1977-01-11
1978-09-05
Safourek, Benedict V.
325 42, H04L 100
Patent
active
041123727
ABSTRACT:
An improved spread spectrum communication system having a transmitter subsystem and a receiver subsystem is disclosed. The transmitter subsystem comprises a data source of 50 bps rate which is modulo-2 added to a C/A (clear/acquisition) code of 1,023K chips/sec in an EXCLUSIVE OR gate, phase modulated on a carrier signal at about 154 f.sub.o where f.sub.o = 10.23 MHz in a phase shift keying modulator and transmitted. The receiver subsystem comprises an antenna for receiving the phase modulated signal, a plurality of filter/amplifier mixer stages for reducing the phase modulated signal to baseband, an in-phase CCD matched filter channel and a quadrature phase CCD matched filter channel for determining the presence of the C/A code and the phase of the incoming C/A code for synchronizing a replica of the C/A code with the incoming C/A code, a mixer for beating the replica C/A code signal with the C/A code signal, a Costas loop for automatic phase control, a sampler for sampling the baseband signal, an integrator for integrating the sampled signals, and a clocked comparator for comparing the integrated signals with a zero voltage at a 50Hz rate to demodulate the data code. Two embodiments of the CCD matched filter are disclosed. The first comprises a CCD having a length equal to five times the number of stages for each period of the C/A code. The second comprises a CCD transversal filter having a feedback loop for use in its transversal filter mode and in a recursive filter mode to enhance C/A code signals relative to noise.
REFERENCES:
patent: 4017798 (1977-04-01), Gordy et al.
patent: 4034199 (1977-07-01), Lampe et al.
patent: 4041391 (1977-08-01), Deerkoski
Hewes Charles R.
Holmes Jerry D.
Johnson Charles R.
Jones Allen S.
Bandy Alva H.
Grossman Rene E.
Safourek Benedict V.
Texas Instruments Incorporated
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