The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 27, 1994
Filed:
Oct. 19, 1993
Mark E Davis, Carlsbad, CA (US);
Hughes Aircraft Company, Los Angeles, CA (US);
Abstract
An adaptively-tuned filter (80) for use within the receiver (14) of a multiple-access code division (CDMA) communication system permits spectrally-inefficient transmissions to be made from each transmitter (12) used with such system, thereby simplifying the transmitter circuits, yet still achieves a signal-to-noise ratio (SNR) that approaches the SNR achieved when spectrally-efficient transmissions are made. The adaptive filter (80) also compensates for signal distortions resulting from multiple signal paths. The receiver (14) includes RF receiving circuits (60, 62), a matched filter (64), downconversion circuits (66, 68, 92), sampling circuits (70, 71, 72), a time acquisition circuit (76), an adaptive filter (80), a decimator circuit (75), a despreader circuit (77), and an accumulator circuit (78). The adaptive filter (80) includes, e.g., two LMS gradient filters (96a, 96b), or equivalent, that operate independently in parallel, with an accurate bit decision being used to select the tap signals to be used as the starting point for the next bit. The filters (80, 96) function as a fractionally-spaced chip-MSE equalizer that improves the bit-SNR in the presence of sufficient multi-access noise, and also provides narrowband noise rejection.