KR19980029356A - Image Test Pattern Signal Generator Using Voice Subcarrier of RF Modulator - Google Patents

Abstract

Disclosed is a video test pattern signal generator using an audio subcarrier of an RF modulator according to the present invention. The configuration of the apparatus includes: an image unit for clamping the video signal output from the video signal source and then switching and amplifying the video mode and the test pattern signal generation mode; A voice unit for amplifying a voice signal output from the voice signal source and then frequency modulating the voice subcarrier frequency; Inputs a signal output from the broadcast method control input terminal to output a broadcast method control signal for controlling the voice broadcast method, and generates a test pattern signal applicable to both PAL broadcast method and NTSC broadcast method by the broadcast method control signal. A logic unit for outputting to the voice unit; And an RF unit configured to amplitude-modulate the video signal output from the video unit and the audio signal output from the audio unit at a specific RF frequency and output the amplitude to the RF output terminal.

Accordingly, as described above, according to the present invention, by providing a channel control circuit that can operate not only in the PAL broadcast but also in the voice subcarrier frequency of the NTSC broadcast, an error does not occur in the horizontal synchronization frequency.

Description

Image Test Pattern Signal Generator Using Voice Subcarrier of RF Modulator

The present invention relates to a video test pattern signal generator using audio subcarriers of an RF modulator. More particularly, the present invention relates to an audio modulator of an RF modulator, which is applicable to both PAL broadcast systems and NTSC broadcast systems by dividing and combining audio subcarrier frequencies. An apparatus for generating an image test pattern signal using a subcarrier.

1 is a diagram illustrating a configuration of an RF modulator.

In Fig. 1, reference numeral 102 denotes a clamp circuit, 104 denotes a switch circuit, 106 denotes an image mode terminal, 108 denotes a test pattern signal generation mode terminal, 110 denotes an image amplification circuit, and 112 denotes an image. Modulation circuit, 114 reference signal generator, 116 carrier generation circuit, 118 audio amplification circuit, 120 audio modulation circuit, 122 frequency conversion circuit, 124 broadcasting system control circuit, 126 audio An oscillation circuit, 128 is a video signal source, 130 is an audio signal source, 132 is a broadcast control input terminal, 134 is an input terminal of the reference signal generator 114, 136 denotes an RF output terminal, and 138 denotes an RF modulator. The RF modulator is largely composed of a video part, an audio part, a logic part, and an RF part. The imaging section is composed of a clamp circuit 102, a switch circuit 104, and an image amplifying circuit 110. The clamp circuit 102 is a circuit for equalizing one DC level of an AC voltage waveform such as a pulse waveform. The switch circuit 104 determines whether the mode is an image mode or a test pattern signal generation mode, and controls a voice signal input to the voice amplification circuit 118 to prevent direct current from going to the voice amplification circuit 118. . The image amplification circuit 110 is used to amplify an image signal and has a broadband frequency characteristic of 0 to several megahertz. The voice unit is composed of a voice amplifier circuit 118, a voice modulator circuit 120 and a voice oscillator circuit 126. The voice amplifier circuit 118 amplifies the voice signal output from the voice signal source 130. The voice modulation circuit 120 inputs a signal output from the voice amplifier circuit 118 and modulates the frequency. The voice oscillator circuit 126 is a circuit for inputting a signal output from the broadcast method control circuit 124 to generate a voice subcarrier frequency and output the voice subcarrier frequency to the voice modulator circuit 120. The logic unit is composed of a reference signal generator 114 and a broadcast type control circuit 124. The reference signal generator 114 includes a programmable divider, a test pattern signal generator, and a channel control circuit, and inputs a signal output from the voice modulation circuit 120 to generate a test pattern signal. The broadcast method control circuit 124 inputs a signal output from the broadcast method control input terminal 132 and outputs a broadcast method control signal to the channel control circuit. Broadcasting methods can be broadly divided into PAL (Phase Alternation by Line) broadcasting methods and NTSC (National Television System Committee) broadcasting methods, and PAL broadcasting methods can be classified into B / G, I, and D / K methods. The B / G, I, and D / K broadcast systems use 5.5, 6.0, 6.5 megahertz as voice subcarrier frequencies, and the NTSC broadcast method uses 4.5 megahertz. The RF unit is composed of an image modulation circuit 112, a carrier generation circuit 116, and a frequency conversion circuit 122. The image modulation circuit 112 is a circuit for amplitude modulation of a video signal. The carrier generation circuit 116 is a circuit for generating a carrier wave, which is a high frequency current used to carry and transmit a low frequency signal, and generates a specific RF channel frequency. The frequency conversion circuit 122 is a circuit for converting a received radio wave into an intermediate frequency, and modulates an amplitude by inputting a signal output from the voice modulation circuit 120. The RF output terminal 136 is connected to a transmission antenna for propagating a signal output from the frequency conversion circuit 122 to a reception antenna such as a VCR. The video signal source 128 and the audio signal source 130 are baseband signals which are reproduction outputs of the recording / reproducing apparatus.

Next, the operation of the RF modulator shown in FIG. 1 will be described.

According to the mode of the switch circuit 104, it is divided into a video mode and a test pattern signal generation mode. First, when the switch circuit 104 is a video mode, the signal output from the video signal source 128 is a clamp circuit 102. After being input to and clamped, the switch circuit 104 is connected to the image mode terminal 106 and input to the image amplification circuit 110. The signal amplified by the image amplifier circuit 110 is input to the image modulation circuit 112 by adjusting the input level. Meanwhile, a signal output from the carrier generation circuit 116 for generating a specific RF channel frequency is also input to the image modulation circuit 108. The image modulation circuit 112 amplitude modulates the signals output from the image amplifier circuit 110 and the carrier generation circuit 116 and outputs the signals to the RF output terminal 136.

Next, when the switch circuit 104 is in the test pattern signal generation mode, the reference signal generator 114 connected to the test pattern signal generation mode terminal 108 is operated, and the signal generated therein is input to the image amplification circuit 110. The subsequent operation is the same as in the above-described image mode. Since the signal output from the voice modulation circuit 120 is used as the reference signal of the reference signal generator 114, the DC signal output from the voice signal source 130 is the voice amplifier circuit 118 and the voice modulation circuit 120. The voice amplification circuit 118 must be controlled using the switch circuit 104 so as not to be input to the voice amplifier. This is because the voice modulation circuit 120 may not be modulated so that a signal having a constant oscillation frequency may be input to the reference signal generator 114 to generate a test pattern signal.

The signal output from the voice signal source 130 is input to the voice amplifier circuit 118, and the voice amplifier circuit 118 adjusts the voltage gain and outputs the voltage gain to the voice modulation circuit 120. The voice modulation circuit 120 modulates the signal output from the voice amplifier circuit 118 to the voice subcarrier frequency oscillated by the voice oscillator circuit 126. Meanwhile, some of the signals output from the voice modulation circuit 120 are input to the reference signal generator 114 through the input terminal 134 of the reference signal generator. The frequency conversion circuit 122 inputs the signal output from the voice modulation circuit 120, amplitude modulates the carrier wave output from the carrier generation circuit 116, and outputs the result to the RF output terminal 136.

FIG. 2 is a diagram illustrating a detailed configuration of the reference signal generator shown in FIG. 1. In Fig. 2, reference numerals 124a and 124b denote first and second output terminals of the broadcast control circuit, 202 denotes a programmable divider, 204 denotes a test pattern signal generator, and 206 denote a channel control circuit. Programmable divider 202 is a circuit that divides frequency. The test pattern signal generator 204 is a circuit which generates a test figure (combination of a figure consisting of a specific circle or line) used for adjusting the television receiver. The channel control circuit 206 generates a division ratio adjustment signal.

Next, the operation of the reference signal generator illustrated in FIG. 2 will be described.

First, when the broadcasting method control signal outputted from the first and second output terminals (the output terminal of the channel control circuit; 124a and 124b) of the broadcasting method control circuit is input to the channel control circuit 206, the division ratio adjustment signal is generated. The output is then output to the programmable divider 202. The programmable divider 202 inputs a voice subcarrier signal output from the input terminal of the reference signal generator (output terminal of the voice modulation circuit; 134) and the voice subcarrier frequency by the division ratio adjustment signal output from the channel control circuit 206. Divide by to output a square wave with a constant frequency. The test pattern signal generator 204 inputs a signal output from the programmable divider 202 to generate a test pattern signal and output the test pattern signal to the test pattern signal generation mode terminal 108.

3 is a diagram showing the configuration of a conventional channel control circuit.

In Fig. 3, reference numerals 302, 304, 308 and 310 denote inverters and 306 denote NOR gates, respectively.

Table 1 is a table showing the input and output terminals and the division ratio of the conventional channel control circuit 206 shown in FIG.

In Table 1, reference numerals 124a and 124b denote first and second output terminals of the broadcast control circuit 124, and 206a to 206d denote first and fourth output terminals of the channel control circuit 206, respectively. In addition, 0 and 1 represent a low (ground) state and a high (open) state, respectively. In addition, the fourth output terminal 206d of the channel control circuit has a high state (1) in both the PAL broadcast method and the NTSC broadcast method.

Next, the operation of the channel control circuit shown in FIG. 3 will be described with reference to Table 1. FIG.

First, in the PAL B / G broadcasting method, since the second output terminal 124b of the broadcasting method control circuit is in a high state (1), the first output terminal (1) of the channel control circuit is controlled by the first and second inverters 302 and 304. 206a goes high. The second output terminal 206b of the channel control circuit is brought high by the first inverter 302 and the NOR gate 306, and the third output terminal 206c of the channel control circuit is the third and fourth inverters 308. 310, the low state (0). Therefore, the PAL B / G broadcasting system divides the voice subcarriers into 11 divisions as shown in the remarks column of Table 1 to generate a signal of 500 kHz. In the same manner, referring to Tables 1 and 3, the PAL I broadcast method and the PAL D / K broadcast method generate a 500 kilohertz signal by performing 12 and 13 divisions of the voice subcarrier signal. Next, the NTSC broadcasting system (voice subcarrier frequency is 4.5 megahertz) is divided into 8 divisions by referring to Tables 1 and 3, and the output of the programmable divider 202 is 562.5 kilohertz (= 4.5 megahertz). / 8 divisions). If you make a test pattern signal with this 562.5 kilohertz square wave, the horizontal synchronizing frequency becomes 17.578 kilohertz. When demodulated on a television, an error occurs in the horizontal synchronizing frequency, causing the television screen to flow left and right, and cannot be viewed properly. This is because the horizontal frequency variation of a television varies somewhat from set to set, but must be entered at a frequency within 15.625 ± 0.5 kilohertz.

Such a conventional channel control circuit can cope with a change in the voice subcarrier frequency of the PAL broadcast method, but it cannot be applied to the NTSC broadcast method.

The present invention was created to solve the above-described problems, and the NTSC broadcasting subcarrier as well as 5.5 (B / G), 6.0 (I), 6.5 (D / K) megahertz, which are voice subcarrier frequencies of the PAL broadcasting method, are provided. An object of the present invention is to provide an image test pattern signal generator using an audio subcarrier of an RF modulator that also operates at a frequency of 4.5 megahertz.

1 is a diagram illustrating a configuration of an RF modulator.

FIG. 2 is a diagram illustrating a detailed configuration of the reference signal generator shown in FIG. 1.

3 is a diagram showing the configuration of a conventional channel control circuit.

4 is a diagram illustrating a configuration of a channel control circuit according to the present invention.

According to the present invention for achieving the above object, the image test pattern signal generator using the audio subcarrier of the RF modulator clamps the video signal output from the video signal source and then switching between the image mode and the test pattern signal generation mode An image unit for amplifying; A voice unit for amplifying a voice signal output from the voice signal source and then frequency modulating the voice subcarrier frequency; Inputs a signal output from the broadcast method control input terminal to output a broadcast method control signal for controlling the voice broadcast method, and generates a test pattern signal applicable to both PAL broadcast method and NTSC broadcast method by the broadcast method control signal. A logic unit for outputting to the voice unit; And an RF unit for amplitude-modulating the video signal output from the video unit and the audio signal output from the audio unit at a specific RF frequency and outputting the amplitude to the RF output terminal.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings.

4 is a diagram illustrating a configuration of a channel control circuit according to the present invention.

In Fig. 4, reference numeral 42 denotes an inverter, 44 denotes an OR gate, and 46 denotes an AND gate. The channel control circuit shown in FIG. 4 includes an inverter 42 for inputting and inverting a control signal output from the first output terminal 124a of the broadcast control circuit, and a signal output from the inverter 42 and a broadcast control circuit. An OR gate which inputs a control signal output from the second output terminal 124b of the circuit and performs a logical sum to output the control signal to the first output terminal 206a of the channel control circuit; And an AND gate for inputting a signal output from the inverter 42 and a control signal output from the second output terminal 124b of the broadcasting method control circuit, performing a logical multiplication, and outputting the AND signal to the second output terminal of the channel control circuit. Include.

Table 2 is a diagram showing the signal state and the division ratio of the input and output terminals of the channel control circuit 206 according to the present invention shown in FIG. In the channel control circuit according to the present invention, the fourth output terminal 206d of the channel control circuit is in a high state (1) in both broadcasting schemes.

Next, the operation of the channel control circuit shown in FIG. 4 will be described with reference to Table 2. FIG. First, in the PAL B / G broadcasting method, since the first and second output terminals 124a and 124b of the broadcasting method control circuit are in the low state (0) and the high state (1), respectively, the inverter 42 and the OR gate 44 are used. As a result, the first output terminal 206a of the channel control circuit becomes high. The second output terminal 206b of the channel control circuit inputs the signal output from the second output terminal 124b of the broadcast control circuit and the signal output from the inverter 42 to perform an AND operation on the AND gate 46. Therefore, the state becomes high. The third output terminal 206c of the channel control circuit is low because it is the same as the signal output from the first output terminal 124a of the broadcast control circuit. Therefore, the PAL B / G broadcasting system divides the voice subcarriers into 11 divisions as shown in the remarks column of Table 2 to generate a signal of 500 kHz. In the same manner, referring to Tables 2 and 4, the PAL I broadcast method and the PAL D / K broadcast method generate a 500 kilohertz signal by performing 12 and 13 divisions of the voice subcarrier signal. That is, in the PAL broadcast method, the signal state of the output terminal of the channel control circuit according to the present invention is the same as that of the output terminal of the conventional channel control circuit. However, the NTSC broadcasting system is divided into 9 divisions by referring to Table 2 and FIG. 4, and the output of the programmable divider 202 is a square wave of 500 kilohertz (= 4.5 megahertz / 9 division). Creating a test pattern signal with this 500 kilohertz square wave results in a horizontal sync frequency of 15.625 kilohertz. This frequency is slightly different from the NTSC broadcasting's horizontal synchronous frequency of 15.734 kHz, but it satisfies the frequency range of 15.625 ± 0.5 kHz, which is the horizontal frequency variation of the TV, so that viewing is possible without any problem.

As described above, according to the present invention, by providing a channel control circuit that can operate not only in the PAL broadcasting but also in the voice subcarrier frequency of the NTSC broadcasting, an error does not occur in the horizontal synchronization frequency.

Claims (3)

An image unit for clamping the image signal output from the image signal source and then switching and amplifying between the image mode and the test pattern signal generation mode; A voice unit for amplifying a voice signal output from the voice signal source and then frequency modulating the voice subcarrier frequency; Inputs a signal output from the broadcast method control input terminal to output a broadcast method control signal for controlling the voice broadcast method, and generates a test pattern signal applicable to both PAL broadcast method and NTSC broadcast method by the broadcast method control signal. A logic unit for outputting to the voice unit; And an RF unit configured to amplitude-modulate the video signal output from the video unit and the audio signal output from the audio unit at a specific RF frequency, and output the amplitude signal to the RF output terminal. . The apparatus of claim 1, wherein the logic unit comprises: a broadcast method control circuit configured to output a broadcast control signal by inputting a signal output from a broadcast method control input terminal; A channel control circuit for inputting the broadcast control signal and outputting a division ratio adjustment signal; A programmable divider configured to input the division ratio adjustment signal to divide a voice subcarrier signal to output a square wave having a constant frequency; And a test pattern signal generator configured to input the square wave and combine with the division to output a test pattern signal. 3. The apparatus of claim 2, wherein the channel control circuit comprises: an inverter for inputting and inverting a control signal output from the first output terminal of the broadcast control circuit; An OR gate for inputting a signal output from the inverter and a control signal output from the second output terminal of the broadcast control circuit and performing a logical sum to output the signal to the first output terminal of the channel control circuit; And an AND gate for inputting a signal output from the inverter and a control signal output from the second output terminal of the broadcasting method control circuit to perform a logical multiplication to output the output signal to the second output terminal of the channel control circuit. Image test pattern signal generator using.