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Abstract

An improvement to a receiver for receiving multiple rays, due to multipath, of a received spread-spectrum signal having a chip-sequence signal with a chip rate embedded therein. The received spread-spectrum signal is sampled by an analog-to-digital converter at approximately twice the chip rate and then the samples are shifted in a shift register. The shift register shifts the chips of the underlying chip-sequence signal at approximately twice the chip rate. A matched filter includes an adder tree which, in cooperation with the shift register, forms an impulse response matched to the chip-sequence signal. The adder tree detects initially the chip-sequence signal embedded in the first ray, and outputs a first correlation signal. The adder tree then detects the chip-sequence signal embedded in the second ray, and outputs a second correlation signal. The adder tree continues to detect the chip-sequence signal of subsequent rays, and outputs subsequent correlation signals. A combiner combines each of the correlation signals using maximal-ratio combining. No tracking loop is required even though the chip clock and the sampling clock have slightly different frequencies.

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First Claim