JPS61152190A - Digital chrominance signal processing circuit - Google Patents

Abstract

PURPOSE:To lead out an AFC signal, an APC signal, and an ACC signal at a high speed and to simplify the circuit constitution by subjecting an input color burst signal to prescribed arithmetic. CONSTITUTION:The phase of the color burst signal is shifted at 90 deg. or $090 deg. by a -90 deg. phase shifter 4, and the output signal of the phase shifter 4 is divided by the input color burst signal in a divider 5, and the output signal of the divider 5 is subjected to inverse trigonometric function arithmetic by a tan<-1> inverse trigonometric function arithmetic unit 6, and the output signal of the unit 6 is delayed in ahone clock delay circuit 7 by one sampling period, and the difference between te output signal of the unit 6 and that of the delay circuit 7 is operated by an adder 8 to obtain the AFC signal. The output signal of the unit 6 is subjected to trigonometric function arithmetic in an sin trigonometric function arithmetic unit 10, and the output signal of the unit 10 is divided by the input color burst signal or the output signal of the phase shifter 4 in a divider 11 to obtain the ACC signal. The difference of phase between the output signal of the unit 6 and a reference signal is operated by an adder 18 to obtain the APC signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a digital carrier color signal processing circuit, and more particularly to a circuit that can obtain control signals necessary for AFC, Ace, and APC from color burst signals at high speed. .

In FIG. 1, the -90° phase shifter 4 is a phase shifting means for shifting the phase of the color burst signal by -90°, and the divider 5 is for dividing the output signal of the phase shifter 4 and the input color burst signal. The first division means for performing tan' inverse trigonometric function calculation unit 6 is the inverse trigonometric function calculation means for performing inverse trigonometric function calculation on the output signal of the first divider 5; The adder 8 is a delay means for delaying the output signal of the arithmetic operation unit 6 by one sampling period, and the adder 8 is a first subtraction means for taking the difference between the output signal of the inverse trigonometric function operation unit 6 and the output signal of the delay unit 7. Trigonometric function Pi
The four-band unit 10 is a trigonometric function calculation means for performing a trigonometric function calculation on the output signal of the inverse trigonometric function calculation unit 6, and the divider 11 is a trigonometric function calculation unit that performs a trigonometric function calculation on the output signal of the trigonometric function calculation unit 6. The adder 18, which is a second division means that performs division with the output signal of 4, is a second subtraction means that takes the difference between the output signal of the inverse trigonometric function calculator 6 and the phase of the reference signal.

Effect: The phase of the color burst signal is changed to 90° by the 90° phase shifter 4.
The output signal of the phase shifter 4 is divided by the input color burst signal in the divider 5.
'The inverse trigonometric function calculator 6 performs an inverse trigonometric function operation on the output signal of the divider 5, and the 1-O-k delay circuit 7 delays the output signal of the inverse trigonometric function operator 6 by one sampling period, and then adds Vessel 8
, the difference between the output signal of the inverse trigonometric function calculator 6 and the output signal of the delay device 7 is obtained to obtain an AFC signal, and the sine trigonometric function calculator 10 performs a trigonometric function calculation on the output signal of the inverse trigonometric function calculator 6. The output signal of the trigonometric function operator 10 is divided by the input color burst signal or the output signal of the phase shifter 4 in the divider 11 to obtain the ACC signal, and the adder 1
At B, the difference between the output signal of the inverse trigonometric function calculator 6 and the phase of the reference signal is obtained to obtain an APC signal.

EXAMPLE FIG. 1 shows a block diagram of a first embodiment of the circuit according to the invention. In the figure, only the color burst signal is extracted from the carrier color signal that has entered terminal 1 by a switch 3 that is turned on by a color burst gate pulse that has entered terminal 2. The carrier color signal is a digital signal sampled at a constant sampling period. Set the amplitude to A1, set the frequency to rc, and set the phase to 0.
1, the color burst signal is represented by a signal a - ASil'l (27t Ct + 01), and -90° phase shifter 4 outputs a signal b, 61c
It is assumed that the signal is os(2πfCt+θ1). When a/b is performed in the divider 5, a signal C is obtained: 0-jan (2πfc T10,).

The signal C is calculated tan-' by the inverse trigonometric function calculator 6, resulting in a signal d of d=l12π fc t+θi, which is one clock driven by a clock having the same period as the sampling period T of the color video signal. The signal is delayed by one clock in the delay circuit 7, and the time is set to -T, resulting in a signal @d' of d'=2π fc(t-T)+θ1. Signal d and signal d' in adder 8
When the difference between (8 is essentially a subtractor) is taken, e-2
A signal e in πfcT is obtained, which has a constant value if the frequency rc of the color burst signal is constant.

However, if the frequency fc of the color burst signal at time (t-T) changes to fc', the above (1)
The formula is: e=2π(fc'-rc)t-2πfc'
It becomes T. Here, -2πfc'T is a constant value, and 2
π(rc' - fC)j is the frequency fc' at time [
The signal e represents the amount of phase change between the signal at the frequency re and the signal at the frequency re, and the signal e represents a signal corresponding to the frequency of the input color burst signal. Therefore, the signal e is used as an AFC signal by l/1 and is supplied to the AFC circuit via the terminal 9.
The frequency of the carrier color signal is automatically adjusted.

On the other hand, the signal d is sin-calculated by the sine trigonometric function calculator 1o to become a signal f of f −3in (27r fc t+θl), and when a/b is performed in the divider 11, a signal g of −A is obtained. can get. Since A represents the amplitude of the input color burst signal, signal 9 can be used as an ACC signal and is fed via terminal 12 to the AC,C circuit to automatically adjust the saturation of the carrier color signal.

By the way, 13 is a CO having a ROM 17, which is a reference signal source. In the ROM 17, the amplitude data shown in the second figure is stored if the data is analog processed, but in this embodiment, the phase data shown in the third figure is stored. 1
The clock delay circuit 16 is configured to be driven by the same clock as the sampling clock of the carrier color signal.

Reference signal oscillation frequency r6 that has entered the terminal 14 and should be output
The data h according to the adder 15.1 clock delay circuit 1
80M address 1III with a circuit composed of 6
The Ill signal i is supplied to the ROM 17. In this case, at the output of the 1-O clock delay circuit 16, the data h is shorelined every sampling period, but since the bit length of the adder 15 is finite, overflow occurs at every fixed period, and R
The data size of the OM address control signal i is as shown in FIG.

By supplying the address control signal : to the ROM 17, the address of the ROM 17 is sequentially updated in accordance with the clock, and phase data j of O to 2π is taken out from the ROM 17. If the phase of the reference signal is θ2, the phase data j at time t is j=! It is expressed as 2π f, t+θ2. If the frequency of the input color burst signal is controlled by AFC to f, then the signal d is d-2π1.1+θ1. When the difference between the signal d and the signal j is taken in the adder 18 (18 is essentially a subtracter), a signal k is obtained, where k=θ2−θ. Since the signal represents the phase difference between the reference signal and the input color burst signal, it can be used as an APC signal and is fed to the APC circuit via terminal 19, so that the phase of the carrier color signal is automatically adjusted. be done.

FIG. 5 shows a block system diagram of a second embodiment of the circuit of the present invention, in which the same components and signals as in FIG. 1 are designated by the same numbers and symbols, respectively. This is applied when there is a relationship fs=N-fe (where N is an integer of 3 or more) between the reference signal frequency to and the sampling frequency rs.

The sampling frequency rs input to the terminal 20 is input to the N-ary counter 2.
1 is counted by N and supplied to the ROM 17, whereby the address of the ROM 17 is updated every N counts and phase data of 0 to 2π corresponding to this address is taken out. This phase data is supplied to the subtracter 18, and the phase difference (θ1-θ2) is extracted as in the first embodiment.

Note that if there is a relationship between the reference signal frequency f and the sampling frequency rs that is simply fs-4M (where M is an integer of 1 or more), the phase shift of 190° as shown in Figures 1 and 5 is applied. As the device 4, a delay circuit that delays the input signal by M clocks may be used.

Also, -90゛ phase shifter 4, divider 5.11, adder 8.1
8, tan' inverse trigonometric function operator 6, sin trigonometric function operator 10.1, clock delay circuit 7.16, and other circuits have R.
A function table based on OM may also be used.

Note that when the division in the divider 5 is b/a, a similar result can be obtained by using a cot' inverse trigonometric function calculator as the calculator 6.

Furthermore, similar results can be obtained by using a -tan-' inverse trigonometric function arithmetic unit as the arithmetic unit 6 and a -sin trigonometric arithmetic arithmetic unit as the arithmetic unit 10.

Furthermore, when the sign of either the arithmetic units 6 or 10 is negative, the sign of the output Q is inverted from the above case.

do.

Furthermore, when the divider 11 is configured to divide the signals f and b, a similar result can be obtained by using a COS trigonometric function unit as the arithmetic unit 10.

Further, a +90° phase shifter may be used instead of the -90° phase shifter 4, and a Hilbert filter may be used as the 90° phase shifter and the -90° phase shifter.

Effects of the Invention The circuit of the present invention changes the phase of a color burst signal extracted from a carrier color signal sampled at a constant sampling period by 90°.
or a phase shifter that shifts the phase by -90°, a first divider that divides the output signal of the phase shifter and the input color burst signal, and performs an inverse trigonometric function operation on the output signal of the first divider. an inverse trigonometric function operator, a delay device that delays the output signal of the inverse trigonometric function operator by one sampling period, and a first subtractor that takes the difference between the output signal of the inverse trigonometric function operator and the output signal of the delay device. a trigonometric function calculator that performs trigonometric function calculations on the output signal of the inverse trigonometric function calculator; and a second trigonometric function calculator that performs division of the output signal of the trigonometric function calculator and the input color burst signal or the output signal of the phase shifter. Since it is composed of a divider and a second subtracter that takes the difference between the output signal of the inverse trigonometric function calculator and the phase of the reference signal, it is possible to obtain the AFC signal, APC signal, and ACC signal at respective speeds. In this case, since no phase comparator is used, the circuit can be easily configured, and it is also possible to
It has features such as being less susceptible to changes over time, easy to integrate the circuit into an IC, and being able to reliably obtain a control signal even if the input color burst signal has a small wave number.

[Brief explanation of the drawing]

FIG. 1 is a block system diagram of the first embodiment of the circuit of the present invention, FIGS. 2 and 3 are diagrams of ROM store data in the case of analog processing and in the case of this embodiment, respectively, and FIG. 4 is a diagram of the R
FIG. 5, which is a diagram of the address control signal of the OM, is a block system diagram of a second embodiment of the circuit of the present invention. 1...Carrier color signal input terminal, 2...Color burst gate pulse input terminal, 3...Switch, 4...=
90° phase shifter, 5.11...divider, 6...jan
-' Inverse trigonometric function calculator, 7.16... 1 clock delay circuit, 8.15.18... Adder, 9... AFC signal output terminal, 10... Sin trigonometric function calculator, 12・
...ACC signal output terminal, 13...-VCO114...
・Data input terminal, 17...ROM, 19...APC
Signal output terminal, 20... Sampling frequency input terminal, 21
...N-ary counter. Figure 1 Figure 4

Claims (2)

[Claims] (1) The phase of the color burst signal extracted from the carrier color signal sampled at a constant sampling period is 90° or -9
A phase shifter that shifts the phase by 0°, a first divider that divides the output signal of the phase shifter and the input color burst signal, and an inverse trigonometric function operation on the output signal of the first divider. an inverse trigonometric function operator, a delay device that delays the output signal of the inverse trigonometric function operator by one sampling period; 1, a trigonometric function calculator that performs a trigonometric function calculation on the output signal of the inverse trigonometric function calculator, and an output signal of the trigonometric function calculator and the input color burst signal or the output signal of the phase shifter. A digital carrier chrominance signal processing circuit comprising: a second divider that performs division; and a second subtracter that takes the difference between the output signal of the inverse trigonometric function calculator and the phase of the reference signal. (2) The phase shifter, the first and second dividers, the inverse trigonometric function operator, the trigonometric function operator, the delay unit, and the first and second subtractors are constructed using function tables based on ROM. A digital carrier color signal processing circuit according to claim 1, characterized in that: