| US 7,602,835 B1 | ||
| Multi-rate spread spectrum composite code | ||
| Samuel C. Kingston, Salt Lake City, Utah (US); Johnny M. Harris, Centerville, Utah (US); Thomas R. Giallorenzi, Riverton, Utah (US); Dan M. Griffin, Bountiful, Utah (US); and David W. Thorson, Salt Lake City, Utah (US) | ||
| Assigned to L-3 Communications Corporation, New York, N.Y. (US) | ||
| Filed on Aug. 10, 2004, as Appl. No. 10/915,777. | ||
| Int. Cl. H04B 1/00 (2006.01) | ||
| U.S. Cl. 375—142 [375/134; 375/135; 375/136; 375/137; 375/140; 375/143; 375/145; 375/146; 375/147; 375/149; 375/150; 375/152; 375/253; 375/306; 375/307; 375/316; 375/326; 375/350; 375/367] | 16 Claims |
| 1. A correlator configured to despread a multi-rate composite long code defining a composite length of at least N*M, where
N and M are integers each greater than one, comprising:
a first stage comprising:
a first plurality of at least N−1 delay elements arranged in series with one another;
a first plurality of at least N filter taps, each having an input that is coupled to one of an input and an output of a delay
element of the first plurality of delay elements; and
a first despread adder having an input coupled to an output of each of the first plurality of at least N filter taps;
a second stage comprising:
a second plurality of at least M−1 delay elements arranged in series with one another;
a second plurality of at least M filter taps, each having an input that is coupled to one of an input and an output of a delay
element of the second plurality of at least M−1 delay elements;
a second despread adder having an input coupled to an output of each of the second plurality of at least M filter taps and
an output coupled to an input of the first plurality of at least N−1 delay elements; and
a shift register having an input coupled to an output of the first despread adder, wherein an energy profile of the shift
register exhibits a peak when contents of the shift register are in proper alignment with the multi-rate composite long code;
wherein the multi-rate composite long code is constructed from at least a first constituent code and a second constituent
code, wherein the first constituent code defines a first length N and the second constituent code defines a second length
M,wherein the second constituent code is a cover code running at a rate of 1/N;wherein the delay elements of the first plurality each delay one unit of time and the delay elements of the second plurality
each delay N units of time;wherein the first stage operates at a rate X and the second stage operates at a rate X/N; wherein N is not equal to M, and
X is an integer greater than one.
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