US 6,212,223 B1 · Demodulation and correlation for spread spectrum communications

Abstract

In a spread spectrum communications system, method and apparatus are provided for reducing transmission error and power consumption despite an increase in sampling. There are serially provided 4k (k denotes a spreading factor) shift registers (1) to (4) to deal with at most four samples to develop input spread signals, which are multiplied by spread-code replica signals from a replica generator. Sums π1 to π4 of respective k products are obtained. An output of a correlator is obtained by further adding the sums. At this time, the shift registers (1) to (4), adders and the replica generator are controlled in response to a control signal depending upon the number of samples. When three samples are sampled for one chip, the shift register (4) is disabled and (1, 1, 1, −1, −1, −1, 1, 1, 1, 1, 1, 1, −1, −1, −1, NA, NA, NA, NA, NA) are prepared as a replica and only adder π4 is disabled and an output of the correlator is obtained from signals stored in the shift registers (1), (2), (3).

Claims15

Dependent claims

A demodulating device in a direct sequence spread spectrum communication system having sampling means for sampling a given number of samples to one chip from input spread signals in a baseband frequency range, which are directly spread with a spread-code, wherein the number of samples to one chip can be controlled in response to a control signal, and wherein a control signal is generated for controlling the number of samples depending upon a multi-valued number of the signal level of the input spread signals.

A demodulating device in a direct sequence spread spectrum communication system adapted to perform despreading based upon discrete sample signals the demodulation device comprising:

means for sampling a driven number of samples from one chip of input spread signals in a baseband frequency range;
sample signal selecting means for selecting a number of samples, the number of which is less than the said given number of samples from one chip of input direct sequence spread spectrum signals obtained by the sampling means to despread only sample signals selected by said sample signal selecting means, wherein the sample signal selecting means selects sample signals in such a timing relationship that a correlation signal is generated, which is detected in a clock regenerating circuit for regenerating sampling clock signals based upon despread signals which are obtained by an addition operation which involves adding correlation signals based on all sample signals which are sampled by the sampling means.

Dependencies are inferred from the claim text.

Demodulation and correlation for spread spectrum communications

Life of this patent

Demodulation and correlation for spread spectrum communications

Life of this patent

Abstract

Claims15