OFDM signal and it is transmitted from a transmission device. The reception device 11-side controls the oscillation frequency of a local oscillation part 12 based on a pilot signal in an IF signal obtained by frequency- converting a transmission signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an OFDM (Orthogonal Frequent) for constructing a terrestrial digital broadcasting network.
The present invention relates to a transmission device and a reception device suitable for use in an ncy Division Multiplex (orthogonal frequency division multiplex) signal transmission / reception system or the like.

[Summary of the Invention] [0002] The present invention is applicable to the construction of a terrestrial digital broadcasting network, the transmission of a program or the like from a performance station to a broadcasting station, or the transmission of a program or the like from a broadcasting station to a broadcasting station. For example, an OFDM signal, which is a digital terrestrial broadcasting system, is converted into a constant frequency band and transmitted as it is, and a pilot signal having a constant frequency relationship is superimposed on a local oscillation frequency on the transmitting device side and transmitted. Therefore, when a program or the like is transmitted from a music station (or a broadcasting station) to a broadcasting station,
The local oscillation frequency required for the frequency conversion unit of the receiving device is controlled with high precision, and the SFN (Single Frequency Network) is controlled.
k) Make it possible to build a network in a manner, thereby promoting effective use of frequency. Furthermore, as a pilot signal, an FFT (high-speed transmission / reception) in transmission / reception of an OFDM signal is performed so as to be orthogonal to a pilot signal arranged at a frequency position slightly higher or lower than the spectrum of the OFDM signal or a multicarrier of the OFDM signal. The use of a pilot signal located at a frequency position within the processing range of the Fourier transform (IFFT) process or the IFFT (inverse fast Fourier transform) process enables processing at baseband.

[0003]

2. Description of the Related Art When a network necessary for realizing a terrestrial television broadcast and a network used for material transmission are respectively constructed by wireless lines, a conventional transmission device of the AM modulation system or FIG. And a transmission apparatus 111 using a digital modulation scheme such as multi-level PSK or multi-level FSK as shown in FIG.

In this case, a transmitting apparatus 101 using the FM modulation scheme shown in FIG. 5 performs an FM modulation on a modulated wave of a program or a material to be transmitted to generate an FM modulated wave signal; Using a local oscillation unit 103 that generates an oscillation signal of a preset frequency, and an oscillation signal output from the local oscillation unit 103,
A frequency conversion unit 104 that converts the frequency of the FM modulated wave signal output from the M modulation unit 102 to generate a transmission signal;
A power amplifying unit 105 for power amplifying the transmission signal output from the frequency conversion unit 104, an output filter unit 106 for regulating the frequency band of the transmission signal output from the power amplification unit 105 to a designated frequency band, A transmission antenna 107 for converting a transmission signal output from the output filter unit 106 into a radio signal and outputting the radio signal is provided. After a modulation wave of a program or a material to be transmitted is FM-modulated,
A transmission signal having predetermined characteristics is generated by executing frequency conversion processing, power amplification processing, and output filtering processing, and this is radiated from the transmission antenna 107 in the form of a radio signal.

Further, a multi-valued PSK and a multi-valued FSK shown in FIG.
The transmission device 111 using a digital modulation method such as
Modulated waves of programs and materials to be transmitted are multi-valued P
A digital modulation unit 112 that generates a digitally modulated wave signal by performing digital modulation using an SK method, a multi-level FSK method, and the like, a local oscillation unit 113 that generates an oscillation signal of a preset frequency, and a local oscillation unit 113 Using the output oscillation signal, a frequency conversion unit 114 that converts the frequency of the digital modulation wave signal output from the digital modulation unit 112 to generate a transmission signal, and a transmission signal output from the frequency conversion unit 114 Power amplifying section 115 for amplifying power, output filter section 116 for regulating the frequency band of a transmission signal output from power amplification section 115 to a designated frequency band, and transmission signal output from output filter section 116 And a transmitting antenna 117 that emits the signal as a radio signal, and modulates a modulated wave of a program or material to be transmitted. After digital modulation by a multi-level PSK scheme or a multi-level FSK scheme, a frequency conversion process, a power amplification process, and an output filtering process are performed to generate a transmission signal having a predetermined characteristic, which is then transmitted. The signal is radiated in the form of a radio signal from 117.

[0006]

By the way, using these transmitting devices 101 and 111, for example, the transmitting device 101 using the FM modulation method, the analog FM in the SHF band is used.
In the case of constructing a modulation system wireless line and transmitting a program or the like via this wireless line, in Japan, currently, one FM line for NTSC television is used.
Because we have to secure 8MHz bandwidth,
The wireless signal output from the transmitting apparatus 101 must also have a frequency bandwidth corresponding to this.

For this reason, such transmitting devices 101, 1
When a network for television of the NTSC system is constructed using the H.11, there is a problem that the frequency use efficiency is deteriorated.

When a network is constructed using the transmission devices 101 and 111, the same transmission devices as the transmission devices 101 and 111 must be arranged not only in the broadcasting hall but also in many relay stations. Therefore, there is a problem that the network itself becomes large-scale.

On the other hand, when constructing a network for digital terrestrial broadcasting in the future, from the viewpoint of effective use of frequency, as shown in FIG. 7, the format of the radio signal transmitted from the transmitting device 101 provided in the broadcasting hall 121 is as shown in FIG. Is transmitted by each relay station 122, so-called SFN (Single Freund) is a system that covers a service area with a single frequency using a number of transmission stations with relatively low power.
It is conceived to relay this at the same frequency f1 using a quency network) method.

However, when the network 123 is constructed by such an SFN system, as shown in FIG. 8, an oscillation phenomenon occurs in the relay station 122 due to the surrounding of the own station, and the relay station 122 is provided with the relay station 122. There is a possibility that the power amplification unit 124 oscillates, making it difficult to relay the broadcast wave or making it impossible to transmit with a desired output.

For this reason, the network 12 is controlled by the SFN method.
In constructing 3, some solution must be used to prevent such wraparound of the own station. Then, depending on the solution, a relatively wide frequency bandwidth, a relatively large-scale transmission device, and the like are required as in the case where the conventionally used transmission devices 101 and 111 are used. There is a problem.

Therefore, the inventors of the present invention have proposed a method for fundamentally solving these problems, in which an OFDM signal used in digital terrestrial broadcasting is relayed to each relay station as it is, so that frequency is effectively used and cost is reduced. I thought about trying.

However, if an OFDM signal, which is a terrestrial digital broadcasting system, is frequency-converted and transmitted as it is,
Even if there is a slight fluctuation in the local oscillation frequency on the receiving device side provided in each relay station, a fatal obstacle is given to the demodulation of the OFDM signal. There has been a strong demand for the development of a technology that can reliably relay data.

In view of the above circumstances, the present invention reliably demodulates an OFDM signal or the like by preventing fluctuations in the local oscillation frequency at each relay station when a terrestrial digital broadcasting network is constructed by the SFN method. And relaying, which allows efficient use of frequency and
It is an object of the present invention to provide a transmitting device and a receiving device capable of reducing costs.

[0015]

In order to achieve the above object, according to the present invention, according to the present invention, a pilot signal having a fixed relationship with a local oscillation frequency is superimposed near a spectrum of a signal to be transmitted. Is transmitted.

According to a second aspect of the present invention, there is provided an apparatus for transmitting a pilot signal having a fixed relation with a local oscillation frequency together with an OFDM signal, wherein the pilot signal is
It is orthogonal to the multicarriers that make up the DM signal,
Further, it is characterized in that it is arranged at a frequency position within the range of the IFFT processing.

According to a third aspect of the present invention, a transmission signal including a pilot signal superimposed near a spectrum of the transmission signal is received, and the local oscillation frequency is controlled using the pilot signal to demodulate the transmission signal. It is characterized by.

According to a fourth aspect of the present invention, there is provided an apparatus for receiving a signal transmitted by the transmitting apparatus according to the second aspect, wherein the pilot signal is extracted by FFT processing, and the pilot signal is used to control the local oscillation frequency. It is characterized by:

According to the above configuration, when constructing a terrestrial digital broadcasting network by the SFN method, each relay station does not generate fluctuations in the local oscillation frequency, thereby reliably demodulating an OFDM signal or the like. Or relaying the same, thereby enabling effective use of frequency and reduction of cost.

[0020]

FIG. 1 is a block diagram showing an embodiment of a transmitting apparatus according to the present invention.

A transmitting apparatus 1 shown in FIG. 1 includes a local oscillating unit 2 for generating an oscillating signal of a preset frequency.
A frequency divider 3 that divides an oscillation signal output from the local oscillator 2 to generate a pilot signal having a constant frequency ratio m _P / n _P, and an oscillation signal output from the local oscillator 2 Multiplying unit 4 for generating a local signal having a constant frequency ratio m _L / n _L and a frequency dividing unit 3 for an OFDM signal containing a program or material to be transmitted.
Is superimposed on the pilot signal output from the OFDM signal so as to be on the upper side (or lower side) of the spectrum as shown in FIG.
A signal superimposing unit 5 that generates a superimposed signal in which a pilot signal is arranged at a frequency position slightly apart from the signal, and a superimposed signal output from the signal superimposing unit 5 based on a local signal output from the multiplier 4 A frequency conversion unit 6 that generates a transmission signal by frequency conversion, a power amplification unit 7 that power-amplifies the transmission signal output from the frequency conversion unit 6, and a frequency band of the transmission signal output from the power amplification unit 7 An output filter unit 8 that regulates a frequency band to a specified frequency band;
A transmission antenna 9 for converting a transmission signal output from the output filter unit 8 into a radio signal and emitting the radio signal is provided.

The transmitting apparatus 1 is located in a broadcasting hall or the like, and includes an OFD including programs and materials to be transmitted.
This OFD signal is applied to an M signal, for example, an OFDM signal including a program or material created by a program production site.
After superimposing a pilot signal on a frequency position near (upper or lower of the spectrum) of the spectrum of the M signal, a frequency conversion process, a power amplification process, and an output filtering process are executed to obtain a predetermined characteristic. Is generated and radiated from the transmitting antenna 9 in the form of a radio signal. The nearby frequency position is a position where the signal can be separated and extracted from the OFDM signal by a filter on the receiving side.

In transmitting apparatus 1, it is important that the pilot frequency and the transmitting local frequency have a fixed frequency relationship, and the input signal is not limited to the OFDM signal.

FIG. 3 is a block diagram showing an embodiment of the receiving apparatus according to the present invention.

The receiving apparatus 11 shown in FIG. 1 includes a local oscillating unit 1 for generating an oscillating signal of a preset frequency.
2, a multiplication unit 13 that multiplies the oscillation signal output from the local oscillation unit 12 to generate a local signal having a constant frequency ratio m _L / n _L, and receives a radio signal to generate a reception signal. A receiving antenna 14 to be performed, an input filter unit 15 that regulates a frequency band of a received signal output from the receiving antenna 14 to a received signal in a specified frequency band,
A frequency converter 16 for frequency-converting the received signal output from the input filter 15 based on the local signal output from the multiplier 13 to generate an IF signal or a transmission signal having a frequency corresponding to the transmission channel; A pilot signal included in an IF signal (or a transmission signal having the frequency of a transmission channel) output from the frequency conversion unit 16 is extracted by a filter and multiplied to obtain a reproduction frequency having a constant frequency ratio m _P / n _P. Multiplier 17 for generating a signal
Is compared with the phase of the reproduction frequency signal output from the multiplier 17 and the phase of the oscillation signal output from the local oscillation circuit 12 to generate a control signal necessary to reduce the phase difference between them. A comparison unit 18 for controlling the oscillation frequency of the local oscillation unit 12.

The receiving device 11 is arranged at each relay station or broadcasting station, receives a transmitting signal transmitted from the transmitting device 1 by the receiving antenna 14, and performs an input filtering process on the received signal. The frequency conversion processing is performed to generate an IF signal (or a transmission signal having the frequency of the transmission channel), and this is supplied to a next-stage device (not shown) or a transmission antenna (not shown). In parallel with this operation, a pilot signal included in the IF signal or the like is multiplied to obtain a constant frequency ratio m _P /
A reproduction frequency signal of n _P is generated, and the oscillation frequency of the local oscillating unit 12 is controlled based on the reproduction frequency signal, so that the accuracy of the frequency conversion process is dramatically increased. Note that the input of the receiving apparatus 11 is not limited to the OFDM signal.

As described above, according to the present embodiment, the transmitting apparatus 1 is slightly apart from the spectrum of the OFDM signal above (or below) the spectrum constituting the OFDM signal so that it can be separated by the filter on the receiving side. While the pilot signal is superimposed on the frequency position and transmitted, the receiving apparatus 11 controls the oscillation frequency of the local oscillator 12 based on the pilot signal in the IF signal obtained by frequency-converting the received signal. ing. For this reason, the frequency deviation of the local signal on the side of the receiving device 11 arranged in each relay station or broadcasting station can be reduced to zero, and thus, when a terrestrial digital broadcasting network is constructed in the SFN system, In each relay station, it is possible to prevent the local oscillation frequency from fluctuating.

Thus, the OFDM signal can be reliably frequency-converted or demodulated, relayed or demodulated, and effective use of frequency and cost reduction can be achieved.

FIG. 4 is a block diagram showing another embodiment of the transmitting apparatus according to the present invention.

The transmitting device 21 shown in FIG. 1 includes a local oscillating unit 2 for generating an oscillating signal of a preset frequency.
2, a frequency divider 23 for dividing the oscillation signal output from the local oscillator 22 to generate a clock signal having a constant frequency ratio m _P / n _P, and an oscillation output from the local oscillator 22. A multiplying unit 24 for multiplying the signal to generate a local signal having a constant frequency ratio m _L / n _L ;
The OFDM signal is generated by performing IFFT conversion on a modulated signal including a program or a material to be transmitted using the clock signal output from the OFDM signal, and the OFDM signal is orthogonalized with respect to the multicarrier of the OFDM signal. And an OFDM modulation / pilot superimposing section 25 for superimposing a pilot signal to generate a superimposed signal so as to fall within the range of IFFT processing and FFT processing, and an OFDM modulation / pilot based on a local signal output from the multiplication section 24. A frequency conversion unit 26 that frequency-converts a superimposed signal output from the superposition unit 25 to generate a transmission signal; a power amplification unit 27 that power-amplifies the transmission signal output from the frequency conversion unit 26; An output filter unit 28 that regulates the frequency band of the transmission signal output from 27 to a designated frequency band; And a transmitting antenna 29 for emitting the transmission signal output from the output filter unit 28 into a radio signal.

The transmitting device 21 is also arranged in a broadcasting hall or the like, and transmits a modulated signal such as a program or material to be transmitted.
For example, an OFDM signal is generated by OFDM-modulating a modulation signal such as a program or a material created by a program production site, and the OFDM signal is orthogonal to the multicarrier of the OFDM signal, and within a range of IFFT processing and FFT processing. After superimposing the pilot signal so as to generate a transmission signal having a predetermined characteristic, the frequency conversion processing, the power amplification processing, and the output filtering processing are performed. Radiate at

As described above, in this embodiment, a modulation signal such as a program or material created by a program production site is OFDM-modulated to generate an OFDM signal, and the OFDM signal has a multicarrier and orthogonal relationship. After the pilot signal is superimposed so as to be within the range of the IFFT processing and the FFT processing, the frequency conversion processing, the power amplification processing, and the output filtering processing are performed, and the transmission signal having the predetermined characteristics is performed. Produces
This is radiated from the transmitting antenna 29 in the form of a radio signal. Therefore, in the process of performing a FFT (Fast Fourier Transform) on a received signal at a receiving device provided at each relay station or a broadcasting station, a pilot signal is extracted and the oscillation frequency of a local oscillation unit on the receiving device is controlled. By doing so, the frequency deviation of the local signal on the receiving device side can be reduced to zero, and when constructing a network for digital terrestrial broadcasting in the SFN system, fluctuations in the local oscillation frequency and the like occur at each relay station. It can be prevented from occurring.

As a result, the OFDM signal can be reliably frequency-converted or demodulated and relayed or demodulated, whereby effective use of frequency and cost reduction can be achieved.

[0034]

As described above, according to the present invention, S
When constructing a network for digital terrestrial broadcasting in the FN system, each relay station can reliably demodulate an OFDM signal or the like or prevent the local oscillation frequency from fluctuating, and relay the same. Thus, effective use of frequency and cost reduction can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a transmission device according to the present invention.

FIG. 2 is a schematic diagram illustrating an example of a spectrum when a pilot signal is superimposed on an OFDM signal by the transmission device illustrated in FIG. 1;

FIG. 3 is a block diagram illustrating an embodiment of a receiving device according to the present invention.

FIG. 4 is a block diagram showing another embodiment of the transmission device according to the present invention.

FIG. 5 is a block diagram illustrating an example of a transmission device using an FM modulation scheme.

FIG. 6 is a block diagram illustrating an example of a transmission device using a digital modulation scheme such as multi-level PSK or multi-level FSK.

FIG. 7 is a block diagram showing an example of a terrestrial digital broadcasting network constructed by the SNF method.

FIG. 8 is an explanatory diagram schematically showing an oscillation problem occurring at each relay station shown in FIG. 7;

[Explanation of symbols]

 1, 21: Transmitting device 2, 12, 22: Local oscillator 3, 23: Divider 4, 13, 17, 24: Multiplier 5: Signal superimposing unit 6, 16, 26: Frequency converter 7, 27: Power amplifying sections 8, 28: output filter section 9: transmitting antenna 11: receiving apparatus 14: receiving antenna 15: input filter section 18: comparing section 25: OFDM modulation / pilot superimposing section 29: transmitting antenna

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H04N 7/081 (72) Inventor Shoichi Noji 2-2-1 Jinnan, Shibuya-ku, Tokyo Inside the Japan Broadcasting Corporation Broadcasting Center (72) Inventor Toru Abe 2-2-1 Jinnan, Shibuya-ku, Tokyo Japan Broadcasting Corporation Broadcasting Center (72) Inventor Kazuyoshi Ichikawa 2-2-1 Jinnan, Shibuya-ku Tokyo, Japan Broadcasting Center

Claims (4)

[Claims] 1. A transmitting apparatus for transmitting a pilot signal having a fixed relationship with a local oscillation frequency by superimposing it near a spectrum of a signal to be transmitted. 2. An apparatus for transmitting a pilot signal having a constant relationship with a local oscillation frequency together with an OFDM signal, wherein the pilot signal has an orthogonal relationship with a multicarrier constituting the OFDM signal, and a range of IFFT processing. A transmission device, wherein the transmission device is arranged at an internal frequency position. 3. Receiving a transmission signal including a pilot signal superimposed near the spectrum of the transmission signal,
A receiving apparatus for controlling a local oscillation frequency using the pilot signal and demodulating the transmission signal. 4. An apparatus for receiving a signal transmitted by the transmission apparatus according to claim 2, wherein the pilot signal is extracted by FFT processing, and the pilot signal is used to control a local oscillation frequency. Receiving device.