JPH0662281A - Ghost detector for received signal - Google Patents

Abstract

PURPOSE:To provide a ghost detector for received signal which can measure the state of ghost on the condition of changing a received electric field with the passage of time. CONSTITUTION:A received signal 1 is synchronously detected by a synchronizing detection circuit 2 and converted to a band limit signal by an LPF 4, a synchronizing component signal is extracted from the detected signal by a horizontal synchronizing separator circuit 5, and a switching control signal is provided by a gate pulse generating circuit 6. A switch circuit 7 inputs the unipolar component signal of a band control signal through a waveform processing circuit 25, this component signal is switched by the switching control signal, and a switching signal is provided. Then, the band of the switching signal is enlarged by the write-in/write-out of a memory 8 based on a clock 9 of the switching signal and the control of a memory mode control circuit 12, and a time compressed processing signal is provided. An inverse scanning signal is provided by a scan inverting circuit 14, and a delay signal delaying the processing signal just for scan inversion processing time is provided by a delay circuit 18. The amplitude of both of signals is modulated by the carrier component signal of a carrier generating circuit 22 at AM amplitude modulators 20 and 21, those signals are inputted to a SAW convolver 23, and a correlation signal containing a significant waveform showing a ghost component is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a received signal ghost detecting apparatus for a television or the like, and more particularly to a received signal ghost detecting apparatus in mobile reception.

[0002]

2. Description of the Related Art A conventional ghost canceller employs a method in which a reference signal in the vertical blanking of a television signal is detected and its waveform distortion is corrected by a transversal filter or the like. The measurement was performed at intervals of 60 seconds (NTSC signal), and it took several seconds until the reference signal was detected and its waveform distortion was corrected.

[0003]

In the above-mentioned conventional method, since it takes time to detect a ghost as described above, it is impossible to measure the ghost occurrence situation in mobile reception, and it is impossible to realize a high-speed ghost canceller. There was a problem. Further, if the SAW convolver is used as it is as a correlator in the above-mentioned conventional system, the time T / n for correlating the convolver is a fraction of the scanning line length of the television, and a ghost with a short delay is detected. There was a drawback that it could not be done (if the time to take the correlation of the convolver is lengthened, the propagation loss increases and it cannot be put to practical use).

The present invention has been made in view of the above problems and drawbacks, and an object of the present invention is to provide a ghost detecting device for a received signal, which can measure a ghost state under the condition that the received electric field changes every moment. And

[0005]

In order to achieve the above object, a received signal ghost detecting apparatus of the present invention synchronously detects a received video signal to obtain a detected signal and converts it into a band-limited signal of a predetermined narrow band. The detection / bandwidth limiting means for conversion, the switching control signal output means for extracting the scanning synchronization component signal from the detection signal, and obtaining the switching control signal in the ghost component detection period based on the synchronization component signal, and the bandwidth control signal are input. A switching means for switching a band control signal by a switching control signal to obtain a switching signal, and writing / writing based on a predetermined control signal of the switching signal to broaden the band of the switching signal and compress the time. The storage means for obtaining the processed signal and the order in which the processed signal is written / written out are reversed. As described above, the time-reversal processing means obtains the time-reversal processed signal, the delay means obtains a delayed signal obtained by delaying the processed signal by the time-reversal processing time, and the time-reversal processed signal and the delayed signal have a predetermined carrier component. A signal is amplitude-modulated by a signal to obtain an amplitude-modulated signal, and an amplitude-modulation unit that receives each amplitude-modulated signal and a correlation-signal output unit that obtains a correlation signal are provided. It is characterized by including a waveform.

In the ghost detecting device for the received signal, further, a differential processing means for differentially processing the band limited signal from the detection / band limiting means to obtain a differential component signal, and a unipolar component signal from the differential component signal. A unipolar component separating means, and a waveform processing means including the switching means,
It is desirable to input the unipolar component signal and switch the unipolar component signal by the switching control signal to obtain the switching signal.

[0007]

With the above-described structure, the ghost detecting apparatus for a received signal according to the present invention performs the synchronous detection of the received video signal by the detection / band limiting means to obtain the detected signal and convert it into the band-limited signal of a predetermined narrow band for switching control. The signal output means extracts the scanning synchronization component signal from the detection signal and obtains the switching control signal in the ghost component detection period based on the synchronization component signal. Further, the switching means inputs the band control signal, the band control signal is switched by the switching control signal to obtain the switching signal, and the writing / writing based on a predetermined control signal of the switching signal is performed by the storage means.
By writing, the band of the switching signal is widened, and a time-compressed processed signal is obtained. Then, the time-reversal processing means performs time-reversal processing so that the processed signals are in the reverse order to the writing / writing order of the processed signals,
After obtaining the time-reversal processing signal, the delay means delays the processing signal by the time-reversal processing time to obtain a delayed signal. Further, the time-reversal processed signal and the delayed signal are amplitude-modulated by the predetermined carrier component signal by the amplitude modulation means to obtain the respective amplitude modulation signals, and the correlation signal output means inputs the respective amplitude modulation signals and the ghost of the received video signal. A correlation signal containing a significant waveform showing the components is obtained.

Further, in the above-mentioned received signal ghost detecting apparatus, if the waveform processing means is further provided, the waveform processing means differentiates the band limited signal from the detection / band limiting means by the differentiating means to differentiate the component signal. Then, the unipolar component separating means can obtain the unipolar component signal from the differential component signal. Then, by inputting this unipolar component signal to the switching means and switching the unipolar component signal by the switching control signal to obtain the switching signal, the correlation signal which is the final output of the ghost detection device indicates the ghost component. , Represents a more significant waveform.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram showing a change in a signal due to compression on a time axis. FIG. 1A shows the signal length T of the original signal,
(B) shows the maximum frequency fm. When the original signal having the signal length T and the highest frequency fm in FIG. 1A is compressed to a length 1 / n, the signal length becomes T / n as shown in (a) of FIG. 1B, and the band (highest frequency) becomes It becomes nfm as shown in (b).

In a configuration example of a ghost detecting apparatus for a received signal according to the present invention described later (see FIG. 3), the length of the signal length T is memorized by a clock of frequency fk in the read mode and reading is performed by the clock of frequency nfk. As a result, the original signal of FIG. 1A is compressed and becomes the signal of FIG. 1B.

FIG. 2 is a diagram showing the timing of time distribution in the compressed mode. If the processing is completed within the time (horizontal scanning line length H of television ≈63.5 μs) which is a unit of the screen configuration, one is displayed. The circuit performs the same process for each line (scan line). In FIG. 2, if the signal length T of one line H is stored at the clock fk and then read at the clock nfk, the signal length becomes T / n. Therefore, if the signal T; line H; satisfies the following equations (1) and (1 '), the processing is completed within one line. T + T / n ≦ H (1) {(1 + n) / n} T ≦ H, (that is, T ≦ {n / (n + 1)} H (1 ′) Here, if n = 4, the above formula (1 ), (1 ')
Therefore, T ≦ 0.5H, and 80% of one line is the target section for ghost detection.

FIG. 3 is a block diagram showing a basic configuration example of a received signal ghost detecting apparatus according to the present invention.
Is an IF (intermediate frequency) signal, 2 is a synchronous detection circuit, 3 is a video carrier generation circuit, 4 is an LPF (low pass filter),
5 is a horizontal sync separation circuit, 6 is a gate pulse generation circuit, 7
Is a switch circuit, 8 is a memory, 9 is a write clock having a frequency of fk, 10 is a read clock having a frequency of nfk, 11 is a gate pulse generation circuit, and 12 is a memory mode for controlling the write / read mode to the memory. Control circuit, 13 is a switch circuit, 14 is a scan inversion circuit (memory) as a time inversion processing means, 15 is a write clock, 16 is a read clock, 17 is a reverse scan signal, 18 is a delay circuit, 19 is a delay signal, 20 , 21 is A
M (amplitude) modulator, 22 is a carrier generation circuit for convolver, 23 is a SAW convolver, 24 is a correlation output, 25 is a waveform processing circuit, and the synchronous detection circuit 2, the video carrier generation circuit 3 and the LPF 4 are detection / band limitation. The horizontal sync separation circuit 5 and the gate pulse generation circuit 6 constitute a switching control signal output means.

In FIG. 3, a video IF signal 1 is input to a synchronous detection circuit 2 and a video carrier generation circuit 3. Also,
The output of the video carrier generation circuit 3 is input to the synchronous detection circuit 2. Then, the coherent detection circuit 2 coherently detects the IF signal 1 with the carrier wave output from the video carrier wave generation circuit 3.

The LPF 4 is a low-pass filter of 0 to 1 MHz (or 0 to 0.5 MHz may be used), and extracts both sideband components of the video carrier signal output from the synchronous detection circuit 2.
The output of the LPF 4 is the waveform processing circuit 25 (see FIG. 4; described later).
After that, the ghost detection period T is alternately switched by the switch circuit 7 for switching.

Therefore, the output of the synchronous detection circuit 2 is input to the horizontal sync separation circuit 5, the output of the horizontal sync separation circuit 5 is input to the gate pulse generation circuit 6, and the output gate pulse of the gate pulse generation circuit 6 ( The switch circuit 7 is gated by the pulse width T (T <H (H; line). The output of the switch circuit 7 is written in the memory 8 at the clock timing of the signal frequency fk of the write clock 9 (write mode).

As shown in FIG. 2, the memory 8 is in the read mode after the writing is completed, and the signal written in the memory 8 is the output pulse (amplitude H−) of the gate pulse generating circuit 6.
According to T), the memory mode control circuit 12 reads out at the clock timing of the signal frequency nfk of the read clock 10. Therefore, the time axis is compressed, and the original signal having the signal length T and the highest frequency fm in FIG. 1A is compressed to the length 1 / n,
The signal length is set to T / n as shown in (a) of FIG. 1B, and the band (highest frequency) is set to nfm as shown in (b).

The output of the horizontal sync separation circuit 5 is also branched and input to the gate pulse generation circuit 11, and the gate pulse generation circuit 11 outputs a gate pulse having a pulse width T / n,
The switch circuit 13 is turned on. The output of the switch circuit 13 is compressed to T / n in time and has a band of nfm as shown in FIG. 1B. Here, LPF4 is 0 to 1 MHz
Therefore, the maximum frequency fm of the original signal is fm = 1 MHz, and when n = 4, the maximum frequency nfm = 4 MHz is extended and widened.

The output of the switch circuit 13 is stored in the memory 14. The memory 14 is a scanning inversion circuit, which stores a signal having a length of T / n at the write clock timing of the write clock 15 and stores a signal at the clock timing of the read clock 16 at the write clock timing of the write clock 15. Reading is performed in order, and the reverse scanning signal 17 is obtained. On the other hand, the output of the switch circuit 13 is branched and input to the delay circuit 18 to obtain the delay signal 19. In addition,
The delay time of the delay circuit 18 is set equal to the processing time of the scan inversion circuit 14.

The reverse scan signal 1 of the scan inversion circuit 14
7 is input to the AM (amplitude) modulator 20, and the delayed signal 19 is input to the AM (amplitude) modulator 21. The carrier generator circuit 22 for the convolver outputs a carrier (for example, about 20 MHz) suitable for propagating through the SAW convolver 23, and is added to the AM (amplitude) modulators 20 and 21. The outputs of the AM (amplitude) modulators 20 and 21 are input to both terminals of the SAW convolver 23 to obtain a correlation output 24. Since the time distribution of the correlation output 24 is compressed to 1 / n in the memory 8 as compared with the correlation of the original signal, the time distribution of the correlation output 24 is 1 / n.

FIG. 4 is a block diagram showing a configuration example of the waveform processing circuit 25. In FIG. 1, the output signal band-limited (1 MHz in the embodiment) by the LPF 4 is the waveform processing circuit 2.
Input to 5. In FIG. 4, 26 is a differentiating circuit, 27
Is a unipolar separation circuit, and in the embodiment, it is assumed that only the positive polarity signal is taken out (for example, a diode). Further, the differentiating circuit 26 and the unipolarity separating circuit 27 form a waveform processing circuit 25. Further, 28 is a mode selection switch, which passes so that the waveform processing circuit 25 does not perform the waveform processing when the waveform processing is unnecessary.

FIG. 5 is an explanatory diagram of the waveform processing by the waveform processing circuit 25. FIG. 5A shows the waveform of the output signal of the LPF 4, which is the main signal shown by the solid line, and the amplitude coefficient delayed following the main signal. Let us assume that a ghost of 0.5 is added as shown by the dashed line. FIG. 5B is the output of the differentiating circuit 26, which is the differential waveform of the signal of FIG. 5A. Also, FIG.
C is the output waveform of the unipolar separation circuit 27. In other words, the unipolar separation circuit 27 takes out the positive polarity portion of the differentiating circuit 26.

FIG. 6 is a waveform diagram of the correlation output depending on the presence or absence of the waveform processing. FIG. 6A shows the main signal (only the solid line portion of FIG. 5A).
6B is a correlation output waveform when the input signal is, FIG. 6B is a correlation output waveform when the ghost of FIG. 5A, a main signal, and ghosts are input signals, and FIG. 6C is a main signal of FIG. 5A. + C is a correlation output waveform of the ghost signal (the output of FIGS. 6A and 6B is added), and FIG.
In the correlation output waveform of, the correlation between the main signal and the ghost is unclear. Further, FIG. 6D shows the correlation output after waveform processing of only the main signal corresponding to FIG. 6A (see FIG. 5C), and FIG. 6E after waveform processing of the main signal + ghost signal corresponding to FIG. 6C (see FIG. 5C). Is a correlation output of, and the relationship between the main signal and the ghost clearly appears.

To display the ghost, the waveform of FIG. 6E is displayed every time the television is scanned. Further, when the horizontal synchronizing signal is generated by the main signal of FIG. 6D or 6E, the ghost distribution of each line can be displayed on the television monitor. Further, the received signal ghost detecting device of the present invention can be applied to the ghost detecting section of a high speed ghost canceller.

[0024]

As described above, according to the ghost detecting apparatus for a received signal of the present invention, it is possible to measure the ghost state under the condition that the received electric field is changing every moment like the mobile reception of television radio waves. . Further, the waveform processing can clarify the correlation between the main signal and the ghost.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing changes in a signal due to compression on a time axis.

FIG. 2 is a diagram showing time distribution in a compressed mode.

FIG. 3 is a block diagram showing a basic configuration example of a received signal ghost detection device according to the present invention.

FIG. 4 is a block diagram showing a configuration example of a waveform processing circuit.

FIG. 5 is an explanatory diagram of waveform processing by a waveform processing circuit.

FIG. 6 is a waveform diagram of a correlation output depending on the presence or absence of waveform processing.

[Explanation of symbols]

2 synchronous detection circuit (detection / band limitation means) 3 video carrier generation circuit (detection / band limitation means) 4 low-pass filter (detection / band limitation means) 5 horizontal sync separation circuit (switching control signal output means) 6 gate pulse generation circuit (Switching control signal output means) 7 Switch circuit (switching means) 8 Memory (storage means) 14 Scan inversion circuit (time inversion processing means) 18 Delay circuit (delay means) 20, 21 AM (amplitude) modulator (amplitude modulation means) ) 23 SAW convolver (correlation signal output means) 24 correlation output 25 waveform processing circuit 26 differentiating circuit (differential processing means) 27 unipolar separation circuit

Claims (2)

[Claims] 1. A detection / band limiting unit for synchronously detecting a received video signal to obtain a detection signal and converting the detection signal into a band-limited signal of a predetermined narrow band, and a sync component signal for scanning is extracted from the detection signal, Switching control signal output means for obtaining a switching control signal in a ghost component detection period based on a synchronization component signal, and inputting the band control signal, and switching the band control signal by the switching control signal to obtain a switching signal Means for writing and writing the processing signal to and from the switching signal by writing / writing the processing signal based on a predetermined control signal to broaden the band of the switching signal and to obtain a processing signal time-compressed. / A time-reversal processing hand that obtains a time-reversal processed signal by performing time-reversal processing so that it is in reverse order to the writing order Stage, and delay means for obtaining a delayed signal obtained by delaying the processed signal by the time inversion processing time,
An amplitude modulation means for amplitude-modulating the time-reversal processed signal and the delayed signal with a predetermined carrier component signal to obtain an amplitude-modulated signal, and a correlation signal output means for inputting each of the amplitude-modulated signals to obtain a correlation signal are provided. The received signal ghost detecting apparatus is characterized in that the correlation signal includes a significant waveform indicating a ghost component of the received video signal. 2. A ghost detecting device for a received signal according to claim 1, further comprising: differential processing means for differentially processing the band limited signal from the detection / band limiting means to obtain a differential component signal.
A unipolar component separating means for obtaining a unipolar component signal from the differential component signal; and a switching means for inputting the unipolar component signal, and switching the unipolar component signal by a switching control signal. A received signal ghost detection device characterized by switching to obtain a switching signal.