Synchronization apparatus and method for spread spectrum receiver
First Claim
1. An apparatus comprising:
- a preamble correlator;
a plurality of symbol code correlators, each symbol code correlator outputting a correlation signal upon receipt of a symbol code for which the symbol code correlator is configured;
a preamble correlation signal output from said preamble correlator; and
a center seeking circuit connected to said preamble correlation signal, said center seeking circuit outputting a timing reference signal indicative of a center of a preamble correlation pulse occurring in said preamble correlation signal.
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Abstract
An apparatus and method for synchronizing a spread spectrum receiver comprises a preamble matched filter and a plurality of symbol code correlators for receiving and correlating to a received spread spectrum signal. The preamble matched filter is preferably non-coherent in nature and outputs a correlation signal including a correlation pulse of variable width. The pulse is converted to a square wave having a duration of a discrete number of chip periods. The correlation pulse is used as a timing reference for the symbol code correlators, which are also non-coherent in nature. A center seeking circuit provides an offset to the timing reference according to the width of the correlation pulse. In a preferred TDMA system, a timing window is used for a subsequent time frame for defining a period of time in which the correlation signal output from the preamble matched filter can yield a valid correlation pulse. In addition to synchronizing the symbol code correlators, the receiver clocks for synchronizing to the TDMA time frame may also be adjusted in response to the correlation pulse.
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Citations
14 Claims
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1. An apparatus comprising:
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a preamble correlator; a plurality of symbol code correlators, each symbol code correlator outputting a correlation signal upon receipt of a symbol code for which the symbol code correlator is configured; a preamble correlation signal output from said preamble correlator; and a center seeking circuit connected to said preamble correlation signal, said center seeking circuit outputting a timing reference signal indicative of a center of a preamble correlation pulse occurring in said preamble correlation signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A spread spectrum receiver comprising:
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a plurality of correlators; a receiver clock; a counting circuit connected to said receiver clock, whereby major time frames and minor time frames within a time division multiple access communication system are measured; a correlation signal output from a first one of said correlators; and a center seeking circuit connected to a first one of said plurality of correlators, said center seeking circuit controlling a timing window during which said correlation signal is deemed valid. - View Dependent Claims (10, 11, 12, 13, 14)
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Specification