| US 7,555,033 B2 | ||
| Binary offset carrier M-code envelope detector | ||
| Walter E. Lillo, Torrance, Calif. (US); Phllip W. Ward, Garland, Tex. (US); and Anthony S. Abbott, Torrance, Calif. (US) | ||
| Assigned to The Aerospace Corporation, El Segundo, Calif. (US) | ||
| Filed on Jun. 22, 2004, as Appl. No. 10/874,965. | ||
| Prior Publication US 2005/0281325 A1, Dec. 22, 2005 | ||
| Int. Cl. H04B 1/00 (2006.01) | ||
| U.S. Cl. 375—150 [375/149] | 19 Claims |

| 11. A system for detecting a broad correlation envelope and a narrow correlation envelope of a received signal comprising
a carrier modulated by a spreading code, the received signal is a binary offset carrier (BOC) signal, the system comprising,
a splitting means for splitting the received signal into an inphase BOC signal and a quadraphase BOC signal, the splitter
means further for coherently demodulating the received signal by mixing the received signal by a carrier replica, the splitter
means further for coherently despreading the received signal by mixing the received signal by code replicas of despreading
codes, the despreading codes and code replicas defining a code phase error between the spreading code and code replicas, the
splitting means serving to demodulate in quadrature and despread and split the inphase BOC signal and the quadraphase BOC
signal into sets of I and Q inphase BOC signals and I and Q quadraphase BOC signals for each of the code replicas,
a correlation means for generating narrow and broad correlation values from broad and narrow code replicas of the code replicas
and from the I and Q inphase BOC signals and I and Q quadraphase BOC signals, the narrow correlation values generated from
the I and Q inphase BOC signals, the broad correlations values generated from the I and Q inphase BOC signals and I and Q
quadraphase BOC signals, the narrow correlation values defining the narrow correlation envelope, the broad correlation values
defining the broad correlation envelope,
a replica code generator means for receiving the code phase error and for generating and shifting the code replicas in time
for generating and aligning a prompt code replica of the code replicas with the received spreading code for coherently despreading
the received signal in synchronism between the prompt code replica and the spreading code, the replica code generator generating
the narrow code replicas and the broad code replicas of the code replicas,
a discriminator means for generating the code phase error from the narrow correlation envelope and the broad correlation envelope,
the discriminator means for adjusting the code phase error over differing narrow and broad correlation values, and
wherein,
the narrow code replicas comprise a narrow early code replica and a narrow late code replica,
the narrow early code replica and the narrow late code replica are separated in time by a narrow time duration,
the narrow correlation values linearly changing over differing values of the code phase error when the code phase error is
less than twice the narrow time duration,
the broad code replicas comprise a broad early code replica and a broad late code replica,
the broad early code replica and the broad late code replica are separated in time by a broad time duration,
the broad duration time is greater than the narrow duration time,
the broad correlation envelope is a unimodal correlation envelope over the broad duration time,
the narrow correlation envelope is also a unimodal correlation envelope over the narrow duration time, and
the broad and narrow correlation envelopes provide for an unambiguous code phase error detection when the code phase error
is less than the narrow time duration.
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