Electrical transmission or interconnection systems – Personnel safety or limit control features – Interlock
Patent
1990-07-02
1992-06-09
Gregory, Bernarr E.
Electrical transmission or interconnection systems
Personnel safety or limit control features
Interlock
375 1, 328114, 328150, H03K 5153, H03K 1713
Patent
active
051209977
ABSTRACT:
A spread spectrum signal detector for sampling a modulated carrier employing a zero-crossing detection means having two independent control loops, a first loop for a zero-mean threshold control and a second loop for AGC control. An IF sampler quantizeds the received spread spectrum signals at IF and provides high immunity to interference or jamming. The IF signal is sampled at a number of quarter cycle intervals to allow sampling in sequence of the in-phase (I) and quadrature-phase (Q) components. The output of the IF sampler is two bits, a sign bit and a magnitude bit. The zero-man threshold control loop using only the sign bit of the I and Q samples sets a threshold level (T0) to detect the zero-crossings of a received waveform. Two magnitude threshold levels are set at fixed offsets from the T0 threshold level. A normalized statistical accumulator using the magnitude bits of the I and Q samples determines the AGC control level for a fixed percentage of outside threshold crossings of the most significant magnitude bit. The I and Q samples are aligned in time, and every other pair of I and Q samples are inverted for digital demodulation of the IF samples to baseband. The baseband samples are provided to a signal processor for generating range and range rate information.
REFERENCES:
patent: 4682302 (1987-07-01), Williams
patent: 4727508 (1988-02-01), Williams
patent: 4749879 (1988-06-01), Peterson et al.
H. Braquet et al., "Zero-Crossing Detector", IBM Technical Disclosure Bulletin, (vol. 18, No. 1; p. 144; Jun. 1975.
Dawson Walter F.
Gregory Bernarr E.
Raytheon Company
Sharkansky Richard M.
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