Dual mode radiotelephone terminal selectively operable for frequ

Details Dual mode radiotelephone terminal selectively operable for frequ Dual mode radiotelephone terminal selectively operable for frequ

1993-04-23

1995-02-21

Urban, Edward F.

Telecommunications

Transmitter and receiver at same station

With frequency stabilization

455 86, 455209, 455314, H04B 152

Patent

active

053924606

ABSTRACT:
A dual-mode radiotelephone terminal includes a .pi./4-shift DQPSK modulator (11). A dual-mode modulation is achieved by mixing an output of a transmitter oscillator (16) with an output of an offset oscillator (18) to form an injection signal (LO) at a final transmitter frequency, the injection signal being further modulated with a quadrature modulator in a digital mode of operation. In an analog mode of operation the transmitter oscillator or the offset oscillator is frequency modulated and the quadrature modulator is disabled, thereby passing the frequency modulated injection signal without substantial attenuation. The LO signal is regenerated and also phase shifted with a circuit (35) having a frequency multiplier (30) and a frequency divider (34). The circuit outputs two local oscillator (LO) signals (LOA and LOB), each of which directly drives an associated quadrature mixer (36, 38) of the modulator. In another embodiment the dual-mode radiotelephone terminal includes a VHF synthesizer (23), a UHF synthesizer (21), and a local oscillator (4C) that provides a signal only when operating in the analog receiving mode. The local oscillator signal is mixed with a first IF signal for providing a second IF signal when operating in the analog receiving mode or in a standby mode. A control signal is employed for selectively enabling and disabling various of these components as a function of the operating mode, thereby conserving power.

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Product Brochure, "ICs For Communications, GSM Transmitter Circuit PBM 2200", Siemens, Ed. 5.90 (1990).

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