JPH07105920B2 - Interference removal receiver - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an interference wave elimination receiving apparatus that removes interfering waves that have been mixed in to receive vestigial sideband modulation type television broadcast waves and the like, and particularly relates to an influence on the image quality of received images. This is designed to remove the interfering wave mixed in the large double sideband transmission band.

BACKGROUND ART Conventionally, in order to remove an interfering wave mixed in a received television broadcast wave, a band elimination filter having a narrow stop band width, that is, a so-called notch filter is used to remove a signal component to be removed together with the interfering wave. I was trying to limit it. However, when the frequency of the interfering wave is close to the video carrier frequency of the residual sideband modulation type television broadcasting wave, particularly when mixed in the both sideband transmission band of the television broadcasting wave, Since the waveform distortion of the demodulated output video signal due to the lack of the signal component generated by the insertion of the notch filter appears significantly, deterioration of the image quality due to the occurrence of the beat between the interfering wave and the video carrier is reduced by inserting the notch filter. However, there is a drawback in that the image quality is deteriorated due to the distortion of the signal waveform that occurs secondarily, and the sufficient image quality cannot be improved.

OBJECT OF THE INVENTION An object of the present invention is to eliminate the above-mentioned conventional drawbacks, and to eliminate an interfering wave that is mixed in a double sideband transmission band such as a received vestigial sideband modulation type television broadcast wave and causes significant reception disturbance. Another object of the present invention is to provide a jamming wave removing receiver capable of sufficiently removing the image without degrading the image quality due to the distortion of the demodulated output signal waveform.

SUMMARY OF THE INVENTION That is, according to the present invention, the interfering wave removing receiver is a carrier signal component of a received modulated wave when an interfering wave is mixed in a double sideband transmission band such as a residual sideband modulation type television broadcast wave. As the quadrature phase component of the demodulated signal, the signal component transmitted in both sidebands does not appear, only the signal component transmitted in single sideband, and interfering waves also appear in it The interference wave is extracted, and by the extracted interference wave,
This is designed to cancel and remove the interfering wave that is mixed in the carrier signal component of the received modulated wave, and recover the carrier component from the carrier signal component of the modulated wave that has the double sideband transmission component received including the interfering wave. Carrier wave regenerating means, a carrier wave phase shifting means for shifting the carrier wave component regenerated by the carrier wave regenerating means by π / 2, and a carrier signal component of the received modulated wave by the carrier wave component regenerated by the carrier wave regenerating means. A first synchronous detection means for synchronously detecting and extracting an in-phase component, and a carrier signal component of the received modulated wave is synchronously detected by a carrier component phase-shifted by π / 2 by the carrier phase shifting means to obtain a quadrature phase component. Second synchronous detection means for extraction, low-pass filtering means for changing the pass band of the quadrature component extracted by the second synchronous detection means to a double sideband transmission band, and the low-pass filtering means. A quadrature phase component phase shifting means for shifting the output by π / 2, an output of the quadrature phase component phase shifting means and an output of the first synchronous detection means are combined and mixed in the double sideband transmission component. The first combining means for canceling and removing the interfering wave, the band-pass filtering means for making the pass band of the quadrature phase component extracted by the second synchronous detection means a single sideband transmission band, and the carrier regenerating means. First modulating means for modulating the reproduced carrier component by the output of the first combining means, and second modulating means for modulating the carrier component phase-shifted by π / 2 by the carrier phase shifting means by the output of the band-pass filtering means. And the second synthesizing means for synthesizing the outputs of the first and second modulating means with each other.

Examples Hereinafter, the present invention will be described in detail with reference to the drawings.

First, the sideband distribution of the residual sideband modulation type television broadcast wave is shown in FIG. 1 (a), which is divided into the in-phase component and the quadrature-phase component shown in FIGS. 1 (b) and (c), respectively. Can be divided. In the figure, ω ₀ is the angular frequency of the video carrier.

Now, the video signal in the television broadcast wave is G (t)
And the angular frequency of the video carrier is ω ₀ , when the amplitude-modulated television broadcast wave G (t) cosω _0t is transmitted in the vestigial sideband as shown in FIG. Can be expressed as

Note that the following relationship is also applied to the intermediate frequency signal obtained by frequency-converting the vestigial sideband modulation type television broadcast wave.

C (t) cos (ω _0t + θ ₀ ) -S (t) sin (ω _0t + θ ₀ )
(1) Here, θ ₀ is the phase of the signal at the video carrier angular frequency ω ₀ , and C (t) and S (t) are the video carrier angular frequency in FIGS. 1B and 1C, respectively. ω
₀ is the output response, each obtained when supplying 0 i.e. video signal G as described above to a circuit having a transfer function of the shift characteristics at zero frequency (t). Therefore, assuming that the frequency band of the video signal G (t) is limited to the range of the band ν shown in FIG. 1 (a), the amplitude characteristic of the transfer function of the in-phase component is flat, and the phase characteristic is When it is linear, C (t) = G (t) / 2. Therefore,
When the output represented by the equation (1) is synchronously detected by the carrier wave of the following equation (2), the original video signal is completely demodulated.

cos (ω _0t + θ ₀ ) (2) The band characteristic of the bandpass filter configured to flatten the amplitude characteristic of the in-phase component is as shown in FIG. 2 (a). Is linear. Therefore, the television broadcast wave having the sideband distribution shown in FIG. 1 (a) is supplied to the bandpass filter having the band characteristic shown in FIG. 2 (a), and its filtered output is the same as that of the video carrier. Synchronous detection with carrier cos (ω _0t + θ ₀ ) having angular frequency ω ₀ and phase θ ₀ gives the original video signal, while the same angular frequency ω as the video carrier
_{When the} carrier wave sin (ω _0t + θ ₀ ) that has a phase of ₀ and the phase is different from the above-mentioned θ _{0 in} the direction of time delay is positive by π / 2, the video signal component is detected in the range of angular frequency 0 to μ. A quadrature phase component of the video signal component that does not include at all is obtained.

Under such a condition, as shown in FIG. 2 (a), the next interfering wave A · cos {(ω ₀ + δ) t + (at a frequency position away from the angular frequency ω ₀ of the video carrier by the angular frequency δ. θ ₀ +)} (3) is mixed. Here, (θ ₀ +) is the phase of the interfering wave. This interference wave has the same angular frequency ω as the video carrier.
A carrier having ₀ and a phase θ ₀ , that is, a carrier represented by the equation (2) and the same angular frequency ω ₀ as the video carrier, but having a phase difference of π / 2.
Synchronous detection by carrier wave sin (ω _0t + θ ₀ ) (4) and the baseband component respectively are extracted and in-phase component is obtained. Quadrature component Two different demodulation outputs are obtained. When the quadrature component of equation (6) is added to a low-pass filter with a bandwidth μ, a component corresponding to the first term of equation (6), that is, an interfering wave component, is added to the output side of the filter. Only can be taken out.

On the other hand, the in-phase component of the equation (5) includes the original video signal component and the interfering wave component even in the range of the bandwidth μ. Therefore, from the interference wave component expressed by equation (7), If a signal component having the following form can be created, the interference wave component can be offset and removed by adding and synthesizing the signal component to the in-phase component of the equation (5).

Then, in order to generate the signal component of the expression (8) from the interference wave component of the expression (7), the phase of the interference wave component of the expression (7) is changed by 90 degrees, that is, by π / 2. / 2 Phase shift, let the circuit pass.

The receiving apparatus of the present invention is configured to realize the above-described operation principle, and the basic configuration on the premise thereof is shown in FIG. In the basic configuration shown, the input terminals
The broadcast wave of the television supplied to 10 or the intermediate frequency signal obtained by frequency-converting it is guided to the bandpass filter 1 with good phase linearity, and corresponds to the double sideband transmission band of the residual sideband modulation type television broadcast wave. Frequency band to
As shown in FIG. 2A, the signal amplitude is halved and then supplied to the synchronous detection circuits 2 and 3 in parallel. The carrier wave for driving the synchronous detection circuits 2 and 3 is supplied with a television broadcast wave or an intermediate frequency signal from the input terminal 10 to the carrier wave reproduction circuit 8 to extract the image carrier wave component,
It is generated in phase with the video carrier component in the filtered output of the bandpass filter 1. The in-phase carrier is directly applied to the synchronous detection circuit 2 to obtain an in-phase component video signal, and the phase is shifted by 90 degrees via the π / 2 phase shift circuit 7, and then applied to the synchronous detection circuit 3. The video signal of the quadrature component and the interfering wave component are extracted as the detection output. The latter synchronous detection circuit 3
Is supplied to the low-pass filter 6 that passes only the video frequency band corresponding to the double sideband transmission band of the residual sideband modulation type television broadcast wave or the intermediate frequency signal, and both sides of the filter 6 from the output side. Only the interference wave component existing in the frequency band corresponding to the waveband transmission band is extracted, and the extracted interference wave component is guided to the π / 2 phase shift circuit 9.
After the phase is shifted by 90 degrees, it is guided to the adder circuit 5 through a level adjusting circuit (not shown) if necessary. The former synchronous detection circuit 2
The video signal component from the delay circuit 4 gives a delay equivalent to the delay exhibited by the low-pass filter 6 in the other system.
After adjusting the timing via
And add and combine with the above-mentioned interfering wave component derived from the other system, a high-quality demodulated output video signal that cancels out the interfering wave mixed in the frequency band corresponding to the double sideband transmission band is output. It can be taken out from the terminal 11.

The π / 2 phase shift circuit 9 that shifts the detected output interference wave component by 90 degrees can be realized by configuring a filter having an impulse response of the transfer function of 1 / πt. As such a filter, For example, a transversal filter configured by using a charge-coupled device CCD that has already been put into practical use can be applied. Also, this π / 2
In the configuration of the phase shift circuit 9, it is possible to include the filtering characteristic of the low pass filter 6. The bandpass filter 1 that gives the characteristics shown in FIG. 2A to a television broadcast wave or an intermediate wave signal is, for example,
It can be easily constructed by using a surface acoustic wave element.

Next, in the basic configuration shown in FIG. 3, a π / 2 phase shift circuit 9 can be simply used without using any special circuit element such as the transversal filter described above in the π / 2 phase shift circuit 9. FIG. 4 shows another basic configuration when the circuit 9 is configured. The circuit portion surrounded by a broken line frame in the basic configuration shown in FIG. 4 is exactly the same as the remaining circuit portion except the .pi. / 2 phase shift circuit 9 in the basic configuration shown in FIG. That is, in the basic configuration shown in FIG. 4, the π / 2 phase shift circuit 9 in the basic configuration shown in FIG.
Multiplier circuit 13, bandpass filter 14, and synchronous detection circuit
15 is replaced by a configuration in which they are sequentially connected,
The baseband interference wave component extracted from the low-pass filter 6 is guided to the multiplication circuit 13 and is multiplied by the reproduced carrier wave from the carrier wave reproduction circuit 8 to restore the carrier interference wave component form once, and the bandpass filter 14 causes the upper sideband to pass. Only the component is extracted and guided to the synchronous detection circuit 15 and synchronously detected by the quadrature phase carrier from the π / 2 phase shift circuit 7, whereby the interfering wave shifted by 90 degrees from the filtered output interfering wave component of the low-pass filter 6. The components are taken out and supplied to the adder circuit 5.

Then, the filtered output of the low-pass filter 6 is the interference wave component of the formula (7), and when the interference wave component of the formula (7) is multiplied by the reproduced carrier wave of the formula (2) obtained from the carrier wave regeneration circuit 8, The carrier interference wave component of the following equation (9) is obtained.

The second term on the right side of the equation (9), that is, the lower sideband component is removed by the bandpass filter 14, and the first term on the right side is removed.
Taking out only the term, upper sideband component, A filtered output carrier disturbance component is obtained. The filtered output carrier interference wave component is guided to the synchronous detection circuit 15 and is synchronously detected by the quadrature phase carrier from the π / 2 phase shift circuit 7 according to the expression (4), and the interference wave component represented by the following expression (11) is obtained. can get.

When the level of the disturbing wave component of the equation (11) is adjusted to 4 times and added and synthesized with the in-phase component video signal from the synchronous detection circuit 2, the mixed disturbing wave component represented by the first term of the equation (5) is generated. Of the second term Only the video signal G remains in the demodulated output video signal G.
Means (t). The multiplication circuit 13 that performs multiplication with the reproduced carrier wave is a kind of modulator, and for example, a balanced modulator can be applied.

Based on the basic configuration detailed above, except that the interfering wave component is removed, the same broadcast wave or intermediate frequency signal as the television broadcast wave or intermediate frequency signal supplied to the input terminal is output. FIG. 5 shows an example of the configuration of the receiving apparatus of the present invention, which is suitable for use as a relay for a television broadcast that appears at the terminal. That is, the main part of the configuration example shown in FIG. 5 has a form in which the bandpass filter 1 at the input end in the basic configuration shown in FIGS. Through the same manner as in the basic configuration shown in FIG. 4, the in-phase component demodulated output video signal C (t) from which the interfering wave component mixed in the frequency band corresponding to the double sideband transmission band is removed is obtained. On the other hand, when the detection output of the synchronous detection circuit 3 is supplied to a bandpass filter 16 having a passband corresponding to the single sideband transmission band of the vestigial sideband modulation type television broadcast wave, the bandpass filter 16 causes both sides to pass. As the interfering wave component mixed in the frequency band corresponding to the waveband transmission band is removed, the quadrature phase component video signal is obtained as can be seen from equation (6). Only get.

In such a state, the in-phase component video signal C (t) from the adding circuit 5 and the in-phase carrier wave of the formula (2) from the carrier wave reproducing circuit 8 are supplied to the multiplying circuit 19 for multiplication to carry out the in-phase carrier video signal component. And the quadrature component video signal of the bandpass filter 16 Through a level adjusting circuit 17 and a delay circuit 18
The quadrature-phase carrier video signal component is formed by supplying the quadrature-phase carrier video signal component of (4) from the π / 2 phase shift circuit 7 to the multiplication circuit 20 and multiplying it. After that, if the carrier video signal components of the in-phase and the quadrature phase are added and synthesized by the adder circuit 21, the mixed interfering wave is removed at the output terminal 22 and is supplied to the input terminal 10 (1).
The carrier video signal wave which is exactly the same as the television broadcast wave of the formula is obtained.

In addition, the detection output of the synchronous detection circuit 3 is set to the low-pass filter 6
If the cascade connection circuit of the multiplication circuit 13, the bandpass filter 14 and the synchronous detection circuit 15 in the basic configuration shown in FIG. 4 is used as the π / 2 phase shift circuit 9 supplied via
Similar to the basic configuration shown in FIG. 4, the configuration of the circuit device can be simplified and realized at low cost without using special circuit elements.

In the above description, it is assumed that the interfering wave is mixed in the upper sideband in the double sideband transmission band of the residual sideband modulation type television broadcasting wave, and the circuit configuration is adapted to the above. The device is capable of canceling out the interference wave in the same manner even when the interference wave is mixed in the lower sideband. That is, in this case, in the circuit configurations shown in FIGS. 3, 4, and 5, the adder circuit 5 is configured to subtract the output of the π / 2 phase shift circuit 9 from the output of the delay circuit 4. However, in the circuit configuration shown in FIG. 4, the adder circuit 5 may be left as it is and the bandpass filter 14 may be changed so as to pass only the lower sideband component.

Effect As is apparent from the above description, according to the present invention, an interfering wave that mixes in the double sideband transmission band of the residual sideband modulation type television broadcast wave and significantly deteriorates the image quality of the received image is generated by the video signal component. Since it is extracted as quadrature phase synchronous detection output in the double sideband transmission band that is not included, there is no characteristic deterioration such as waveform distortion of the video signal due to secondary video signal component deletion when canceling the interference wave. , It is possible to sufficiently cancel and remove the image to ensure a high quality image quality.

Further, as in the basic configuration shown in FIG. 4, when a signal component over a wide frequency band is phase-shifted by 90 degrees, a complicated transversal filter is not used and only conventional circuit elements are used. Of signal components over a wide band
It is possible to perform a 90-degree phase shift, sufficiently remove interference waves with a circuit device having a simple and inexpensive structure, and perform high-quality reception. In addition, in the basic configuration examples shown in FIGS. 3 to 4, the bandpass filter 1 at the input end is similar even if the bandpass filter 1 at the input end is given the baseband filtering characteristic as shown in FIG. The effect is obtained.

Further, in the configuration example shown in FIG. 5, the interfering wave mixed in the double sideband transmission band is almost completely removed without requiring the bandpass filter having the filtering characteristic as shown in FIG. Other than that, since the television broadcast wave signal or the intermediate frequency signal which is exactly the same as the input can be obtained, it is possible to easily remove the interference wave of the television broadcast reception by placing it in a ready-made receiver. For example, if a receiving device in a satellite station in a broadcast wave relay network is preceded by the device of the present invention having the configuration shown in FIG. 5, good quality broadcast wave relay can be easily achieved. Further, if the device of the present invention having the configuration shown in FIG. 5 is configured to be inserted in the intermediate frequency amplifying stage of a normal receiver, the interference wave can be removed regardless of the channel selection in the receiver. .

Furthermore, according to the present invention, from the operating principle thereof,
Regardless of whether the interfering wave is mixed or non-modulated, the modulation format is not limited, and the modulated wave having a double sideband transmission component is not limited to the television broadcast wave of the residual sideband modulation method. It is possible to sufficiently remove all the interfering waves that are asymmetrically mixed in the carrier signal component with respect to the carrier regardless of the number of mixed signals and the frequency change of the interfering waves.

[Brief description of drawings]

1 (a), (b) and (c) are characteristic curve diagrams showing sideband distribution, in-phase component and quadrature component of television broadcast wave, respectively, and FIGS. 2 (a), (b) and (). FIG. 3C is a characteristic curve diagram showing the characteristics of the bandpass filter used in the device of the present invention and the modes of interfering wave mixing in the in-phase component and the quadrature phase component. FIG. 3 shows the basic configuration of the interfering wave removing receiver according to the present invention. Block diagram FIG. 4 is a block diagram showing another basic configuration of the receiving device, FIG. 5 is a block diagram showing a configuration example of the interference wave canceling receiving device of the present invention, and FIG. 6 is the device of the present invention. 6 is a characteristic curve diagram showing a characteristic example of a baseband filter used in FIG. 1,14,16 …… Band pass filter 2,3,15 …… Synchronous detection circuit 4,18 …… Delay circuit, 5,21 …… Adding circuit 6 …… Low pass filter, 7,9 …… π / 2 shift Phase circuit 8 …… Carrier wave regeneration circuit, 10 …… Input terminal 11,22 …… Output terminal, 13,19, 20 …… Multiplication circuit 17 …… Level adjustment circuit.

Claims (2)

[Claims] 1. A carrier regenerating unit for regenerating a carrier component from a carrier signal component of a modulated wave having a double sideband transmission component received including an interfering wave, and the carrier component regenerated by the carrier regenerating unit by π / 2. Carrier shifting means for shifting the phase, first synchronous detecting means for synchronously detecting the carrier signal component of the received modulated wave by the carrier component reproduced by the carrier reproducing means, and extracting the in-phase component; Second synchronous detection means for synchronously detecting the carrier signal component of the received modulated wave by the carrier component phase-shifted by π / 2 by the phase means to extract the quadrature phase component, and the second synchronous detection means for extracting the quadrature phase component. Low-pass filtering means for changing the pass band of the quadrature-phase component to the double-sided band transmission band, quadrature-phase component phase shifting means for shifting the output of the low-pass filtering means by π / 2, and its quadrature-phase component phase shifting Of means And the output of the first synchronous detection means are combined to cancel and eliminate the interfering wave mixed in the double-sideband transmission component, and the second synchronous detection means is used for extraction. Band-pass filtering means for making the pass band of the quadrature phase component a single sideband transmission band; first modulating means for modulating the carrier component reproduced by the carrier reproducing means by the output of the first combining means; Second modulating means for modulating the carrier component phase-shifted by π / 2 by the carrier phase shifting means by the output of the band-pass filtering means and second output means for synthesizing the outputs of the first and second modulating means with each other. An interfering wave removing receiver, comprising: combining means. 2. The receiving device according to claim 1, wherein the interfering wave is mixed with an upper side band or a lower side band of a carrier signal component of the received modulated wave. An interference wave canceling receiving device, characterized in that the first synthesizing means is configured by using an adding means and a subtracting means, respectively.