JPS6079879A - Modulator - Google Patents

Abstract

PURPOSE:To miniaturize the constitution and to attain economy by selecting a frequency dividing ratio in a modulator for a CATV or the like and using a changeover switch so as to select a desired channel. CONSTITUTION:A reference signal frequency divider 18 is constituted by the cascade connection of a frequency dividing stage of frequency dividing ratio N3 (1/256) and a frequency dividing stage of frequency dividing ratio N2 (1/8). Moreover, a video carrier frequency divider 24 is constituted with the 1st stage of frequency dividing ratio 1/64 and the 2nd stage whose frequency dividing ratio is switched by a changeover switch SW2 so that the frequency dividing ratio of the 2nd stage is switched into 1/2173 and 1/2205. Furthermore, a frequency division output Fs has the identical frequency to that of a frequency division output Fr2 of the frequency divider 18 by setting a frequency dividing ratio N4 of an intecarrier frequency divider 24 to 1/176. Thus, the PAL system two-channel changeover is sttained by switching the frequency dividing ratio of the frequency divider 24 by using the changeover swithc SW2.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a modulation device that modulates and transmits a video signal and an audio signal.

PRIOR ART AND PROBLEMS A modulation device in CATV etc. modulates and combines a video signal and an audio signal and transmits it as a television signal. Conventionally, the configuration shown in FIG. It was getting worse. In the figure, X1 to X3 are crystal oscillators,
1 and 2 are basic oscillators for forming one video transmission wave, 3 is a multiplier, and 4! J video modulator, 5 is a bandpass filter, 6 is a basic audio oscillator, 7 is a multiplier, 8 is a frequency converter, 9 is a bandpass filter, 1o is a diplexer, and SWI is a changeover switch. This changeover switch SWI is used to change over the output of the basic oscillator 1 with frequency f1 and the output of basic oscillator 2 with frequency f2 in order to transmit on a desired channel. is multiplied by n1 by the multiplier 3, resulting in a desired video carrier signal. This video carrier signal is applied to a video modulator 4 and a frequency converter 8. The video signal VID is applied to the video modulator 4, subjected to AM modulation, and applied to the guiplexer 1o via the bandpass filter 5.

Also, the audio signal AUD is added to the basic oscillator 6 and F
M modulated. In this case, since a crystal oscillator is configured, the fundamental frequency f3 has high stability.
Since the frequency deviation cannot be increased, the multiplier 7
is multiplied by n2 to increase the actual frequency shift.

The output signal of this multiplier 7 is applied to a frequency converter 8,
The signals are converted to a frequency higher than the video carrier frequency by, for example, 4.5 MHz, and are applied to the Gyplexer 10 via the bandpass filter 9, where they are synthesized and output as a television signal.

In such a conventional modulation device, as mentioned above, the audio basic oscillator 6 cannot increase the frequency deviation, so it multiplies the frequency by n2 to increase the frequency deviation.
Therefore, it is necessary to have a configuration that oscillates at a frequency that is 1/(n'2) of the intercarrier frequency. That is, it was not possible to set the oscillation frequency high.

In addition, the large number of multipliers such as the multiplier 3.7 has the disadvantage of causing a spurious problem, and in order to achieve multi-channel design, it is necessary to prepare a larger number of basic oscillators 1.2, resulting in space and other problems. It had the disadvantage of causing economic problems. Furthermore, since the audio signal is applied to a crystal oscillator and FM modulated, it has the disadvantage that FM modulation distortion is likely to occur. Furthermore, since it is composed of analog linear circuits, it is difficult to integrate it into an integrated circuit, making it difficult to make it smaller and more economical.
It was t.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a modulation device which can be made compact and economical by digitalization, can be easily multi-channeled, and can improve spurious characteristics.

Structure of the Invention The present invention is 6 years old, a reference signal frequency divider that divides the output signal of a reference signal oscillator, and a video tlllll transmission frequency divider that can divide the output signal of a video carrier wave oscillator and switch the frequency division ratio. A phase comparator for video carrier wave, for intercarrier use, which compares the phases of the frequency division output of the video carrier wave frequency divider and the frequency division output of the reference signal frequency divider, and uses the comparison output as a control voltage of the video carrier wave oscillator. An intercarrier phase comparator that divides the output of an oscillator and compares the phase with the divided output of the reference signal frequency divider, and controls the intercarrier oscillator by superimposing an audio signal on the comparison output of the phase comparator. a voltage mixer, a video modulator that modulates the video signal by adding the output of the video carrier oscillator, and a frequency that converts the frequency by adding the output of the intercarrier oscillator and the output of the video 1 transmission wave oscillator. It is equipped with a converter and a guiplexer that adds and synthesizes the output of the frequency converter and the output of the video converter, and can be switched to a desired channel by selecting a frequency division ratio. Since these components are constructed using digital circuits, integrated circuits can be easily constructed. Examples will be described in detail below.

Embodiment of the Invention FIG. 2 is a block diagram of an embodiment of the present invention, in which 11 is a video carrier wave oscillator, 12 is a video modulator that modulates the video signal VID, 13 is a frequency converter, 14 is an intercarrier oscillator, 15 is a bandpass filter for video signals, 16 is a bandpass filter for audio signals, 17 is a guiplexer, 18 is a reference signal frequency divider, 19 is a reference signal oscillator, 2
0 is a frequency divider for intercarriers, 21 is a mixer, 22 is a phase comparator for intercarriers, 23 is a phase comparator for video carrier waves, 24 is a frequency divider for video carrier waves, XL is a crystal oscillator, and SW2 is a switch. It's a switch.

The oscillation frequency FO of the reference signal oscillator 19 is divided by the frequency divider I8, and the divided output FrI and the video 1 transmission wave oscillator 1
The phase comparator 23 compares the frequency-divided output Fv of the frequency divider 24 which divides the output of the oscillator 24 with the frequency-divided output Fv of the frequency divider 24, and uses the comparison output as a control voltage for the video carrier oscillator 11 to output a video carrier signal of frequency F1 or F2. That is, it constitutes a phase locked circuit (PLL),
By controlling the frequency division ratio of the frequency divider 24, a desired video carrier frequency can be output.

Furthermore, a phase comparator outputs the frequency divided output Fr2 obtained by dividing the oscillation frequency F of the reference signal oscillator 19 by the frequency divider 18 and the frequency divided output Fs of the frequency divider 20 which frequency divides the output of the intercarrier oscillator 14. 22, and the comparison output is used as a control voltage for the intercarrier oscillator 14 via the mixer 21, and the intercarrier frequency F3 is output. In other words, a phase-locked circuit (
PLL) and sends the audio signal AUD to the mixer 21.
By adding and superimposing it on the control voltage, the output of the intercarrier oscillator 14 can be FM-modulated by the audio signal AUD. The oscillation frequency of the intercarrier oscillator 14 is 4.5 in the NTSC system.
In the PAL system, the frequency is 5.5 MHz.

A video carrier signal of frequency F1 or F2 from the video carrier oscillator 11 and an output signal modulated by the audio signal AUD from the intercarrier oscillator 14 are input to the frequency converter 13, and the bandpass filter 16 inputs ( A signal with a frequency of FI+F3) or (F2+F3) is input to the diplexer 17. Further, the output signal of the video modulator 12 is input to the diplexer 17, and the AM-modulated video signal and the FM-modulated audio signal are combined and output.

A case where the method is applied to the PAL system in the UHF band will be described below. When switching between 2 channels, set the video carrier frequency F1 to 543.25MHz and F2 to 55125MHz.
z, the intercarrier frequency F3 is 5.5 MHz, and the oscillation frequency of the reference signal oscillator 19 is 8 MHz, the frequency divider 18 is configured with a two-stage frequency divider, and the frequency division ratio of the first stage is N3. For example, 1/256, the second stage frequency division ratio N2
When is set to 1/8, the divided output Fr2 applied to the phase comparator 22 becomes 31.25 KHz, and the divided output Frl applied to the phase comparator 23 becomes 3.90625 KHz.

The reason why there are two types of divided outputs to be applied to the phase comparators 22 and 23 is to improve the response of the phase-locked circuit and to make the handling frequency as high as possible. The frequency unit 18 can be configured by cascading a frequency division stage with a frequency division ratio N3 and a frequency division stage with a frequency division ratio N2.

The frequency division ratio of the frequency divider 24 is determined by the frequency division output Fv and the frequency divider 18.
The frequency division output Fr is set to be equal to the image carrier frequency FI of 543.25MHz.
When the frequency division ratio N1 and the video carrier frequency F2 are 5
The frequency division ratio Nl' when the frequency is 51.25 MHz is as follows: N1=139072 NI'=141120. Therefore, the frequency divider 24 is 1/2 as shown in FIG.
It consists of a first stage with a frequency division ratio of 64 and a second stage whose frequency division ratio is switched by a changeover switch SW2, and the frequency division ratio of the second stage is 1.
A configuration that can switch between /2173 and 1/2205 would suffice.

Also, by setting the frequency division ratio N4 of the frequency divider 20 to 1/176, the frequency divided output Fs becomes 31.25KHz, and the frequency division ratio N4 of the frequency divider 1
It has the same frequency as the frequency-divided output F r 2 of 8.

As mentioned above, frequency divider 18. [By selecting a frequency division ratio of 4 or 20 and switching the frequency division ratio of the frequency divider 24 using the changeover switch SW2, it is possible to perform two-channel switching in the PAL system. By selecting the dividing ratio of the frequency divider, it is possible to select the Japanese NTSC system channel or the US N
Of course, it is also possible to enable TSC channel switching, modulate and synthesize the video signal VID and audio signal A'UD, and output the television signal.

As described in detail, the present invention includes a reference signal frequency divider 18 that frequency divides the output signal of the reference signal oscillator 19, and a switch that frequency divides the output signal of the video carrier wave oscillator 11 and changes the frequency division ratio. SW
Video carrier frequency divider 2 that can be switched by 2 etc.
4, and a video carrier phase that compares the phases of the divided output of the video carrier frequency divider 24 and the divided output of the reference signal frequency divider 18 and uses the comparison output as the control voltage of the video II transmission wave oscillator 11. A comparator 23 , an intercarrier phase comparator 22 that divides the output of the intercarrier oscillator 14 and compares the phase with the divided output of the reference signal frequency divider 18 , and an audio signal to the comparison output of the phase comparator 22 . a mixer 21 that superimposes the signal AUD to provide a control voltage for the intergear oscillator 14; a video modulator 12 that adds and changes the output of the video carrier oscillator 11 and the video signal VID; and the intercarrier oscillator 14. a frequency converter 13 that adds the output of the video carrier oscillator 14 and the output of the video carrier wave oscillator 11 to perform frequency conversion; and a diplexer 17 that adds and synthesizes the output of the frequency converter 13 and the output of the video modulator 12. With only the reference signal oscillator 19 as a crystal oscillator, the reference signal frequency 1? By stabilizing o,
A highly accurate modulation device can be constructed.

Furthermore, since the signal is not multiplied by a multiplier, there is an advantage that spurious characteristics are improved. Also, the reference signal oscillator 191
The phase comparators 22, 23, frequency dividers 1B, 20, 24, etc. can be constructed by digital circuits, and therefore can be easily integrated into an integrated circuit, resulting in a compact and economical construction.

In addition, when increasing the number of channels, this can be achieved by simply changing the frequency division ratio of the frequency divider, resulting in an economical configuration.

Furthermore, since the audio signal AUD is superimposed on the control voltage of the intercarrier oscillator 14 and subjected to FM modulation, FM modulation distortion can be reduced. Note that if a channel offset is required to reduce the influence of external noise, this can be done by simply changing the frequency of the reference signal oscillator 19 slightly. For example, set the video carrier frequency to 250
In the case of KHz offset, it is only necessary to shift the reference signal frequency F by about 3.6 KHz, and the intercarrier frequency shift in that case is 2.25 KH.
z, which is a negligible value.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional modulation device, Fig. 2 is a block diagram of an embodiment of the present invention, Fig. 3 is a block diagram of an embodiment of an ink-carrier frequency divider, and Fig. 4 is a block diagram of an embodiment of an ink-carrier frequency divider. FIG. 2 is a block diagram of an embodiment of a frequency divider. 11 is a video carrier wave oscillator, 12 is a video modulator, 13 is a frequency converter, 14 is an intercarrier oscillator, 15
16 is a bandpass filter for video signals, 16 is a bandpass filter for audio signal sequences, 17 is a guiplexer, I8 is a reference signal frequency divider, 19 is a reference signal oscillator, 20 is an intercarrier frequency divider, 21 is a mixer, 22 is a phase comparator for intercarriers, 23 is a phase ratio divider for video 1 general wave transmission, 24 is a video Iffff transmission frequency divider, L is a crystal oscillator, SW2
is a changeover switch. Patent applicant: Alps Electric Co., Ltd. Representative Patent Attorney Akio Aitani Representative Patent Attorney Hiroshi Watanabe - Figure 1 Figure 3

Claims (1)

[Claims] a reference signal divider that divides the output signal of the reference signal oscillator;
A video carrier wave frequency divider capable of frequency dividing the output of a video carrier wave oscillator and switching the frequency division ratio; a phase between the frequency division output of the video carrier wave frequency divider and the frequency division output of the reference signal frequency divider; A phase comparator for video 1 general wave transmission whose comparison output is used as the control voltage of the video carrier wave oscillator, divides the output of the intercarrier oscillator, and compares the phase with the divided output of the reference signal frequency divider. an intercarrier phase comparator, a mixer that superimposes an audio signal on the comparison output of the phase comparator to provide a control voltage for the intercarrier oscillator, and modulates the output of the video carrier oscillator by adding the video signal to the intercarrier oscillator. a video modulator, a frequency converter that adds the output of the intercarrier oscillator and the output of the video one-way transmission oscillator and converts the frequency, and adds and synthesizes the output of the frequency converter and the output of the video modulator; A modulation device characterized by comprising a guiplexer.