JPS59101982A - Television synchronizing receiver - Google Patents

Abstract

PURPOSE:To eliminate a disturbance due to a noise component to a demodulated video signal and sound signal by forming a costas loop and a frequency pulling- in circuit as described. CONSTITUTION:A costas loop is formed by synchronizing detectors 10, 11, LPFs 12, 13, signal amplifiers 14, 15 LPFs 16, 17, a phase detector 18, an LPF19 and a voltage control oscillator 20, and a 90 deg. phase shifter 21. Also, a frequency pulling-in circuit is formed by a voice intermediate frequency discriminator 23, a voltage subtracter 24, and an LPF25. An output of this LPF25 is added to an output of the LPF19 of the costas loop and is fed back to the voltage control oscillator 20. By forming in this way, a noise component can be eliminated from control voltage for controlling the voltage control oscillator, and accordingly, a disturbance due to the noise component to a demodulated video signal and sound signal can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a television synchronization receiver that can be used in television receivers and VTR video tuners.

Conventional Structures and Their Problems In recent years, so-called electronic tuners using variable capacitance diodes as tuning elements have been widely used in television receivers and VTR video tuners.

Electronic tuners have advantages such as being non-contact, so there is no problem of contact failure, and being electronically controllable, making it convenient for multi-functionality such as remote control. However, because there are variations in the characteristics of variable capacitors and because an inductor is required for tuning, it is difficult to manufacture them without adjustment or automatically.

Therefore, in order to construct a receiver that is easy to integrate without using a tuning circuit using a variable capacitance diode and an inductor, it is possible to use a synchronous reception method. A synchronous carrier regeneration method is suitable for synchronizing the synchronous carrier wave with a television signal weaker than , /i. This method is known as the Costas loop method.

FIG. 1 is a block diagram of main parts showing the configuration of a conventional synchronous carrier regeneration type synchronous receiver using a Costas loop.

(1) is a first synchronous detector that synchronously detects the in-phase component of the 1JICJ wave human power, (2) a second synchronous detector that synchronously detects the orthogonal component, (: ツ) and (4) are these. A low-frequency P-wave device that converts the outputs of the two synchronous detectors (1) and (2) into low-frequency P waves, and (5) a low-frequency P-wave device (3) that converts the outputs of the two synchronous detectors (1) and (2) into low-frequency P waves.
and (4) a phase detector that detects the phase of the synchronous carrier wave with respect to the modulated carrier wave by multiplying the output by voltage, (
6) is a low-frequency P-wave device that converts the output of this phase director into a low-frequency P wave, (7) IJ is a voltage-controlled oscillator that is controlled by the output of this low-pass filter (6), and (8) is this voltage This is a 90° phase shifter that shifts the output of the controlled oscillator (7) by 90°.

In this Costas loop type synchronous receiver, the in-phase and quadrature component signals obtained from the first and second quadrature detectors (1) and (2) are added to the phase detector (5), and this phase detection The ta pressure proportional to the phase error between the collected wave and the synchronized carrier wave which is output from the voltage controlled oscillator (7) for 1 hour is applied to the receiver manually from the receiver (5), and this voltage is applied to the voltage controlled oscillator (
7), the phase error is controlled to be zero.

If the conventional example shown in Fig. 1 is applied directly to a television receiver, the output of the low-frequency P wave generator (6) will contain noise components because the television (speech) has residual sideband characteristics. This noise component phase-modulates the synchronous carrier wave in the voltage controlled oscillator and also frequency-modulates the nfJ frequency signal in the voice.Therefore, the demodulated image signal and voice signal are disturbed by the noise component.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a television synchronization receiver capable of removing interference caused by noise components remaining in the output of a phase detector that is a low-frequency P wave on demodulated video and audio signals. It's about doing.

Structure of the Invention In order to achieve the above object, the present invention provides cardiac pressure iI! The oscillator and this voltage;:;U output phase 0 of the oscillator
A 90° phase shifter that shifts the phase, the output of the voltage control 11 oscillator, and the output of the 90° phase shift H3 are respectively used as synchronous carrier waves, and these two synchronous carrier waves generate a video carrier signal input from the receiver input section. The first and @2 same JUL detectors detect in-phase and quadrature components, and the @1 and second synchronous detectors l! ! first and second low-frequency P-wave generators that convert the output of the low-frequency P-wave generator into low-frequency P waves at the frequencies of the video signal baseband and the audio intermediate frequency signal; third and fourth low-frequency P-wave generators that generate low-frequency P waves from the frequency portions having out-of-band characteristics of both Il and iJ waves in the vestigial sideband of the television signal;
A detector for detecting the phase difference between the transmitted wave and the synchronous carrier wave from the output of the low frequency transducer, and (a) means for feeding back the output of the f-phase detector to the voltage controlled oscillator. This makes it possible to remove the noise component from the control voltage that controls the voltage controlled oscillator, even though the television signal has residual sideband characteristics, and therefore the demodulated video and audio signals It is possible to eliminate interference caused by noise components.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 2 shows a block diagram of essential parts of a television synchronous receiver according to an embodiment of the present invention. In FIG. 2, (9) is a high frequency input section, αQ is a first synchronous detector, Qυ is a second synchronous detector, (6) and C10 are first and second low-pass filters, α Xun and 05 are signal amplifiers, OQ and αη are third and fourth low-frequency P wave amplifiers, (
(to) is a phase detector, Ql is a low-frequency P wave generator of the Costas loop, (1) is a voltage controlled oscillator, and 3υ is a 90' shifter, and these constitute the Costas loop. (A) is an audio intermediate frequency amplifier, (E) is a frequency discriminator, t241
is a voltage subtracter, and (c) is a low-frequency P-wave device, which constitute a frequency pull-in circuit, whose output is a voltage adder that connects the low-frequency P-wave device O! of the above Costas loop. It is added to the output of 1. The slope is the voltage storage device, the (support) is the voltage selector, (29)
is a human control device, which constitutes a tuning voltage generation circuit. The output voltage of the voltage selector (c) is also determined by the voltage addition RRI (
b)] is added to the output of the low-frequency P wave generator 0 of the Costas loop. (11) is a video signal amplifier, 011 is a video output device, and C (2 is an audio output device).

The operation of the television synchronous receiver of this embodiment configured in this manner will be described below. The video carrier signal of the receiving iW channel input to the high frequency input section (9) is assumed to be rv(t), and the audio carrier wave signal is assumed to be vs(t). Since vV(t) is modulated by residual sideband, it can be expressed as follows1, vv(t)=Re((1(t)+jQ(t)) e
xp j (ωv1+ψv))=I(t) cos
(ωV[+ψν)−Q(L) sin (ωv(4ψv
)...(1) Here, 1<7. is the real part of the expression in (). (2) ([) includes a video signal in the signal lever of the in-phase component with respect to the carrier wave signal. Q (0 is the signal of the orthogonal component to the carrier signal, ω9 is the angular frequency of the video carrier signal, ψ9
is the phase of the video carrier signal.

Furthermore, narrowband Gaussian noise n (t) is expressed as n (t) = n((t) cos (ωv1+ψV
)−n5(t) sin (ωvt+ψV)...
... (2), and the above vV(t) and this n (t
) is applied to one terminal of each of the first and second synchronous detectors 01 and 0υ.

Now, the output of the m-pressure controlled oscillator (E) is expressed as fJ(, (t)=A, cos (ω.1+ψo)
-... (3), and when this is applied to the other terminal of the first synchronous detector OI consisting of a voltage multiplier, the output υp v (t) is υPv L) = AoL v
v(t)+n(t)) cos (ωo1 +ψ0
) + cos ((ω1, -ωo)t+ψ7-ψ.])
' (Q(t)+n5(t)) (sin ((ω, l
-ωo)t+ψv4ψ0]+sin[(ωV-ωo)t
+97−ψ. Moon ° - (4) When the voltage controlled oscillator output is synchronized to the video carrier wave, ω. Since 2ω7, ......(If the 2O2 signal is removed by the 5-inch low-frequency P-wave generator (2), here,
ψ is ψ9=ψ. is the phase difference between the video carrier wave and the voltage controlled oscillator output. If ψ=O then Ao
-Song・ (7)”rv(t)=TC
I(t) + nc(t) ). That is, V, a signal of an in-phase component with respect to the image carrier wave and noise are obtained as a detection output. However, orthogonal components are not detected. This detection output is converted into a video one-image detection output and is amplified by a signal amplifier 0→ through a C1 low-pass P-wave device θ, and is outputted to a video output device O via a video signal amplifier.

The P-wave characteristics of the low-frequency P-wave device θ are shown in FIG.

The low video signal is converted into a P wave at the baseband as shown in this figure. t(i) When a television signal is received using the American superhetero gain reception system, the overall baseband frequency characteristic can be considered flat due to the Nyquist P-wave characteristics of the intermediate frequency amplifier. In the synchronous reception method of the present invention, it must be assumed that the situation is as shown in Fig. 4(a).In other words, the voltage gain in the low frequency range is twice the gain in the high frequency range. In the embodiment shown in FIG. 2, the frequency characteristics of the video signal amplifier are corrected as shown in FIG. 4(b).

Since the audio carrier wave signal t'5(t) of television broadcasting is frequency modulated, vs(t) −= AS cos ωs+5(t))t
+ψJ ++・+++ (expressed as 81), where A8 is the amplitude of the audio carrier signal, ω is the angular frequency of the audio carrier signal, s (t) is the audio signal, and ψ5 is the phase of the audio carrier signal.

This vs(t) and υ of equation (3). (1) Synchronous detector O
I, its output is vps(t)=As cos ((ωs”5(t))
t + ψs] AoCO8 (ω. t + ψ.) ω, + ω in the low-frequency p-wave device θ group. By removing the frequency component of 'ps(t)
=! "!" cos ((ω5-ωo) t + 5
(t) t+ψ, -ψ. ]...αQωIF”ω8−ω0
．． If ω0=ω7, then vps(j)=””cos((
a+tp'+s(t>) j+9's-9+. ) ・
t) PSCt) in equation (11) DI is nothing but the audio carrier signal shown in equation (8) transformed into an audio intermediate frequency signal with an angular frequency of ω, F.

The P-wave characteristics of the low-frequency cutter (181) cover the frequency 03.P of the audio intermediate frequency signal as shown in Figure 3. (2)
The output is demodulated by the frequency discriminator (to), and the audio signal s(t) is converted to j9.5 (
t) is supplied to the audio output device 04.

In the above, it has been explained that there is no difference between the phase of the video carrier signal vv(t) and the phase of the synchronous carrier signal f3vo([) output from the voltage controlled oscillator ■, which is ψ20.
This situation can be obtained as follows.

Output V of the 90° phase shifter. (1) is a voltage controlled oscillator (e)
Since it has a phase difference of 90° with the output of
) ”・”' θgong This is υV of equation (1)
A second synchronous detector O consisting of a voltage multiplier together with ([)
In addition to η, its one output v5. . (1) Low-frequency P wave device 03
When ω is passed, ω is obtained in the same way as when formula (6) was obtained. −ω7. This I! 'PQ(t) is amplified by a signal amplifier tm and applied to a phase detector (t).

In the phase detector OFQ consisting of a voltage ratio multiplier, t'PV(t
) and E'PQ(t) are multiplied by voltage, and as a result, a control voltage υC(t) is generated.

vc(tJ2vpv(t) −vro(t)′ −””
((1(t)+.(t))'CQ(t)...5(1)
)・)・i・θ8, where θ=2ψ. However, the amplification degrees of the first and second signal amplifiers are assumed to be 1 here.

The video carrier signal υV(1) is transmitted in the vestigial sideband (however, its transmission characteristics are different from the usual vestigial sideband transmission,
It consists of a part using double sideband transmission and a part using single sideband transmission. That is, the residual sideband characteristics of the video carrier signal UV(t) shown in FIG. 5(a)1 are the double sideband characteristics shown in FIG. 5(b) and the single sideband characteristics shown in FIG. 5(C). It is a superimposition of

A signal by double sideband transmission consists only of in-phase components with respect to the phase of the carrier wave, and a signal by single sideband transmission consists of in-phase components and orthogonal components. Now, I L(t) is the in-phase component of N number v v(t) by double-sideband transmission, and Iu(t) is simply '(1+,(t)+I U(t)+n((t), )
(Qu(t)+ns(t)) CO5θ・・・・・・
It becomes IJ5.

If the low-pass P wave characteristics of the low-pass filters αQ and αη are
However, if the band is narrower than that shown in Figure 6 or Figure 6, nc(t)
and n,'(t) are the synchronous and orthogonal components of the narrowband Gaussian noise n(t) after passing through the low-band P-wave device M.

IL(t)≧nc(t), IL(L)≧ns′(t
)... Since li(IL(t))2\0, if the loop bandwidth is narrow enough to remove the second term component of 2, the voltage controlled oscillator slope is It is controlled so that θ20. That is, the video carrier wave signal vv(t) and the output V of the voltage controlled oscillator (e). The phase closing error ψ of (t) is in the state of ψ=0.

Here, even if the loop bandwidth is narrow enough to make ψ=0, the average value of ψ will be 0, and the equation Qη
The noise component shown by the second term remains to some extent. This noise component gives fluctuations to the output phase and output frequency of the voltage controlled oscillator (E).

However, when comparing the second term of equation (a) with the second term of equation (a), the difference in amplitude is much larger. 0U(t)≧n 5
(t), ns(j)2>ns'(t)2, and formula Q'i) does not include to(t). However, ns(t)2 and ns'(t)'' are each ns
(t) and ns'(t).

In this way, by inserting the low-pass P wave filter Q1 and θη as shown in FIG. 2, the noise component, that is, the second
term or the influence of the second term of equation Q4 can be significantly reduced.

Furthermore, if the band of the low-band P-wave device α and (17) is made narrower, the dispersion ns/(t)g of ns(t) becomes smaller in proportion to the band. The fluctuations in the output phase and output frequency of the voltage 1r controlled oscillator (a) are reduced accordingly.

The procedure for selecting a desired channel for reception by the television receiver of this embodiment and entering the reception form is as follows.

Select the selected channel voltage stored in the voltage storage device (in the voltage selector) corresponding to the desired reception channel input from the control input device (c), and input this into the voltage adder (c). Add. Voltage controlled oscillator by this tuning voltage? The car is controlled and a synchronous carrier signal 1o(t) is generated. Audio carrier wave signal v5(t) and this synchronous carrier wave signal V. (1) is added to the synchronous detector OQ, resulting in the audio intermediate frequency signal I
JPs(t) occurs. The frequency of the audio intermediate frequency signal 7J, 5(1) is changed by the frequency pull-in circuit to
The carrier frequency ω7 of the broadcast video carrier signal v v(t) and the carrier frequency ω of the audio carrier signal +1', (t)
, that is, equal to ω1F. The frequency of ([) is controlled.

When this frequency falls into the frequency pull range of the Costas loop, the Costas loop rapidly enters a state of phase locking. When the Costas loop is phase synchronized, the synchronous detector 00 outputs the video signal vpv(t) and the audio intermediate frequency signal ', r;, 5
(t) is obtained. These aunts pass through the low-frequency P wave generator 0, etc., and the video signal is sent to the video output device (1), and the audio intermediate frequency signal is demodulated by the frequency discriminator (e), and the demodulated signal U is the audio signal. It is output to the audio output device 02.

Effects of the Invention As is clear from the above explanation, according to the present invention, the outputs of the first and second synchronous detectors of the Costas loop are
and a second low-band P-wave device generates low-band P-waves at the frequencies of the video signal baseband and the audio intermediate frequency signal, and residual side waves of the television signal output from the first and second low-band P-wave devices. The frequency portion having double-side band characteristics in the band is further low-pass filtered by the eighth and fourth low-pass P-wave filters, and the video carrier wave and the output of the third and fourth low-pass P-wave filters are filtered. It is configured to detect the phase difference between the synchronous carrier waves, thereby having the effect of significantly reducing fluctuations in the phase and frequency of the synchronous carrier wave, that is, the output of the voltage controlled oscillator.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the main part of the conventional example, Fig. 2 is a block diagram of the main part of an embodiment of the present invention, and Fig. 3 is a frequency characteristic diagram of a low-pass P-wave generator that generates P waves from the output of a synchronous detector. , Fig. 4(a) is a frequency characteristic diagram of the video signal base), Fig. 4(b) is a frequency characteristic diagram of the video signal amplifier, and Fig. 5(a) is the residual side type transmission of the television signal. Figure 5(b) is a characteristic diagram showing double sideband transmission during vestigial sideband transmission of a television signal, and Figure 5(c) is a characteristic diagram showing double sideband transmission during vestigial sideband transmission of a television signal. Characteristic diagram showing sideband transmission, Figure 6 is 3
FIG. 4 is a frequency characteristic diagram of a fourth low-pass P-wave device. θ1...first synchronous detector, 0υ...second synchronous detector, (2)...first low-pass filter, 03...second
low-frequency P-wave device, OQ...8th low-frequency P-wave device, αη...
・Fourth low-frequency P wave device, 0 mark...Phase detector, (E)...
・Voltage controlled oscillator, QI)...90° phase shifter agent Yoshihiro Morimoto Figure 3 Figure 4 M) Circumference 3i number (MHz) Side 7Z number (Mlh) 5th
Figure 6 (P) Hz Figure 6

Claims (1)

[Claims] 1. A voltage controlled oscillator, a 90° phase shifter that shifts the phase of the output of the voltage controlled oscillator by 90', and the output of the voltage controlled oscillator and the output of the 90° phase shifter, respectively, as synchronous carrier waves. first and second synchronous detectors that detect in-phase and quadrature components of a video carrier signal input from the receiver input section using two synchronous carrier waves; first and second low-frequency P-wave devices that generate low-frequency P-waves at the frequency of the audio intermediate frequency signal; and residual sidebands of the television signal output from the first and second low-frequency P-wave devices. The 8th and 4th waves generate low-frequency p-waves in the frequency portion with double-side band characteristics.
a low-pass filter, a phase detector that detects the phase difference between the video carrier wave and the synchronous carrier wave from the outputs of the eighth and fourth low-pass filters, and a phase detector that detects the phase difference between the video carrier wave and the synchronous carrier wave, and the output of the phase detector is connected to the voltage controlled oscillator. 5. A television synchronous receiver configured with means for returning.