JP2683533B2 - Broadcast receiver and receiving system, and color signal recording / reproducing device and recording / reproducing system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention particularly relates to an NTSC satellite broadcast receiving apparatus and receiving system.

The present invention further relates to an NTSC color television signal recording / reproducing apparatus and recording / reproducing system.

B. Outline of the Invention In a satellite broadcasting receiving apparatus for FM-modulating and broadcasting an NTSC signal according to the present invention, when the intermediate frequency signal is restored to a baseband signal other than a normal positive phase signal, the polarity of the signal changes. A pulse of cos ω _SC t and sin ω _SC t obtained by performing FM demodulation by creating an IF of opposite phase that reverses the positive phase and adding this to an electronic switch
_The positive phase and the negative phase are switched by the pulse of _SC t, and the outputs are demodulated by the demodulators to obtain E _I and E _Q signals, which are combined with the luminance signal E _Y to be the S terminal output. In addition, E _I , E _Q , and E _Y are matrixed to produce three primary color outputs of E _R , E _G , and E _B.

Further, in the color signal recording / reproducing apparatus according to the present invention, the FM modulated wave of the NTSC color television signal is used for recording, and the FM modulated wave (baseband signal positive polarity is ) FM demodulation is performed to generate a subcarrier having a phase corresponding to the time axis fluctuation of one line period from the burst subcarrier. (2) The frequency converter generates an FM modulated wave in which the baseband signal has the opposite polarity. (3)
Two types of FM modulated waves with positive and reverse polarities in the baseband (1)
The reference carrier for each line (actually cosω _SC t and si
Outputs switched with nω _SC t (two orthogonal signals) are each FM.
Demodulators -2 and -3 form a baseband signal, a low-pass filter obtains two chromaticity signals, and the chrominance signal E _Y obtained from (1) is used as an S terminal output. In addition, a matrix is formed into the three primary color signals E _R , E _G , and E _B.

C. Conventional Technology Satellite broadcasting by the NTSC system, which is the Japanese standard system,
The frequency distribution of the baseband signal of the video signal is shown in FIG. Here, the NTSC signal is a luminance signal E _Y and a chrominance signal E _C with a subcarrier (frequency 3.579545 MHz) balanced-balanced (AM) and multiplexed. The baseband signal E _M is given by equation (1).

_{E M = E Y + E C} cos (ω SC t + θ) = E Y + E I cosω SC t + E Q sinω SC t ............ (1) ω SC: In subcarrier frequency satellite by frequency modulating the formula (1) Send out. Therefore, in principle, the receiver demodulates the FM modulated wave by FM demodulation to restore the baseband signal of equation (1), and the color receiver demodulates color to restore E _C (E _I , E _Q ). , Further luminance signal E
The three primary color signals E _R , E _G , and E _B are output via _Y and a matrix. When demodulating the FM modulated wave to obtain E _M of equation (1), so-called triangular noise having a frequency distribution of noise amplitude proportional to the frequency of the baseband signal peculiar to FM demodulation occurs. For this reason, the amplitude of the high frequency component is increased by pre-emphasis on the transmitting side, and the amplitude of the high frequency component is reduced by de-emphasis on the receiver side. However, as can be seen from the emphasis characteristic of FIG. 8, the SN ratio of the chromaticity signal is worse than that of the luminance signal. In FIG. 8, the solid line represents the characteristics of the pre-emphasis circuit, and the broken line represents the FM demodulation noise distribution. This is also mentioned in “Broadcast Satellite Technology” edited by Japan Broadcasting Corporation 2.8, Special transmission method, page 63.

In the NTSC color television signal recording / playback signal processing system, the NTSC signal is a luminance signal E _Y , a chromaticity signal E _C (E _I
It is multiplexed subcarriers E consisting _Q) and AM modulation with.
If the NTSC transmission signal is E _M , then equation (2) is obtained.

_{E M = E Y + E C} cos (ω SC t + θ) = E Y + E I cosω SC t + E Q sinω SC t ............ (2) ω SC: subcarrier frequency (3.579545 MHz) theta: color carrier phase equation ( The frequency distribution of 2) is shown in FIG.

As for the recording / reproducing method of the NTSC signal, in the VTR, in order to avoid the influence of the fluctuation of its time axis and the temporal fluctuation of the electromagnetic conversion gain of the tape head, it is recorded by FM (frequency modulation) modulation.

During FM demodulation, transmission system noise is added as triangular noise that increases in proportion to the frequency of the baseband signal (E _{M in this case} ) (Fig. 15).

Current VTRs are roughly classified into the following two methods.

(1) a E _M of the NTSC signal SonomaゝFM-modulated and recorded / reproduced.

(2) Separate the NTSC color carrier E _C cos (ω _SC t + θ),
Only E _Y is FM-modulated, and ω _SC is converted to a low carrier wave to E _Y
The low carrier color signal is separated at the time of reproduction, converted into the subcarrier ω _SC , and added to the FM demodulated E _Y.

D. Problems to be Solved by the Invention As a measure against the deterioration of the SN ratio of the chromaticity signal in NTSC broadcast reception, the chromaticity signal is not multiplexed with the luminance signal in the baseband,
A system has also been proposed in which E _Y and E _C are temporally compressed and transmitted to one horizontal scanning line, and the receiver side temporally expands each line to 1 line (1H). In this case, the receiver requires a circuit for extending the time axis, which has the drawback of increasing the cost.

The (1) described in the recording / reproducing signal processing method of the NTSC color television signal is used for business purposes, and the noise accompanying recording / reproducing is reduced in order to suppress the noise of the color signal. For this reason, there is a drawback that the amount of tape used increases, and (2) is used for home use and converts a color signal into a low carrier wave, so that noise of the color signal is reduced. However, since the amplitude modulation is generally performed, there is a drawback that it is easily affected by a non-linear effect of recording / reproduction and a time variation of the sensitivity of electromagnetic conversion.

[Object of the Invention] A first object of the present invention relating to the reception of NTSC broadcast is a color due to noise (triangular noise) proportional to the baseband frequency generated at the time of FM demodulation in a satellite broadcast receiver (NTSC television). It is to provide a broadcast receiving apparatus and a receiving system that suppresses a change in the SN ratio of the frequency signal and that can obtain redevelopment with high image quality even in weak electric field reception (including the influence of rainfall).

A second object of the present invention relating to recording / reproducing of color signals is to improve the SN ratio of the color signals when recording / reproducing the transmission signals in the recording / reproducing of the NTSC color television signals, thereby achieving high quality. It is an object to provide a color signal recording / reproducing apparatus and a recording / reproducing system capable of obtaining a reproduced image.

E. Means for Solving the Problem In order to achieve the first object, the broadcast receiving apparatus according to the present invention generates an anti-phase IF signal in which the signal polarity is inverted with respect to the composite video signal in the intermediate frequency signal stage. Means, a demodulator for demodulating an IF signal (positive phase) or a negative phase IF signal, and a color burst signal extracted from the demodulation signal by a synchronization signal in the demodulation signal to generate a continuous first subcarrier signal A means for generating a continuous second subcarrier signal orthogonal to the first subcarrier, and a means for alternately switching the IF signal and the anti-phase IF signal based on the first subcarrier signal. No. 1 switching means, second switching means for alternately switching the IF signal and the anti-phase IF signal based on the second subcarrier signal, and the output of the first switching means is demodulated to obtain the first color. Means for extracting the component signals and And, second demodulating the output of the switching means, and summarized in that includes means for extracting the second color component signals.

The broadcast receiving method for achieving the first object of the present invention comprises a step of generating a reverse phase IF signal in which the polarity of the signal is inverted with respect to the baseband signal at the intermediate frequency signal stage, and an IF signal (positive phase). Alternatively, a step of demodulating the anti-phase IF signal, a step of extracting a color burst signal from the demodulated signal by a synchronizing signal in the demodulated signal and generating a continuous first subcarrier signal, and a step of orthogonal to the first subcarrier Then, a step of generating a continuous second sub-carrier signal, a first switching step of alternately switching the IF signal and the anti-phase IF signal based on the first sub-carrier signal, and an inverse of the IF signal A second switching step of alternately switching the phase IF signal based on the second subcarrier signal; a step of demodulating the output of the first switching step to extract a first color component signal; and 2 switching work It demodulates the output of the gist that it comprises a step of extracting the second color component signals.

In order to achieve the second object, a color signal recording / reproducing apparatus according to the present invention comprises means for generating a reverse-phase FM signal whose polarity is reversed with respect to a baseband signal of a reproduction FM signal, and a reproduction IF signal. A demodulator for demodulating a (normal phase) or a negative phase FM signal, a means for extracting a color burst signal from the demodulated signal by a synchronizing signal in the demodulated signal, and generating a continuous first subcarrier signal; Orthogonal to the subcarrier of
Means for generating a continuous second sub-carrier signal, first switching means for alternately switching the reproduction FM signal and the anti-phase FM signal based on the first sub-carrier signal, and the reproduction FM signal Second switching means for alternately switching the phase FM signal based on the second subcarrier signal; means for demodulating the output of the first switching means to extract a first color component signal; and Means for demodulating the output of the second switching means and extracting the second color component signal;
The gist is to include

The color signal recording / reproducing method for achieving the second object of the present invention is a step of generating an anti-phase IF signal whose polarity is reversed with respect to a base band signal of a reproducing FM signal, and a reproducing IF signal ( Demodulating a positive phase) or negative phase FM signal;
A step of extracting a color burst signal from the demodulation signal by a synchronization signal in the demodulation signal to generate a continuous first subcarrier signal; and a step of generating a continuous second subcarrier signal orthogonal to the first subcarrier. The step of generating, the first switching step of alternately switching the reproduction FM signal and the anti-phase FM signal based on the first subcarrier signal, and the reproduction FM signal and the anti-phase FM signal of the second sub-carrier. A second switching step of alternately switching based on a carrier signal; a step of demodulating the output of the first switching step to extract a first color component signal; and a step of demodulating the output of the second switching step. , And a step of extracting the second color component signal.

F. Action The broadcast receiving device and receiving method of the present invention act as follows.

(1) The positive and negative signals of the baseband signal are generated at the IF (intermediate frequency) stage (herein referred to as positive phase IF and negative phase IF).

(2) demodulates the positive or reverse phase IF in the FM demodulator, sampling a color burst, and controls the phase of the subcarrier oscillator, further outputs the components perpendicular to each other of cos .omega _SC t and sin .omega _SC t.

(3) Square wave based on subcarriers (cosω _SC t and sinω _SC t
The IF signal of the positive phase and the negative phase is switched by the), the output is demodulated by the FM demodulator, and the low frequency of the baseband signal is taken out (E _C ).

(4) The luminance signal E _Y which is the low frequency component of the FM demodulator obtained in (2) and the chromaticity signal E _C obtained in (3) are output. Or E _Y
And E _{C are used as a} matrix to obtain the three primary color signals E _R , E _G , and E _B.

The color signal recording / reproducing apparatus and the recording / reproducing system of the present invention operate as follows.

(1) The reproduced signal is FM demodulated, and the reference signal (burst) of the luminance _EY and the subcarrier is taken out.

(2) The reference of the phase of the subcarrier of the reproduced signal which is changing with time is set for each line.

(3) Generate a reproduced FM signal (positive polarity is called positive phase in baseband) and its reverse phase signal (reverse polarity in baseband).

(4) Two orthogonal switching signals (cos ω _SC t and sin ω _SC t) are created from the subcarriers for each line obtained in (2), and the positive and negative phase FM signals in (3) are switched.

(5) Two chromaticity signals are obtained by FM demodulating each of the two FM modulated waves of (4).

(6) E _Y and two types of E _C (E _I , E _Q ) are output signals.

G. Examples Hereinafter, the present invention will be described in more detail by way of examples with reference to the drawings, but these are merely examples, and various modifications and improvements can be made without departing from the scope of the present invention. Of course, this is possible.

FIG. 1 is a block diagram showing a configuration of a broadcast receiving apparatus according to the present invention, in which 1 is a high frequency amplifier, 2 is a frequency converter, 3 is a local oscillator, 4 is a frequency converter (reverse phase generation), and 5 is fixed. Oscillator, 6 is FM demodulator-1, 7 is sync separator, 8 is burst gate, 9 is subcarrier generator (3.58
MHz) cosω _SC t, 10 is E _Y separation filter, the electronic switches 11 and 12, 13 and 14 FM demodulator -2,15 is 90 ° phase shifter, the 16, 17 low-pass filters, 18 and 19 Is a delay line, 20, 21, 22 are S terminal outputs, 23 is a matrix, and 24 is R, G, B outputs.

 The operation of the above embodiment will be described below.

The received signal is applied from the high frequency amplifier 1 to the frequency converter 2, and the difference signal with the output of the local oscillator 3 is used as an IF signal with the FM modulated wave. The output of the frequency converter 2 is added to the frequency converter 4, a difference component from the frequency of the fixed frequency oscillator 5 is created, and the output of the frequency converter 2 is positive-phased.
If it is IF, the output of the frequency converter 4 is an antiphase IF.

If the output frequency of the frequency converter 2 corresponding to the unmodulated FM wave is f _io , the output frequency of the frequency converter 2 is f _i
Becomes equation (3).

f _i = f _io + Δf (positive phase IF) (3) If the frequency of the fixed oscillator 5 is 2f _io and the frequency converter 4 is a balanced modulation type frequency converter, the frequency f _i 'of the output of the frequency converter 4 Becomes equation (4).

f _i '= 2f _io − (f _io + Δf) = f _io −Δf (reverse-phase IF) ... (4) The output of the frequency converter 2 is used as a baseband signal by the FM demodulator -16, and the sync separator 7, Cosω _SC t is obtained through the burst gate 8 and the subcarrier generator 9. Figure 2 shows this f
Explain _SC = 3.579545MHz generation.

2A shows the baseband signal of the FM demodulator-16, and FIG. 2B shows the output of the sync separator 7 which is a horizontal sync pulse. (B) is delayed to form the burst gate pulse of (c), and (a) is gated by this (d).
The subcarrier burst shown in is extracted. F _{SC according} to (d)
The oscillator 9 is coupled in phase to obtain continuous cos ω _SC t.

The positive phase IF of the output of the frequency converter 2 and the negative phase IF of the output of the frequency converter 4 are shown by the solid line and the broken line in FIG. In Fig. 3, cos ω _SC t (output of subcarrier generator 9)
Shows switching by. That is, to the electronic switch 11 of FIG. 1, the output of the frequency converter 2 having a positive phase IF and the output of the frequency converter 4 having a negative phase IF are added, and the pulse of cos ω _SC t of the output of the subcarrier generator 9 is added. In a certain FIG. 3 (b), the output of the frequency converters 2 and 4 is switched every T / 2 = 1 / 2f _SC to be the output of the electronic switch 11. The thick line in FIG. 3 (a) is output. When this is demodulated to a baseband signal by the FM demodulator-213 and passed through the low-pass filter 16, the result is as shown in Fig. 3 (c), which is the cosω of the NTSC chromaticity signal.
_The signal E _I modulated by _SC t can be extracted.

The cos ω _SC t of the output of the subcarrier generator 9 is shifted by 90 °.
In addition to, create sin ω _SC t, frequency converter 2 and 4
The positive-phase and negative-phase IFs that are the outputs of are added to the electronic switch 12 and switched by the 90 ° phase shifter 15, and the output is FM demodulator −
A signal E _Q obtained by modulating sin ω _SC t of NTSC as a low-pass component is extracted by a low-pass filter 17 as a baseband signal at 314.

On the other hand, take out the E _Y by adding the output of the FM demodulator -1 6 E _Y separation low-pass filter 10 to obtain an output 20 in addition to the delay line 18. E _I also obtains output 21 through delay line 19. E _Q output 22
Together with this, the outputs 20, 21, 22 become so-called S terminal output signals, and become NTSC transmission signals.

In order to drive a display device such as a color CRT, the outputs of the low pass filter 17 and the delay lines 18 and 19 are arranged in a matrix 23.
In addition to the above, E _Y , E _I , and E _Q are converted into three primary color signals E _R , E _G , and E _B to obtain an output 24.

NTSC chromaticity signals E _I cos ω _SC t and E _Q sin orthogonal to Fig. 4
The separation of ω _SC t at the IF stage is shown. FIG. 4 (a) shows the signal distribution of the IF stage when E _I cos ω _SC t (solid line) and E _Q sin ω _SC t (broken line) coexist with E _Y omitted (chain line). Figure 4 (b) and (c) respectively cos .omega _SC t and sin .omega _SC t
Is a square wave corresponding to, which controls the electronic switch.

FIG. 4 (d) shows a pulse of cos ω _SC t and the signal of (a) (I
This is an example of switching F). Precisely, if FIG. 4 (a) is a positive-phase IF signal, if the opposite-phase IF signal is switched by (b), the IF output of FIG. 4 (d) is obtained. In FIG. 4 (d), the solid line corresponds to E _I and the broken line corresponds to E _Q.
E _Q Whereas the E _I in this example with respect to f _io exist towards the positive (Δf> 0) is the distribution cancel each other in positive and negative with respect to f _io. Therefore, when (d) is demodulated into a baseband signal by the FM demodulator-2, only the E _I component of the solid line remains, and this is passed through the low-pass filter 16 in FIG. E _I is obtained.

Regarding the component of E _Q sin ω _SC t, the E _Q component can be obtained by switching (a) with (c).

FIG. 5 shows E _Y , E _I , E _Q in the baseband signal according to the present invention.
The change of the spectrum distribution of is shown.

FIG. 5 (a) is the NTSC signal shown in equation (1), and E _Y
Is a subcarrier at f _SC = 3.579545MHz, and E _C cos (ω _SC t + θ) that is amplitude-modulated is multiplexed.

In FIG. 5A, the chromaticity signal component of E _C cos (ω _SC t + θ) is located at a high frequency in the baseband signal. Fig. 5 (b) shows the change of the baseband due to the switching of IF, where E _C is a low frequency and luminance signal E _Y is E _Y cos ω _SC t.
A modulated wave centered on f _SC . Due to this switching of IF, E _C becomes a low frequency component.

FIG. 5 (c) is a low-pass filter for extracting E _C , which is 1.5 MHz for E _I and 0.5 MHz for E _Q. The simple method uses 0.5 MHz for both E _I and E _Q. In this case, the delay line 19 shown in FIG. 1 becomes unnecessary.

FIG. 6 illustrates the noise level reduction of the chromaticity signal E _C according to the present invention. In this example, we will use a simple method in which both E _I and E _Q have a bandwidth of 0.5 MHz. Fig. 6 (a) shows a normal positive phase IF with FM.
This is the noise distribution for the NTSC signal when demodulated by the demodulator-1. Since the noise generated by FM demodulation is proportional to the frequency of the baseband signal, the triangular distribution shown in Fig. 6 (a) is obtained, and the chromaticity signal is f Since it exists at _SC = 3.58MHz, the noise in the shaded area shown in (a) has an effect. On the other hand, when the positive-phase and negative-phase IFs are switched by ω _SC as in the present invention, the frequency distribution of the baseband signal in this case becomes as shown in FIG. ) Is reduced to the shaded area.

FIG. 9 is a block diagram showing the configuration of a color signal recording / reproducing apparatus according to the present invention, in which 31 is an NTSC input, 32 is an FM modulator, 33 is a recording amplifier, 34 is a recording head, 35 is a magnetic tape, 36 is a reproducing head, 37 is a reproducing amplifier equalizing circuit, 38 is FM
Demodulator-1, 39 is a sync separator, 40 is a burst gate, 41
Is a 1 line length f _SC oscillator, 42 is a 90 ° phase shift circuit, 43 and 44 are electronic switches, 45 is FM demodulator-2, 46 is FM demodulator-3 and 47
Is a delay line, 48 is a YC separation circuit, 49 is a delay line, 50 is an E _Y output,
51 is an E _I output, 52 is an E _Q output, 53 is a matrix, 54 is an E _R output, 55 is an E _G output, 56 is an E _B output, 67 is a fixed oscillator (2
f _io ), 68 represents a frequency converter (reverse-phase FM generation). For the sake of explanation, the recording system and the reproducing system are separated from the head here, but in many recording / reproducing apparatuses, the head is shared, and the circuit is switched between the recording mode and the reproducing mode.

 The operation of the above embodiment will be described below.

The NTSC signal 31 is converted to an FM modulated wave by the FM modulator 32, and the recording amplifier
At 33, a signal suitable for recording is supplied to the recording head 34.
Recording is performed while tracing the magnetic tape 35 with the recording head 34. In the reproducing mode, the reproducing head 36 reads the pattern recorded on the magnetic tape 35 and reproduces the FM modulated wave recorded by the reproducing amplifier equalizing circuit 37. The input of the FM demodulator-1 38 is a positive phase FM modulated wave using the equation (2) as the baseband signal. The horizontal sync signal is taken out from the output of the FM demodulator-138 by the sync separation circuit 39, the output of the FM demodulator-138 is gated by the burst gate 40, and the color burst is taken out. 10 (a) shows the output of the FM demodulator-138, the output of the sync separator 39 is shown in FIG. 10 (b), and the output of the burst gate 40 is shown in FIG. 10 (c). The output of burst gate 40 is applied to a one line length f _SC oscillator 41. The oscillator 41 will be described later with reference to FIG.

Adding the output of the oscillator 41 in the 90 ° phase shifter 42, to obtain two quadrature switching signal to the of sin .omega _SC t of the output of the cos .omega _SC t and the phase shifter 42 of the output of the oscillator 41.

Now, the positive-phase FM modulated wave (frequency f _io at the time of non-modulation) of the output of the regenerative amplifier equalization circuit 37 is added to the frequency converter 68. The fixed frequency of 2f _io of the fixed oscillator 67 is added to the frequency converter 68, and the difference frequency is output. Of course, in the principle configuration, the frequency converter 68 is a balanced modulation type,
The output of the regenerative amplifier equalization circuit 37 is the direct frequency converter 68.
However, it suffices that the output of the frequency converter 68 or the output of the regenerative amplifier equalization circuit 37 and the baseband signal have opposite polarities by the frequency conversion technique. If the frequency change due to the positive-phase baseband signal is Δf, the frequency f of the positive-phase FM modulated wave output from the regenerative amplifier equalization circuit 37 is given by the equation (3).

f = f _io + Δf (3) The frequency f ′ of the FM modulated wave of the opposite phase is given by the equation (4).

f ′ = 2f _io −f = f _io −Δf (4) The solid line in FIG. 12 (a) is the positive phase FM modulated wave, and the broken line is the reverse phase FM modulated wave. Positive and negative phase FM modulated waves of the regenerative amplifier equalization circuit 37 and the frequency converter 68 are added to the electronic switches 43 and 44 of FIG. 9, and the cos ω _SC t of the oscillator 41 and the phase shifter are added.
Switching between positive phase and negative phase is performed with sin ω _SC t of 42, and the output is used as the baseband signal with FM demodulator −2 45 and FM demodulator −3 46. This state is shown by the solid-line positive phase FM in Fig. 12 (a).
The modulated wave and the FM modulated wave of the broken line are switched by the switch pulse of (b), and the signal of the bold line in FIG. 12 (a) is used as the output of the electronic switch. This is FM demodulated into a baseband signal, and a chromaticity signal E _C (for example, E _I ) in FIG. 12C is obtained by a low pass filter. In the FIG. 12 shows an example of a cos .omega _SC t, but also towards the sin .omega _SC t.

Now, remove the E _C of the FM demodulator-1 38 FM demodulation (positive phase) output with a YC separation circuit 48 (for example, a low-pass filter).
And E _Y output 50 via the delay line 49.

On the other hand, the output E _I of the FM demodulator-2 45 also becomes the output E _I 51 via the delay line 47. The output of the FM demodulator-3 46 is its output 52
Becomes The delay lines 47 and 49 compensate for the difference in delay due to the difference in the Ey, E _I , and E _Q bands. Therefore, in the simple method in which both E _I and E _Q are not distinguished and 0.5 MHz is used, the delay line
47 becomes unnecessary. E _Y 50, E _I 51, and E _Q 52 are so-called S terminal output signals. Reference numeral 53 is a matrix for converting E _Y , E _I , E _Q into E _R 54, E _G 55, E _B 56, which is suitable for R, G, B type monitors.

FIG. 11 shows an example of the 1-line f _SC oscillator 41 shown in FIG. In recording / playback systems such as VTR, there is a change in the time axis,
In particular, the phase of sub-conveyance changes significantly. FIG. 11 shows an example of a circuit for absorbing the change. In the figure, reference numerals common to FIG. 9 indicate the same or corresponding portions as in FIG. 9, 57 is a crystal oscillator, and 58 is a crystal oscillator. Is a 90 ° phase shift circuit, 59, 60 are synchronous detection circuits, 61, 62 are 1H holding circuits, 63, 64
Is a multiplication circuit, 65 is an addition circuit, and 66 is an output.

The burst gate 40 in FIG. 11 is a subcarrier burst. The phase of the crystal oscillator 57 (f _SC = 3.579545MHz) is constant for the time period of the VTR time fluctuation. This is cosω
_{Let SC} t. The output of the 90 ° phase shift circuit 58 is sin ω _SC t.

Since the reproduced signal of the FM demodulator-138 changes with time, the burst signal is set to cos (ω _SC t + Δ). Δ indicates a phase change with time. Therefore, since the output signal of the crystal oscillator 57 matches the phase of the long burst, cosω
_SC t.

Synchronous detection circuit for the subcarrier regenerated by burst gate 40
When the synchronous detection is performed with 59 and 60, the output of the synchronous detection circuit 59 is And take out cos Δ / 2 with a low-pass filter. Similarly, as the output of the synchronous detection circuit 60 Take out. The 1-line memories 61 and 62 of cos Δ and sin Δ are held only for 1H period. Applicable 1 of multiplication circuits 63 and 64
The output of the line by cos .omega _SC t · cos and sinω _SC t · sinΔ next, adding thereto at the adding circuit 65 (or subtracted) Get. Therefore, the output 66 serves as a reference subcarrier having a varied phase Δ in the one line.

Figure 13 shows the changes in the frequency distribution of the baseband signal due to the positive and negative phase FM modulated waves. The chromaticity signal E _C is located at a low frequency in the NTSC of (a) as in (b). Therefore, the triangular noise due to FM demodulation also becomes as shown in Fig. 14, and the noise of the chromaticity signals (E _I , E _Q ) has a small low-frequency noise level. 38 outputs E _Y 50
The level will be commensurate with the noise level of.

H. Effect of the Invention As described above, when the broadcast receiving apparatus according to the present invention is used, a positive phase and a negative phase IF are created in the IF stage of FM modulation, and this is
By switching with a pulse for a period of 2 = 1/2 f _SC , the chromaticity signal can be converted to a low frequency of the baseband at the IF stage, so the noise generated during FM demodulation is significantly higher than in normal IF demodulation. becomes small, and it is possible to keep the SN ratio of the same level as E _Y at the reception of a weak electric field, the advantage of reproducing the image with less color noise is obtained.

With the color signal recording / reproducing apparatus according to the present invention,
The FM modulated wave can be accurately switched by using the subcarrier that follows the fluctuation of the NTSC signal with time axis fluctuation, and the FM modulated wave of the positive phase and the negative phase can be switched by the orthogonal subcarrier.
By FM demodulating each of these, the chromaticity signal multiplexed on the sub-carrier (3.58MHz) in the base band is FM demodulated with a low frequency signal, so that the effect of high level high frequency noise accompanying FM demodulation Can be avoided, and the SN ratio of the chromaticity signal can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a broadcast receiving apparatus according to the present invention, FIG. 2 is a waveform diagram for explaining the generation of f _SC , and FIG. 3 is a diagram for explaining switching between a positive phase and a negative phase IF. Waveform diagram of FIG. 4, FIG. 4 is a waveform diagram for explaining separation of two orthogonal phases,
Fig. 5 is a frequency distribution diagram by FM demodulator-2, and Fig. 6 is E _C
7 is a diagram showing changes in the noise component of a signal, FIG. 7 is a frequency distribution diagram of an NTSC baseband signal, FIG. 8 is a diagram showing pre-emphasis characteristics of satellite broadcasting and FM demodulation noise distribution, and FIG. 9 is according to the present invention. FIG. 10 is a block diagram showing the configuration of a color signal recording / reproducing apparatus. FIG. 10 is a waveform diagram showing the operation of the burst gate.
Fig. 11 is a block diagram showing the specific configuration of the 1-line length f _SC oscillator, Fig. 12 is a waveform diagram for explaining the positive and negative phase FMs and their switching, and Fig. 13 is the conversion of the baseband frequency distribution. FIG. 14 is a distribution diagram for explanation, FIG. 14 is a noise distribution diagram of E _C of FM demodulation after switching the positive phase and negative phase, and FIG. 15 is a frequency distribution diagram of noise of FM demodulation. 1 ... High-frequency amplifier, 2 ... Frequency converter, 3 ...
Local oscillator, 4 ... Frequency converter (reverse phase generation), 5
... fixed oscillator, 6 ... FM demodulator-1, 7 ... sync separator, 8 ... burst gate, 9 ... subcarrier generator (3.
58MHz) cosω _SC t, 10 …… E _Y separation filter, 11,12 …… electronic switch, 13,14 …… FM demodulator −2,3,15 …… 90 ° phase shifter, 16,17 …… Low Bandpass filter, 18, 19 ... Delay line, 2
0,21,22 …… S terminal output, 23 …… Matrix, 24 …… R,
G, B output, 31 …… NTSC input, 32 …… FM modulator, 33 …… Recording amplifier, 34 …… Recording head, 35 …… Magnetic tape, 36…
… Playback head, 37 …… Playback amplifier equalization circuit, 38 …… FM demodulator-1, 39 …… Synchronous separator, 40 …… Burst gate,
41 …… 1 line length f _SC oscillator, 42 …… 90 ° phase shift circuit, 43,
44 ...... electronic switch, 45 ...... FM demodulator -2,46 ...... FM demodulator -3,47 ...... delay line, 48 ...... YC separation circuit, 49 ...... delay line, 50 ...... E _Y output, 51 …… E _I output, 52 …… E _Q output, 53
...... matrix, 54 ...... E _R output, 55 ...... E _G output, 56 ......
E _B output, 57 …… Crystal oscillator, 58 …… 90 ° phase shift circuit, 59,6
0 …… Synchronous detection circuit, 61,62 …… 1H holding circuit, 63,64 ……
Multiplier circuit, 65 ... Adder circuit, 66 ... Output, 67 ... Fixed oscillator (2f _io ), 68 ... Frequency converter (reverse-phase FM generation).

Claims (4)

(57) [Claims] 1. A means for generating an anti-phase IF signal in which the polarity of the signal is inverted with respect to the composite video signal in an intermediate frequency signal stage, and (b) an IF signal (normal phase) or an anti-phase IF signal is demodulated. A demodulator, (c) means for extracting a color burst signal from the demodulated signal by a synchronizing signal in the demodulated signal and generating a continuous first subcarrier signal, (d) orthogonal to the first subcarrier, and continuous Means for generating the second subcarrier signal, (e) first switching means for alternately switching the IF signal and the antiphase IF signal based on the first subcarrier signal, (f) the IF signal Second switching means for alternately switching the anti-phase IF signal based on the second subcarrier signal, (g) means for demodulating the output of the first switching means and extracting the first color component signal, and (H) Output of second switching means Demodulated broadcast receiving apparatus characterized by comprising means for extracting a second color component signal. 2. A step of: (a) generating an anti-phase IF signal in which the polarity of the signal is inverted with respect to the baseband signal at the intermediate frequency signal stage; (b) demodulating the IF signal (normal phase) or the anti-phase IF signal. A step (c) extracting a color burst signal from the demodulation signal by a synchronization signal in the demodulation signal to generate a continuous first subcarrier signal, (d) orthogonal to the first subcarrier and continuous A step of generating a second sub-carrier signal, (e) a first switching step of alternately switching the IF signal and the anti-phase IF signal based on the first sub-carrier signal, (f) an inverse of the IF signal A second switching step of alternately switching the phase IF signal based on the second subcarrier signal; (g) a step of demodulating the output of the first switching step and extracting a first color component signal; h) Output of the second switching step Demodulates the broadcast receiving method which comprises a step, for extracting a second color component signals. 3. (a) means for generating a reverse-phase IF signal whose polarity is reversed with respect to the baseband signal of the reproduced FM signal, (b) demodulation for demodulating the reproduced IF signal (positive phase) or the reverse-phase FM signal (C) means for extracting a color burst signal from the demodulated signal by a synchronizing signal in the demodulated signal to generate a continuous first subcarrier signal, (d) orthogonal to the first subcarrier and continuous Means for generating a second subcarrier signal, (e) first switching means for alternately switching the reproduction FM signal and the anti-phase FM signal based on the first subcarrier signal, (f) the reproduction FM signal And second switching means for alternately switching the anti-phase FM signal based on the second subcarrier signal, (g) means for demodulating the output of the first switching means and extracting the first color component signal, And (h) the second switching hand It demodulates the output of the means for extracting the second color component signals, color signals recording / reproducing apparatus which comprises a. 4. A step of: (a) generating an anti-phase IF signal whose polarity is inverted with respect to the base band signal of the reproduced FM signal; and (b) demodulating the reproduced IF signal (normal phase) or the anti-phase FM signal. (C) extracting a color burst signal from the demodulation signal by a synchronization signal in the demodulation signal to generate a continuous first subcarrier signal, (d) orthogonal to the first subcarrier, and a continuous first subcarrier signal. 2) a step of generating a subcarrier signal, (e) a first switching step of alternately switching the reproduced FM signal and the anti-phase FM signal based on the first subcarrier signal, (f) the reproduced FM signal A second switching step of alternately switching the anti-phase FM signal based on the second subcarrier signal, (g) demodulating the output of the first switching step, and extracting the first color component signal, and (H) Second switching step It demodulates the output color signal recording / reproducing system, which comprises a step, for extracting a second color component signals.