Direct conversion receiver
First Claim
1. A direct conversion receiver comprising:
- a local oscillator for generating a local oscillator signal having a frequency within a preselected frequency range and being varied in response to a variable low frequency signal;
a balanced mixer for generating a difference signal by mixing the oscillator signal with a received signal; and
a controlled oscillator for generating the variable low frequency signal more than an octave lower than a signal intended for reception and in inverse relationship to a direct current component in said difference signal, whereby a substantially direct conversion of the received signal is obtained.
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Accused Products
Abstract
In a frequency modulation radio receiver with direct conversion, a local oscillator signal is generated having a frequency within a preselected frequency range and the frequency is varied in response to a variable low frequency signal; the local oscillator signal is mixed with a received signal to provide a baseband signal. The variable low frequency signal is generated by a controlled oscillator in inverse relationship to a direct current component in said baseband signal. In a frequency modulation radio transceiver a broadcast function is provided by varying the low frequency signal with an information signal with the resulting local oscillator frequency being varied accordingly and amplified for broadcast. The transceiver is controlled to operate alternately in either a receive mode and a broadcast mode at substantially the same frequency. While in the receive mode the controlled oscillator causes the local oscillator signal to be drawn toward the carrier frequency of a received signal yielding preferred direct conversion of modulating information into the base band.
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Citations
12 Claims
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1. A direct conversion receiver comprising:
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a local oscillator for generating a local oscillator signal having a frequency within a preselected frequency range and being varied in response to a variable low frequency signal;
a balanced mixer for generating a difference signal by mixing the oscillator signal with a received signal; and
a controlled oscillator for generating the variable low frequency signal more than an octave lower than a signal intended for reception and in inverse relationship to a direct current component in said difference signal, whereby a substantially direct conversion of the received signal is obtained. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A radio receiver comprising:
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a local oscillator for producing a local oscillator signal and being responsive to a low frequency signal for varying the phase of the local oscillator signal;
a mixer for mixing the local oscillator signal with received signals to produce a direct conversion of received signals having a frequency substantially similar to the local oscillator signal;
a low pass filter having a bandpass characteristic with a roll-off frequency corresponding to a highest frequency with which a signal intended for reception has been modulated; and
a controlled oscillator responsive to a direct current signal coupled via the lowpass filter for generating an ac signal of a frequency inversely related to an amplitude of the direct coupled signal and more than a plurality of octaves lower than the frequency of the signal intended for reception; and
said local oscillator generating a signal of a predetermined frequency and upconverting the ac signal to a multiple of a predetermined frequency;
whereby the local oscillator signal is adjusted toward a centre frequency of the signal intended for reception. - View Dependent Claims (12)
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Specification