GB2259418A - Receivers - Google Patents

Receivers Download PDF

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Publication number
GB2259418A
GB2259418A GB9119020A GB9119020A GB2259418A GB 2259418 A GB2259418 A GB 2259418A GB 9119020 A GB9119020 A GB 9119020A GB 9119020 A GB9119020 A GB 9119020A GB 2259418 A GB2259418 A GB 2259418A
Authority
GB
United Kingdom
Prior art keywords
frequency
carrier
oscillator
circuit
carrier oscillator
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB9119020A
Other versions
GB2259418B (en
GB9119020D0 (en
Inventor
Hirofumi Nogawa
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
JALCO Co Ltd
Original Assignee
JALCO Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by JALCO Co Ltd filed Critical JALCO Co Ltd
Priority to GB9119020A priority Critical patent/GB2259418B/en
Publication of GB9119020D0 publication Critical patent/GB9119020D0/en
Publication of GB2259418A publication Critical patent/GB2259418A/en
Application granted granted Critical
Publication of GB2259418B publication Critical patent/GB2259418B/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
    • H03J1/00—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general
    • H03J1/0008—Details of adjusting, driving, indicating, or mechanical control arrangements for resonant circuits in general using a central processing unit, e.g. a microprocessor
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
    • H03B5/08—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance
    • H03B5/12—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device
    • H03B5/1203—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device the amplifier being a single transistor
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
    • H03B5/08—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance
    • H03B5/12—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device
    • H03B5/1231—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device the amplifier comprising one or more bipolar transistors
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
    • H03B5/08—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance
    • H03B5/12—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device
    • H03B5/1237—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device comprising means for varying the frequency of the generator
    • H03B5/124—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device comprising means for varying the frequency of the generator the means comprising a voltage dependent capacitance
    • H03B5/1243—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device comprising means for varying the frequency of the generator the means comprising a voltage dependent capacitance the means comprising voltage variable capacitance diodes
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B5/00—Generation of oscillations using amplifier with regenerative feedback from output to input
    • H03B5/08—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance
    • H03B5/12—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device
    • H03B5/1296—Generation of oscillations using amplifier with regenerative feedback from output to input with frequency-determining element comprising lumped inductance and capacitance active element in amplifier being semiconductor device the feedback circuit comprising a transformer
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03B—GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS
    • H03B2200/00—Indexing scheme relating to details of oscillators covered by H03B
    • H03B2200/0002—Types of oscillators
    • H03B2200/0006—Clapp oscillator

Landscapes

  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Transmitters (AREA)
  • Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)

Abstract

An RF modulator comprises an RF carrier oscillator 17 having a resonance circuit including a variable capacity diode capable of varying the frequency of oscillation, the RF carrier oscillator outputting a carrier to a mixer 15; a frequency synthesiser circuit 18 for receiving the output signal of the RF carrier oscillator and for outputting phase comparison information formed by phase comparing the carrier oscillator signal and a signal generated by a reference frequency oscillator; a control circuit 19 for receiving the phase comparison information and detecting the deviation from a desired phase for controlling the frequency of oscillation of the RF carrier oscillator 17 to a predetermined frequency; and a voltage varying circuit 20 for applying a predetermined voltage on the basis of the output signal of the control circuit 19 to vary the junction capacity of the variable capacity diode in the RF carrier oscillator 17 by means of an inverse bias voltage to thereby vary the frequency of oscillation of the RF carrier oscillator. The controller 19 may include a microcomputer or other suitable hardware. The control loop arrangement enables uniform performance of the oscillator 17 to be maintained over a wide variable frequency range. The modulator may form part of VCRs, VCPs or satellite receivers. <IMAGE>

Description

"RF MODULATOR" The present invention relates to an RF modulator for use in VCRs, VCPs or satellite receivers.
Conventional RF modulators have a structure shown in Figure 4 of the accompanying drawings. An RF carrier. oscillator 40, shown in Figure 3, is of the type which uses a variable capacitor 31 and an inductor 32. Therefore, it is difficult to vary the frequency over a wide range, and it is impossible to maintain a uniform performance in the variable frequency range due to shift in the desired oscillation frequency. When such a carrier is used to obtain an RF output from a mixer 41, the image quality may deteriorate.
The RF modulator shown in Figure 4 is for use in VCRs. A video input signal is input to a clamping circuit 42. The clamped video signal passes through a switch-over circuit 44 which switches over the output signal between a test pattern signal generated by a test pattern signal generator circuit 43 and the clamped video signal, is clipped by a clipper circuit 45, and is then input to the mixer 41 together with an audio signal obtained by modulating a carrier by an audio frequency modulator 46 using an audio input signal as well as a carrier from the RF carrier oscillator 40. The mixer 41 outputs a mixed RF output. The RF carrier oscillator 40 is a Clapp oscillator, as shown in Figure 3.
As stated above, in the conventional RF modulator, it is difficult to vary the frequency over a wide range and to maintain a uniform performance over the variable frequency range due to shift in the desired oscillation frequency. Consequently, the image quality of VTR may be adversely affected.
In view of the aforementioned problems of the conventional RF modulators, the present invention seeks to provide an RF modulator in which the frequency can be varied over a wide range, and in which shift in the desired oscillation frequency can be minimised so that the image quality of VTRs is not adversely affected.
The present invention provides an RF modulator for delivering an RF output obtained by mixing an input signal, such as a video or audio signal, with a predetermined carrier with a mixer. The RF modulator includes an RF carrier oscillator having a resonance circuit with a variable capacity diode capable of varying an oscillating frequency, the RF carrier oscillator outputting a carrier to the mixer; a frequency synthesiser circuit for receiving the output signal of the RF carrier oscillator and for outputting phase comparison information formed by phase comparing the input signal and a signal generated by a reference frequency oscillator; a control circuit for receiving the phase comparison information of the frequency synthesiser circuit and for controlling the oscillating frequency of the RF carrier oscillator to a predetermined frequency; and a voltage varying circuit for applying a predetermined voltage on the basis of an output signal of the control circuit to vary a junction capacity of the variable capacity diode of the RF carrier oscillator by an inverse bias voltage and thereby vary the oscillating frequency of the RF carrier oscillator.
In the RF modulator, to monitor the output signal of the RF carrier oscillator, the output signal of the RF carrier oscillator is input to the frequency synthesiser circuit which outputs to the control circuit comprising a microcomputer or the like, a signal obtained by frequency synthesising the input signal. When it is desired to vary the frequency, for example, over a wide range, the control circuit is programmed or constructed by hardware beforehand such that a predetermined frequency pattern can be obtained on the basis of the input signal from the frequency synthesiser circuit.Consequently, the control circuit sends an instruction to the voltage generating circuit to generate a voltage which ensures a desired frequency, and the voltage generating circuit applies an inverse bias voltage to the variable capacity diode of the RF carrier oscillator on the basis of the instruction from the control circuit. Therefore, the frequency of the RF carrier oscillator can be varied over a wide range. Furthermore, since the control circuit controls the voltage generating circuit on the basis of the output signal from the frequency synthesiser circuit, the RF carrier oscillator can be controlled in such a manner that shift in the desired oscillating frequency can be reduced.
In order that the invention may be better understood an embodiment thereof will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 is a block diagram of an embodiment of a RF modulator according to the present invention; Figure 2 is a circuit diagram of an example of an RF carrier oscillator used in the RF modulator according to the present invention; Figure 3 is a circuit diagram of an example of an RF carrier oscillator used in a conventional RF modulator; and Figure 4 is a block diagram of an example of the conventional RF modulator.
A typical embodiment of the present invention will be described below with reference to Figures 1 and 2. As in the case of the conventional RF modulator, in the present embodiment, an RF modulator is applied to a VCR. A video input signal is input to a clamping circuit 11. The clamped video signal passes through a video switch 13 which switches over the output signal between a test pattern signal generated by a test pattern signal generator 12 and the clamped video signal, is clipped by a clipper circuit 14, and is then input to a mixer 15 together with an audio signal obtained by modulating a carrier by an audio frequency modulator 16 using an audio input signal and a carrier of an RF carrier oscillator 17. The mixer 15 outputs a mixed RF output.
As shown in Figure 2, the RF carrier oscillator 17 is a Clapp oscillator which employs a variable capacitor 21 and an inductor 22. The frequency can be varied by applying an inverse bias voltage to the variable capacitor 21.
The RF carrier oscillator 17 delivers a carrier to the mixer 15. It also outputs a highfrequency voltage to a frequency synthesiser circuit 18 through a buffer amplifier circuit 23, as shown in Figure 2.
The frequency synthesiser circuit 18 compares the phase as between the input signal and a reference signal generated by a reference frequency oscillator.
The phase comparison information output from the frequency synthesiser circuit 18 is input to a control circuit 19 comprised of, for example, a microcomputer.
The control circuit 19 controls a voltage varying circuit 20 on the basis of the input phase comparison information so that the voltage varying circuit 20 generates a predetermined voltage and thereby applies an inverse bias voltage to the variable capacitor 21 of the RF carrier oscillator 17.
The oscillating frequency varying operation of the RF carrier oscillator 17 will now be described.
The output voltage of the RF carrier oscillator 17 is input to the frequency synthesiser circuit 18 through the buffer amplifier circuit 23, as shown in Figure 2.
The frequency synthesiser circuit 18 phase compares between the output signal of the RF carrier oscillator 17 and the reference signal generated by the reference frequency oscillator, and outputs the resultant phase comparison information. Therefore, the output signal of the frequency synthesiser circuit 18 represents the output signal of the RF carrier oscillator 17: if the signal oscillated by the RF carrier oscillator 17 is frequency or phase shifted from what is desired, the phase comparison information of the frequency synthesiser circuit 18 contains that shift.
The control circuit 19 receives the phase comparison information of the frequency synthesiser circuit 18, detects the shift from the desired frequency or phase, and gives an instruction to the voltage varying circuit 20 so as to compensate for the shift. The voltage varying circuit 20 applies an inverse bias voltage to the variable capacitor 21 of the RF carrier oscillator 17 so as to compensate for a shift in the frequency or phase, by which the capacity of the variable capacitor 21 is varied and the oscillation condition established between the variable capacitor 21 and the inductor 22 is thereby varied so as to obtain a desired frequency or phase.
The output signal of the RF carrier oscillator 17, having a desired frequency or phase, is input to the control circuit 19 through the frequency synthesiser circuit 18. When the frequency or phase of the output signal is as desired, the control circuit 19 maintains that frequency or phase, and outputs the resultant instruction signal to the voltage varying circuit 20. Consequently, an RF carrier oscillator 17 capable of outputting a high quality carrier can be provided.
The oscillating frequency of the RF carrier oscillator 17 can be varied over a wide range by the aforementioned operation by programming the control circuit 19 such that it varies the frequency over a wide range. In this embodiment, the control circuit 19 comprising a microcomputer has been described.
However, the control circuit 19 may also be constructed by means of hardware. Furthermore, the RF carrier oscillator 17 is not limited to the Clapp oscillator. Any oscillator whose voltage can be controlled by a variable capacity diode can also be used as the RF carrier oscillator.
As will be understood from the foregoing description, in the RF carrier oscillator according to the present invention, the oscillating frequency can be varied over a wide range and shift in the frequency or phase can be greatly reduced. Therefore, an RF carrier oscillator capable of oscillating a high quality carrier can be provided. This in turn provides an RF modulator which is capable of outputting a high image and audio quality signal.

Claims (2)

1. An RF modulator for producing an RF output obtained by mixing an input signal, such as a video or audio signal, with a predetermined carrier in a mixer, said modulator comprising an RF carrier oscillator including a resonance circuit having a variable capacity diode capable of varying the frequency of oscillation, said RF carrier oscillator outputting a carrier to said mixer, a frequency synthesiser circuit for receiving the output signal of said RF carrier oscillator and for outputting phase comparison information formed by phase comparing the input signal and a signal generated by a reference frequency oscillator, a control circuit for receiving the phase comparison information of said frequency synthesiser circuit and for controlling the frequency of oscillation of said RF carrier oscillator to a predetermined frequency, and a voltage varying circuit for applying a predetermined voltage on the basis of an output signal of said control circuit to vary the capacity of the variable capacity diode to thereby vary the frequency of oscillation of said RF carrier oscillator.
2. An RF modulator substantially as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.
GB9119020A 1991-09-05 1991-09-05 RF modulator Expired - Fee Related GB2259418B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9119020A GB2259418B (en) 1991-09-05 1991-09-05 RF modulator

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9119020A GB2259418B (en) 1991-09-05 1991-09-05 RF modulator

Publications (3)

Publication Number Publication Date
GB9119020D0 GB9119020D0 (en) 1991-10-23
GB2259418A true GB2259418A (en) 1993-03-10
GB2259418B GB2259418B (en) 1995-10-11

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB9119020A Expired - Fee Related GB2259418B (en) 1991-09-05 1991-09-05 RF modulator

Country Status (1)

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GB (1) GB2259418B (en)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2041682A (en) * 1979-02-08 1980-09-10 Jerrolds Electronics Corp Digital frequency lock tuning system
US4613826A (en) * 1985-05-03 1986-09-23 Kabushiki Kaisha Toshiba Frequency synthesizer for CATV tuner
GB2173661A (en) * 1985-03-22 1986-10-15 Victor Company Of Japan Superheterodyne television tuner

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2041682A (en) * 1979-02-08 1980-09-10 Jerrolds Electronics Corp Digital frequency lock tuning system
GB2173661A (en) * 1985-03-22 1986-10-15 Victor Company Of Japan Superheterodyne television tuner
US4613826A (en) * 1985-05-03 1986-09-23 Kabushiki Kaisha Toshiba Frequency synthesizer for CATV tuner

Also Published As

Publication number Publication date
GB2259418B (en) 1995-10-11
GB9119020D0 (en) 1991-10-23

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Date Code Title Description
PCNP Patent ceased through non-payment of renewal fee

Effective date: 20080905