Pulse or digital communications – Repeaters – Testing
Patent
1985-09-13
1989-08-22
Griffin, Robert L.
Pulse or digital communications
Repeaters
Testing
375 97, 375 87, 331 64, H03D 324, H04L 700
Patent
active
048603210
ABSTRACT:
A receiver is disclosed for acquiring and tracking a data signal in a highly stressed environment. The receiver comprises first and second I.F. sections, a mixer for translation from the first I.F. frequency to the second I.F. frequency, a 2 kHz bandpass filter at the second I.F. frequency, signal translator for synchronous translation of the signal at the second I.F. frequency to baseband, a digitizer for complex sampling operation on the baseband signal, a microprocessor for processing the digital samples, and a numerically controlled oscillator coupled to the mixer and controlled by the microprocessor. The microprocessor formulates matched digital discrete Fourier transform filters which drive frequency, phase and symbol lock loops at the symbol rate. Each of the loop filters is formed by symbol-rate recursive, first-order equations. A novel mode control system is employed to implement an orderly transition through the receiver modes, comprising (i) out-of-band noise estimation, (ii) coarse frequency and time acquisition of the data signal employing a sequential probability ratio test and a handover process, (iii) frequency and symbol synchronization with the data signal, (iv) phase and symbol synchronization with the data signal, and (v) feedback loop lock confirmation. After loss of lock, the mode controller transfers the receiver operations back to the appropriate restart operation. The receiver includes a novel lock detector system adapted to determine whether the feedback loops are properly locked to the signal. The system is operable over the range of frequency and time offsets and over a wide variation in received carrier-to-noise power densities.
REFERENCES:
patent: 4100503 (1978-07-01), Lindsey et al.
patent: 4320345 (1982-03-01), Waggener
patent: 4351064 (1982-09-01), Ewanus
patent: 4435822 (1984-03-01), Spencer et al.
patent: 4466108 (1984-08-01), Rhodes
patent: 4507617 (1985-03-01), Sasaki
Griffin Robert L.
Hughes Aircraft Company
Huseman Marianne
Karambelas A. W.
Meltzer M. J.
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