Synchronous receiver with direct mixing
AssigneeTelefunken electronic GmbH
InventorGeorg Frank
Life of this patent
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Abstract
A synchyronous receiver with direct mixing comprising a phase detector and an amplitude demodulator is provided with a square-law envelope detector and means for making the envelope signal audible or visible for tuning purposes.
Claims28
A direct conversion synchronous receiver which tunes the frequency of an oscillator signal to an input signal, comprising:
- a phase-lock loop including a regulating filter, a voltage controlled oscillator controlled by an output of said regulating filter to generate first and second oscillator signals which are respectively 90 degrees out of phase with one another, and a first phase detector in the form of an amplitude demodulator which synchronously demodulates an input signal by mixing the input signal with the second oscillator signal to produce a first mixed signal, said regulating filter filtering the first mixed signal, such that the first oscillator signal is tuned in frequency and phase to that of the input signal;
- a second phase detector which demodulates the input signal by mixing the input signal with the first oscillator signal to produce a second mixed signal;
- first and second low-pass filter means respectively coupled to said first and second phase detectors, for respectively low-pass filtering the first and second mixed signals,
- means, coupled to said first and second filter means for quadrating the respective low-pass filtered outputs of said first and second filter means;
- means for summing together the quadrated outputs of said quadrating means to obtain a square law envelope signal;
- and
- means for making the envelope signal audible or visible during tuning.
A direct conversion synchronous receiver having an input port and an output port, which fine tunes the frequency of an oscillator signal to a modulated audio or video input signal received at the input port and provides at the output port a demodulated signal for driving an audio or video transceiver, comprising:
- a phase-lock loop including a regulating filter, a voltage controlled oscillator means, controlled by an output of said regulating filter to generate first and second oscillator signals which are respectively 90 degrees out of phase with one another, and a first phase detector in the form of an amplitude demodulator which synchronously demodulates an input signal by mixing the input signal with the second oscillator signal to produce a first mixed signal, said regulating filter filtering the first mixed signal, such that the first oscillator signal is tuned in frequency and phase to that of the input signal;
- a second phase detector which demodulates the input signal by mixing the input signal with the first oscillator signal to produce a second mixed signal;
- first and second low-pass filter means respectively coupled to said first and second phase detectors, for respectively low-pass filtering the first and second mixed signals,
- means, coupled to said first and second filter means for quadrating the respective low-pass filtered outputs of said first and second filter means;
- means for summing together the quadrated outputs of said quadrating means to obtain a square law envelope signal;
- and
- an output port;
- and
- means for selectively applying at least a portion of the square law envelope signal to said output port during tuning.
Dependencies are inferred from the claim text.