Allen C Jones

US Patent:

41123727, Sep 5, 1978

Filed:

Jan 11, 1977

Appl. No.:

5/758520

Inventors:

Jerry D. Holmes - Dallas TX
Charles R. Johnson - Garland TX
Allen S. Jones - Dallas TX
Charles R. Hewes - Richardson TX

Assignee:

Texas Instruments Incorporated - Dallas TX

International Classification:

H04L 100

US Classification:

325321

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.