JPH03204286A - Rf modulator - Google Patents

Abstract

PURPOSE:To attain miniaturization by constituting the entire circuit with a one-chip IC for an FM modulator receiving an audio signal, an AM modulator receiving an FM modulated output and a video signal, an audio subcarrier signal oscillator and a main carrier signal oscillator, constituting both the oscillators with a VCO of a PLL circuit respectively. CONSTITUTION:A main carrier signal is AM-modulated by an FM-modulated output resulting from FM-modulating an audio subcarrier signal with an audio signal and a video signal and the AM-modulated output is used to vary a frequency division ratio of a variable frequency divider of a 1st PLL circuit 15 to obtain a desired channel frequency signal. Moreover, a frequency of an audio subcarrier signal is varied by varying the frequency division ratio of the other variable frequency divider of a 2nd PLL circuit 23. Thus, the FM modulator 22, the AM modulator 25 and the 1st and 2nd PLL circuits 15, 23 are constituted by one-chip IC. Then miniaturization is attained and the frequency of the main carrier signal and the audio subcarrier signal is made stable against temperature change.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an RF modulator that frequency division multiplexes and transmits audio signals and video signals, and in particular
The present invention relates to a miniaturized RF modulator suitable for TV use.

(Summary of the Invention) The RF modulator of the present invention includes an FM modulator to which an audio signal is supplied, an AM modulator to which an FM modulated output and a video signal are supplied, an audio subcarrier signal oscillator, and a main carrier signal oscillator. The device is characterized in that both of the generators are each configured by a Vco of a PLL circuit, and the entire device is configured with a single chip IC to achieve miniaturization.

[Prior Art] Conventionally, as described in, for example, Japanese Unexamined Patent Publication No. 1-129614, PLL (Phase Locked
An FM modulator using the Loop) is known.

That is, in the block diagram shown in FIG. 3 showing an example of an FM modulator using a conventional PLL, 1 indicates the PLL as a whole.
The circuit is shown in which 2a is a reference oscillator, and 2b is a reference frequency divider that divides the oscillation output of the reference oscillator 1 to output a reference frequency f. 3 is a VCO (voltage controlled oscillator), and a phase comparator 5 divides the oscillation output of the VCO 3 by a variable frequency divider 4 with a frequency division ratio N and the reference frequency f of the reference frequency divider 2b. This comparison output is sent to the VC via a charge pump 6 and an LPF (low pass filter) 7.
03 to control the frequency and phase of VCO3.

8 is a lock detector, 9 is a transmitting unit, and 10 is an F
This is an output terminal to which the M modulated signal is output. In addition, MC
indicates a microphone for inputting modulated signals.

In the above configuration, the reference frequency of the reference frequency divider 2b is set to f
, , the divided output frequency of variable frequency divider 4 is f, , VCO 3
If the oscillation frequency of VCO 3 is fo, then fv--=r when low, so by varying N, the oscillation frequency f of VCO 3 can be adjusted. (=N・“r)” can be controlled.

For example, if the reference frequency f is set to 100 KHz and N is changed within the range of 8°O to 900, the oscillation frequency f. 80
and 90 MHz with a channel spacing frequency of 100 KHz.

Problem to be solved by the invention] However, the above-mentioned FM modulator modulates only audio signals, and cannot be immediately applied as an RF modulator that transmits frequency division multiplexed audio signals and video signals. At the same time, no proposal was made regarding IC (integrated circuit).

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an RF modulator that overcomes the above-mentioned drawbacks.

[Means to solve the problem]

The RF modulator of the present invention includes an FM modulator to which an audio signal is supplied, an AM modulator to which an FM modulated output of the FM modulator and a video signal are respectively supplied, and an audio subcarrier signal to the FM modulator. an audio subcarrier signal oscillator for supplying an audio subcarrier signal, and a main carrier signal oscillator for supplying a main carrier signal to the AM modulator, the reference oscillator has a reference oscillator, a phase comparator, a VCO, a variable frequency divider, and an output of the reference oscillator. and a frequency-divided output obtained by dividing the output of the VCO by the variable frequency divider using the phase comparator, and controlling the VCO based on this comparison output; It has a phase comparator, a VCO 1, and a variable frequency divider, and divides the divided output of the reference oscillator of the first PLL circuit and the output obtained by dividing the output of the other VCO by another variable frequency divider into the separate frequency divider. a second PLL circuit that compares the phases with a phase comparator and controls the other VCO by the phase comparison output, and the vCO of the first PLL circuit is used as the main carrier signal oscillator. and another VCO of the second PLL circuit.
as the audio subcarrier signal oscillator, the FM modulator, the AM modulator, the first PLL circuit, and the second PLL circuit.
The circuit is composed of one chip IC.

[Effect]

According to the RF modulator of the present invention, the main carrier signal is AM-modulated by the FM-modulated output obtained by FM-modulating the audio subcarrier signal with the audio signal and the video signal, and the FM-modulated output that is frequency division multiplexed is the first FM-modulated output. A desired channel frequency signal can be obtained by varying the frequency division ratio of the variable frequency divider of the PLL circuit, and an audio subcarrier signal can be obtained by varying the frequency division ratio of another variable frequency divider of the second PLL circuit. Frequency can be changed. Also, FM modulator, A
M modulator, first PLL circuit and second PLL circuit
Since it is constructed using a chip IC, it is possible to achieve miniaturization, and at the same time, it is possible to stabilize the frequencies of the main carrier signal and the audio subcarrier signal against temperature changes.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing the basic configuration of the RF modulator of the present invention, and 14 indicates a one-chip IC (integrated circuit) as a whole. 15 is a first PLL circuit, which includes a reference oscillator 16 that generates a reference frequency signal with a reference frequency f;
It consists of a VCO (voltage controlled oscillator) 17, a variable frequency divider 18 with a frequency division ratio N, and a phase comparator 19, and the output obtained by dividing the oscillation output of the VCO 17 by the variable frequency divider 18 and the reference frequency of the reference oscillator 16. f, by a phase comparator 19, and the comparison output is supplied to c017 via an LPF (low pass filter) 20 to control the frequency and phase of the VCO 17. P is the video signal (V)
P2 indicates an input terminal to which the audio signal (A) is supplied. 21 is an amplifier connected to the input terminal P, 22 is an FM modulator, and FM modulator 2
2 is supplied with an audio signal (A) at an input terminal P2 and an audio subcarrier signal with a frequency f from a second PLL circuit 23 configured as an audio subcarrier signal oscillator. 24 is the video signal (V) amplified by the amplifier 21 and the FM
This is a mixer that mixes the FM modulated output of the modulator 22, and the output of the mixer 24 is supplied to one input of the AM modulator 25.

The other input of the AM modulator 25 is supplied with the main carrier signal of frequency f0 from the VCO 17 of the first PLL circuit 15, and the FM modulated output (TV signal) S is supplied to the output terminal P.
Supply yv. Note that 16a is a crystal connected externally to the reference oscillator 16 between the terminals P4 and P. P6 is a channel frequency setting terminal, and the control voltage Vcl of the terminal P is converted into a predetermined digital value by, for example, the A/D converter 18a, and the frequency division ratio N1 of the variable frequency divider 18 is adjusted according to this digital value. Make it variable. Said second
The PLL circuit 23 has a phase comparator 26 separate from the first PLL circuit 15, a VCO (voltage controlled oscillator) 27, and a variable frequency divider 28, and the reference oscillator 16 of the first PLL circuit 15 The output is frequency-divided by a fixed frequency divider 29 with a frequency division ratio M, and another phase comparator 26 compares the phase of the output, and this phase comparison output is supplied to another VCO 27 through an LPF (low-pass filter) 30. The subcarrier signal is configured to control a frequency f1 of the subcarrier signal.

P is a frequency setting terminal for the audio subcarrier signal, and the control voltage ■c2 of the terminal P7 is, for example, 3-state inch 28
a to a predetermined digital value, and the frequency division ratio N2 of the variable frequency divider 28 is controlled according to this digital value. Note that P8 is a grounding terminal for the 1-chip IC14;
is the power terminal.

In the above configuration, a video signal (V) is input to the input terminal P1.
When the audio signal (A) is supplied to the input terminal P2, the video signal (V) is amplified by the amplifier 21 (white clipping may be performed if necessary) and supplied to the mixer 24.

On the other hand, the audio signal (A) is supplied to the FM modulator 22, which performs FM modulation on an audio subcarrier signal having a frequency f of, for example, 6 MH2, and supplies the FM modulated output to the mixer 24. The output of the mixer 24 is supplied to the AM modulator 25, which performs AM modulation on the main carrier signal of frequency f0 supplied from the VCO 17 of the first PLL circuit 15, and outputs it to the output terminal P3. In this case, the frequency f of the modulated output srv. For example, the European UHFTV band (544MHz ~ 6
16MHz), the frequency division ratio N1 of the variable frequency divider 18 is varied in accordance with each channel frequency of channels 30 to 39 within 16MHz. - For example, if the reference oscillator 160 reference frequency f is set to 8 M)lz, when the PLL circuit 15 is locked, f.

Since it becomes N, -, set N to 68 f.

By varying the frequency between 77 and 77, the desired channel frequency can be set in 8 MHz steps.

Further, the audio subcarrier signal frequency f of another VCO 27 of the second PLL circuit 23 is determined by dividing the reference frequency f1 of the reference oscillator 16 by 8 MHz, by setting the frequency division ratio of the fixed frequency divider 29 by M, and by using another variable frequency divider. If the frequency division ratio of 28 is N, then it is the second, so N
By varying , f can be changed. For example, fl
When 8MH2, M is 16, and N2 is varied between 11, 12, and 13, f is 5.5 Mn2 (West German PAL system), 6.0 MHz (British PAL system), 6.5 MHz ( (French SECAM system). Furthermore, according to the invention, F.M.
Modulator 22, audio subcarrier signal oscillator 23, AM modulator 25, first PLL circuit 15, and second PLL circuit 2
3 is configured with one chip IC 14, it is possible to reduce the size and also reduce the frequency f of the main carrier signal.

The audio subcarrier signal frequency f can be stabilized against temperature changes.

Next, a block diagram showing an embodiment of the present invention shown in FIG. 2 in which the present invention is applied to a VTR (video tape recorder) will be described.

In FIG. 2, 31 is a TV antenna, 32 is a distributor, and the TV signal from the distributor 32 is supplied to one input of a TV tuner 33 and a mixer 34, respectively.

The other input of the mixer 34 is connected to the output terminal P of the chip IC 14 and is supplied with the AM modulated output S'rV from the AM modulator 25, and the output of the mixer 34 is supplied to the RF output terminal 35. The rest of the configuration is the same as the circuit shown in FIG. 1, so a detailed explanation will be omitted.

In the above configuration, the input terminal P of the one-chip IC 14,
A video signal (V) is supplied to the first PLL circuit 15, and an audio signal (A) is supplied to the input terminal P2.
If the frequency division ratio N1 of the variable frequency divider 18 is set to 68, for example, the RF output terminal 35 receives the frequency f of the main carrier signal. An AM modulated output StV of 544 Hz is obtained, and by sending it to a TV receiver (not shown), the reproduction output of the VTR can be monitored. Further, a TV signal from a TV antenna 31 is received by a TV tuner 33 via a distributor 32, and is also sent to an RF output terminal 35 via a mixer 34.
Outputs a monitor signal to. The above-described embodiment shown in FIG. 2 can also be expected to have the same effects as the RF modulator shown in FIG. 1.

Furthermore, since the reference oscillator is shared by the first and second PLL circuits, there is an advantage that the configuration can be simplified.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, a main carrier signal is AM-modulated by an FM-modulated output obtained by FM-modulating an audio subcarrier signal with an audio signal and a video signal, and a frequency-division multiplexed AM The modulation output is the first PL
By varying the frequency division ratio of the L circuit, a desired channel frequency signal is obtained, and by varying the frequency division ratio of another variable frequency divider of the second PLL circuit, the frequency of the audio subcarrier signal is changed. There is an advantage that it can be done.

In addition, an FM modulator, an audio subcarrier signal oscillator, an AM modulator, a first PLL circuit and a second PLL circuit are integrated into one chip.
Since it is constructed from C, it has the advantage that it can be miniaturized and at the same time, the frequencies of the main carrier signal and the audio subcarrier signal can be stabilized against temperature changes.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of an RF modulator of the present invention, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG. 3 is a block diagram showing an example of an FM modulator using a conventional PLL. It is a diagram. 14-----------1 chip IC15-
---------1.-First PLL circuit 16----
------------Reference oscillator 17-----
------V CO (voltage controlled oscillator) I Et--
--------------- One variable frequency divider 19-----
----------- Phase comparator 2O ------------------------
-----L P F (Low pass filter) 21・-・
−−−−−−−−−−Amplifier 22−−−−−−−・・
-FM modulator 23-----------Second P
LL circuit (audio subcarrier signal oscillator) Mixer AM modulator Phase comparator VCO Variable frequency divider Fixed frequency divider PF ・-TV antenna distributor mixer RF output terminal block diagram

Claims (1)

[Claims] an FM modulator supplied with an audio signal; an AM modulator supplied with an FM modulated output of the FM modulator and a video signal, respectively; and an audio subcarrier signal oscillator supplying an audio subcarrier signal to the FM modulator. and a main carrier signal oscillator that supplies a main carrier signal to the AM modulator, a reference oscillator, a phase comparator, a VCO, and a variable frequency divider, and divides the output of the reference oscillator and the output of the VCO into the variable frequency divider. a first PLL circuit that compares the phase of a frequency-divided output obtained by frequency division by a frequency generator with the phase comparator and controls the VCO based on the comparison output; and another phase comparator;
the first PLL having a VCO and a variable frequency divider;
The divided output of the reference oscillator of the circuit and the output obtained by dividing the output of the other VCO by the another variable frequency divider are phase-compared by the another phase comparator, and this phase comparison output is used to determine the frequency of the other VCO. a second PLL circuit configured to control a VCO, the VCO of the first PLL circuit being used as the main carrier signal oscillator;
An RF modulator characterized in that another VCO of the circuit is used as the audio subcarrier signal transmitter, and the FM modulator, AM modulator, first PLL circuit, and second PLL circuit are configured with a one-chip IC. .