JPH0326178A - Signal processing circuit - Google Patents

Abstract

PURPOSE:To reduce a hardware scale and power consumption by detecting a mutual delay difference between chrominance signal and luminance signal circuits generated in a digital signal processing course with a digital signal processing means, generating a control signal and controlling a phase shifting circuit. CONSTITUTION:A phase shifting circuit 3 is provided between an analog chrominance signal processing circuit 1 to input analog chrominance signal components and an A-D converter 4, and simultaneously, a control circuit 8 to detect the mutual delay difference between digital chrominance signal and luminance signal processing circuits 6 and 7 is provided in a digital signal processing circuit 11. A mutual delay difference control output detected by the control circuit 8 is inputted through an interface circuit 14 to the control input point of the phase shifting circuit 3. The phase shifting circuit 3 is composed of, for example, a coil and a variable capacity element, and the capacity value of the variable capacity element is controlled by the control signal after smoothed. Thus, the compensating action of the delay difference can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a signal processing circuit, and particularly to delay control of a signal processing circuit including analog signal processing and digital signal processing.

[Conventional technology]

In recent years, the digitalization of image processing has progressed particularly rapidly, and with this, home video magnetic recording and reproducing devices (hereinafter referred to as V
Digital signal processing has also been introduced in the field of consumer images such as TR) and TV receivers. Here, regarding the conventional example of digital signal processing in VTR,
This will be explained using Figure 4. Figure 4 shows a block diagram of the reproduced signal processing system in a VTR. In the figure, an analog color signal processing circuit 1 inputs a color signal component recorded on a VTR magnetic tape and subjected to low frequency conversion from an input terminal 25, and performs processing such as amplification, amplitude control, and band limitation. In addition, the analog luminance signal processing circuit 2
inputs the FM'IR modulated luminance signal recorded on the VTR magnetic tape from the terminal 26 and amplifies it. Performs processing such as fja width control and bandwidth restriction. Each output of these analog color signal processing circuit 1 and analog luminance signal processing circuit 2 is as follows.
Each of the signals is converted into a digital signal by an A-D converter 4.5 operating at a predetermined sampling frequency. The color signal signal converted into a digital signal is restored to a color subcarrier signal by a digital color signal processing circuit 6, and after noise removal and the like are performed, it is sent to one delay adjustment circuit and an output circuit 9. is input to the D-A converter 12, where it is converted into an analog color signal and output as a reproduced color signal. On the other hand, the luminance signal component converted into a digital signal is subjected to FM demodulation, de-emphasis processing, noise elimination, and so on by a digital luminance signal processing circuit 7. After dropout compensation processing etc. are performed, D is output via the output circuit 1i'810.
-A converter l3, where it is converted into an analog luminance signal and output as a reproduced luminance signal. Further, the reproduced color signal and the reproduced luminance signal are added by an adder circuit 15,
A composite signal is obtained. [Problems to be Solved by the Invention] The luminance signal processing system in the conventional example described above has more processing steps than the color signal processing system. If processing is performed using , the processing steps will further increase. For this reason, the color signal processing system is relatively faster than the luminance signal processing system, and in order to match the timing of both signals in the D-A converters 12 and 13, the color signal processing system is processed as shown in the figure. In contrast, the delay adjustment circuit 19 is required. As a delay adjustment method using digital signal processing, for example, a shift register can be considered, but normally in a VTR, the number of quantization bits for the color signal processing system requires 8 bits or more for image quality. The register circuit scale is
It becomes quite large. In addition, in order to reduce the cost of the hardware required for such signal processing, a digital signal processing circuit 11a is configured by a digital color signal processing circuit 6, a digital luminance signal processing circuit 7, output circuits 9 and 10, and a delay adjustment circuit 19. When all or a part of the image signal is realized by a semiconductor integrated circuit, the sampling frequency is, for example, four times the color subcarrier frequency, or about 14.3 MHz, which is a high-speed operation due to the image signal band of the VTR.
The power consumption in the delay adjustment circuit 19 also increases, which has the drawback of being constrained by both an increase in circuit scale and an increase in power consumption. The purpose of the present invention is to convert a plurality of analog signals into digital signals, such as color signals and luminance signals in image signal processing,
After each desired process is performed, in the circuit that restores the analog signal again, the digital signal processing means detects the mutual processing time difference, that is, the mutual delay difference, which occurs in the digital signal processing process, and the control signal is A control signal is sent to the phase shift circuit via the interface circuit, and the delay difference in the digital signal processing process is corrected in advance by analog processing in the phase shift circuit, thereby reducing the hardware scale and power consumption. The object of the present invention is to provide a signal processing circuit that makes possible the following.

[Means to solve the problem]

The signal processing circuit of the present invention includes a phase shift circuit that inputs a first analog signal, a first A-D converter that inputs the output of this phase shift circuit and converts the analog signal into a digital signal, and a second A-D converter that converts the second analog signal into a digital signal, and each of the first and second A-D converters;
First and second digital signal processing circuit groups each receiving the output of the converter, and converting each digital signal into an analog signal by inputting each output of the first and second digital signal processing circuit groups. a first and second D-A converter, and a control means for monitoring the difference information of the signal processing time required by each of the first and second digital signal processing circuit groups; The control signal is input to the control input of the phase shift circuit via an interface circuit to control the phase shift of the signal. [Example] Next, the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention, and parts that perform the same functions and operations as the conventional example shown in FIG. 4 are given the same numbers. In this embodiment, a phase shift circuit 3 is provided between an analog color signal processing circuit 1 to which analog color signal components are input and an A-D converter 4, and a digital color signal processing circuit 6 and a digital luminance signal processing circuit are provided. A control circuit 8 is provided in the digital signal processing circuit 11 for detecting the mutual processing time difference between the signals 7 and 7, that is, the mutual delay difference. The mutual delay difference control output detected by this control circuit 8 is interfaced #! 14 to the control input point of the phase shift circuit 3, and the phase shift circuit 3 is connected to the digital signal processing circuit 1.
The processing time difference between the chrominance signal and the luminance signal generated in 1 is compensated for. Here, the operation period of the control circuit 8 is determined by the control signal 3 from the outside.
0, for example, at a predetermined timing using a horizontal synchronization signal, etc.
The control circuit 8 may output a control output during the period. In this way, the analog phase shift circuit 3 can compensate for mutual processing time differences in color signal and luminance signal processing that occur during the digital signal processing process. FIG. 2 shows an example of a specific structure of the control circuit 8, interface means, and phase shift circuit 16 shown in FIG. In the figure, the control circuit 8 includes a delay difference detection circuit 18 and a PWM modulation circuit 1.
The delay difference detection circuit 18 is operated by a control signal 30 inputted from the outside, and detects the mutual processing time difference between the color signal and the luminance signal generated in the digital signal processing circuit 11. The PWM modulation circuit 17 converts the detection output from the delay difference detection circuit 18 into a PWM signal, and then outputs the signal as a control output signal.

A smoothing circuit is used as the interface means 14 for guiding the control output from the PWM modulation circuit 17 to the phase shift circuit 3. After smoothing the control output subjected to PWM modulation, the smoothing circuit is input to the control input point of the phase shift circuit 3. ing. The phase shift circuit 3 may be composed of, for example, a coil and a variable capacitance element, and by controlling the capacitance value of the variable capacitance element using a smoothed control signal, it is possible to compensate for the delay difference. FIG. 3 is a block diagram showing a second embodiment of the invention. In this embodiment, the functions of the analog color signal processing circuit 1 and the phase shift circuit 3 shown in FIG. 1 are provided on the same semiconductor integrated circuit board.

In the figure, a low-frequency converted color signal is inputted from a terminal 31, and after being amplified to a predetermined level by the amplifier 20 and AGC circuit 21, the amplitude is controlled to be at a constant level. The signal whose amplitude has become constant is limited to a predetermined band by a filter 22, and then sent to a gyroscope circuit 23.
The phase shift adjustment is performed by . This gyrator 3 is controlled by a control signal obtained by smoothing a phase shift control signal from a digital signal processing circuit inputted from a terminal 32 by a smoothing circuit 14. Further, the output signal from the gyrator circuit 23 is input to the A/D converter 4 via the terminal 33. In this way, preamplifier 20, AGC circuit 21, filter 2
The object of the present invention can be achieved by configuring the analog color signal processing circuit 1a constituted by the analog color signal processing circuit 2 and the phase shift means 23 on the same semiconductor 4A integrated circuit board. The scale and cost of hardware for this purpose can be further reduced. [Effects of the Invention] As explained above, the present invention provides a circuit that digitizes a plurality of analog signals, performs desired processing on each signal, and then restores the analog signal. The processing time difference is detected by a digital signal processing means and a control signal is generated, and this control signal is used to control a phase shift circuit placed before the digital signal processing process via an interface circuit. By correcting the delay difference in advance using analog processing using a phase shift circuit, the hardware scale can be reduced.
This also makes it possible to reduce power consumption. Although one embodiment of the present invention has been explained using a VTR signal processing circuit, it goes without saying that the present invention is not limited to only this field and has a large degree of freedom. Furthermore, the signal processing circuit according to the present invention can achieve more significant effects by implementing it using the semiconductor integrated circuit MrgI'#1.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing a control circuit portion of this embodiment, and FIG. 3 is a block diagram showing an analog signal processing circuit portion of a second embodiment of the present invention. FIG. 4 is a block diagram showing a conventional signal processing circuit. 1, 1a... Analog color signal processing circuit, 2... Analog luminance signal processing circuit, 3... Phase shift circuit, 4 5...
A-D converter, 6...Digital color signal processing circuit, 7
...Digital luminance signal processing circuit, 8...Control circuit, 9,10...Output circuit, 11,lla...Digital signal processing circuit, 12.13...D-A converter, 1
4...Interface circuit (smoothing circuit), ]5...
Addition circuit, 17... PWM modulation circuit, 18... Delay difference detection circuit, one... Delay adjustment circuit, 20... Preamplifier, 21... AGC circuit, 22... Filter, 23
... Gyrator circuit, 25-33... Input/output terminal.

Claims (3)

[Claims] (1) A phase shift circuit that inputs a first analog signal, a first A-D converter that inputs the output of this phase shift circuit and converts the analog signal into a digital signal, and a second analog signal that converts the analog signal into a digital signal. a second A-D converter that converts into a digital signal, first and second digital signal processing circuit groups that receive the outputs of the first and second A-D converters, respectively; first and second D-A converters that input the respective outputs of the first and second digital signal processing circuit groups and convert each digital signal into an analog signal, and the first and second digital signal processing circuits; control means for generating difference information on the signal processing time required by each of the circuit groups, and a control signal from the control means is inputted to the control input of the phase shift circuit via an interface circuit to shift the signal phase. A signal processing circuit characterized by being controlled. (2) The control means generates difference information between the signal processing times of the first and second digital signal processing circuit groups, PWM-modulates it, and outputs it, and the interface circuit comprises a smoothing means ( 1) The signal processing circuit described above. (3) The signal processing circuit according to claims (1) and (2), wherein the phase shift circuit includes at least a variable capacitance element, and the capacitance value of the variable capacitance element is controlled by a control signal from the control means.