High frequency receiving apparatus
First Claim
1. A high frequency receiving apparatus comprising:
- a mixer for mixing a local oscillation signal with a high frequency input signal to obtain an intermediate frequency signal;
a local oscillation device for controlling a frequency of an oscillator with a PLL system on the basis of an oscillation frequency of a reference solid-state oscillation element and for sending said local oscillation signal to said mixer;
a detection oscillator for generating an oscillation signal for picture synchronous detection;
a picture synchronous detector for producing a detection output having a specific phase difference from said oscillation signal of said detection oscillator based upon said intermediate frequency signal;
a phase comparator for comparing a phase difference between said intermediate frequency signal and said oscillation signal of said detection oscillator;
a variable capacitive element equivalently connected in parallel to said reference solid-state oscillation element of said local oscillation device for converting a voltage change into a capacitance change; and
a voltage feedback device for applying an output voltage of said phase comparator to said variable capacitive element.
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Abstract
A high frequency television signal receiving apparatus providing excellent linear detection of output characteristics by improving the phase characteristic of the picture synchronous detector. A variable capacitive element is equivalently connected in parallel to a reference solid-state oscillation element. The reference solid-state oscillation element controls the frequency of a local oscillation device including a PLL circuit for feeding a local oscillation signal to a mixer for converting a high frequency signal into an intermediate frequency signal. A first low pass filter is connected between a phase comparator for detecting a phase difference of the intermediate frequency signal and the output of a detection oscillator for generating a detection oscillation signal with a specific phase difference. A second low pass filter having a larger time constant than the first low pass filter is connected to the variable capacitive element. The capacitance of the variable capacitive element is varied by the output voltage of the phase comparator. The signal frequency of the local oscillation device is shifted, and is controlled to converge the frequency of the intermediate frequency signal within the frequency range of the detection oscillation signal.
134 Citations
7 Claims
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1. A high frequency receiving apparatus comprising:
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a mixer for mixing a local oscillation signal with a high frequency input signal to obtain an intermediate frequency signal; a local oscillation device for controlling a frequency of an oscillator with a PLL system on the basis of an oscillation frequency of a reference solid-state oscillation element and for sending said local oscillation signal to said mixer; a detection oscillator for generating an oscillation signal for picture synchronous detection; a picture synchronous detector for producing a detection output having a specific phase difference from said oscillation signal of said detection oscillator based upon said intermediate frequency signal; a phase comparator for comparing a phase difference between said intermediate frequency signal and said oscillation signal of said detection oscillator; a variable capacitive element equivalently connected in parallel to said reference solid-state oscillation element of said local oscillation device for converting a voltage change into a capacitance change; and a voltage feedback device for applying an output voltage of said phase comparator to said variable capacitive element. - View Dependent Claims (2, 5, 6)
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3. A high frequency receiving apparatus comprising:
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a first mixer for mixing a first local oscillation signal with a high frequency input signal to obtain a first intermediate frequency signal; a first local oscillation device for controlling a frequency of a first oscillator with a PLL system on the basis of an oscillation frequency of a first reference solid-state oscillation element, and for sending said first local oscillation signal into said first mixer; a second mixer for mixing a second local oscillation signal with said first intermediate frequency signal to obtain a second intermediate frequency signal; a second local oscillation device for controlling a frequency of a second oscillator with a PLL system on the basis of an oscillation frequency of a second reference solid-state oscillation element and for sending said second local oscillation signal to said second mixer; a detection oscillator for generating an oscillation signal for picture synchronous detection; a picture synchronous detector for producing a detection output having a specific phase difference from said oscillation signal of said detection oscillator based upon said second intermediate frequency signal; a phase comparator for comparing a phase difference between said second intermediate frequency signal and said oscillation signal of said detection oscillator; a variable capacitive element equivalently connected in parallel to said second reference solid-state oscillation element of said second local oscillation device for converting a voltage change into a capacitance change; and a voltage feedback device for applying an output voltage of said phase comparator to said variable capacitive element. - View Dependent Claims (4)
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7. A method for synchronous detection of high frequency signals, comprising the steps of:
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receiving a high frequency input signal; providing a local oscillator for sending a local oscillation signal to a mixer; controlling a frequency of said local oscillator with a PLL system on the basis of an oscillation frequency of a reference solid-state oscillation element; connecting a variable capacitive element equivalently in parallel to said reference solid-state oscillation element for converting a voltage change to a capacitance change to control said reference solid-state oscillation element; mixing said local oscillation signal with said high frequency input signal by said mixer to obtain an intermediate frequency signal; generating an oscillation signal by a detection oscillator for picture synchronous detection based on said intermediate frequency signal; comparing a phase difference between said intermediate frequency signal and said oscillation signal of said detection oscillator; producing a detection output based on a specific phase difference between said oscillation signal of said detection oscillator and said intermediate frequency signal; and applying an output voltage of the phase comparison to said variable capacitive element to change a capacitance of said variable capacitive element such that said intermediate frequency converges within an oscillation frequency range of said detection oscillator.
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Specification