US 5,757,870 A · Spread spectrum communication synchronizing method and its circuit

Abstract

A synchronizing method and circuit accurately and stably operates a direct spread spectrum multiple access communication system. A signal transmitted by modulating the spreading code with data at the transmission side is sampled by a signal of n times (n: 1 or larger integer) the clock speed of the spread spectrum signal at the reception side, and the correlation is detected by a digital matched filter. Consequently, the detection output in every sample in the symbol period is compared with the envelope detection output determined in every sampling period, and the sample positions for a specific number of determined samples are stored in the descending order of the output. The number of times of storage of large sample positions in the stored detection output is counted in every symbol period, and the position of the largest number of storage times is detected as the peak position. From this peak position, capturing or holding the symbol period and setting of the reception window position results.

Claims24

Dependent claims

A spread spectrum communication synchronizing method for sampling a spread spectrum signal comprising the steps of:

modulating a spreading code with data by using a sampling clock having a rate which is an integer multiple of a spreading code chip speed for detecting correlation of the spread spectrum signal,
comparing a magnitude of each detection output in a symbol period from an envelope detection output determined in each sample period,
storing the sample position of a large output signal,
counting numbers of times sample positions are stored in each symbol period, and
synchronizing the data symbol with the largest stored sample position used as a peak position of the envelope detection output,
wherein the peak position is based on the largest number of times the sample position is stored in each sample period.

3 more elements

A spread spectrum communication synchronizing apparatus for use in direct sequence spread spectrum multiple access communication systems, comprising:

a sampler for sampling a received signal comprising a spreading code modulated by data using a sampling clock,
a digital matched filter coupled to the sampler for detecting a correlation of the spread spectrum signal,
an envelope detector, having an output, for detecting an envelope of the correlated spread spectrum signal in a sampling period,
a sample counter for counting the sampling clocks,
a comparator for comparing a magnitude of the detector output in each sample in a symbol period,
a sample position memory for storing sample positions for a predetermined number of samples in descending order of magnitude based on is the detector output,
a ranking accumulation memory for counting and storing the number of times of storage of the largest sample positions from the detector output in each symbol period,
a peak position detector for detecting the sample position corresponding to the largest number of storage times, the sample position being a peak position, and
a window position setter for i) holding the symbol period, and ii) setting a reception window position based on the peak position.

6 more elements

Dependencies are inferred from the claim text.

Spread spectrum communication synchronizing method and its circuit

Life of this patent

Spread spectrum communication synchronizing method and its circuit

Life of this patent

Abstract

Claims24