JP2000151553A - Signal transmitteir - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain signal transmission with high reliability by eliminating an effect of a phase noise due to an oscillation circuit or the effect of frequency fluctuation in high speed digital signal transmission. SOLUTION: In this signal transmitter that mainly converts an IF signal to a microwave band signal and transmits the converted signal, pilot signals fP1s, fP2s that are generated by a synchronizer and whose frequency difference is equal to a reference frequency are added to the main signal to modulate the main signal and the resulting signal is transmitted. A receiver side receives and demodulates this signal, separates the signal into a main signal fIF22, pilot signals fP1r', fP2r', a reference frequency signal fREF2 is recovered from the frequency difference between the pilot signals fP1r', fP2r', a pilot signal fP2r resulting from correction the pilot signal fP2r' based on the reference frequency signal is generated and the pilot signal component is completely eliminated from the main signal fIF22 by the pilot signal fP2r to obtain the main signal component without disturbance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention mainly relates to OFDM (Orthogonal Frequency Division Multiple Multiple) using microwaves.
The present invention relates to a signal transmission device for transmitting a multicarrier signal such as an xing (orthogonal frequency division multiplex) signal.

[0002]

2. Description of the Related Art In general, a signal transmission apparatus modulates a signal, transmits the signal, demodulates the signal at the time of reception, and obtains an original signal, and transmits an already modulated signal as it is without demodulation. There are devices of the system.

As shown in FIG. 2, a conventional microwave-based signal transmission apparatus uses a transmission converter to transmit an IF signal "IF" in a frequency band of 50 MHz or less, for example.
(IN) "and the local oscillator" LO1 "in the microwave band
MIX is supplied to a frequency mixer "MIX", and a microwave band signal obtained by heterodyne conversion is amplified by a linear power amplifier "PA" and transmitted from a transmission antenna. Thus, a microwave reception signal from a reception antenna is amplified by a low-noise amplifier, and is similarly converted to an IF frequency by using a local oscillation frequency of a local oscillator “LO1” in a microwave band.

[0004] In the signal transmission device having such a configuration, in particular, due to the frequency fluctuation and the phase noise of the local oscillator,
The frequency deviation of the IF signal obtained by transmission increases,
There is a drawback that it is greatly affected by phase noise. Conventionally, methods for reducing the frequency fluctuation and phase noise of the local oscillator itself and low noise local oscillation frequency generating means have been studied. For example, low phase noise in the case of an FPU device as a relay device for digital transmission has been studied. An example using the microwave band frequency synthesizer is disclosed in Japanese Patent Laid-Open Publication No. Hei 10-247851, "Fractional-N frequency synthesizer and repeater using the same."

[0005] In the OFDM system, which is being studied in Europe and Japan as a terrestrial digital broadcasting system, a large number of mutually orthogonal carriers are multiplexed in a band, so that the flatness of the phase characteristics and amplitude characteristics of the band is important. is there. Further, when phase noise is superimposed in the transmission device, orthogonality between the carrier waves is destroyed, and the error rate is deteriorated. Therefore, it is important to reduce the phase noise of the reception device. "Variable Frequency Oscillator and OFDM Receiver" discloses a wideband variable frequency oscillator that realizes low phase noise required for a receiver.

[0006]

However, in the case of a device for transmitting a broadcast wave signal to a transmitting station of terrestrial digital television broadcasting, the IF signal is an OFDM signal, and SFN is utilized by taking advantage of the features of OFDM. (Single Fre
It is assumed that the signal is transmitted as a broadcast wave in a quency network (single frequency network), and the frequency fluctuation and phase noise of the IF signal are expected to be fatal drawbacks.

[0007] First, regarding the frequency fluctuation, in the case of SFN (Single Frequency Network) in which OFDM broadcast waves of the same program are transmitted from a plurality of transmitting stations in terrestrial digital television broadcasting, a plurality of transmitting stations are used. About 6 MH at the point where broadcast waves from
If the carrier interval of an OFDM signal having thousands of carriers in the z band is 1 KHz, it is considered that the frequency deviation is required to be within 0.1% for each carrier. Transmission frequency deviation between stations is 1
Hz or less. In order to realize the requirement of the frequency accuracy, the distribution of the frequency deviation allowed for the transmission device of the broadcast wave signal to the transmitting station is further reduced, and the requirement becomes more severe when multistage relay is performed. For example, even if the standard distribution between the broadcaster and the transmission device is 50% and 50%, the frequency deviation allowed per stage is 0.1 Hz or less when five stages are relayed.

In order to reduce the frequency deviation of the IF signal transmitted by the transmission device having the conventional configuration to 0.1 Hz or less, the frequency variation allowed by the transmission conversion (up-conversion) and the reception conversion (down-conversion) of the transmission device is allowed. The frequency fluctuation is ± 0.02 Hz or less, and the frequency fluctuation allowed for the local oscillator of the transmission conversion or the reception conversion is ± 0.02 Hz.
5 Hz. This is because in the case of a microwave transmission device in the 7 GHz band, the local oscillator of the microwave transmission device is “± 3.5 × 10−”.
A frequency stability of about 12 "is required.

Next, with respect to the phase noise, in the case of the transmission apparatus having the above configuration, the phase noise of the local oscillator similar to the problem in the above document is added in both the transmission conversion and the reception conversion. Since the frequency band is in the microwave band, the phase noise characteristic required for the local oscillator becomes extremely severe, and the phase noise of the local oscillator in the transmission converter and the local oscillator in the reception converter is the highest performance currently available. Even if a noise oscillator is used, it is not sufficient because deterioration is added by multi-stage relay, and in order to prevent IF frequency fluctuation after each reception conversion, for example, a highly accurate and highly stable device such as a rubidium oscillator is used. A reference signal oscillator is required or synchronization means such as using GPS is required. In case of had the disadvantage that sufficient performance even rubidium oscillator or a GPS synchronization can not be realized.

[0010] Even if the frequency stability of the local oscillator can satisfy the required performance statically, it is called microphonic noise generated when mechanical or acoustic vibration is applied to the oscillation circuit element or the like. It has been almost impossible to completely solve the problem that the oscillation frequency is mainly subjected to FM modulation caused by mechanical vibration.

[0011]

In order to solve the above-mentioned problems, according to the present invention, two types of pilot signals based on a reference signal on the transmission side are provided to a device on the transmission side. There are provided means for generating the difference so as to be equal to the reference signal, means for combining the two kinds of pilot signals and the main signal, and means for modulating and transmitting the combined signal.

At the same time, means for receiving and demodulating the transmitted signal, and transmitting the demodulated signal to
Means for demultiplexing into two types of pilot signals and a main signal, means for generating a signal having a frequency difference between the two types of demultiplexed pilot signals, and a frequency difference between the two types of pilot signals. Means for generating a new pilot signal based on the signal to be generated, and generating a signal indicating a variation of one of the two types of pilot signals based on the new pilot signal and one of the two types of pilot signals. Means and means for generating a final main signal based on a signal obtained by correcting one frequency of the two types of pilot signals and a split main signal.

[0013]

According to the above-mentioned configuration, according to the present invention, in addition to the main signal, two types of pilot signals generated so that the frequency difference becomes equal to the reference signal are modulated and transmitted from the transmitting side. You. On the receiving side, on the other hand, the received signal is split into a main signal and two types of pilot signals,
A reference signal is generated based on a frequency difference between pilot signals.

At the same time, a signal indicating one variation of the pilot signal is generated based on the frequency difference between the pilot signals, and the main signal separated based on the signal indicating the variation is generated. The effect of the fluctuation of the pilot signal remaining in the main signal is removed from the main signal to obtain an output of the main signal without disturbance.

[0015]

FIG. 1 is a block diagram showing a first embodiment of the present invention. In FIG. 1, the transmission conversion is a transmission conversion device installed on the transmission side, and the reception conversion is a reception conversion device installed on the reception side, that is, a reception point separated by a transmission distance.

An IF signal input terminal 1 is mainly connected to an IF output of an OFDM modulator (not shown), and receives an OFDM signal in an IF frequency band. The reference signal input terminal 2 is connected to a reference signal source (not shown), and receives a highly stable reference frequency. In this embodiment, the reference frequency is 10 MHz.
z. In the configuration of FIG. 1, the above two types of signals,
That is, receiving the IF signal and the reference signal, the IF signal is converted into a microwave band signal, and the microwave output terminal 3
And a reception converter for receiving the microwave band signal at a microwave input terminal 4 via a reception antenna, converting the signal again into an IF signal, and outputting the IF signal from an IF signal output terminal 5. It consists of two devices. A broken line SHF between the microwave output terminal 3 of the transmission converter and the microwave input terminal 4 of the reception converter is a microwave transmission line, and a power amplifier and filters may be inserted in addition to the antenna. Since the description of the present invention is not directly related, the illustration is omitted. Note that, in the block diagram of FIG. 1, the illustration of an actually necessary amplifier or filter is omitted for neither the transmission conversion device nor the reception conversion device unless they are directly related to the description of the present invention.

The transmission converter includes a multiplexing circuit, a frequency generating circuit Synthesizer, a second local oscillator LO12 in the microwave band, and two mixer circuits M1 and M2.
The reference signal frequency signal fref1 from the reference signal input terminal 2 is connected to a terminal 15 of the frequency generation circuit Synthesizer, and three types of frequencies fp1s, fp2s, and fL12 are set based on the reference signal frequency signal fref1. And output from the input terminal 11, the input terminal 12, and the output terminal 13 of the frequency generation circuit Synthesizer, two waves from the input terminal 11, the input terminal 12 and the IF signal from the IF signal input terminal 1. The multiplexing circuit, the multiplexed IF signal input terminal 21, the input terminal 22, and the input terminal 2
3 and a multi-wave signal output obtained by multiplexing from the multiplexing output terminal “out” and a third output signal from the output terminal 13 of the frequency generation circuit Synthesizer. The converted signal obtained by heterodyne conversion by the mixer circuit M1 is further frequency-converted into a microwave band by the second local oscillator LO12 by another mixer circuit M2 and output from the microwave output terminal 3. Be composed.

The reception conversion device includes a demultiplexing circuit, a demultiplexing circuit, a frequency generation circuit Synthesizer, a second local oscillator LO22 in the microwave band, and three mixer circuits M3, M4, M
5, M6, a band-pass filter BPF1 and a band-pass filter BPF2, and the microwave signal received from the microwave input terminal 4 and the local oscillator LO22 are connected to the mixer circuit M3,
The output of the mixer circuit M3 is connected to the input terminal "in" of the demultiplexing circuit.

Branching circuit Branching output IF signal input terminal 4
From 1 and 43, two of the three divided outputs are input to the mixer circuit M6, and the output of the mixer circuit M6 is output to the frequency generation circuit Synthesizer through the BPF2.
To the terminal 33 of the demultiplexing circuit.
(Frequency is fp2r ') and the frequency generation circuit S
The generated frequency fp2r from the output terminal 31 of the synthesizer is mixed by the mixer circuit M5 and the difference frequency f
The output of the p2r'-fp2r signal and the output from the demultiplexing output terminal 42 are connected to the mixer circuit M4, and the output of the mixer circuit M4 is output to the IF signal output terminal 5 via the bandpass filter BPF1. It is configured to be.
Further, the reference frequency fREF2 is output from the terminal 34 of the frequency generation circuit Synthesizer to the reference frequency output terminal 6.

Next, an example of the frequency generation circuit Synthesizer constituting the transmission conversion device and the reception conversion device will be described with reference to FIG. The frequency generation circuit Synthesizer used in the transmission conversion device and the frequency generation circuit Synthesizer used in the reception conversion device have the same configuration in the above embodiment.

Referring to FIG. 7, the description of the input / output terminals is given below. Terminal 101: output terminal for pilot signal P1 (frequency
32.15 MHz) Terminal 102: Output terminal for pilot signal P2 (frequency
42.15 MHz) Terminal 103: second local oscillation output terminal (frequency
Terminal 104: Microwave local oscillator control output terminal (frequency 10 MHz) Terminal 105: External reference signal input terminal (frequency 10M)
Hz) Terminal 108: External reference signal output terminal (frequency 10M
Hz)

A signal from a terminal 105 and an output of a high-stable crystal oscillator (10 MHz) are selected by a changeover switch SW, and either signal is input to a phase lock circuit PLL1. A voltage / frequency control terminal “vt” of the voltage controlled crystal oscillator VCXO1 is provided with the phase lock circuit PLL.
1 is connected to a control signal. Voltage controlled crystal oscillator VC
The oscillation output of XO1 is output from the phase lock circuit PLL1.
, The reference frequency to the phase lock circuit PLL3, the reference frequency to the phase lock circuit PLL3,
It is connected as a reference frequency to the phase comparator PC and is output from terminals 108 and 104 via buffer amplifiers BA1 and BA2, respectively.

The output of the phase lock circuit PLL2 is connected to a voltage / frequency control terminal "vt" of the voltage controlled crystal oscillator VCXO3, and the output of the phase lock circuit PLL3 is connected to the voltage / frequency control terminal "vt" of the voltage controlled crystal oscillator VCXO4.
t ", respectively, and the voltage-controlled crystal oscillator VC
XO3 and voltage controlled crystal oscillator VCXO4 output the phase-locked oscillation output to terminals 102 and 103, respectively.
Output more. The voltage of the voltage controlled crystal oscillator VCXO2
A control voltage of the phase comparator PC is connected to the frequency control terminal “vt”, and an output signal of a 10 MHz band-pass filter BPF is connected as a comparison frequency input of the phase comparator PC. The input of the BPF is connected to the output of the mixer M to which the output of the voltage controlled crystal oscillator VCXO2 and the output of the voltage controlled crystal oscillator VCXO3 are connected as input signals.

Next, the operation of the frequency generation circuit having such a configuration will be described. First, an external reference signal (10 MHz) from the terminal 101 is normally selected by the changeover switch SW. However, only when an external reference signal cannot be used, the output of the high stability crystal oscillator (10
MHz) is selected. The above phase lock circuit PLL
1 so as to lock to the reference signal selected by the changeover switch SW.
1 is controlled, and the voltage-controlled crystal oscillator VCXO1 supplies a reference 10 MHz signal synchronized with the reference frequency. (Hereinafter, the frequency of the supplied 10 MHz reference signal is simply referred to as a reference frequency.)

Next, in the phase lock circuit PLL2, the output of the voltage controlled crystal oscillator VCXO3 (4
(2.15 MHz), ie, 42.15 ÷ 281 = 0.15 (MHz), as a comparison frequency.
The phase lock circuit PLL2 operates to control the voltage / frequency control terminal "vt" of the voltage controlled crystal oscillator VCXO3 to generate 42.15 MHz locked to the reference frequency by comparing with 15 MHz.

Similarly, a voltage controlled crystal oscillator VCXO4
1/331 of the output (115.85 MHz) of the VCXO4 by the circuit using the phase lock circuit PLL3.
, That is, 115.85 ÷ 331 = 0.35 (MHz) as a comparison frequency.
The phase lock circuit PLL3 operates so as to control the voltage / frequency control terminal "vt" of the voltage controlled crystal oscillator VCXO4 to generate 115.85 MHz locked to the reference frequency by comparing with 35 MHz.

On the other hand, the voltage controlled crystal oscillator VCXO4
At 32.15 MHz, which is exactly 10 MHz lower than the frequency of the voltage-controlled crystal oscillator VCXO3, a frequency component having a difference between the two is generated by the mixer M, and only the difference frequency is used as a 10 MHz band-pass filter BPF.
, And applied to the phase comparator PC, the voltage-controlled crystal oscillator VCXO2 is 32.1
The output of the voltage controlled crystal oscillator VCXO2 precisely controlled to 5 MHz is output from the terminal 101.

In this way, a reference frequency synchronized with the external reference signal is generated and output from the terminal 108, and three types of signals synchronized with the reference frequency are generated and output from the terminals 101, 102 and 103, respectively. is there.

In the transmission conversion apparatus shown in FIG. 1, first, in the multiplexing circuit, the main signal (OFDM modulated wave, center frequency: fIF11, input to the IF band, input from the IF signal input terminal 1 to the input terminal 22 in the multiplexing circuit). A portion not including the pilot signal thus obtained is hereinafter referred to as an IF main signal) and a frequency generation circuit Synthesizer.
The three signals of the two pilot signals P1 and P2 (frequency: fp1s, fp2s) input from 23 are combined, and the combined signal is output from the output terminal out. This synthesized signal is frequency-converted collectively by the mixer circuit M1.

FIG. 3 is a frequency allocation diagram of pilot signals showing an example of a frequency relationship between the IF main signal and pilot signals P1 and P2. In this example, the center frequency of the IF main signal: fIF11 is 37.15 MHz, and the pilot signal P
1. The frequencies of P2 are 32.15 MHz and 42.15 MHz, respectively.
z, and the frequency difference between pilot signals P1 and P2 is 10M
Hz and the reference signal frequency (frequency: fREF1 = 10 MHz)
The frequency is generated by the frequency generation circuit Synthesizer so that the frequency becomes exactly the same as that of z).

A mixer circuit for generating the synthesized signal for the frequency conversion in the mixer circuit M1
The local frequency (fL11) supplied to M1 is generated by the frequency generation circuit Synthesizer on the transmission side. The three signals (frequency: fp1s, fp2s, fL11) from the frequency generation circuit Synthesizer are used as reference signals (fREF
Since it is generated based on 1), it is synchronized with the reference signal.

The output of the mixer circuit M1 has a main signal of the second intermediate frequency band (the center frequency of the IF signal: fIF12) obtained by performing frequency conversion (up-conversion) collectively by the local frequency (fL11). Is obtained.
The mixer circuit M1 has a band pass filter function (not shown) for selecting only the signal of the second intermediate frequency band in the output circuit. Further, the signal in the second intermediate frequency band is input to a mixer circuit M2, frequency-converted (up-converted) into a microwave band by a second local oscillator LO12, and transmitted via a BPF in a transmission frequency band (not shown). , Transmitted from a transmission antenna (not shown). The local oscillator LO12 is locked by the frequency of the reference signal (fref1), and the locking function is performed by IF frequency synchronization (fIF11 = fIF1) according to the present invention.
The arrow from the frequency generation circuit Synthesizer is indicated by a dotted line because it is not an essential condition for realizing 21).

Next, in the reception conversion device, the microwave signal transmitted from the transmission conversion device via the microwave transmission line SHF is received via an antenna and an input filter (not shown). Is input to the mixer circuit M3, is further frequency-converted (down-converted) by the local frequency fL22 of the local oscillator LO22 connected to the mixer circuit M3, and is input to the output of the mixer circuit M3. Input to terminal "in"
A main signal whose center frequency is fIF22 is output from the demultiplexing output terminal 42 and is input to the mixer circuit M4. From the demultiplexing circuit demultiplexing output terminals 41 and 43, the two signals whose frequencies are fP1r 'and fP2r' are output. Wave pilot signal P1,
P2 is split and extracted. The extracted pilot signals P1 and P2 of the two waves are generated by the mixer circuit M6 to generate the frequency of the difference between the two waves, and only the frequency of the difference is converted to the BPF.
2, the signal is supplied to the terminal 33 of the frequency generation circuit Synthesizer as a reference signal input, so that the frequency generation circuit Synthesizer outputs the output signal (frequency: fP2r) of the output terminal 31 and the output / output terminal based on the frequency of the difference. Force reference frequency fREF2 to 34 (10 MHz in this embodiment)
Generate

Further, the signal (frequency is fp2r ') from the output microwave output terminal 43 of the demultiplexing circuit is output to the mixer circuit M5 together with the generated frequency fp2r from the output terminal 31 of the frequency generation circuit Synthesizer. Are connected and mixed in the mixer circuit M5. The output of the mixer circuit M5 has the difference frequency fp2r'-fp2r
The signal of the following frequency is obtained. The above mixer circuit M4
In, the main signal whose center frequency is fIF22 is converted to a fIF21 using the output of the mixer circuit M5 as a local signal, and further added to the IF signal on the transmission side by the band-pass filter BPF1. All the pilot signal components are removed, and only the original IF signal is output to the IF signal output terminal 5.

In the manner described above, the IF signal output terminal 5 of the output of the reception conversion device obtains the IF signal obtained by performing the frequency conversion four times. At the converter output, the center frequency of the main signal,
The frequencies of P1 and P2 are transmission conversion output main signal: fIF11 + fL11 + fL12 transmission conversion output P1 signal: fP1s + fL11 + fL12 transmission conversion output P2 signal: fP2s + fL11 + fL12.

In the receiving conversion device, the intermediate frequency obtained by the first frequency conversion is the received intermediate converted main signal: fIF22 = fIF11 + fL11 + fL12-fL22 The received intermediate output P1 signal: fP1r '= fP1s + fL11 + fL12-fL22 Received intermediate output P2 signal: fP2r '= fP2s + fL11 + fL12-fL22.

[0037] Received final converted main signal: fIF21 = fIF22-(fP2r '-fP2r) = fIF11 + fL11 + fL12-fL22-(fP2s + fL11 + fL12-fL22-fP2r) = fIF11-(fP2s-fP2r). The frequency fP2s of the pilot signal P2 generated based on the reference frequency and the frequency fP2r of the pilot signal P2 generated based on the reference frequency on the receiving side
Is exactly the same frequency, the center frequency fIF21 of the final converted main signal received completely matches the center frequency fIF11 of the main signal from the IF signal input terminal 1 of the transmission converter, and the frequency deviation of the main signal due to transmission is reduced. It turns out that it does not occur.

On the other hand, regarding the pilot signals P1 and P2, the reception intermediate output P1 signal: fP1r '= fP1s + fL11 + fL12-fL22 The reception intermediate output P2 signal: fP2r' = fP2s + fL11 + fL12-fL22 On the side as well, when the frequency difference (fP2r′−fP1r ′) of the two extracted pilot signals is obtained, fP2r′−fP1r ′ = fP2s + fL11 + fL12−fL22− (fP1s + fL11 + fL12−fL22) = fP2s-fP1s, and the local oscillation frequencies (fL11, fL11) used for all frequency conversions of the transmission converter and the reception converter
12, fL22), the frequency difference between the two pilot signals at the transmitting converter is the same as the frequency difference between the two pilot signals extracted at the receiving converter.

That is, by generating the reference signal frequency fref2 of the reception conversion apparatus based on the frequency of the difference (fP2r'-fP1r ') between the frequencies of the two pilot signals extracted on the reception side, fref1 = fref2 is realized, and the frequency of the reference signal of the receiving converter is
Frequency of pilot signal P2 generated based on fref2
fP2r can be made exactly the same frequency as the frequency fP2s of the pilot signal P2 generated on the transmitting side based on the reference frequency fref1.

Thus, the above condition, that is,
fP2s = fP2r can be satisfied, and the center frequency of the main signal after final conversion: fIF21 becomes fIF21 = fIF11 from fIF21 = fIF11-(fP2s-fP2r), and is used for frequency conversion of the transmission converter and the reception converter. The local oscillation frequency (fL1
2, a transmission device that does not cause a frequency shift of the transmitted main signal regardless of the fluctuation of fL22) is realized.

By generating the reference frequency of the transmission converter based on the reference signal from the reference signal input terminal 2, it is possible to lock the frequency to an external reference signal. Can output the reference frequency fREF2 reproduced at the same frequency as the transmitting side from the reference frequency output terminal 6.

As described above, there is no frequency shift without being affected by the frequency fluctuation / phase fluctuation of the microwave oscillator local oscillator LO12 of the transmission converter and the microwave oscillator local oscillator LO22 of the reception converter. IF
The main signal and the reference signal without any frequency shift can be transmitted stably.

As a result, (1) the performance of the microwave local oscillator, ie, the frequency accuracy, frequency stability,
The requirements for frequency / phase noise and microphonic noise are extremely relaxed and can be realized economically within the current established technical scope. (2) In a terrestrial digital television broadcasting system, the OFDM-modulated IF signal from the same studio is distributed to the broadcasting devices of each broadcasting station by the signal transmission device of the present embodiment, so that the frequencies of the broadcasting waves of the respective stations match. Therefore, an excellent effect that digital terrestrial television broadcasting by SFN (single frequency network) can be easily realized can be expected.

FIG. 4 is a block diagram showing a second embodiment of the present invention, in which the transmission conversion is a transmission conversion device installed on the transmission side, and the reception conversion is performed on the reception side, that is, a transmission distance. It is a receiving conversion device installed at the receiving point, the frequency conversion in the transmission conversion is one time, the processing of the second local oscillation signal for conversion in the reception conversion, the generation method is different, and the reception conversion device This is the same as the first embodiment except that the extraction of the two pilot signals for the reference frequency control is performed after the second frequency conversion.

The IF signal input terminal 1 is connected to an IF
A signal input terminal, one of the input terminals 6 of the multiplexing circuit;
2 is connected. The reference signal input terminal 2 is connected to a terminal 55 of the frequency generation circuit Synthesizer, and receives a reference signal from an external reference signal source. In the block diagram of FIG. 4, similarly to the description of the first embodiment, the transmission conversion device and the reception conversion device do not directly relate to the description of the present invention.
Actually, illustration of necessary amplifiers and filters is omitted.

The transmission converter includes a multiplexing circuit, a frequency generation circuit Synthesizer, a second local oscillator LO112 in the microwave band, and a phase locked loop oscillator PLL.
The reference signal frequency signal fref1 from the reference signal input terminal 2 is connected to a terminal 55 of the frequency generation circuit Synthesizer, and two kinds of frequencies are set based on the reference signal frequency signal fref1. Generates fp1s and fp2s to generate the frequency generation circuit Sy
The outputs from the output terminals 51 and 52 of the nthesizer, and the two waves from the output terminals 51 and 52 and the IF signal from the IF signal input terminal 1 are input to the multiplexing circuit multiplexing input terminals 62 and 61, respectively. , And 63, and outputs a plurality of signal outputs obtained by multiplexing from the multiplexing output terminal “out” of the multiplexing circuit.
12, the local oscillator LO112 converts the frequency to a microwave band, and the microwave output terminal 3
It is configured to output more.

The receiving conversion device includes a demultiplexing circuit, a demultiplexing circuit 1, a demultiplexing circuit, a demultiplexing circuit 2, a frequency generation circuit Synthesizer, a second local oscillator LO22 in the microwave band, three mixer circuits M3, M4, M6, M25, and a band. Pass filter
BPF1, BPF2 and BPF3, and the microwave input terminal 4
Microwave signal and the local oscillator LO2
2 is connected to the mixer circuit M3, the output of the mixer circuit M3 is connected to the input terminal "in" of the branching circuit 1 and the pilot signal from the output output terminal 83 of the branching circuit 1 One wave goes to the input of the mixer circuit M25, from the output 71 of the frequency generation circuit Synthesizer to another input of the mixer circuit M25, to the mixer circuit M2.
The output of 5 is input to the input of a band-pass filter BPF3, and the output of the band-pass filter BPF3 is input as a reference signal of a phase locked loop oscillator PLL OSC.

Further, the mixer circuit M4 is connected to the oscillation output of the phase-locked loop oscillator PLLOSC and the output from the output terminal 82 of the demultiplexing circuit demultiplexer 1. The output of the mixer circuit M4 is further Another demultiplexing circuit is input to demultiplexing 2.

Demultiplexing circuit Outputs 91 and 9 of demultiplexing 2
3 is input to the mixer circuit M6, and the output of the mixer circuit M6 is input to the input terminal 73 of the frequency generation circuit Synthesizer via the BPF2.
The output 92 of the demultiplexer 2 is output to the IF signal output terminal 5 via the band pass filter BPF1, and the reference frequency fREF2 is output to the reference frequency output terminal 6 from the terminal 74 of the frequency generation circuit Synthesizer. You.

In the transmission converter, first, in the multiplexing circuit, the main signal (O) from the IF signal input terminal 1 is multiplexed.
FDM modulated wave, center frequency: fIF11, a portion not including a pilot signal inserted into the IF band is hereinafter referred to as an IF main signal), and two pilot signals P1, P2 (frequency: fp1s, generated by a frequency generation circuit Synthesizer) fp2s) 3
The signals of the systems are synthesized, and the synthesized signal is mixed into a mixer circuit M1
The frequency is converted (up-converted) to the microwave band by the local oscillation frequency of the local oscillator LO12, and the BPF in the transmission frequency band (not shown)
, And is transmitted from a transmission antenna (not shown).

Although the local oscillator LO12 is locked by the reference frequency (fref1), the lock function is not an essential condition for realizing IF frequency synchronization (fIF11 = fIF21) according to the present invention. Generation circuit
Arrows from Synthesizer are indicated by dotted lines.

Next, in the reception conversion device, the microwave signal transmitted from the transmission conversion device via the microwave transmission line SHF is received via an antenna and an input filter (not shown), and the microwave input terminal 4 Is input to the mixer circuit M3, and is further frequency-converted (down-converted) by the local frequency fL22 of the local oscillator LO22 connected to the mixer circuit M3. A main signal having a center frequency of fIF22r, a pilot signal P2, and an IF signal including the pilot signal P2 are output from the output terminal 82 of the demultiplexing circuit 1 to the mixer circuit M4. And a pilot signal whose frequency is fP2rr 'from the output terminal 83 of the demultiplexer 1 at the same time. P2 is extracted demultiplexed.

The demultiplexing circuit The signal (frequency is fp2rr ') from the output terminal 83 of the demultiplexing 1 is supplied to the frequency generation circuit Synt.
It is also connected to the mixer circuit M25 together with the generated frequency fp2rr from the output terminal 71 of the hesizer, and is mixed in the mixer circuit M25 to form the mixer circuit M2.
In the output of No. 5, a bandpass filter BPF3 for passing a signal having a frequency of the difference frequency fp2rr'-fp2rr is inserted, so that the difference frequency fp2rr'-fp2rr is obtained.

A signal having a frequency of fp2rr'-fp2rr obtained at the output of the BPF3 is a phase locked loop oscillator PLL.
Since the signal is input as the OSC reference signal, a signal of the frequency fp2rr'-fp2rr is obtained as the oscillation output of the phase locked loop oscillator PLL OSC.
Assuming that the loop band of the phase-locked loop oscillator PLL OSC and the pass band of the BPF3 are set to given sizes, the frequency and phase of the output of the phase-locked loop oscillator PLL OSC have frequency components within the broad range. In the above, the frequency and phase fluctuations of the input reference signal are followed.

On the other hand, the output of the mixer circuit M4 includes the IF main signal and the two-wave pilot signal which have been frequency-converted collectively by the oscillation output of the phase-locked loop oscillator PLL OSC. Demultiplexing circuit The signal is demultiplexed into three waves by the demultiplexing circuit 2. From the outputs 91 and 93 of the demultiplexing circuit 2, two pilot signals (the frequencies of which are fP1rr and fP2rr) are input to the mixer circuit M6. Therefore, the above mixer circuit M
6, the frequency component of the difference is obtained.
2, only the frequency component of the difference, that is, 10 MHz, is extracted and input as a reference signal to the terminal 73 of the frequency generation circuit Synthesizer. Therefore, as in the first embodiment, the frequency generation circuit Synthesizer A reference frequency is generated on the side of the reception conversion device based on the frequency “fP2rr−fP1rr”.

The branching circuit A band-pass filter BPF1 for blocking the passage of the two-wave pilot signal and passing only the IF main signal is inserted into the output terminal 92 of the branching wave 2, so that the IF signal output terminal 5 is the IF main signal from which the two pilot signals have been removed (the center frequency is fIF2
1) is output, and the above frequency generation circuit Synthesizer
The reference frequency fREF2 is output to the reference frequency output terminal 6 from the terminal 74 of FIG.

As described above, an IF signal obtained through three frequency conversions is obtained at the IF signal output terminal 5 of the output of the reception conversion device. At the converter output, the center frequency of the main signal and the frequencies of P1 and P2 are: transmission conversion output main signal: fIF11 + fL12 transmission conversion output P1 signal: fP1s + fL12 transmission conversion output P2 signal: fP2s + fL12.

In the receiving conversion device, the intermediate frequency obtained by the first frequency conversion is the receiving intermediate conversion main signal: fIF22r = fIF11 + fL12-fL22 The receiving intermediate output P1 signal: fP1rr '= fP1s + fL12-fL22 The receiving intermediate output P2 Signal: fP2rr '= fP2s + fL12-fL22.

[0059] Reception final conversion main signal: fIF21 = fIF22r-(fP2rr '-fP2rr) = fIF11 + fL12-fL22-(fP2s + fL12-fL22-fP2rr) = fIF11-(fP2s-fP2rr), and the reference frequency on the transmission side. And the frequency fP2r of the pilot signal P2 generated based on the reference frequency on the receiving side.
If r is exactly the same frequency, the center frequency fIF21 of the final received converted main signal is the IF signal input terminal of the transmitting converter.
It can be seen that the center frequency fIF11 of the main signal from FIG.

On the other hand, for the pilot signals P1 and P2, the reception intermediate output P1 signal: fP1rr '= fP1s + fL12-fL22 The reception intermediate output P2 signal: fP2rr' = fP2s + fL12-fL22, and the mixer circuit M4 Local frequency of
(fP2rr′−fP2rr), the difference between the frequencies of the two extracted pilot signals (fP2rrx−fP1rrx) is also obtained on the receiving side.

FP2rrx-fP1rrx = fP2s + fL11 + fL12-fL22- (fP2rr'-fP2rr)-(fP1s + fL11 + fL12-fL22- (fP2rr'-fP2rr)) = fP2s-fP1s The local oscillation frequencies (fL11, fL11) used for all frequency conversions of the device
12, fL22), the frequency difference between the two pilot signals at the transmission converter is the same as the frequency difference between the two pilot signals extracted at the reception converter, and the reference signal of the reception converter is obtained. By generating the signal frequency fref2 based on the frequency of the difference (fP2r′−fP1r ′) between the frequencies of the two pilot signals extracted on the receiving side, fref1 = fref2 is stably realized,

The frequency f of the reference signal of the receiving converter
frequency of pilot signal P2 generated based on ref2
Since the frequency fP2r can be made exactly the same as the frequency fP2s of the pilot signal P2 generated on the transmitting side based on the reference frequency fref1, the above condition, that is, fP2r
2s = fP2r can be satisfied, and the center frequency of the final signal of the final received conversion: fIF21 is fIF21 = fIF11 from fIF21 = fIF11-(fP2s-fP2r), and is used for frequency conversion of the transmission converter and the reception converter. The local oscillation frequency (fL1
2, a transmission device that does not cause a frequency shift of the transmitted main signal regardless of the fluctuation of fL22) is realized.

The reference frequency of the transmission conversion device can be locked to an external reference signal by generating the reference frequency from the reference signal input terminal 2 as a reference. Can output the reference frequency fREF2 reproduced at the same frequency as the transmitting side from the reference frequency output terminal 6.

As described above, there is no frequency shift without being affected by the frequency fluctuation / phase fluctuation of the microwave oscillator local oscillator LO12 of the transmitting converter and the microwave oscillator local oscillator LO22 of the receiving converter. The IF main signal and the reference signal without any frequency shift can be transmitted stably.

This is similar to the case of the first embodiment. (1) The performance of the microwave local oscillator, ie, the frequency accuracy, the frequency stability,
The requirements for frequency / phase noise and microphonic noise are extremely relaxed and can be realized economically within the current established technical scope. (2) In a terrestrial digital television broadcasting system, the OFDM-modulated IF signal from the same studio is distributed to the broadcasting devices of each broadcasting station by the signal transmission device of the present embodiment, so that the frequencies of the broadcasting waves of the respective stations match. Therefore, an excellent effect that digital terrestrial television broadcasting by SFN (single frequency network) can be easily realized can be expected.

In the first and second embodiments, the signal transmission device between two points has been described. However, as shown in FIG. 5, the transmission device of the present invention is connected in multiple stages to When used as a device that relays a reference frequency to a broadcasting station,
Since the IF signal frequency and the reference signal frequency in all the relay stations are the same, the local signal is used as a local frequency reference signal of a broadcasting transmitter for transmitting a broadcast wave of an OFDM signal obtained by frequency-converting the IF signal having the same frequency. By using the reference frequency of the exact same frequency,
An SFN (single frequency network) forwarding system can be realized.

In the first and second embodiments, the difference between the two pilot frequencies is used to transmit the reference frequency. One of the two waves is the pilot frequency of the first and second embodiments. Similarly to the signal P2, it is used for frequency / phase fluctuation absorption, another pilot signal is modulated by a reference frequency to be transmitted, and the reference frequency obtained by demodulation on the receiving side is used to equalize the reference frequency for transmission and reception. This can be performed, or at least one of the two pilots can be modulated at a level that does not impair the object of the present invention, and can be used for transmitting an auxiliary signal.

In the first and second embodiments, the example in which the signal converted into the microwave band is wirelessly transmitted has been described. However, the transmission signal in the microwave band is linearly converted into an optical signal by E / O conversion. Transmit by optical fiber and O / E on the receiving side
The same effect can be achieved even in a configuration in which the signal is converted again into an electric signal by the conversion. In these embodiments, the description has been given of the transmission by converting the signal into the microwave band in which the influence of the phase noise and the frequency fluctuation of the local oscillator is large.However, the present invention is not limited to the microwave band, but may be applied to any frequency band. However, it is clear that the same effect is realized in all cases.

FIG. 6 shows the configuration of an embodiment using an optical fiber for signal transmission. In FIG. 6, as in the first embodiment, the transmission conversion is a transmission conversion device installed on the transmission side, and the reception conversion is a reception conversion device installed on the reception side, that is, a reception point separated by a transmission distance. .

The IF signal input terminal 1 is mainly connected to an IF output of an OFDM modulator (not shown), and receives an OFDM signal in an IF frequency band. The reference signal input terminal 2
It is connected to a reference signal source (not shown) and receives a highly stable reference frequency. In this embodiment, the reference frequency is 10M
Hz. In the configuration shown in FIG. 6, the above two types of signals, ie, an IF signal and a reference signal, are received, the IF signal is converted into a microwave band signal, and further converted into an optical signal by an E / O converter. A transmission converter for transmitting the signal from the signal output terminal 3 via the optical fiber, and receiving the optical signal by the optical signal input terminal 4 via the optical fiber;
/ E converter, converts the signal into an electric signal, converts the signal again into an IF signal, and outputs the IF signal from an IF signal output terminal 5.
It consists of two devices. In the block diagram of FIG.
When neither the transmission conversion device nor the reception conversion device is directly related to the description of the present invention, illustrations of amplifiers and filters that are actually required are omitted.

The transmission converter includes a multiplexing circuit, a frequency generating circuit Synthesizer, a second local oscillator LO12 in the microwave band, and two mixer circuits M1 and M2.
Signal input terminal 7, auxiliary signal encoder C
OD, a pilot signal modulator MOD, a transmission filter BPF-T, and an E / O converter E / O, and the terminal 5b of the frequency generation circuit Synthesizer includes:
The reference signal frequency signal fref from the reference signal input terminal 2
1 is connected to generate three types of frequencies fp1s, fp2s, and fL12 based on the reference signal frequency signal fref1 and output them from the output terminal 1b, the output terminal 2b, and the microwave output terminal 4b of the frequency generation circuit Synthesizer.

At the same time, the pilot signal P1s from the output terminal 1b is connected to the multiplexed IF signal input terminal 1a.
The pilot signal P2s from the terminal 2b is connected to the terminal "1e" of the pilot signal modulator MOD, and the modulated signal from the output terminal 2e of the pilot signal modulator and the IF signal from the output terminal 1 are combined. Circuit Combination input terminal 3
a and a plurality of signal outputs obtained by multiplexing from the output terminal “out” of the multiplexing circuit and the third output signal from the frequency generation circuit Synthesizer 3b. The converted signal obtained by heterodyne conversion by the mixer circuit M1 is further converted into the second local oscillator LO by another mixer circuit M2.
A microwave signal obtained by frequency conversion into a microwave band by 12 is connected to an E / O converter, and a microwave electric signal having only a transmission frequency obtained through a transmission filter BPF-T is converted to an optical signal. It is configured to output from the optical signal output terminal 3.

The receiving converter includes a demultiplexing circuit, a demultiplexing circuit, a frequency generation circuit Synthesizer, a second local oscillator LO22 in the microwave band, and three mixer circuits M3, M4, M
5. Bandpass filter BPF1, Bandpass filter BPF2, O / E converter O / E, Receive filter BPF-R,
Pilot signal demodulator DEMO1, pilot signal demodulator DEM
O2, an auxiliary signal decoder DEC and an auxiliary signal output terminal 8, and the optical signal from the optical signal input terminal 4 is O / E
The microwave band signal converted into an electric signal by the converter O / E and the local oscillator LO22 are connected to the mixer circuit M3, and the output of the mixer circuit M3 is an input terminal “in” of the demultiplexer. And a demultiplexing circuit. The pilot signal from the microwave output terminal 1c for demultiplexing is divided into a pilot signal demodulator DEMO1 and a pilot signal demodulator D.
The output of the pilot signal demodulator DEMO1 is connected to the EMO2 and the frequency generator Synthesizer
Further, the output of the pilot signal demodulator DEMO1 is connected to the auxiliary signal decoder DEC, and the decoded output is connected to the auxiliary signal output terminal 8. A signal (frequency is fp1r ') from the output terminal 1c of the demultiplexing circuit and a generation frequency f from the output terminal 1d of the frequency generation circuit Synthesizer
The signal p1r is mixed by the mixer circuit M5, and the output of the signal of the difference frequency fp1r'-fp1r and the output terminal 2c of the demultiplexed signal are mixed.
Is connected to the mixer circuit M4, and the output of the mixer circuit M4 is connected to the band-pass filter BPF.
1 to the IF signal output terminal 5.

Further, the frequency generation circuit Synthesizer
The reference frequency fREF2 is output from the reference frequency output terminal 6 from the terminal “8”.

The operation of the circuit of the third embodiment is different from that of the first embodiment in the following points. In the transmission converter, (1) First, the method of transmitting the reference signal is that the modulation frequency of the pilot signal is changed from the frequency of the difference between the two pilot signals. For example, an FM-modulated modulated signal, in which a frequency that is an integer fraction of the reference frequency from the terminal 6b of the circuit Synthesizer as a modulation signal and a pilot signal P2 from the output terminal 2b of the frequency generation circuit Synthesizer as a carrier wave, is used as the modulation signal, Wave circuit Input from the multiplexed input terminal 3a and added to the IF signal together with the pilot signal P1. (2) Further, the pilot signal modulator has an AM modulation function by another modulation input terminal 4e, and receives an auxiliary signal from the auxiliary signal input terminal 7 for inputting a low-speed auxiliary signal such as a remote control signal. A by the auxiliary signal encoder
It is converted into a code as an M modulation input and performs low-speed AM modulation. This auxiliary signal is, for example, an ON / OFF signal for control or monitoring.
This is an off signal. (3) From the output of the mixer circuit M2, a microwave signal of a frequency band to be transmitted is selected by the transmission filter BPF-T, and the electric signal is converted into an optical signal by the E / O converter E / O. The linear signal is converted and output from the optical signal output terminal 3.

(1) The optical signal from the optical signal input terminal 4 is transmitted to the O / E
It is converted to an electric signal in the microwave band by the converter O / E,
A microwave reception signal in a required band is input to the mixer circuit M3 via the reception filter BPF-R. (2) The demultiplexing circuit The frequency fp1r 'of the pilot signal P1 demultiplexed and extracted from the IF signal input terminal 1c of the demultiplexing and the generation frequency fp1r from the output terminal 1c of the frequency generation circuit Synthesizer are determined by the mixer circuit M5. The mixed signal having the difference frequency fp1r'-fp1r is supplied to the mixer circuit M4 as a local signal. (Contrary to the first embodiment, the pilot signal P1 added to the lower side than the main signal is used for local signal processing in the second reception conversion, that is, for frequency / phase fluctuation cancellation.) ) Microwave output terminal 3c of the above demultiplexing circuit
The demodulated pilot signal P2 that has been demultiplexed and extracted is FM-demodulated by a first pilot signal demodulator DEMO1, and only a modulation frequency component is extracted from the demodulated signal by a band-pass filter BPF2. A signal is given as a reference frequency input to the frequency generation circuit Synthesizer, and the frequency generation circuit Synthesizer realizes an operation based on the same reference frequency as the transmission side. (4) Microwave output terminal 3c for the demultiplexing circuit
The demodulated pilot signal P2 that has been demultiplexed and extracted is subjected to AM demodulation by a second pilot signal demodulator DEMO2, and an auxiliary signal is obtained from the demodulated signal code by an auxiliary signal decoder.

Although the above-described seven points are different from the first embodiment, first, the transmission path is not a microwave radio line, but is transmitted by an optical fiber. An E / O converter for converting to an optical signal, and an O / E for converting again linearly to an electric signal on the receiving side
This is made possible by providing a converter. Next, since a modulation signal obtained by FM-modulating the pilot signal P2 on the transmission side is generated based on the reference frequency fREF1 on the transmission side, the demodulated signal obtained by FM demodulation on the reception side is determined by the transmission side and the modulation frequency. It is well known that even if the modulated signal is frequency-converted, the frequency of the modulated signal of the modulated signal before and after the frequency conversion does not fluctuate, and the demodulated signal is used as a reference signal, and the receiving-side reference signal frequency fREF2 Is generated, it is possible to make the transmission-side reference frequency fREF1 and the reception-side reference signal frequency fREF2 exactly the same.

The pilot signal for canceling the frequency / phase fluctuation need not necessarily be the pilot signal P2 having a higher frequency than the main signal as in the first and second embodiments. The fact that the wave may be on the high side or on the low side may be understood from the fact that there was no element with a restriction on the height relationship of the pilot signal frequency particularly in the description of the effect of the first embodiment. . Therefore, in the third embodiment, for the IF frequency stabilization processing circuit, the pilot signal P1 having a lower frequency than the main signal is used.

In this way, it is possible to generate exactly the same reference frequency on the transmitting side and the receiving side. Therefore, even when pilot signal P1 is used, pilot signal P1
The pilot signal P1 which is collectively converted together with the main signal in the transmission conversion device and also converted together with the main signal in the receiving device M3, and which has been subjected to the frequency conversion, is the pilot signal P1 extracted from the demultiplexing circuit. Since it has undergone the same fluctuation as the frequency / phase fluctuation, it can be used to generate a local signal for canceling the frequency / phase fluctuation of the IF signal, that is, an M5 output just like the first embodiment, Further, as described above, since the same reference frequency can be generated on the transmission side and the reception side, the IF of the same frequency can be generated as in the first embodiment.
A signal transmission device that outputs an output and a reference frequency is realized.

Further, in this embodiment, since the pilot signal modulator MOD is provided with an AM modulation function by the modulation input terminal 4e, the auxiliary signal input terminal 7
Is converted into a code as an AM modulation input by the auxiliary signal encoder, and given as a low-speed AM modulation signal to the modulation input terminal "4", the pilot signal P2 Receives shallow AM modulation in addition to FM modulation. However, since the AM modulation has a low speed and a low degree of modulation, it does not affect the extraction of the reference frequency component by the FM demodulation. Thus, the transmission of the auxiliary signal is enabled. The auxiliary signal can be used, for example, for transmitting an on / off signal for control or monitoring.

In this embodiment, an example has been described in which AM modulation is performed on a pilot signal for reference frequency transmission for transmitting an auxiliary signal, but a low speed signal is used for any of the pilot signals in the first and second embodiments. In addition, even when AM modulation with a low modulation factor is performed, the transmission of the auxiliary signal can be performed without impairing the frequency synchronization and the frequency / phase fluctuation removal function.

Although not shown in any of the embodiments, at least one of the pilot signals added in these embodiments is extracted and detected to realize the AGC function of the signal transmission device. Signal level detection is easily realized.

[0083]

As described above, even in an apparatus for linearly converting a microwave into an optical signal and transmitting the signal, the frequency and phase noise of the present invention can be reduced and the IF frequency and the reference frequency can be accurately transmitted. S using optical fiber transmission network
An excellent signal transmission device that can easily realize the construction of the FN broadcasting system can be provided.

The IF signal output terminal 5 of the output of the reception conversion device is connected to an IF signal obtained by four times frequency conversion.
A signal is obtained, but as shown below, at the output of the transmission converter, the center frequency of the main signal, the frequencies of P1 and P2 are the transmission conversion output main signal: fIF11 + fL11 + fL12 Transmission conversion output P1 signal: fP1s + fL11 + fL12 Transmission conversion output P2 signal: fP2s + fL11 + fL12

In the receiving conversion device, the intermediate frequency obtained by the first frequency conversion is the received intermediate converted main signal: fIF22 = fIF11 + fL11 + fL12-fL22 The received intermediate output P1 signal: fP1r '= fP1s + fL11 + fL12-fL22 Received intermediate output P2 signal: fP2r '= fP2s + fL11 + fL12-fL22.

Reception final conversion main signal: fIF21 = fIF22− (fP1r′−fP1r) = fIF11 + fL11 + fL12−fL22− (fP1s + fL11 + fL12−fL22−fP1r) = fIF11− (fP1s−fP1r) The frequency fP2s of the pilot signal P2 generated based on the reference frequency and the frequency fP2r of the pilot signal P2 generated based on the reference frequency on the receiving side
Is exactly the same frequency, the center frequency fIF21 of the main signal after the final reception conversion completely matches the center frequency fIF11 of the main signal from the IF signal input terminal 1 of the transmission converter, and the It can be seen that no frequency shift occurs.

This means that, similarly to the first and second embodiments, the local oscillation frequencies (fL12, fL22) in the microwave band used for the frequency conversion of the transmission converter and the reception converter.
), A transmission device that does not cause a frequency shift of the transmitted main signal is realized.

The reference frequency of the transmission converter can be locked to an external reference signal by generating the reference frequency from the reference signal input terminal 2 as a reference. Can output the reference frequency fREF2 reproduced at the same frequency as the transmitting side from the reference frequency output terminal 6.

As described above, there is no frequency shift without being affected by the frequency fluctuation / phase fluctuation of the microwave oscillator local oscillator LO12 of the transmitting converter and the microwave oscillator local oscillator LO22 of the receiving converter. The IF main signal and the reference signal without any frequency shift can be transmitted stably.

As described above, also in the signal transmission device of this embodiment, (1) the performance of the microwave local oscillator, ie, the frequency accuracy, the frequency stability,
The requirements for frequency / phase noise and microphonic noise are extremely relaxed and can be realized economically within the current established technical scope. (2) In a terrestrial digital television broadcasting system, the OFDM-modulated IF signal from the same studio is distributed to the broadcasting devices of each broadcasting station by the signal transmission device of the present embodiment, so that the frequencies of the broadcasting waves of the respective stations match. Therefore, an excellent effect that digital terrestrial television broadcasting by SFN (single frequency network) can be easily realized can be expected. (3) Further, since an auxiliary signal can be transmitted, when used in a relay device for distributing broadcast waves from a studio to each broadcasting station, there is no need to provide a separate line for a signal for remote control or monitoring. . Such an excellent transmission device is realized.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of a conventional signal transmission device.

FIG. 3 is an example of arrangement of pilot signals and main signals.

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

FIG. 5 is a block diagram of an SFN broadcasting system using the transmission device of the present invention.

FIG. 6 is a block diagram illustrating another use mode of the signal transmission device of the present invention.

FIG. 7 is a block diagram illustrating a configuration of a frequency generation device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 IF signal input terminal 2 Reference signal input terminal 3 Microwave output terminal 4 Microwave input terminal 5 IF signal output terminal 6 Reference frequency output terminal 7 Auxiliary signal input terminal

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoshio Aono 1-7-12 Toranomon, Minato-ku, Tokyo Oki Electric Industry Co., Ltd. F-term (reference) 5C025 AA05 AA06 AA07 AA27 DA01 5C056 FA01 GA11 GA14 HA01 HA04 5K020 AA08 BB06 DD22 EE05 FF04 GG01 GG11 GG22 5K022 DD01 DD18 DD19 DD21 DD31 DD43

Claims (5)

[Claims] 1. A signal transmission apparatus for transmitting a frequency-converted IF signal on a transmission side and transmitting a frequency-converted signal on a reception side to obtain an IF signal, comprising: means for generating a pilot signal on the transmission side; Means for adding a pilot signal to the IF signal; means for extracting the pilot signal on the receiving side; means for frequency-converting the pilot signal; and means for localizing the pilot signal obtained by frequency conversion. A signal transmission device characterized by obtaining an IF signal by performing frequency conversion as a signal. 2. A transmitting side comprising: means for generating a reference frequency; and means for generating a plurality of pilot signals based on the reference frequency. On a receiving side, a difference between two waves in the pilot signal is calculated. 2. The signal transmission apparatus according to claim 1, further comprising a unit that generates a reference frequency based on the frequency. 3. A means for generating a reference frequency on the transmitting side, means for generating a plurality of pilot signals based on the reference frequency, means for modulating the pilot signal, and a modulation signal based on the reference frequency. And a means for generating a reference frequency on the receiving side based on a frequency obtained by demodulating the modulated pilot signal. apparatus. 4. A means for inputting an auxiliary signal to a transmitting side,
Means for modulating a pilot signal with the auxiliary signal, and demodulating means for demodulating the pilot signal modulated by the auxiliary signal to obtain an auxiliary signal on a receiving side. Signal transmission equipment. 5. A transmitting side comprising: a synchronizing means for locking a reference frequency by an external signal; and an external reference signal input terminal; a receiving side comprising a reference signal input terminal; 5. The signal transmission device according to claim 1, wherein the output and the reference signal output are used as an IF signal input and a reference signal input of a (separate) transmission conversion device in the next stage, so that the transmission device according to claim 1 is connected in multiple stages.