Subscriber unit for wireless digital telephone system

Details Subscriber unit for wireless digital telephone system Subscriber unit for wireless digital telephone system

1988-10-12

1990-07-24

Safourek, Benedict V.

Pulse or digital communications

Repeaters

Testing

375 67, 375 8, 375 56, H04L 2718

Patent

active

049439839

ABSTRACT:
A digital wireless subscriber telephone unit for wireless connection with a base station. The subscriber unit has a baseband processor which is coupled to storage means for the baseband functions. The baseband processor is direct access coupled to a modem processor whereby the two processors may communicate with each other. The modem processor generally acts as the master in the system, although lock-out means may be used in certain circumstances. The signal from the modem processor is converted to an analog signal, which is subjected to deglitching, and the deglitched signal is then upconverted and filtered to form an IF signal which is thereafter amplified. The amplified IF signal is combined with a signal generated by a synthesizer to provide an RF signal. On the basis of certain signals received from the base station, the baseband processor produces initiating signals which determines whether the subscriber unit will be in the transmit mode or the receive mode. In intervals between actuation of the system, a training mode is used wherein a known signal from the modem processor is compared with a looped-back signal to produce correction constants to compensate for undesirable variations in the IF, these constants being stored for use in correcting actual received signals. During demodulation, the modulated digital signals are fed to the modem processor in the form of time multiplexed I and Q samples and are demultiplexed. The demultiplexed I and Q samples are fed to an equalizer and frequency correction circuit for minimization of errors and for production of a frequency correction signal which is used to correct any errors in the timing of the system and in the output of the synthesizer.

REFERENCES:
patent: 3891959 (1975-06-01), Tsuji et al.
patent: 4481640 (1984-11-01), Chow et al.
patent: 4825452 (1989-04-01), Wong
patent: 4851841 (1989-07-01), Sooch

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