JPS5992692A - Carrier signal generating circuit - Google Patents

Abstract

PURPOSE:To eliminate the need for an expensive filter and to improve performance by operating a limiter so that a signal of fSC(chrominance subcarrier frequency) with a 90 deg. phase shift is increased in amplitude equivalently and sufficiently and a dynamic range is not deficient. CONSTITUTION:A signal of 160fH (horizontal scanning frequency) outputted by a VCO1 is frequency-divided by a 1/4 frequency dividing circuit 2 to output four 90 deg.phase shift 40fH signals to a phase selecting circuit 3. Those signals are switched and outputted at intervals of a horizontal scanning period H by a horizontal synchronizing pulse signal from a terminal 14 and beaten again through D-type FFs 4 and 5 by the 160fH signal. Then, Q outputs of the D-type FFs 4 and 5 have higher-hamonic components reduced through LPFs 6 and 7 and are applied to multipliers 8 and 9. The output of an oscillator 13 which oscillates at a frequency fsc is applied to a limiter circuit 25 through a 90 deg. phase shifting circuit 11 and then supplied to the multipliers 8 and 9. The outputs of the multipliers 8 and 9 are added together and outputted as a carrier signal to an output terminal 15 through a BPF.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention is for generating carriers necessary for frequency conversion of a color signal of a magnetic recording/reproducing apparatus (VTR).

The present invention relates to a carrier signal generation circuit. .

□ [Prior Art] 10 In home VT) L, the color signal is F'M modulated and is band-converted to a low frequency band with a frequency lower than the luminance signal frequency band and is recorded and reproduced. The range-converted color signal carrier frequency is 40fH (fH: horizontal scanning frequency)
In the VTR of the following system, the frequency of the carrier signal required for these 13 band conversions is off.

Loma subcarrier frequency fsc+40fH, ie approx.

4.21 MHa. In other words, the carrier wave frequency when recording.

Multiply the color signal whose number is fsc by this carrier signal.

Among the resulting sum and difference frequency components, the difference frequency acid,.

If you take out the minute, the carrier frequency is a low frequency change of 40fH.

A color changing signal is obtained. On the other hand, during playback, this low range converted color signal is multiplied by the carrier signal.

When the difference frequency component is extracted, it is the original carrier frequency.

This means that the fsc color signal can be reproduced. 'A carrier signal generation circuit is an example of a carrier signal generation circuit that performs band conversion as described above.

There is. Figure 1 shows the carrier coefficient generation circuit.

An example of a block diagram applied to an R color signal system is shown.

vinegar. In Figure 1, 1 is the 110th oscillating at 160 fH.
voltage-controlled oscillator (hereinafter abbreviated as ■CO), 2° is a sufficient circuit, 3 is a signal switching circuit, 4 and 5 are D-type F-IJ tube flops (hereinafter abbreviated as F', F') ,・6.7
is the LPF, and 8 is the 2nd (7)th V that oscillates at the frequency fsc.
Co, 9.10 is converter, 11 is adder - 12 is 9
0 degree phase shift circuit, 13 BPF114 is horizontal synchronization.

A pulse input terminal, 15 is a carrier output terminal.

The carrier signal generation circuit includes two converters 9. .

10, each input to the two converters.

The phase difference between the respective 40fH signals and the phase difference between the f8o signals is
．． .

The angle of each output is 90 degrees, and the sum frequency component in the two outputs is removed. FIG. 1 will be explained.

The 160 fH signal that is the output of V and COl is divided by j in the sufficient frequency circuit 2, and the signal of 160 fH, which is the output of V and COl, is divided by j and outputted with a phase shift of 90 degrees, Oo and 90'.
, 180', and a 40 fH signal having phases of 27 degrees is output to the phase selection circuit 3. The phase selection circuit 3 is
゛These four 40fH signals are horizontally opened from the input terminal 14.

The horizontal scanning period (hereinafter abbreviated as H) is determined by the periodic pulse signal.
It is switched and outputted every time, and the output is about 90 degrees every H.

Create a 40fH signal with a phase shift. This 40f1 (signal is '.

Furthermore, the 90 degree phase relationship is maintained accurately.

D type F, F, 4.5, 160fH signal number is re-done from this ≦ This phase shift processing is a cross from an adjacent track.

This is done to reduce the amount of talk. Naoko.

It is input to the D input of the D type F, F, 45 when . 4Qf
In the HI5 signal, the signal input to the D input of the D type F, F, 4 always leads the signal input to the D input of the D type F, F, 5 by 90 degrees. Q of each of D type F, F, 4.5
output.

The 40fH signal is generally a rectangular wave, so the signal is 40fH high.

Since it contains many harmonic components, this height of 2° with LPF6.7
3. After reducing harmonic components, to converters 8 and 9.

Each is supplied. Further, the output of the oscillator 13 which oscillates at the frequency fsc is input to a 90 degree phase shift circuit 24.

from the 90 degree phase shift circuit 11 to the converters 8 and 9.

The phase of the fsc signal input to the converter 9 is
The fsc signal delayed by 0 degrees is input to the converter 8. Frequency applied to converters 8 and 9.

The multiplication of is expressed as follows.　　　.

In converter 8, m1an' (2πfsc” −+ ) X n+■
(2g-4of, t + l ”W--1(,, 2π 5 (+40f a ) t 10(Xm (2π(, f
8j-4Of,)t・-π)] = 7 (-2" 5°+4OfH)t-ccm2π 5c-40fH)t) ・For converter 9, m-2xf8ot X n-2yr*40fHt
15-JQFJI2 (01152πge,
,,-)-4Qf,) is 10 cm 2π(,f8.-40
．． f,) t).

Here, rro and mz are amplitude components n1. of fsc. n2 is 4
The outputs of the converters 8 and 9, which are amplitude components of 0fH, are added together by an adder 1o.

Then, the (-fsc +40fH) component is ・4 ・+ (m1nl +mzn2)
・・・・・・(Type 0.

(fsc-4OfH) component is 4 (mtnt -m2n2)...
...It is possible to obtain an output signal expressed by equation (2). In the carrier 5 signal generation circuit, this circuit is integrated into an IC.

By doing so, the greatest advantage of ICs is the sameness of the elements.

By taking advantage of the fact that the ratio accuracy of the target is extremely high (absolute value accuracy of 1 to 3% or less of the resistance value of the same shape), it is possible to calculate the difference.

The component (f8o-40fH) is eliminated, and (f
8dO-4OfH) signal traps are removed to reduce costs and improve performance. Distortion in the phase, amplitude, and width of the 4OfH signal caused by the remaining difference frequency components will be explained.

Assuming that the color signal 15 having a phase difference ψ with respect to the carrier signal is input, it is expressed by the following equation.

The frequency is converted in such a way that

(2) (2π-fsc-t+ψ)・02πCf8c+
4Of,)t.

+alla(2πf8cmt+ψ) *ays2rr,c+4ofH)t.

Ten faces (2πf8c ” to 1ψ)・kcos 2π,
. -4of,) t 2゜=+[C1ys2π((2
f8c+4ofH)t+ψ)-)-co8(2rc*
4QfH$ t-ψ)]+4(a2π((2fsc
-40fH) t+ψ) 1■(2π・40fH-t+ψ
)] ・・・・・・(3)5 (However, k is for the carrier (f8o+4ofH).

Level ratio of Rusubrias (f8o-4ofH)).

When only the 40fH frequency component is extracted with LPF5 (3)
.

As can be easily seen from the equation, the following equation is performed.

+■(2π・40fH@1ψ)+4−a(2π・40
f1t+ψgl=+■(2πφ4OfH- to -ψ)+)
(2) ((2π number 40f1, φt−ψ).

12ψ) ・ =+1(2π・40f1(・−ψ)+←(2π・40
fH−t−ψ) (9)2ψ”−+ affl (2π*
4of, @ in 2ψ=-4-(1+kcm2ψ
) cxs (2π・40fH−t−ψ)1)−+ ei2ψ
5in (2π*40fH"t-ψ) In other words, depending on the phase of the color signal (i.e. hue), the amplitude of the converted color signal will vary from (1-k) to (1+k), that is, from the original amplitude. , the amplitude ratio changes only in ±.The phase is also the original phase.

It fluctuates by ±arctank from ψ. In this way, achromatic 5
Two colors of color saturation depending on the phase (i.e. hue) of the number.

The phase can be changed.

However, this circuit was realized with the circuit shown in Section 24.

When doing so, the following problem arises. Note that R1-R17 are resistors,
C1 to C18 are transistors, E1 to E3 are 10 constant voltage sources, C1 to C4 are capacitors, and 17 is an input of f8C.

Terminals 16 and 18 are the output terminals of LPF6.7. .

That is, the 90 degree phase shift circuit of -fsc is made of the built-in resistor and capacitor of the IC, which consists of resistor R2' and capacitor zc2.

By obtaining signals at both ends of the resistance and capacitance of the LPF (15), a 90 degree phase difference is obtained. However, the absolute value accuracy of the built-in resistance and built-in capacitance varies widely, approximately ±30%. For this reason, there is an exchange between the two parties.

-Dance varies widely due to 90 degree phase difference of fsc.

The signal amplitude will also vary greatly. others.

・ 7 ・ The amplitude components ml and m2 of fsc are not equal (2)
In the ceremony.

+(m1nt of the obtained (fsc -40fH) component
-m2n2)' is no longer completely O. (It should be noted that n
1 and 02 are made digitally, so they are approximately nl + n2. ゛Moreover, it is overwhelmingly cheaper to mass produce a small number of ICs than to produce a small number of holes.

In order to benefit people, it is important to make ICs more general-purpose.

Common. Carrier generation circuit according to this principle.

The color signal processing IC including the NTSC system and PA'L system has been devised so that it can be compatible with both 10 systems by simply changing the external IC parts. NT/SC system and PAL
The frequency of -fsc is different in each method. For this reason fsc
It is necessary that the alternating current impedance variation of the 90-degree phase shift circuit has an intermediate value that is the same for both types.

Therefore, the signal component m1 with a phase difference of 90+s degree of fsc
The variation in and m2 is large.

The (f8o-4ofH) component is sufficiently erased.

This causes distortion in the phase and amplitude of the color signal and is positive.

Colors cannot be reproduced.

[Purpose of the invention]

・ 8 ・ The object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, eliminate the need for expensive filters, and improve performance.

It is an object of the present invention to provide an improved carrier signal generator.

[Summary of the Invention] 5 The present invention provides fBr2 signal component variation in fBr2 signal components.
etc. Signal amplitude with 90 degree phase difference of sc.

It's thick enough in terms of measurement, and it's probably Dynamitsufure.

To ensure that there is no shortage of frequency, the phase difference of fBt2 is 90 degrees.

It applies a limiter to a certain signal. 10 [Embodiments of the Invention] FIG. 3 shows carrier signal generation in which the present invention is implemented.

A block diagram of the circuit is shown.

A limiter circuit 25 applies a limiter to the output of the 90 degree phase shift circuit 11 and outputs a signal with a 90 degree phase difference to all 15 multipliers 8 and 9.

FIG. 4 shows an embodiment of the limiter circuit of the present invention.

Show and explain.

R18 to R23 are resistors, and Q19 to Q26 are transistors.

R4 is a constant voltage source. In this case, a signal with a phase difference of 9 degrees of f8c is generated as follows.

A resistor R2 and a capacitor C2 are connected to the base of the transistor Q20.
A signal URC having a frequency of -fsc, which is the vector addition of signals at both ends of the capacitor C2, is inputted to the bases of the transistors Q21 and Q2i, and a signal Uc at both ends of the capacitor C2 is inputted to the base of the transistor Q23.

is entered. At this time, the transistor Q21.

The microwave contains URC-Uc acid components, that is, UR acid components.

A -Uc component signal is obtained at the collector of Q22. The phase difference between these two signals is 90 degrees.

This occurs at the collectors of transistors Q21 and Q22.

The amplitude of the signal is the signal input to each differential pair.

The amplitude difference is the emitter resistance of each differential pair.

It is multiplied by the gain determined by the load on the lid. .

For example, the current flowing through resistors R21, 22, and 234 is 0.
4 m Al1, the resistance value of resistor R, 18, 19 is 1
If the resistance 1 (, 20) is 500 Ω, the gain of the differential pair is approximately 11.7 dB.When the signal input difference of the differential pair is approximately 0.2 Vpp, the gain of the differential pair is approximately 11.7 dB.

The signal generated at the collectors of transistors Q21 and Q22 is approximately.

0.77Vpp, o, aVpp) at Lt t, 15
Vppi toner 6o L capr1, which is actually the limiter effect of a differential transistor pair.

and the emitter potential of transistor Q19 is (E4-'VB
E) V (VBE: base-emitter voltage).

The upper limit is limited, and the lowest potential of the fsc output terminal, which corresponds to the colentor of transistors Q21 and Q22, is also limited (E45-
VBB -I Xo, 4) ■== (E 4-VBE
-0,4) V'. In this way, the dynamic range.

is only about 0.4V, and the amplitude is limited to 0.4Vpp.

It becomes a limiter circuit. Therefore, the fsc signal input to the multipliers 8 and 9 degrees has a waveform close to a trapezoidal wave of 0 and 4 Vpp with limited upper and lower IQs of the sine wave.The fundamental wave (fsc) component of such a waveform becomes the graph shown in Fig. 5 by expanding it into a Two-Rier series. Note that the signal amplitude is at point A (approximately 0.18 Vpp).

The limiter effect of the differential pair transistors was set at 15 points. As can be seen from Figure 5, UR.

The larger the signal amplitude of tJc, the more the fundamental wave is formed.

The increase in minutes becomes smaller and approaches ten. therefore.

NTSC system by using a limiter circuit.

And resistance R2 in PAL system, capacitor-JiC2 i.
11 - There is almost no generation of the (jsc -40fH) signal in the carrier signal generation circuit due to variations in impedance.

The color signal with correct phase and saturation is recorded and re-recorded.

will be born.

In addition, by using a limiter circuit, input terminal 1
Reduce the f8c signal level input from 7.

The dynamic range of the multiplier can be widened.Also, the input angle to the multiplier can be about 90 degrees.

The fsc number level with a difference is also O13~0.4V1)
1) is sufficient, and it is also advantageous against carrier leakage due to coreg zero or base capacitance in the differential pair transistors of the multiplier.

〔Effect of the invention〕

As explained above, ・f8o9 of the carrier signal generation circuit
By inserting a limiter circuit into the 0 degree phase shift circuit15, it becomes NTSC and PAL systems.

Also, the variation in the amplitude component of fsc can be eliminated.

Generated in the carrier signal generation circuit (f8cm40.fH
).

It is now possible to eliminate frequency components.

When the knob and its adjustment are no longer necessary and it is converted to an IC, 20.1
2. It can be made at low cost and the brown color can be reproduced correctly.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional carrier signal generation circuit.
FIG. 2 is a circuit diagram of a portion of FIG. 1, and FIG. 3 shows carrier signal generation employing the present invention. FIG. 4 is a block diagram of one embodiment of the circuit; FIG. 4 is a circuit diagram of a partial embodiment of FIG. 3; FIG. 5 is an input signal diagram. FIG. 3 is a characteristic diagram showing the relationship between the signal amplitude and the fundamental wave component. Ru. 10
11...90 degree phase shift circuit 25...Limiter circuit 5 Pot Yl

Claims (1)

[Claims] A first oscillator that oscillates at an integral multiple of the horizontal frequency, a divide-by-one circuit that divides the output of the first oscillator into - and - (m is a positive 4m integer) number. frequency divider circuit. m 4m n for each horizontal period from the output of the frequency divider circuit. ×90 degree (n is a positive integer) signal switching with phase shift. a first and second IJ circuit that generates two signals having a phase difference of 90 degrees by inputting the two output signals of the signal switching circuit and the one-frequency divider output signal; The output of either one of the first and second flip-flop circuits is input. 1 converter and the other flip-flop circuit. a second converter into which the output of the second oscillator is input, a second oscillator that oscillates at a subcarrier frequency of one color, and the output of the second oscillator into two signals having a phase difference of 906. and converting one signal to the first converter. Then, send the other signal to the second converter. The outputs of the first converter and the second converter are added or subtracted from each other. In a device having a circuit for calculating the above phase estimation. It is characterized by a built-in transfer circuit and limiter circuit. carrier signal generation circuit.