JPH01164183A - Multiplex transmission signal reproducing device - Google Patents

Abstract

PURPOSE:To reduce the disturbance between multiplex-transmitted signals by an orthogonal modulation by detecting the deterioration degree of transmission line characteristics by a transmission line analyzing circuit and making the transmission line characteristics closer to ideal transmission line characteristics by a transmission line correcting circuit. CONSTITUTION:After a necessary band is selected out of the output of a frequency converting circuit 3 by a band pass filter 12, and the transmission line characteristics are corrected through a transmission line correcting circuit 13, a signal multiplex- transmitted in an orthogonal direction to an amplitude modulation components is detected and demodulated at a synchronization detecting circuit 16 by using another signal, which is synchronized with the carrying path reproduced in a carrier wave reproducing circuit 15. At a transmission line analyzing circuit 14, the deterioration degree of the transmission line is detected from the output signal waveform of the transmission line correcting circuit 13, and a negative feedback is executed so that the characteristics of the transmission up to the output of the transmission line correcting circuit 13 can be corrected. Thus, the disturbance between multiplex signals caused by the deterioration of the transmission line such as the ghost of the signal multiplex-transmitted by the orthogonal modulation can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multiplex transmission system, and more particularly to a multiplex transmission signal reproducing apparatus for receiving a transmission signal in which other information is multiplexed onto a current television signal.

[Conventional technology]

Conventionally, a method for multiplexing other information onto a television signal is as described in Japanese Patent Laid-Open No. 49-84728.
An orthogonal modulation method has been known in which a carrier wave having an orthogonal phase relationship with a video carrier wave is modulated with other information, combined with a video carrier wave modulated by a video signal, and transmitted.

On November 27, 1986, the Association published a report on adding the inverse characteristics of the Nyquist filter of the television receiver to the multiplexed signal on the transmitting side as a method for reducing interference caused by multiplexed signals to current television receivers using this orthogonal modulation method. IEICE Technical Research Report, published by IEICE Corporation, V
OL, 86 NIL 246, pages 65 to 72, communication system No. 586-82 [Transmission of high-definition images by orthogonal modulation of video carrier waves] is discussed.

In addition, a method for removing interference caused by ghosts in current television broadcast receivers is to set up a group of delay elements as described in Japanese Patent Publication No. 62-4894, and send a signal delayed by the time corresponding to the ghost to the delay element. It is known that after selection from the group, the amplitude corresponding to the level of the ghost is removed by a gain polarity adjustment circuit. A known method for measuring ghost delay time is to measure the time between the edge of a vertical sync pulse of a television signal and the edge of a vertical sync pulse caused by a ghost, as described in Japanese Patent Publication No. 61-60658. ing.

[Problem that the invention seeks to solve]

The above conventional technology does not take into account deterioration of transmission path characteristics due to ghosts etc. in orthogonal modulation transmission.
There was a problem of interference between multiplexed signals.

SUMMARY OF THE INVENTION An object of the present invention is to provide a multiplex transmission signal reproducing device that is effective in reducing multiplex signal amount interference due to deterioration of transmission path characteristics such as ghosting of signals multiplexed by orthogonal modulation.

[Means for solving problems]

The above purpose is to provide a transmission line correction circuit that inputs a multiplexed transmission signal and corrects deterioration of transmission line characteristics, and a transmission line analysis circuit that analyzes the output waveform of the transmission line correction circuit to detect deterioration of transmission line characteristics. This is achieved by controlling the transmission line correction circuit with the output of the transmission line analysis circuit.

[Effect]

The transmission path analysis circuit detects the deviation of the transmission path characteristics from the originally ideal characteristics, and the transmission path correction circuit operates to bring them closer to the ideal transmission path characteristics, thereby eliminating interference between signals multiplexed by orthogonal modulation. can be reduced.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a television receiver according to an embodiment of the present invention.

1 is an antenna, 2 is a high frequency amplification circuit, 3 is a frequency conversion circuit, 4 is a reproduction IF filter for the receiver, 5 is an intermediate frequency amplification circuit, 6 is a video signal detection circuit, 7 is a video signal processing circuit, 8 is a video Signal output terminal, 9 is an audio intermediate frequency amplification circuit, 10 is an audio FM detection circuit, 11 is an audio signal output terminal, 12 is a band pass filter, 2 is a transmission path correction circuit, 2 is a transmission path analysis circuit, 15 is an audio signal output terminal. 1 is a carrier wave regeneration circuit, 16 is a synchronous detection circuit, 17 is a signal processing circuit for multiplexed signals, 1
8 is an output terminal for multiplexed signals, 1001.100
2゜1003, 1004, 1005 are delay circuits, 10
06 , 1007° 1008 , 1009 , 1010
, 1011 is a variable gain amplifier circuit, 1012 is an adder circuit, 1021 is a waveform memory, 1022 is a cepstrum analysis circuit, and 1023 is a gain control circuit.

The television signal input from the antenna 1 is amplified by the high-frequency amplifier circuit 2, frequency-converted to an intermediate frequency for demodulation by the frequency conversion circuit 3, and transmitted through the reproduction IF filter 4 for the receiver to the intermediate-frequency amplifier circuit 5. Amplify with. Tuning is performed by changing the local oscillation frequency of the frequency conversion circuit 3. The video signal band from the signal amplified by the intermediate frequency amplifier circuit 5 is detected by a video signal detection circuit 6, and the video signal is processed by a video signal processing circuit 7 to obtain a video signal at a video signal output terminal 8.

On the other hand, for the audio signal band, the audio intermediate frequency amplification υ1
The signal is amplified by the path 9, detected and demodulated by the audio FM filter circuit 10, and an audio signal is obtained at the audio signal output terminal 11.

The above is the same as a conventional television receiver.

In addition to the above, in order to reproduce multiplexed signals,
Perform the following actions. A necessary band is selected from the output of the frequency conversion circuit 3 by a band pass filter 12, and the transmission path characteristics are corrected by passing the output through a transmission path analysis circuit, and then the amplitude is determined using a signal synchronized with the carrier wave regenerated by a carrier wave regeneration circuit 15. A synchronous detection circuit 1 detects signals that are multiplexed and transmitted orthogonally to the modulation components.
6 for detection demodulation. The output is processed by a signal processing circuit 17 and obtained at an output terminal 18 for multiplexed signals. The transmission line analysis circuit detects the degree of deterioration of the transmission line from the output signal waveform of the transmission line correction circuit RO, and provides negative feedback so as to correct the characteristics up to the output of the transmission line correction circuit RO.

In FIG. 1, a delay circuit 1001 is used as a transmission path correction circuit U.
1005, variable gain amplifier circuits 1006 to 1011, and an adder circuit 1012, a transmission path analysis circuit 1 and a waveform memory 1021 are used.
A cepstrum analysis circuit 1022 and a gain control circuit 1023 detect the delay time by Fourier transforming the transmitted waveform twice.
An example is shown below. This configuration is particularly effective in correcting transmission path deterioration due to ghosts. The output signal waveform of the transmission line correction circuit is stored in a waveform memory 1021K. The cepstrum analysis circuit 1022 performs a Fourier transform on the waveform to obtain the power spectrum of the output signal of the transmission line correction circuit H, and performs so-called cepstrum analysis in which the envelope a of the spectrum is Fourier-transformed again. Find the delay time and amplitude of the ghost added to the output signal. A negative feedback loop is configured to change the gain of the variable gain circuit of the delay circuit output corresponding to the delay time of the obtained ghost.

As a result, ghosts in the output signal of the transmission line correction circuit are reduced. Furthermore, the waveform memory 1021 and cepstrum analysis circuit 1022 calculate the delay time and amplitude from the signal with reduced ghosts, and further change the gain control circuit 1023 so that the cepstrum is reduced.
Remove.

In addition to ghosts in television transmission, cepstral analysis can also detect ripples within the passband that are sometimes seen in bandpass filters configured with surface acoustic wave filters (hereinafter referred to as SAW filters), so transmission This can be corrected by the path correction circuit 7υ-.

According to this embodiment, the degree of deterioration of the transmission line is detected from the output signal of the transmission line correction circuit H by the transmission line analysis circuit LOW,
Since the transmission path can be corrected by negative feedback to the transmission path correction side #8m, it is possible to bring the transmission path closer to an ideal state and stably demodulate all multiplexed signals.

FIG. 2 shows an example of the signals transmitted and generated by the transmitter of the present invention in the above embodiment. 31 is an audio signal input terminal; 5
2 is an FM modulator, 36 is an audio signal carrier generator, 54 is a video signal input terminal, 35 is a video signal processing circuit, 36 is a video modulator, 37 is a video signal carrier generator, and 58 is a residual sideband amplitude. A transmission VSB filter for modulation, 39 is an adder, 40 is an antenna, 41 is an input terminal for multiplexed signals, 42 is a signal processing circuit for multiplexed signals, 45 is a phase shifter, 44 is a modulator, 45 is an equalizer, 46 is a band pass filter, and 47 is an adder.

The audio carrier wave from the audio signal carrier generator 53 is FM-modulated by the audio signal from the audio signal input terminal 31 in the FM modulator 32 . A video signal processing circuit 35 performs video signal processing on the video signal input to the video input terminal 34 for television transmission, such as luminance signal processing and color difference signal processing of a luminance signal and a color difference signal. Then the video signal carrier generator 3
The carrier wave from 7 is modulated using a video modulator 36, band-limited to the television broadcast band by a transmission VSB filter 38, added to the audio signal by an adder 39, and transmitted through an antenna 40.

The above is the same as conventional terrestrial television broadcasting. Add the following to transmit a signal to be multiplexed to the above signals.

A signal to be multiplexed is added to the input terminal 41, and the signal processing circuit 42
Processes the signal into a form that is easy to transmit. With that signal, phase shifter 4
3, the video signal carrier wave phase-shifted by 90 degrees is transmitted to the modulator 4.
Modulate with 4. After that, the frequency characteristics are corrected by an equalizer 45 having characteristics opposite to those of the video reception IF Nyquist filter, and the band is limited by a bandpass filter 46.
7, it is added to the carrier wave modulated by the video signal. As a result, the video carrier wave is modulated in an orthogonal relationship by the video signal and the multiplexed signal. equalizer 45
This is because the multiplexed signals have an orthogonal relationship when detecting the video of the Nyquist filter output of the television receiver, and a detailed explanation can be found in "Transmission of high-definition images by orthogonal modulation of video carrier waves" explained in the conventional technology. It is omitted here because it is shown here.

FIG. 3 shows the modulated spectrum, and FIG. 4 shows a vector diagram of the modulation state of the video signal of the video carrier wave and the signal to be multiplexed.

In FIG. 3, 51 is the spectrum of the video signal after the VSB filter, 52 is the spectrum of the FM-modulated audio signal, and 53
shows the spectrum of the signal to be multiplexed and transmitted. Here, the video signal spectrum 51 and the spectrum 5 of the signal to be multiplexed are transmitted.
2 is shown divided into two stages in FIG. Furthermore, the spectrum of the signal to be multiplexed and transmitted is shown when the carrier wave is modulated in a band of 500KH2. Note that the spectrum 53 of the signal to be multiplexed and transmitted is shown as a spectrum with the characteristics of the equalizer 45 omitted.

In FIG. 3 -0.75 MH for the video carrier.

The following spectra are attenuated by a VSB filter with vestigial sideband amplitude modulation.

Up to 4.2 MHz, a video signal exists, and near 4.5 MHz there is a spectrum in which the audio carrier wave is FM modulated. ±o with respect to the video carrier wave, and since both sidebands are transmitted for 75 MHz, general amplitude modulation (DSB
). If the amplitudes modulated by multiplexed signals within ±0.75 MHz orthogonal to the carrier wave having both sidebands are A and -A, the vector of the carrier wave is ωat±Athωct(t). Here, ωC is the angular frequency of the carrier wave.

It is.

In addition, if the slope of the VSB filter is also taken into consideration, it will be 1 to 1.
．． Multiplex transmission at 25 MHz is also possible.

Another embodiment of the invention is shown in FIG. Components with the same symbols as in FIG. 1 indicate the same functions. The difference from FIG. 1 is that the signal regenerated by the carrier regeneration circuit 15 from the output signal of the transmission path correction circuit H is applied to the video signal detection circuit 6, and the video signal is synchronously detected.

According to this embodiment, the carrier wave for synchronous detection of video signal detection can be regenerated stably, so in addition to the effect of stably demodulating the multiplexed signal shown in FIG. 1, the video signal can also be stably demodulated. effective.

Still another embodiment of the invention is shown in FIG. Reference numeral 61 is a video signal ghost removal circuit, and the same reference numerals as in FIG. 5 indicate the same functions. In this embodiment, a ghost removal circuit 61 is added to FIG. 5, and ghost components are removed from the synchronously detected video signal.

According to this embodiment, ghosts can be removed after the video signal is synchronously detected using a stably reproduced carrier wave, so there is an effect that the video signal can be demodulated stably and with less ghosts.

Still another embodiment of the invention is shown in FIG. 72 is a band pass filter, 71 is a frequency conversion circuit, and the same symbols as in FIG. 1 indicate the same functions.

The difference from FIG. 1 is that a bandpass filter 72 and a frequency conversion circuit 71 are provided in order to lower the frequency for demodulating the multiplexed signal than the frequency for demodulating the video signal.

According to this embodiment, the intermediate frequency of the output of the frequency conversion circuit 3 (58.75 MH for Japanese terrestrial television broadcasting,
The synchronous detection circuit demodulates the video signal using the frequency conversion circuit 71 (often used for boat fishing), and demodulates the multiplexed signal using the lower intermediate frequency (for example, about 5 MH2) output from the frequency conversion circuit 71. By lowering the frequency, the phase error due to the circuit delay time of the carrier wave regenerated by the carrier wave regeneration circuit 15 used in the carrier wave regeneration circuit 15 used in the carrier wave regeneration circuit 16 is reduced, and there is an effect that the multiplexed signal can be stably demodulated.

Still another embodiment of the present invention is shown in FIG. 8. 0 The same reference numerals as in FIGS. 1 and 7 indicate the same functions. 71 is a frequency conversion circuit, 73 is a mixing circuit, 74 is a voltage-controlled local oscillator, 75 is a reference signal generator, 76 is a low-pass filter, and the frequency conversion circuit 71 in FIG. It consists of a local oscillator 74.

The difference from FIG. 7 is that in FIG. 7, the signal is regenerated by the carrier wave reproducing circuit 15, modulated and multiplexed by being orthogonal to the video signal of the carrier wave, and detected by the synchronous detection circuit 16. In comparison, in FIG. 8, the modulation by the multiplexed signal and the modulation by the video signal are orthogonal, and the phase difference between the reference signal generator 75 and the intermediate frequency signal including the carrier wave is detected by the synchronous detection circuit. 16 and low pass filter 76
By detecting the signal and feeding it back to the voltage-controlled local oscillator 74, the intermediate frequency carrier wave is synchronized with the output of the reference signal generator, and the output of the synchronous detection circuit 16 is used as the detected output.

According to this embodiment, since it is a negative feedback loop in which the intermediate frequency for demodulation matches the frequency of the reference signal generator 75, the frequency deviation of the bandpass filter 120 due to frequency drift of the frequency conversion circuit 3, etc. and the demodulation frequency drift This embodiment has the effect of making demodulation more stable than the embodiment shown in FIG. 7.

Still another embodiment of the present invention is shown in FIG. Reference numeral 81 is a baseband ghost removal circuit, and the same reference numerals as in Fig. 7 indicate the same functions. This embodiment differs from FIG. 7 in that the output signal of the synchronous detection circuit 16 is further passed through a baseband ghost removal circuit 81. The deterioration of the transmission path characteristics caused by ghosts and the like is detected by the transmission path analysis circuit (2), and after the transmission path characteristics are corrected by the transmission path correction circuit 18H, the signal is detected with the multiplexed signal by the synchronous detection circuit 16. From the detected output signal, a ghost is further detected using a transmitted signal such as a synchronization signal, as described in Japanese Patent Publication No. 61-60638, which describes the prior art, and the ghost is removed.

According to this embodiment, the ghost removal effect is increased by the transmission path analysis circuit 2 before detection and the baseband ghost removal circuit a after detection. Further, in areas where ghosts are so large that even synchronization signals such as television broadcast signals cannot be reproduced due to ghosts, the baseband ghost removal circuit alone will not work because the synchronization signals cannot be detected.

However, according to this embodiment, the transmission path analysis circuit 81 has a ghost removal effect and the ghosts in the output of the synchronous detection circuit 16 are reduced, so the baseband ghost removal circuit 81 can operate stably and the multiplex transmission This has the effect of stably demodulating the signal.

Still another embodiment of the present invention is shown in FIG.

82 is an analog-to-digital conversion circuit (hereinafter referred to as ADC).
83 is a digital-to-analog conversion circuit (hereinafter abbreviated as DAC), and the same reference numerals as in FIG. 9 indicate the same functions. This embodiment shows an example in which the transmission line correction circuit (2) and the transmission line analysis circuit (ILk) are constructed from a digital circuit.

According to this embodiment, since the transmission line correction circuit U and the transmission line analysis circuit can be constructed of digital circuits, there is an effect that the circuit operation can be stabilized.

Still another embodiment of the present invention is shown in FIG.

Components with the same symbols as in FIG. 10 indicate the same functions. In this embodiment, the transmission path correction circuit U, the transmission path analysis circuit, the carrier regeneration circuit 15, the synchronous detection circuit 16, the baseband ghost removal circuit 81, and the signal processing circuit 17 for multiplexed signals are configured with digital circuits. This is an example of a case.

According to this embodiment, the signal processing circuit 17 for multiplexed signals from the transmission path correction circuit to the signal processing circuit 17 can be constructed of digital circuits, which has the effect of stabilizing the circuit operation.

Although FIGS. 10 and 11 show examples in which part of the configuration of the embodiment is constructed using digital circuits, it is generally better to use digital circuits for parts that can be constructed using digital circuits in other figures as well. Stable circuit operation is maintained.

Another embodiment of the invention is shown in FIG. 1 is a transmission path correction circuit, 1 is a transmission path analysis circuit, 2001 is a variable band pass filter, 2002 is a waveform memory, 2006 is a spectrum analysis circuit, 2004 is a control circuit, and the same symbols as in FIG. Shows the same functionality.

In this embodiment, a variable bandpass filter 2001 is used as a transmission path correction circuit, a waveform memory 2002 is used as a transmission path analysis circuit 141-, a spectrum analysis circuit 2003 for Fourier transforming a transmission waveform to obtain a spectrum, and a control circuit 2004 are used. An example of the configuration is shown below. The output signal waveform of the transmission line correction circuit and series is stored in the waveform memory 2002. The spectrum analysis circuit 2005 performs Fourier transform on the waveform to obtain a spectrum. The control circuit 2004 is designed to gradually change the tuning point of the variable bandpass filter from a high-level frequency to a low-level frequency so that this spectrum becomes flat or symmetrical with respect to the carrier wave.
is a negative feedback loop that controls the variable bandpass filter 2001.

According to this embodiment, the transmission path can be corrected by the transmission path analysis circuit V1 from the output signal of the transmission path correction circuit so that the transmission spectrum is flat or symmetrical with respect to the carrier wave. It is possible to reduce leakage from the video signal to the orthogonal component due to the asymmetry of the transmission path amplitude characteristics, and there is an effect that the multiplexed signal can be stably demodulated.

Yet another embodiment of the invention is shown in FIG.

101 is a transmission path analysis correction circuit, which is shown in FIGS. 1, 6,
Components with the same symbols as in FIGS. 9 and 12 indicate the same functions. The transmission line analysis and correction circuit 101 can be configured by a combination of a transmission line correction circuit or a transmission line correction circuit j± and a transmission line correction circuit or a transmission line analysis circuit 141-. In this embodiment, a transmission path analysis correction circuit 101 and a ghost removal circuit 61t are provided in the video signal transmission system, and a baseband ghost removal circuit 81 is also provided in the multiplexed signal system.

According to this embodiment, it is possible to stably demodulate multiplexed signals and also stably demodulate video signals.

FIG. 14 shows the spectrum near the video carrier wave in television broadcasting. 151 is the spectrum of the video signal, 1
52 is an envelope of the video signal spectrum. 1st
In the operation shown in FIG. 2 or FIG. 13, when a video signal is received and subjected to SiFourier transformation using the waveform memory 2002 to obtain a spectrum, the spectrum becomes like the spectrum 151 in FIG. 14 when the transmission path characteristics are ideal. - Since television broadcasting during boat fishing is modulated with residual sideband amplitude, the spectrum shown on the left side of FIG. 14 has a narrower spread than the spectrum shown on the right side, so a bandpass filter 12 is provided. The spectrum after passing through the bandpass filter 12 is made to be symmetrical.

However, if the transmission spectrum is inherently asymmetric due to the multiplexing method or transmission method of multiplexed signals, the control circuit 2003 uses the difference between the ideal spectrum as a reference and the result of spectrum analysis from the waveform as the output signal of the spectrum analysis circuit 2003. It is necessary to output to . An example of that case is shown in FIG. Furthermore, when spectrum is analyzed from a waveform at a certain time interval, it is possible that the spectrum may change depending on the transmission content, so in such a case, it is possible to reduce analysis errors by averaging the results of several spectrum analyzes.

In addition, spectrum 1 of television broadcasting shown in FIG.
When the cepstrum is obtained by performing Fourier transform from 51, the level change in the spectrum for each fH, which is expressed by the strength of correlation for each horizontal scanning line period of the video signal, is expressed as a delay time of 1/fH, as shown in Fig. 15. It becomes a cepstrum as shown in . Since this cepstrum is not caused by ghosts and is unique to video signals, either obtain the cepstrum by Fourier transforming the spectrum envelope 152 in Figure 14, or obtain the cepstrum using ideal transmission without ghosts as shown in Figure 15. Finally, it is necessary to use the difference between the cepstrum and the cepstrum from the transmitted waveform as the output signal of the cepstrum analysis circuit 1022. An example of that case is shown in FIG.

16 and 17, 2003 is a spectrum analysis circuit, 161 is a spectrum analysis circuit input terminal, 1
62 is a spectrum analysis circuit output terminal, 163 is a spectrum analysis circuit, 164 is a reference spectrum generation circuit, 165
is a subtraction circuit, 1022 is a cepstrum analysis circuit, 171
is a cepstrum analysis circuit input terminal, 172 is a cepstrum analysis circuit output terminal, 173 is a cepstrum analysis circuit,
174 is a reference cepstrum generation circuit, and 175 is a subtraction circuit.

According to the spectrum analysis circuit or cepstral analysis circuit shown in Fig. 16 or 5X17, the ideal transmission shape B
Since the difference can be output as an analysis result based on the reference value, it is possible to easily correct the transmission path even when transmitting a signal with a complex transmission signal spectrum.

When multiplexing another signal onto a television signal, it is advantageous to have the inter-signal spectrum fully frequency interleaved in terms of reducing signal amount interference, so let us consider such a case. FIG. 18 shows a spectrum when a spectrum 181 of a signal to be multiplexed and transmitted is multiplexed onto a video signal spectrum 151 of a television signal. In such a case, when the spectrum analysis circuit 2003 and the cepstrum analysis circuit 1022 perform the spectrum analysis, the data of the spectrum analysis results are converted to (FFT) for each frequency fH corresponding to the horizontal scanning line period starting from the video carrier wave.
information related to the video signal is extracted by extracting (on the data of It is also possible to extract signal-related information. FIG. 19 shows the data area after Fourier transform of the waveform. 191 is the data after Fourier transform.The data after Fourier transform is stored in data area 1.
After being stored once in 91, it is separated into a data area 192 and a data area 195 for each row. Cepnutrum analysis is performed from each of the output data, and the difference from each other reference spectrum or reference cepstrum can be used as a spectral analysis output or a cepstrum analysis output.

By performing these analyzes in line 5, in the case of multiplex transmission with spectra as shown in Figure 18, the spectra between multiplexed signals can be processed separately, allowing more precise control and reducing the signal amount. O [Effects of the Invention] According to the present invention, the transmission path analysis circuit detects the degree of deterioration of the transmission path characteristics, and the transmission path correction circuit can bring the characteristics closer to the ideal transmission path characteristics. This has the effect of reducing interference between signals multiplexed and transmitted using orthogonal modulation.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a multiplex transmission signal reproducing device as an embodiment of the present invention, FIG. 2 is a block diagram of a transmitter corresponding to an embodiment of the present invention, and FIG. 3 is a diagram for explaining the present invention. Spectrum diagram, Figure 4 is a spectrum diagram for explaining the present invention, Figures 5 to 13
The figures are block diagrams of other embodiments of the present invention, Figure 14 is a television signal spectrum diagram for explaining the present invention, Figure 15 is a Keb Nutram diagram for explaining the present invention, Figures 16 and 14 are Fig. 17 is a block diagram of a specific example of a spectrum analysis circuit used in the present invention, Fig. 18 is a multiple signal spectrum diagram for explaining the present invention, and Fig. 19 is a spectrum analysis Fourier transform for explaining the present invention. It is a later data area diagram. 12... Bandpass filter, transmission line correction circuit 1. Lee, ``Yu...Transmission path analysis circuit, 15. ■
...Carrier regeneration circuit, 16...Synchronized detection circuit, 45
... Equalizer, 47 ... Adder, 1021, 2
002... Waveform cutting, 175, 1022... Cepstrum analysis circuit, 1023... Gain control circuit, 16
3, 2003...Spectrum analysis circuit, 2004.
...Control circuit. Fig. 3 Conveying cutting edge “Jikin” 4% (t-7s
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tL/ct 74th layer meeting? 0 Eヱstop Sat f, j□ Ka□ j□ Kef L Reggie Man //
= Figure 78 Figure fH Edition 79

Claims (1)

[Claims] 1. A first carrier wave whose amplitude is modulated by a first signal;
A second carrier wave having a quadrature phase relationship with the first carrier wave, which is amplitude-modulated by the second signal, is received, and a multiplexed transmission signal is transmitted, and the first signal is received from among the multiplexed transmission signals. In the multiplex transmission signal reproducing device for reproducing the second signal as a signal multiplexed with the multiplex transmission signal, extracting a second carrier wave whose amplitude is modulated by the second signal from the received multiplex transmission signal and passing it. A bandpass filter, a transmission line correction circuit that receives the output of the bandpass filter and corrects its transmission line characteristics, and a transmission line that analyzes the output waveform of the transmission line correction circuit to detect the degree of deterioration of the transmission line characteristics. A multiplex transmission signal reproducing device comprising: an analysis circuit; and a control circuit that controls the transmission path correction circuit based on the analysis result of the transmission path analysis circuit. 2. In the multiplex transmission signal reproducing device according to claim 1, when the amplitude modulation is vestigial sideband amplitude modulation, the passband width of the bandpass filter is set to the vestigial sideband amplitude modulation. A multiplex transmission signal reproducing device characterized in that the signal is limited to within a double-sided band. 3. A multiplex transmission signal reproducing device according to claim 1 or 2, wherein the transmission path correction circuit is constituted by a variable bandpass filter. 4. The multiplex transmission signal reproducing device according to claim 1 or 2, wherein the transmission path correction circuit is connected in series to a plurality of delay circuits, a connection end of the plurality of delay circuits;
A multiplex transmission signal reproducing device comprising: a plurality of variable gain amplifier circuits receiving input signals from input/output terminals; and an adder circuit for synthesizing the outputs of the plurality of variable gain amplifier circuits. 5. In the multiplex transmission signal reproducing device according to claim 1, 2, 3, or 4, the transmission path analysis circuit is a Fourier transform circuit that obtains a Fourier transform of an input signal; A multiplex transmission signal reproducing device comprising: a carrier regenerating circuit that regenerates a carrier wave of an input signal; and an arithmetic circuit that obtains transmission path characteristics from the frequency of the output of the carrier regenerating circuit and the spectrum of the output of the Fourier transform circuit. 6. The multiplex transmission signal reproducing device according to claim 1, 2, 3, or 4, in which the transmission path analysis circuit is connected to a first Fourier transform that calculates a Fourier transform of an input signal. A transform circuit, a spectrum calculation circuit that calculates a spectrum from the output of the first Fourier transform circuit, and a second Fourier transform circuit that calculates the Fourier transform of the output of the spectrum calculation circuit or the logarithmically transformed signal of the output thereof. A multiplex transmission signal reproducing device.