JP4560103B2 - Relay device - Google Patents

Description

The present invention relates to a relay apparatus used in a system for transmitting a multicarrier signal such as an OFDM (Orthogonal Frequency Division Multiplexing) signal mainly by a microwave.

  In general, signal transmission devices include a device that modulates a signal, transmits the signal, and obtains a signal that is demodulated at the time of reception, and a device that transmits a signal that has already been modulated without being demodulated. is there.

  As shown in FIG. 2, a conventional microwave signal transmission apparatus using a conventional microwave has an IF signal “IF (IN)” of a frequency band of, for example, 50 MHz or less and a local oscillator “LO1” of a microwave band by a transmission conversion device. 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. Then, with one reception conversion device, the microwave reception signal from the reception antenna is amplified by the low noise amplifier, and similarly converted to the IF frequency using the local oscillation frequency of the local oscillator “LO1” in the microwave band. It is configured.

  The signal transmission device having such a configuration has a drawback that the frequency deviation of the IF signal obtained by transmission increases due to frequency fluctuation and phase noise of the local oscillator, and is greatly affected by the phase noise.

  Conventionally, a technique for reducing frequency fluctuation and phase noise of a local oscillator itself and a low noise local oscillation frequency generating means have been studied. For example, an example of using a low-frequency-noise microwave band frequency synthesizer in the case of an FPU device as a relay device for digital transmission is disclosed in Japanese Patent Application Laid-Open No. 10-247851 “Fractional-N frequency synthesizer and using it” It is disclosed in “Relay Device”.

  Further, in the OFDM system studied in Europe and Japan as a terrestrial digital broadcasting system, since a large number of mutually orthogonal carriers are multiplexed in the band, the flatness of the band phase characteristics and amplitude characteristics is important. Further, when phase noise is superimposed in the transmission apparatus, orthogonality between the carriers is lost and the error rate is deteriorated. Therefore, it is important to reduce the phase noise of the reception apparatus. "Variable Frequency Oscillator and OFDM Receiver" discloses a wideband variable frequency oscillator that achieves the low phase noise required for a receiver.

  However, in the case of an apparatus for transmitting a broadcast wave signal to a transmitting station for terrestrial digital television broadcasting, the IF signal is an OFDM signal, and the SFN (Single Frequency Network) is utilized by taking advantage of OFDM. ) Is assumed to be transmitted as a broadcast wave, and the frequency fluctuation and phase noise of the IF signal are expected to be fatal defects.

  That is, regarding frequency fluctuations, in the case of SFN (Single Frequency Network) that transmits OFDM broadcast waves of the same program from a plurality of transmitting stations in terrestrial digital television broadcasting, broadcasting from a plurality of transmitting stations is performed. At a point where a wave is received, assuming that the carrier interval of an OFDM signal having several thousand carriers in a band of about 6 MHz is 1 KHz, the frequency deviation must be within 0.1% for each carrier. Therefore, the transmission frequency deviation between transmission stations must be 1 Hz or less. In order to realize this frequency accuracy requirement, the distribution of frequency deviations allowed to the transmission device of the broadcast wave signal to the transmitting station is further reduced, and the requirement becomes more severe when it is relayed in multiple stages. For example, even if the standard distribution between the broadcaster and the transmission device is 50% and 50%, when relaying five stages, the frequency deviation allowed per stage is 0.1 Hz or less.

In order to reduce the frequency deviation of the IF signal transmitted by the transmission apparatus of the conventional configuration to 0.1 Hz or less, the frequency fluctuation allowed in the transmission conversion (up conversion) and reception conversion (down conversion) of the transmission apparatus is ± The frequency fluctuation is 0.05 Hz or less, and the frequency variation allowed for the local oscillator for transmission conversion or reception conversion is ± 0.025 Hz. In the case of a 7 GHz band microwave transmission device, the local oscillator is required to have a frequency stability of about “± 3.5 × 10 ⁻¹² ”.

  Next, regarding the phase noise, in the case of the transmission device having the above-described 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, and the frequency band of the local oscillator is Due to the microwave band, the phase noise characteristics required for local oscillators are extremely severe, and the highest-performance low-noise oscillator that can currently obtain the phase noise of the local oscillator of the transmission converter and the local oscillator of the reception converter Even if it is used, a high-precision and high-stability reference signal oscillator such as a rubidium oscillator is used in order to prevent the disadvantage that deterioration is added by multi-stage relay and is not sufficient, and to prevent fluctuations in IF frequency after each reception conversion. Or synchronization means such as using GPS, especially when multistage relay is used Iterator had the disadvantage that sufficient performance even rubidium oscillator or a GPS synchronization can not be realized.

  Also, even if the frequency stability of the local oscillator can satisfy the required performance statically, it is called microphonic noise that occurs when mechanical and acoustic vibrations are applied to the oscillation circuit elements, etc. It has been almost impossible to completely solve the problem that the oscillation frequency is subjected to FM modulation due to mechanical vibration.

In order to solve the above-described problems, in the present invention, a main signal in the IF (intermediate frequency) band is converted into a transmission frequency band on the transmission side and transmitted, and a signal in the transmission frequency band received on the reception side is converted into an IF band. In a relay apparatus used in a signal transmission system that obtains the main signal by frequency conversion, the transmission side of the system generates first and second pilot signals having a certain frequency difference from each other based on a reference frequency signal, The first and second pilot signals are distributed to both the lower band and the upper band of the main signal or arranged together in either one to generate a transmission signal. The frequency is converted into a frequency band and transmitted. The receiving side of the system receives the signal in the transmission frequency band, converts the frequency of the received signal into the IF band, and combines the signals. The synthesized signal is separated into the main signal and the first and second pilot signals, the frequency difference between the separated first and second pilot signals is obtained, and the frequency difference is used as a reference. When the signal having the same frequency as the reference frequency signal on the transmitting side is reproduced and the received signal is converted based on the reproduced reference frequency signal, the signal in the transmission frequency band is received and the received signal Is converted to the IF band to obtain the synthesized signal, the synthesized signal is separated into the main signal and the first and second pilot signals, and the separated first and second pilot signals are separated. A receiver that obtains a frequency difference, reproduces a signal having the same frequency as the reference frequency signal on the transmission side on the basis of the frequency difference, and performs frequency conversion of the received signal based on the reproduced reference frequency signal; Inside The reference frequency signal is generated in accordance with the reference frequency signal, and the reference frequency signal has a certain frequency difference from each other and is distributed to both the lower band and the upper band of the main signal or arranged in one of them. First and second pilot signals are generated, the first and second pilot signals are combined with the main signal to generate a transmission signal, and the transmission signal is frequency-converted to the transmission frequency band and transmitted. And a transmitting unit.

  With the configuration described above, in the present invention, in addition to the main signal, two types of pilot signals generated so that the frequency difference is equal to the reference signal are modulated and transmitted from the transmission side.

  On the other hand, the receiving side demultiplexes the received signal into a main signal and two types of pilot signals, and generates a reference signal based on the frequency difference between the 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 remains in the main signal demultiplexed based on the signal indicating the variation. The influence of the fluctuation of the pilot signal is removed from the main signal, and the main signal output without disturbance is obtained.
In the above system, the present invention provides a relay device including a receiving unit having the same configuration as the receiving side and a transmitting unit having the same configuration as the transmitting side in order to realize multistage transmission.

  FIG. 1 is a block diagram showing a first embodiment of the present invention. In FIG. 1, transmission conversion is a transmission conversion device installed on the transmission side, and 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 the 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. In the configuration of FIG. 1, the above two types of signals, that is, the IF signal and the reference signal are received, the IF signal is converted into a microwave band signal, and transmitted from the microwave output terminal 3 via the transmission antenna. A transmission conversion apparatus that receives the microwave band signal through the reception antenna at the microwave input terminal 4, converts the signal again into an IF signal, and outputs the IF signal from the IF signal output terminal 5. Is done.

  A broken line SHF between the microwave output terminal 3 of the transmission conversion device and the microwave input terminal 4 of the reception conversion device is a microwave transmission path, 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. In the block diagram of FIG. 1, in the case where neither the transmission conversion apparatus nor the reception conversion apparatus is directly related to the description of the present invention, illustration of actually required amplifiers and filters is omitted.

The transmission conversion apparatus includes a multiplexing circuit (multiplexing), a frequency generation circuit (Synthesizer), a second local oscillator LO12 in the microwave band, and two mixer circuits M1 and M2, and is a terminal of the frequency generation circuit (Synthesizer). 15 is connected to the reference signal frequency signal f _REF1 from the reference signal input terminal 2, and generates three types of frequencies f _p1s , f _p2s and f _L11 using the reference signal frequency signal f _REF1 as a reference. Output from the input terminal 11, input terminal 12 and output terminal 13 of the generation circuit (Synthesizer), and the two waves from the input terminal 11 and input terminal 12 and the IF signal from the IF signal input terminal 1 are combined. Multiple-wave signals obtained by inputting from the IF signal input terminal 22, the input terminal 21 and the input terminal 23 of the circuit (combining) and combining from the output terminal “out” of the combining circuit (combining) And a third output signal from the output terminal 13 of the frequency generation circuit (Synthesizer) are subjected to heterodyne conversion by the mixer circuit M1, and the second mixer circuit M2 further converts the second conversion signal to the second output signal. The frequency is converted into a microwave band by the local oscillator LO12 and output from the microwave output terminal 3.

  The reception conversion apparatus includes a demultiplexing circuit (demultiplexing), a frequency generation circuit (Synthesizer), a second local oscillator LO22 in the microwave band, four mixer circuits M3, M4, M5, and M6, a bandpass filter BPF1, and a bandpass filter. The received microwave signal from the microwave input terminal 4 and the local oscillator LO22 are connected to the mixer circuit M3, and the output of the mixer circuit M3 is an input terminal of a branching circuit (demultiplexing). Connected to “in”.

Two of the three demultiplexed outputs are input to the mixer circuit M6 from the output IF signal input terminals 41 and 43 of the demultiplexing circuit (demultiplexing), and the output of the mixer circuit M6 passes through the BPF 2 above. A signal (frequency is f _p2r ′) from the output terminal 43 of the demultiplexing circuit (demultiplexing) to the terminal 33 of the frequency generation circuit (Synthesizer) and generation from the output terminal 31 of the frequency generation circuit (Synthesizer) The frequency f _p2r is mixed by the mixer circuit M5, and the output of the difference frequency f _p2r '-f _p2r and the output from the demultiplexing output terminal 42 are connected to the mixer circuit M4. The M4 output is configured to be output to the IF signal output terminal 5 via the bandpass filter BPF1. Further, the reference frequency f _REF2 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.

  In FIG. 7, the description of the input / output terminals is shown below first.

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: Output terminal for second local oscillation (frequency 115.85 MHz)
Terminal 104: Microwave local oscillator control output terminal (frequency 10 MHz)
Terminal 105: External reference signal input terminal (frequency 10 MHz)
Terminal 108: External reference signal output terminal (frequency 10 MHz)
The signal from the terminal 105 and the output of the high stability crystal oscillator (10 MHz) are selected by the change-over switch SW, and one of the signals is input to the phase lock circuit PLL1. A control signal from the phase lock circuit PLL1 is connected to the voltage / frequency control terminal “vt” of the voltage controlled crystal oscillator VCXO1. The oscillation output of the pressure controlled crystal oscillator VCXO1 is connected as a comparison frequency to the phase lock circuit PLL1, a reference frequency to the phase lock circuit PLL2, a reference frequency to the phase lock circuit PLL3, and a reference frequency to the phase comparator PC. At the same time, the signals are output from the terminals 108 and 104 through the buffer amplifiers BA1 and BA2, respectively.

  The output of the phase lock circuit PLL2 is connected to the 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. Voltage controlled crystal oscillator VCXO3 and voltage controlled crystal oscillator VCXO4 output phase-locked oscillation outputs from terminals 102 and 103, respectively.

  The control voltage of the phase comparator PC is connected to the voltage / frequency control terminal “vt” of the voltage controlled crystal oscillator VCXO2, and the output signal of the 10 MHz bandpass filter BPF is used as the comparison frequency input of the phase comparator PC. And the output of the voltage controlled crystal oscillator VCXO2 and the output from the mixer circuit M to which the voltage controlled crystal oscillator VCXO3 output is connected as an input signal are connected to the input of the bandpass filter BPF. ing.

  Next, the operation of the frequency generation circuit having such a configuration will be described.

First, although the external reference signal (10 MHz) from the terminal 101 is normally selected by the changeover switch SW, the output of the high-stable crystal oscillator (10 MHz) provided therein is only provided when the reference signal from the outside cannot be used. ) Is selected. The voltage controlled crystal oscillator VCXO1 is controlled by the phase lock circuit PLL1 so as to lock to the reference signal selected by the changeover switch SW, and the voltage controlled crystal oscillator VCXO1 generates a reference 10 MHz signal synchronized with the reference frequency. Supply. (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 frequency of 1/281 of the output (42.15 MHz) of the voltage controlled crystal oscillator VCXO3, that is, 42.15 ÷ 281 = 0.15 (MHz) is used as a comparison frequency. The phase lock circuit is configured to control the voltage / frequency control terminal “vt” of the voltage controlled crystal oscillator VCXO3 so as to generate 42.15 MHz locked to the reference frequency by comparing with the reference frequency of 0.15 MHz. PLL2 operates.

  Similarly, the voltage control crystal oscillator VCXO4 and the phase lock circuit PLL3 are used to compare the frequency of 1/331 of the output of the VCXO4 (115.85 MHz), that is, 115.85 ÷ 331 = 0.35 (MHz) as the comparison frequency. As described above, the voltage / frequency control terminal “vt” of the voltage controlled crystal oscillator VCXO4 is controlled so as to generate 115.85 MHz locked to the reference frequency by comparing with the reference frequency of 0.35 MHz. The phase lock circuit PLL3 operates.

  On the other hand, the voltage controlled crystal oscillator VCXO4 generates a frequency component of the difference between the two frequencies by the mixer M at 32.15 MHz, which is exactly 10 MHz lower than the frequency of the voltage controlled crystal oscillator VCXO3. Since it is extracted by the band pass filter BPF and supplied to the phase comparator PC, the voltage controlled crystal oscillator VCXO2 output from the terminal 101 is accurately controlled so that the voltage controlled crystal oscillator VCXO2 becomes 32.15 MHz which is 10 MHz lower. Is output.

  Thus, 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.

In the transmission conversion apparatus shown in FIG. 1, first, in a multiplexing circuit (multiplexing), a main signal (OFDM modulated wave, center frequency: f _IF11 , which is input from the IF signal input terminal 1 to the input terminal 22 is inserted into the IF band. The portion that does not include the pilot signal is hereinafter referred to as an IF main signal) and a frequency generation circuit (Synthesizer), and two-wave pilot signals P1 and P2 (frequency: f _p1s ) input from the input terminals 21 and 23, respectively. f _p2s ) of the three systems of signals are combined, and the combined signal is output from the output terminal “out”. The synthesized signal is frequency-converted at once by the mixer circuit M1.

FIG. 3 is a pilot signal frequency allocation diagram showing an example of the frequency relationship between the IF main signal and the pilot signals P1 and P2. In this example, the center frequency of the IF main signal: the f _IF11 37.15MHz, respectively the frequency of the pilot signal P1, P2 32.15MHz, and 42.15MHz, and 10MHz frequency difference of the pilot signals P1, P2, reference It is generated by the frequency generation circuit (Synthesizer) so as to be exactly the same frequency as the signal frequency (frequency: f _REF1 = 10 MHz).

The local frequency (f _L11 ) supplied to the mixer circuit M1 in order to generate the synthesized signal for frequency conversion in the mixer circuit M1 is generated by the frequency generator circuit (Synthesizer) on the transmission side. The three signals (frequency: f _p1s , f _p2s , f _L11 ) from the frequency generation circuit (Synthesizer) are generated based on the reference signal (f _REF1 ), and thus are synchronized with the reference signal.

At the output of the mixer circuit M1, the main signal (the center frequency of the IF signal: f _IF12 ) in the second intermediate frequency band obtained by performing frequency conversion (up-conversion) all at once with the local frequency (f _L11 ). can get. The mixer circuit M1 has a band-pass filter function (not shown) for selecting only a signal in the second intermediate frequency band in the output circuit. Further, the signal of the second intermediate frequency band is input to the mixer circuit M2, and is frequency-converted (up-conversion) to the microwave band by the second local oscillator LO12, and then via the BPF of the transmission frequency band (not shown). Are transmitted from a transmission antenna (not shown).

It said local oscillator LO12 is locked by the frequency of the reference signal (f _REF1), since the lock function is not an essential condition for realizing the IF frequency synchronization (f _IF11 = f _IF21) by the present invention, An arrow from the frequency generation circuit (Synthesizer) is indicated by a dotted line.

Next, in the reception conversion device, the microwave signal from the transmission conversion device transmitted through the microwave transmission path SHF is received via an antenna and an input filter (not shown), and the mixer circuit M3 is received from the microwave input terminal 4. Is further frequency-converted (down-converted) by the local frequency f _L22 of the local oscillator LO22 connected to the mixer circuit M3, and an input terminal of a demultiplexing circuit (demultiplexing) from the output of the mixer circuit M3 The main signal whose center frequency is f _IF22 is output from the output terminal 42 of the branching circuit (demultiplexing) and input to the mixer circuit M4 and output from the branching circuit (demultiplexing). From the terminals 41 and 43, two pilot signals P1 and P2 whose frequencies are f _P1r ′ and f _P2r ′ are demultiplexed and extracted. The extracted pilot signals P1 and P2 of the two waves are generated by the mixer circuit M6 so as to generate a frequency difference of the two waves, and only the frequency of the difference is extracted by the BPF 2, and is supplied to the terminal 33 of the frequency generation circuit (Synthesizer). By giving as a reference signal input, the frequency generation circuit (Synthesizer) outputs the output signal (frequency: f _P2r ) from the output terminal 31 and the force reference frequency f _REF2 to the output terminal 34 based on the difference frequency (this embodiment) Is 10 MHz).

Further, a signal (frequency is f _p2r ′) from the output microwave output terminal 43 of the demultiplexing circuit (demultiplexing) is _combined with the mixer circuit together with the generated frequency f _p2r from the output terminal 31 of the frequency generating circuit (Synthesizer). M5 is also connected to and mixed in the mixer circuit M5, to the mixer circuit M5 output frequency f _P2R of the difference '- f _P2R become the frequency signal is obtained. In the mixer circuit M4, main signal whose center frequency is f _{IF 22} is an output of the mixer circuit M5 as a local signal, the center frequency is frequency-converted to f _{IF 21,} further by the band-pass filter BPF1, sender Thus, all pilot signal components added to the IF signal are removed, and only the original IF signal is output to the IF signal output terminal 5.

As described above, the IF signal output terminal 5 of the output of the reception conversion apparatus can obtain the IF signal obtained by performing the frequency conversion four times. As shown below, the output of the transmission conversion apparatus is obtained. , The center frequency of the main signal, the frequencies of P1 and P2, are
Transmission conversion output main signal: f _IF11 + f _L11 + f _L12
Transmission conversion output P1 signal: f _P1s + f _L11 + f _L12
Transmission conversion output P2 signal: f _P2s + f _L11 + f _L12
It becomes.

In the receiving conversion device, the intermediate frequency by the first frequency conversion is
Receiving intermediate converted main _{signal: f IF22 = f IF11 + f} L11 + f L12 - f L22
Received intermediate output P1 signal: f _P1r '= f _P1s + f _L11 + f _L12 -f _L22
Received intermediate output P2 signal: f _P2r '= f _P2s + f _L11 + f _L12 -f _L22
It becomes.

Also,
Received final conversion main signal: f _IF21 = f _IF22- (f _P2r '-f _P2r )
_{= F IF11 + f L11 + f} L12 - f L22 - (f P2s + f L11 + f L12 -f L22
-f _P2r )
_{= F IF11 - (f P2s -} f P2r)
If the frequency f _P2s of the pilot signal P2 generated based on the reference frequency on the transmission side and the frequency f _P2r of the pilot signal P2 generated based on the reference frequency on the reception side are exactly the same frequency, the final reception conversion center frequency f _{IF 21} of the main signal is completely coincident with the center frequency f _{IF 11} of the main signal from the IF signal input terminal 1 of the transmission converter, it can be seen that no frequency deviation of the main signal due to transmission.

On the other hand, for pilot signals P1 and P2,
Received intermediate output P1 signal: f _P1r '= f _P1s + f _L11 + f _L12 -f _L22
Received intermediate output P2 signal: f _P2r '= f _P2s + f _L11 + f _L12 -f _{L22
Therefore} , on the receiving side as well, when the difference in frequency between the extracted two pilot signals (f _P2r '-f _P1r ') is obtained,
_{f P2r '- f P1r' =} f P2s + f L11 + f L12 - f L22 - (f P1s + f L11 + f L12 - f L22)
= f _P2s -f _P1s
Regardless of fluctuations in the local oscillation frequencies (f _L11 , f _L12 , f _L22 ) used for all the frequency conversions of the transmission conversion device and the reception conversion device, the frequency difference between the two pilot signals in the transmission conversion device Is the same as the frequency difference between the two pilot signals extracted by the reception converter.

That is, f _REF1 is generated by generating the reference signal frequency f _REF2 of the reception conversion device based on the frequency difference (f _P2r ′ −f _P1r ′) of the two pilot signals extracted on the receiving side. = f _REF2 is achieved, the frequency f _P2s of the pilot signal P2 frequency f _P2r, generated based on the reference frequency f _REF1 at the transmission side of the pilot signal P2 generated based on the reference signal frequency f _REF2 of the reception converter And the same frequency.

In this way, the above condition, that is, f _P2s = f _P2r can be satisfied, and the center frequency of the received final converted main signal: f _IF21 is
_{f IF21 = f IF11 - (f} P2s - f P2r)
Than,
f _IF21 = f _{IF11
Therefore} , there is a transmission device that does not cause a frequency shift of the transmitted main signal regardless of fluctuations in the local oscillation frequency (f _L12 , f _L22 ) of the microwave band used for frequency conversion of the transmission conversion device and the reception conversion device. It is realized.

The reference frequency of the transmission conversion device can be locked to the reference signal from the outside by generating the reference signal from the reference signal input terminal 2 as a reference. The reference frequency f _REF2 reproduced at the same frequency as the side can be output from the reference frequency output terminal 6.

  As described above, the IF main signal has no frequency deviation without being affected by the frequency fluctuation / phase fluctuation of the microwave band local oscillator LO12 of the transmission conversion apparatus and the microwave band local oscillator LO22 of the reception conversion apparatus. In addition, it is possible to stably transmit a reference signal having no frequency shift.

As a result,
(1) The requirements for the performance of the microwave local oscillator, that is, the frequency accuracy, the frequency stability, the frequency / phase noise, and the microphonic noise, which were the biggest problems in the prior art, are extremely relaxed, and within the currently established technical scope. Can be realized economically.

(2) In a terrestrial digital television broadcasting system, the frequency of each station's broadcast wave is matched by distributing the OFDM modulated IF signal from the same studio to the broadcasting device of each broadcasting station by the signal transmission device of this embodiment. Therefore, it is possible to expect an excellent effect that terrestrial digital television broadcasting by SFN (single frequency network) can be easily realized.

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

  The IF signal input terminal 1 is an input terminal for an IF signal to the transmission device, and is connected to one input terminal 62 of the multiplexing circuit. The reference signal input terminal 2 is connected to a terminal 55 of a frequency generation circuit (Synthesizer), and receives a reference signal from an external reference signal source. In the block diagram of FIG. 4 as well, in the same way as in the description of the first embodiment, if neither the transmission converter nor the reception converter is directly related to the description of the present invention, the illustration of actually required amplifiers and filters is omitted. is doing.

The transmission conversion device includes a multiplexing circuit (multiplexing), a frequency generation circuit (Synthesizer), a second local oscillator LO112 in the microwave band, a phase-locked loop oscillator PLL-OSC, and a mixer circuit M12, and the frequency generation circuit ( The reference signal frequency signal f _REF1 from the reference signal input terminal 2 is connected to the terminal 55 of the Synthesizer), and two types of frequencies f _p1s and f _p2s are generated using the reference signal frequency signal f _REF1 as a reference. Output from the output terminals 51 and 52 of the frequency generation circuit (Synthesizer), and the two waves from the output terminal 51 and the output terminal 52 and the IF signal from the IF signal input terminal 1 are respectively combined with the multiplexing circuit (multiplexing). ) Input terminals 62, 61, and 63, and a plurality of signal outputs obtained by combining from the output terminal “out” of the combining circuit (combining), The Kisa circuit M12, and to output from the microwave output terminal 3 and the frequency converting the microwave band by the local oscillator LO112.

  The reception conversion device includes a demultiplexing circuit (demultiplexing) 1, a demultiplexing circuit (demultiplexing) 2, a frequency generation circuit (Synthesizer), a second local oscillator LO22 in the microwave band, four mixer circuits M3, M4, M6, M25, a bandpass filter BPF1, a bandpass filter BPF2, and a bandpass filter BPF3. The received microwave signal from the microwave input terminal 4 and the local oscillator LO22 are connected to the mixer circuit M3, and the mixer The output of the circuit M3 is connected to the input terminal “in” of the demultiplexing circuit (demultiplexing) 1, and one wave of the pilot signal from the output terminal 83 of the demultiplexing circuit (demultiplexing) 1 is input to the input of the mixer circuit M25. The output of the mixer circuit M25 from the generation circuit (Synthesizer) output 71 to another input of the mixer circuit M25 is a bandpass filter BP. 3 to the input, the output of the band pass filter BPF3 is input as a reference signal for phase-locked loop oscillator PLL-OSC.

  Further, the mixer circuit M4 is connected to the oscillation output of the phase-locked loop oscillator PLL-OSC and the output from the output terminal 82 of the demultiplexing circuit (demultiplexing) 1, and the output of the mixer circuit M4 is further It is input to another demultiplexing circuit (demultiplexing) 2.

The outputs 91 and 93 of the branching circuit (demultiplexing) 2 are input to the mixer circuit M6, and the output of the mixer circuit M6 is supplied to the input terminal 73 of the frequency generation circuit (Synthesizer) via the BPF2. Further, the output 92 of the demultiplexing circuit (demultiplexing) 2 is output to the IF signal output terminal 5 via the bandpass filter BPF1, and the reference frequency f _REF2 is further _supplied from the terminal 74 of the frequency generating circuit (Synthesizer). It is output to the reference frequency output terminal 6.

In the transmission conversion device, first, in the multiplexing circuit (multiplexing), the main signal from the IF signal input terminal 1 (OFDM modulated wave, center frequency: f _IF11 , the portion not including the pilot signal inserted in the IF band) (Hereinafter referred to as the IF main signal) and the three signals of the two-wave pilot signals P1 and P2 (frequency: f _p1s and f _p2s ) generated by the frequency generation circuit (Synthesizer) are synthesized, and the synthesized signal is synthesized by the mixer circuit M1. Collectively, the frequency is converted (up-conversion) to the microwave band by the local oscillation frequency of the local oscillator LO12, and is transmitted from a transmission antenna (not shown) via a BPF in a transmission frequency band (not shown).

It said local oscillator LO12 is locked by the reference frequency (f _REF1), since the lock function is not an essential condition for realizing the IF frequency synchronization (f _IF11 = f _IF21) by the present invention, the frequency An arrow from the generation circuit (Synthesizer) is indicated by a dotted line.

Next, in the reception conversion device, the microwave signal from the transmission conversion device transmitted through the microwave transmission path SHF is received via an antenna and an input filter (not shown), and the mixer circuit M3 is received from the microwave input terminal 4. Is further frequency-converted (down-converted) by the local frequency f _L22 of the local oscillator LO22 connected to the mixer circuit M3, and an input terminal of the demultiplexing circuit (demultiplexing) 1 from the output of the mixer circuit M3 The IF signal including the main signal having the center frequency f _IF22r , the pilot signal P2, and the pilot signal P2 is output from the output terminal 82 of the demultiplexing circuit (demultiplexing) 1 and input to “in”. A pilot signal P whose frequency is f _P2rr ′ is input to M4 and simultaneously from the output terminal 83 of the branching circuit (demultiplexing) 1 2 is demultiplexed and extracted.

The signal (frequency is f _p2rr ') from the output terminal 83 of the demultiplexing circuit (demultiplexing) 1 is connected to the mixer circuit M25 together with the generation frequency f _p2rr from the output terminal 71 of the frequency generation circuit (Synthesizer). And mixed in the mixer circuit M25. Since the band-pass filter BPF3 that passes the signal having the difference frequency f _p2rr '-f _p2rr is inserted in the output of the mixer circuit M25, the difference frequency f _p2rr ' -f _p2rr is obtained. .

The BPF 3 f _P2rr resulting in the output '- _f p2rr comprising frequency signal is, since the input as a reference signal for phase-locked loop oscillator PLL-OSC, the oscillation output of the phase locked loop oscillator PLL-OSC, the frequency f _p2rr′− f _p2rr can be obtained. If the loop band of the phase-locked loop oscillator PLL-OSC and the pass band of the BPF 3 are set to given magnitudes, the phase-locked loop oscillator The frequency and phase of the PLL-OSC output follows the frequency and phase fluctuations of the input reference signal in the frequency component within the band.

On the other hand, the output of the mixer circuit M4 includes the IF main signal and the two pilot signals that are collectively frequency-converted by the oscillation output of the phase-locked loop oscillator PLL-OSC. The signal is demultiplexed into three waves by the circuit (demultiplexing) 2, and two pilot signals (having frequencies f _P1rr and f _P2rr ) are output from the outputs 91 and 93 of the demultiplexing circuit (demultiplexing) 2 in the mixer circuit. Since the difference frequency component is obtained at the output of the mixer circuit M6, only the difference frequency component, that is, 10 MHz, is extracted by the BPF 2 and supplied to the terminal 73 of the frequency generation circuit (Synthesizer). since the input as the reference signal, as in the first embodiment, the frequency generation circuit (Synthesizer) the frequency of the difference - receiving convert "f _P2rr f _P1rr" as a reference Generating a reference frequency at 置側.

Since the band-pass filter BPF1 that blocks the passage of the pilot signal of the two waves and passes only the IF main signal is inserted into the output terminal 92 of the branching circuit (demultiplexing) 2, the IF signal output terminal 5 2 outputs an IF main signal from which two pilot signals have been removed (its center frequency is f _IF21 ), and the reference frequency f _REF2 is _supplied from the terminal 74 of the frequency generator (Synthesizer) to the reference frequency output terminal 6. It is output.

As described above, the IF signal output terminal 5 of the output of the reception conversion device can obtain the IF signal obtained by performing the frequency conversion three times. , The center frequency of the main signal, the frequencies of P1 and P2, are
Transmission conversion output main signal: f _IF11 + f _L12
Transmission conversion output P1 signal: f _P1s + f _L12
Transmission conversion output P2 signal: f _P2s + f _L12
It becomes.

In the receiving conversion device, the intermediate frequency by the first frequency conversion is
Receiving intermediate converted main _{signal: f IF22r = f IF11 + f} L12 - f L22
Received intermediate output P1 signal: f _P1rr '= f _P1s + f _L12 -f _L22
Received intermediate output P2 signal: f _P2rr '= f _P2s + f _L12 -f _L22
It becomes.

Received final conversion main signal: f _IF21 = f _IF22r- (f _P2rr '-f _P2rr )
_{= F IF11 + f L12 - f} L22 - (f P2s + f L12 - f L22 - f P2rr)
_{= F IF11 - (f P2s -} f P2rr)
Next, the frequency f _P2s of the pilot signal P2 generated based on the reference frequency on the transmission side, if exactly the same frequency is the frequency f _P2rr pilot signal P2 generated based on the reference frequency at the receiving side, the receiving end converts center frequency f _{IF 21} of the main signal is completely coincident with the center frequency f _{IF 11} of the main signal from the IF signal input terminal 1 of the transmission converter, it can be seen that no frequency deviation of the main signal due to transmission.

On the other hand, for pilot signals P1 and P2,
Received intermediate output P1 signal: f _P1rr '= f _P1s + f _L12 -f _L22
Received intermediate output P2 signal: f _P2rr '= f _P2s + f _L12 -f _L22
Furthermore, since it is converted by the local frequency (f _P2rr ′ −f _P2rr ) of the mixer circuit M4, the frequency difference (f _P2rrx −f _P1rrx ) of the extracted two pilot signals is also obtained on the receiving side. When asked
_{f P2rrx - f P1rrx = f P2s} + f L11 + f L12 - f L22 - (f P2rr '- f P2rr)
_{- (f P1s + f L11 +} f L12 - f L22 - (f P2rr '- f P2rr))
= f _P2s -f _P1s
Regardless of fluctuations in the local oscillation frequencies (f _L11 , f _L12 , f _L22 ) used for all the frequency conversions of the transmission conversion device and the reception conversion device, the frequency difference between the two pilot signals in the transmission conversion device Is the same as the frequency difference between the two pilot signals extracted by the reception conversion device, and the reference signal frequency f _REF2 of the reception conversion device is set to the difference between the frequencies of the two pilot signals extracted at the reception side (f _P2r By generating based on the frequency of “− f _P1r ”), f _REF1 = f _REF2 is stably realized.

In this way, the frequency f _P2r of the pilot signal P2 generated based on the reference signal frequency f _REF2 of the reception conversion device is exactly the same as the frequency f _P2s of the pilot signal P2 generated based on the reference frequency f _REF1 on the transmission side. Since the frequency can be set, the above condition, that is, f _P2s = f _P2r can be satisfied. Therefore, the center frequency of the received final converted main signal: f _IF21 is
_{f IF21 = f IF11 - (f} P2s - f P2r)
Than,
f _IF21 = f _{IF11
Therefore} , there is a transmission device that does not cause a frequency shift of the transmitted main signal regardless of fluctuations in the local oscillation frequency (f _L12 , f _L22 ) of the microwave band used for frequency conversion of the transmission conversion device and the reception conversion device. It is realized.

The reference frequency of the transmission conversion device can be locked to the reference signal from the outside by generating the reference signal from the reference signal input terminal 2 as a reference. The reference frequency f _REF2 reproduced at the same frequency as the side can be output from the reference frequency output terminal 6.

  As described above, the IF main signal has no frequency deviation without being affected by the frequency fluctuation / phase fluctuation of the microwave band local oscillator LO12 of the transmission conversion apparatus and the microwave band local oscillator LO22 of the reception conversion apparatus. In addition, it is possible to stably transmit a reference signal having no frequency shift.

As in the case of the first embodiment, this is because (1) there is a demand for the performance of the microwave local oscillator, that is, the frequency accuracy, the frequency stability, the frequency / phase noise and the microphonic noise, which were the biggest problems in the prior art. Extremely relaxed and economically feasible with the current established technology range.

(2) In a terrestrial digital television broadcasting system, the frequency of each station's broadcast wave is matched by distributing the OFDM modulated IF signal from the same studio to the broadcasting device of each broadcasting station by the signal transmission device of this embodiment. Therefore, it is possible to expect an excellent effect that terrestrial digital television broadcasting by SFN (single frequency network) can be easily realized.

  In the first embodiment and the second embodiment, the signal transmission apparatus between two points has been described. However, as shown in FIG. 5, the transmission apparatus of the present invention is connected in multiple stages, and the IF signal and the reference frequency are set. When used as a device that relays to a broadcast station, the IF signal frequency and the reference signal frequency at all relay stations are the same, so a broadcast that transmits a broadcast wave of an OFDM signal obtained by frequency-converting the IF signal of this same frequency A complete SFN (single frequency network) transmission system can be realized by using the same reference frequency as the reference signal of the local frequency of the transmitter.

  In the first and second embodiments, the difference between the two pilot frequencies is used for transmission of the reference frequency, but one of the two waves is the same as the pilot signal P2 in the first and second embodiments. In addition, the reference frequency for transmission and reception can be made identical by using the reference frequency obtained by modulating the other pilot signal with the reference frequency to be transmitted and demodulating on the receiving side, which is used for frequency / phase fluctuation absorption. It is possible to apply a level of modulation that does not impair the object of the present invention to at least one of the two-wave pilots, and it can be used for transmission of auxiliary signals.

  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 and transmitted through the optical fiber. However, the same effect can be realized even if the receiving side is configured to convert it again into an electrical signal by O / E conversion.

  In these embodiments, transmission was described after being converted to a microwave band that is greatly affected by the phase noise and frequency fluctuation of the local oscillator. However, the transmission is not limited to the microwave band, and any frequency band is used for conversion. However, it is clear that all the same effects can be realized.

  The configuration of an embodiment using an optical fiber for signal transmission is shown in FIG. In FIG. 6, as in the first embodiment, the transmission conversion is a transmission conversion apparatus installed on the transmission side, and the reception conversion is a reception conversion apparatus 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 the 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. In the configuration of FIG. 6, the above two types of signals, that is, the IF signal and the 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 from the signal output terminal 3 via an optical fiber and the optical signal received by the optical signal input terminal 4 via an optical fiber, converted into an electrical signal by an O / E converter, and converted back to an IF signal, It is composed of two devices, a receiving conversion device that outputs from the IF signal output terminal 5. In the block diagram of FIG. 6, in the case where neither the transmission conversion device nor the reception conversion device is directly related to the description of the present invention, illustration of actually required amplifiers and filters is omitted.

The transmission conversion device includes an auxiliary signal input terminal 7, an auxiliary signal code, in addition to a multiplexing circuit (multiplexing), a frequency generation circuit (Synthesizer), a second local oscillator LO12 in the microwave band, and two mixer circuits M1 and M2. The COD, the pilot signal modulator MOD, the transmission filter BPF-T, and the E / O converter (E / O) are connected to the terminal 5b of the frequency generation circuit (Synthesizer) from the reference signal input terminal 2. The reference signal frequency signal f _REF1 is connected, and three types of frequencies f _p1s , f _p2s , and f _L11 are generated using the reference signal frequency signal f _REF1 as a reference, and the output terminal 1b of the frequency generation circuit (Synthesizer) is output. Output from terminal 2b and microwave oscillator control output terminal 4b.

  At the same time, the pilot signal P1s from the output terminal 1b is sent to the IF signal input terminal 1a for the multiplexing, the pilot signal P2s from the terminal 2b is sent to the terminal 1e of the pilot signal modulator MOD, and the pilot signal modulator The modulated signal from the output terminal 2e and the IF signal from the output terminal 1 are input from the input terminal 3a and the input terminal 2a of the multiplexing circuit (multiplexing). Then, a signal output of a plurality of waves obtained by combining from the output terminal “out” of the combining circuit (combining) and a third output signal from the frequency generating circuit (Synthesizer) 3b are combined with the mixer circuit. Heterodyne conversion is performed by M1. The converted signal thus obtained is frequency-converted into a microwave band by the second local oscillator LO12 in yet another mixer circuit M2, and this microwave signal is converted to a microwave having only the transmission frequency via the transmission filter BPF-T. After the electrical signal is obtained, it is configured to be converted into an optical signal by an E / O converter and output from the optical signal output terminal 3.

The reception conversion device includes a demultiplexing circuit (demultiplexing), a frequency generation circuit (Synthesizer), a second local oscillator LO22 in the microwave band, three mixer circuits M3, M4, and M5, a bandpass filter BPF1, a bandpass filter BPF2, The optical signal input terminal 4 includes an O / E converter O / E, a reception filter BPF-R, a pilot signal demodulator DEMO1, a pilot signal demodulator DEMO2, an auxiliary signal decoder DEC, and an auxiliary signal output terminal 8. The optical signal is a microwave band signal converted into an electric signal by the O / E converter O / E, and the local oscillator LO22 is connected to the mixer circuit M3. The pilot signal from the microwave output terminal 1c of the demultiplexing circuit (demultiplexing) is a pilot signal. The pilot signal demodulator DEMO1 is connected to the demodulator DEMO1 and the pilot signal demodulator DEMO2, the output of the pilot signal demodulator DEMO1 is supplied to the terminal 5d of the frequency generation circuit (Synthesizer) via the BPF 2, and the pilot signal demodulator DEMO1 output is further connected to the auxiliary signal. Connected to the decoder DEC, the decoded output is connected to the auxiliary signal output terminal 8. The signal (frequency is f _p1r ′) from the output terminal 1c of the branching circuit (demultiplexing) and the generation frequency f _p1r from the output terminal 1d of the frequency generation circuit (Synthesizer) are mixed by the mixer circuit M5. The output of the difference frequency f _p1r ′ −f _p1r and the output from the demultiplexing output terminal 2c are connected to the mixer circuit M4, and the output of the mixer circuit M4 is IF through the band-pass filter BPF1. It is configured to be output to the signal output terminal 5.

Further, the reference frequency f _REF2 is output from the reference frequency output terminal 6 from the terminal “8” of the frequency generation circuit (Synthesizer).

  The operation of the circuit of the third embodiment differs from the first embodiment in the following points.

In the transmission converter,
(1) First, the transmission method of the reference signal is that the frequency of the difference between the two pilot signals is changed to the modulation frequency of the pilot signal. In the pilot signal modulator MOD, the terminal of the frequency generation circuit (Synthesizer) 6b, for example, an FM-modulated modulated signal using, as a modulation signal, a frequency that is an integer of the reference frequency and a pilot signal P2 from the output terminal 2b of the frequency generation circuit (Synthesizer) as a carrier wave. (Multiplexing) input from the 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, receives an auxiliary signal from the auxiliary signal input terminal 7 for inputting a low-speed auxiliary signal such as a remote control signal, and the like. It is converted into a code as an AM modulation input by an auxiliary signal encoder, and low-speed AM modulation is performed. The auxiliary signal is, for example, an on / off signal for control or monitoring.

(3) A microwave signal in a frequency band to be transmitted is selected from the output of the mixer circuit M2 by the transmission filter BPF-T, and an electrical signal is converted into an optical signal by the E / O converter E / O. A straight line is converted and output from the optical signal output terminal 3.

In the receiving conversion device,
(1) An optical signal from the optical signal input terminal 4 is converted into an electric signal of a microwave band by the O / E converter O / E, and a microwave reception of a necessary band is received via the reception filter BPF-R. A signal is input to the mixer circuit M3.

(2) The frequency f _p1r ′ of the pilot signal P1 demultiplexed and extracted from the IF signal input terminal 1c of the demultiplexing circuit (demultiplexing) and the generation frequency f _p1r from the output terminal 1c of the frequency generation circuit (Synthesizer) _Are mixed by the mixer circuit M5 and given to the mixer circuit M4 as a local signal of the difference frequency f _p1r ′ −f _p1r . (Contrary to the first embodiment, the pilot signal P1 added to the lower side of the main signal is used for local signal processing in the second reception conversion, that is, for frequency / phase fluctuation cancellation.)
(3) The modulated pilot signal P2 demultiplexed and extracted from the microwave output terminal 3c of the demultiplexing circuit (demultiplexing) is FM demodulated by the first pilot signal demodulator DEMO1, and bandpass from the demodulated signal. Only the modulation frequency component is extracted by the filter BPF2, the obtained single frequency signal is given as a reference frequency input of the frequency generation circuit (Synthesizer), and the frequency generation circuit (Synthesizer) is based on the same reference frequency as the transmission side. Realize operation.

    (4) The modulated pilot signal P2 demultiplexed and extracted from the microwave output terminal 3c of the demultiplexing circuit (demultiplexing) is AM demodulated by the second pilot signal demodulator DEMO2 and demodulated by the auxiliary signal decoder. An auxiliary signal is obtained from the signal code.

  Although the above 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. This is possible by providing an E / O converter for conversion and an O / E converter for linearly converting again to an electric signal on the receiving side.

Next, since the modulation signal FM-modulated to the pilot signal P2 on the transmission side is generated based on the reference frequency f _REF1 on the transmission side, the demodulated signal obtained by FM demodulation on the reception side is the same as the modulation frequency between the transmission side and the modulation frequency. It is well known that the frequency of the modulated signal of the modulated signal before and after frequency conversion does not fluctuate even if the modulated signal is frequency-converted, and the reference signal frequency on the receiving side using this demodulated signal as a reference signal By generating f _REF2 , the reference frequency f _REF1 on the transmission side and the reference signal frequency f _REF2 on the reception side can be made exactly the same.

  The pilot signal for canceling the frequency / phase fluctuation does not necessarily need to be the pilot signal P2 on the higher frequency side than the main signal as in the first and second embodiments. It can be understood from the fact that there may be no restriction on the pilot signal frequency in the explanation of the effect of the first embodiment, in particular, in the explanation 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 frequency lower than that of the main signal is used.

  Thus, since it is possible to generate exactly the same reference frequency on the transmission side and the reception side, even when the pilot signal P1 is used, the pilot signal P1 is converted together with the main signal in the transmission conversion apparatus, and the reception apparatus The pilot signal P1 that is converted together with the main signal in M3 and extracted from the branching circuit (demultiplexing) is subjected to the same fluctuation as the frequency and phase fluctuations that the main signal has received by the frequency conversion. Therefore, it can be used to generate a local signal for canceling the frequency / phase fluctuation of the IF signal, that is, the M5 output, exactly as in the first embodiment, and further, as described above, the transmitting side and the receiving side Since it is possible to generate the same reference frequency, the IF output and the reference frequency of the same frequency are output as in the first embodiment. No. transmission device can be realized.

  Further, in this embodiment, since the pilot signal modulator MOD has an AM modulation function by the modulation input terminal 4e, a low-speed auxiliary signal such as a remote control signal from the auxiliary signal input terminal 7 is supplied to the auxiliary signal input terminal 7e. When converted into a code as an AM modulation input by a signal encoder and given to the modulation input terminal “4” as a low-speed AM modulation signal, the pilot signal P2 undergoes shallow AM modulation in addition to FM modulation. However, since this AM modulation has a low speed and a low modulation degree, it does not affect the reference frequency component extraction by the FM demodulation. Thus, the auxiliary signal can be transmitted. The auxiliary signal can be used, for example, for transmitting an on / off signal for control or monitoring.

  In this embodiment, for the transmission of the auxiliary signal, an example in which AM modulation is performed on the pilot signal for reference frequency transmission has been shown. However, the pilot signal of the first and second embodiments is low in speed and low modulation. Even if AM modulation is performed, auxiliary signals can be transmitted without impairing frequency synchronization and frequency / phase fluctuation removal functions.

  Although not shown in any of the embodiments, signal level detection for realizing the AGC function of the signal transmission apparatus is performed by extracting and detecting at least one of the pilot signals added in these embodiments. Is easily realized.

  As described above, even in an apparatus that converts microwaves into optical signals by linear conversion, the frequency / phase noise reduction of the present invention and accurate transmission of IF and reference frequencies are possible, and an optical fiber transmission network is used. Thus, it is possible to provide an excellent signal transmission apparatus that can easily realize the construction of the existing SFN broadcasting system.

Further, the IF signal output terminal 5 of the output of the reception conversion device can obtain an IF signal obtained through four frequency conversions. As shown below, at the output of the transmission conversion device, the main signal The center frequencies of P1 and P2 are
Transmission conversion output main signal: f _IF11 + f _L11 + f _L12
Transmission conversion output P1 signal: f _P1s + f _L11 + f _L12
Transmission conversion output P2 signal: f _P2s + f _L11 + f _L12
It becomes.

In the receiving conversion device, the intermediate frequency by the first frequency conversion is
Receiving intermediate converted main _{signal: f IF22 = f IF11 + f} L11 + f L12 - f L22
Received intermediate output P1 signal: f _P1r '= f _P1s + f _L11 + f _L12 -f _L22
Received intermediate output P2 signal: f _P2r '= f _P2s + f _L11 + f _L12 -f _L22
It becomes.

As a result,
Received final conversion main signal: f _IF21 = f _IF22- (f _P1r '-f _P1r )
_{= F IF11 + f L11 + f} L12 - f L22 - (f P1s + f L11 + f L12 - f L22
-f _P1r )
_{= F IF11 - (f P1s -} f P1r)
If the frequency f _P2s of the pilot signal P2 generated based on the reference frequency on the transmission side and the frequency f _P2r of the pilot signal P2 generated based on the reference frequency on the reception side are exactly the same frequency, the final reception conversion center frequency f _{IF 21} of the main signal is completely coincident with the center frequency f _{IF 11} of the main signal from the IF signal input terminal 1 of the transmission converter, it can be seen that no frequency deviation of the main signal due to transmission.

This is the same as in the first and second embodiments, regardless of fluctuations in the local oscillation frequency (f _L12 , f _L22 ) of the microwave band used for frequency conversion of the transmission conversion device and the reception conversion device. Thus, a transmission device that does not cause a frequency shift of the main signal is realized.

The reference frequency of the transmission conversion device can be locked to the reference signal from the outside by generating the reference signal from the reference signal input terminal 2 as a reference. The reference frequency f _REF2 reproduced at the same frequency as the side can be output from the reference frequency output terminal 6.

  As described above, the IF main signal has no frequency deviation without being affected by the frequency fluctuation / phase fluctuation of the microwave band local oscillator LO12 of the transmission conversion apparatus and the microwave band local oscillator LO22 of the reception conversion apparatus. In addition, it is possible to stably transmit a reference signal having no frequency shift.

As explained above, also in the signal transmission device of this embodiment,
(1) The requirements for the performance of the microwave local oscillator, that is, the frequency accuracy, the frequency stability, the frequency / phase noise, and the microphonic noise, which were the biggest problems in the prior art, are extremely relaxed, and within the currently established technical scope. Can be realized economically.

    (2) In a terrestrial digital television broadcasting system, the frequency of each station's broadcast wave is matched by distributing the OFDM modulated IF signal from the same studio to the broadcasting device of each broadcasting station by the signal transmission device of this embodiment. Therefore, it is possible to expect an excellent effect that terrestrial digital television broadcasting by SFN (single frequency network) can be easily realized.

    (3) Furthermore, since auxiliary signals can be transmitted, there is no need to provide a separate line for remote control or monitoring signals when used in a relay device for distributing broadcast waves from the studio to each broadcasting station. .

Such an excellent transmission device is realized.

1 is a block diagram of a signal transmission apparatus according to a first embodiment of the present invention. Conventional signal transmission device block diagram Example of pilot signal and main signal arrangement Block diagram of signal transmission apparatus according to second embodiment of the present invention Block diagram of an SFN broadcasting system using the transmission apparatus of the present invention The block diagram explaining the other utilization form of the signal transmission apparatus of this invention Block diagram explaining the configuration of the frequency generator

Explanation 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

Claims (4)

A signal transmission system for converting a main signal in an IF (intermediate frequency) band to a transmission frequency band on the transmission side and transmitting the signal and converting a received transmission frequency band signal to an IF band on the reception side to obtain the main signal. In the relay device used,
The transmission side of the system generates first and second pilot signals having a certain frequency difference from each other based on the reference frequency signal, and the first and second pilot signals are used as the lower band and the upper band of the main signal. A transmission signal is generated by allocating to both or arranging and synthesizing the signals together in either one, and frequency-converting this transmission signal to the transmission frequency band and transmitting it,
The receiving side of the system receives the signal in the transmission frequency band, converts the frequency of the received signal to the IF band to obtain the combined signal, and combines the combined signal with the main signal and the first and second signals. A pilot signal is separated, a frequency difference between the separated first and second pilot signals is obtained, a signal having the same frequency as the reference frequency signal on the transmission side is reproduced based on the frequency difference, and the reproduced signal is reproduced. When performing the frequency conversion of the received signal based on the reference frequency signal
A signal in the transmission frequency band is received, the received signal is frequency converted to the IF band to obtain the synthesized signal, and the synthesized signal is separated into the main signal and the first and second pilot signals. Then, a frequency difference between the separated first and second pilot signals is obtained, a signal having the same frequency as the reference frequency signal on the transmission side is reproduced based on the frequency difference, and based on the reproduced reference frequency signal A receiving unit for performing frequency conversion of the received signal;
Generates the reference frequency signal internally, has a certain frequency difference from each other based on the reference frequency signal, and distributes to both the lower band and the upper band of the main signal or arranges them together First and second pilot signals are generated, a transmission signal is generated by combining the first and second pilot signals with the main signal, and the transmission signal is frequency-converted to the transmission frequency band. A relay apparatus comprising: a transmitting unit that transmits the data. It said first and second pilot signals, the relay apparatus according to claim 1, characterized in that the frequency of the frequency difference is equal to the frequency of the reference frequency signal. The transmitting unit modulates the first and second pilot signals and combines them with the main signal, and the receiving unit converts the combined signals into the main signal and the first and second pilot modulation signals. Separating, demodulating the separated first and second pilot modulation signals, obtaining a frequency difference between the demodulated first and second pilot signals, and reproducing the reference frequency signal based on the frequency difference The relay apparatus according to claim 1, wherein: The transmitting unit receives an auxiliary signal and modulates the first and second pilot signals, and the receiving unit demodulates the auxiliary signal from the first and second pilot modulation signals. The relay device according to claim 3 .

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