Transceiver circuits for TDMA system with variable frequency second local oscillator
First Claim
1. A transceiver circuit for use with a time division multiple access system, the transceiver circuit comprising:
- a first local oscillator for generating a first local frequency signal;
a second local oscillator comprising a frequency synthesizer having a reference frequency that is higher than a frequency channel step, and generating a second local frequency signal having a frequency dependent on whether the transceiver circuit is in the transmitting mode or the receiving mode;
a heterodyne receiver circuit comprising;
a first frequency converter for converting a received signal into a first intermediate frequency signal, anda second frequency converter for converting the first intermediate frequency signal into a second intermediate frequency signal having a frequency equal to a differential frequency between the first intermediate frequency and the second local frequency signal; and
a transmitter circuit.
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Accused Products
Abstract
A transceiver circuit with a heterodyne receiver circuit is provided. Output signals of first and second local oscillator 103, 104 are mixed by a local frequency converter 105. An output signal of the converter 105 passes a filter 106 and inputs a modulator 111 of a transmitter circuit 101 as well as a first frequency converter 122 of a receiver circuit 102. The second local oscillator 104 comprises a frequency synthesizer whose output signal varies for a transmission or a receiving mode. The output signal of the second local oscillator 104 also inputs the second frequency converter 124 of the receiving mode. A reference frequency of the second local oscillator 104 is set higher than a frequency step between communication channels so that a quick switching of the frequency is performed. Thus, the transceiver circuit of this invention is suitable for a compact size and hardly generates unwanted spurious components at transmission mode.
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Citations
13 Claims
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1. A transceiver circuit for use with a time division multiple access system, the transceiver circuit comprising:
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a first local oscillator for generating a first local frequency signal; a second local oscillator comprising a frequency synthesizer having a reference frequency that is higher than a frequency channel step, and generating a second local frequency signal having a frequency dependent on whether the transceiver circuit is in the transmitting mode or the receiving mode; a heterodyne receiver circuit comprising; a first frequency converter for converting a received signal into a first intermediate frequency signal, and a second frequency converter for converting the first intermediate frequency signal into a second intermediate frequency signal having a frequency equal to a differential frequency between the first intermediate frequency and the second local frequency signal; and a transmitter circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification