Pulse or digital communications – Repeaters – Testing
Patent
1991-07-18
1994-11-15
Gregory, Bernarr E.
Pulse or digital communications
Repeaters
Testing
380 34, H04L 2730
Patent
active
053655508
ABSTRACT:
A direct sequence digital spread spectrum receiver acquires and maintains synchronization in a reliable, yet simple manner, even under severe multipath and interference conditions. A sliding correlator and a voltage controlled crystal oscillator (VCXO) cooperate to acquire initial synchronization, and once synchronization is acquired, the VCXO is linearly frequency modulated (FM) for accurate tracking. The difficult problem of keeping the receiver code clock synchronized to that of the transmitter under severe multipath and interference conditions is solved by virtue of a dual switched bandwidth low pass filter section of the tracking circuit, allowing a wide bandwidth for initial acquisition and tracking but once the clocks are aligned, a narrow loop takes over that follows the transmitter closely. A commercially available intermediate frequency (IF) integrated circuit (IC) is used as an amplitude modulated (AM) detector to achieve the large dynamic range required. The IF IC has an internal received signal strength indicator (RSSI) output which is used to demodulate the amplitude variations generated by the tracking circuit.
REFERENCES:
patent: 3402265 (1968-09-01), Couvillon, Jr.
patent: 4039749 (1977-08-01), Gordy et al.
patent: 4122393 (1978-10-01), Gordy et al.
patent: 4351064 (1982-09-01), Ewanus
Gregory Bernarr E.
Pulse Electronics, Inc.
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