Pulse or digital communications – Spread spectrum – Direct sequence
Reexamination Certificate
1999-03-29
2001-07-03
Le, Amanda T. (Department: 2634)
Pulse or digital communications
Spread spectrum
Direct sequence
C375S150000, C375S152000, C375S347000, C375S348000, C455S139000, C455S276100, C342S375000, C342S378000
Reexamination Certificate
active
06256340
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to spread-spectrum communications and more particularly to a method and apparatus for enhancing communications by using phased array principles for increasing signal-to-noise ratio for a spread spectrum signal with multipath arriving at a receiver.
DESCRIPTION OF THE RELEVANT ART
Achieving sufficient signal strength when a received signal comes from two paths is a problem when communicating with spread-spectrum modulation in a multipath environment. The received signal from the two paths may have phase cancellation, yielding no reception, or reception with an unacceptable error rate.
Phased arrays, as is well known in the art, require N antenna elements for distinguishing up to N-
1
signals arriving at the phased array from different paths or directions. This concept of spatial diversity is well developed in antenna theory.
SUMMARY OF THE INVENTION
A general object of the invention is an improved system and method for receiving spread-spectrum signals in a multipath environment.
Another object of the invention is to increase the received signal-to-noise ratio or reduce the probability of error of a spread-spectrum signal arriving from two or more paths.
Another object of the invention is to receive a plurality of spread-spectrum signals arriving at the antenna from a multiplicity of different directions, independent of the number of antenna elements.
According to the present invention, as embodied and broadly described herein, a phased array spread-spectrum system is provided comprising receiving means, delaying means, combining means, despreading means, generating means, storing means, and comparing means. The receiving means receives a plurality of spread-spectrum signals and a plurality of phased versions of the plurality of spread-spectrum signals. Typically, the plurality of spread-spectrum signals is received by a first plurality of receivers coupled to a first antenna, and the plurality of phased versions of the plurality of spread-spectrum is received by a second plurality of receivers coupled to a second antenna. The plurality of received spread-spectrum signals and the plurality of phased versions of the plurality of spread-spectrum signals are digitized. The delaying means can delay the plurality of received spread-spectrum signals with respect to the plurality of phased versions of the plurality of spread-spectrum signals by a plurality of delays. The plurality of received spread-spectrum signals consequently becomes a plurality of delayed signals.
The combining means combines the plurality of delayed signals and the plurality of phased versions of the plurality of spread-spectrum signals as a plurality of combined signals. An in-phase component of each delayed signal is combined with an in-phase component of each phased version of each spread-spectrum signal, respectively. A quadrature-phase component of each delayed signal is combined with a quadrature-phase component of each phased version of each spread-spectrum signal, respectively.
The despreading means despreads the plurality of combined signals as a plurality of despread signals. This may be accomplished using a plurality of product detectors with a plurality of chipping sequences matched to the plurality of received spread-spectrum signals, respectively, or a plurality of matched filters having a plurality of impulse functions matched to the plurality of chipping sequences of the plurality of received spread-spectrum signals, respectively.
The generating means generates from the plurality of despread signals a plurality of magnitude values. Each magnitude value may be an absolute value, or the square of the in-phase component and quadrature-phase component of the despread signal.
The storing means stores a plurality of previous-magnitude values previously generated by the generating means and a plurality of present-magnitude values presently generated by the generating means. The plurality of previous-magnitude values and the plurality of present-magnitude values, respectively, are compared by the comparing means. In response to the result of this comparison, the comparing means outputs a plurality of comparison signals. The delaying means may change any or all of the plurality of delays based on the plurality of comparison signals, respectively.
The present invention also includes a method for maximizing the signal strength of a plurality of spread-spectrum signals with multipath comprising the steps of receiving the plurality of spread-spectrum signals and a plurality of phased versions of the plurality of spread-spectrum signals. The received plurality of spread-spectrum signals is delayed with respect to the plurality of phased versions of the spread-spectrum signals by a plurality of delays, to generate a plurality of delayed signals. The plurality of delayed signals and the plurality of phased versions of the plurality of spread-spectrum signals are combined as a plurality of combined signals, and the plurality of combined signals is despread as a plurality of despread signals, respectively.
The method includes generating a plurality of magnitude values from the plurality of despread signals, and storing a plurality of previous-magnitude values and a plurality of present-magnitude values. The plurality of previous-magnitude values and the plurality of present-magnitude values are compared, and a plurality of comparison signals is output based on this comparison. Using the plurality of comparison signals, the plurality of delays is changed. The step of generating the plurality of magnitude values is a way of locating a maximum. Other procedures for locating a maximum or equivalent may be used.
Additional objects and advantages of the invention are set forth in part in the description which follows, and in part are obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention also may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
REFERENCES:
patent: 4189733 (1980-02-01), Malm
patent: 4291410 (1981-09-01), Caples et al.
patent: 4361891 (1982-11-01), Lobenstein et al.
patent: 4549303 (1985-10-01), Gutleber
patent: 4587661 (1986-05-01), Schiff
patent: 4587662 (1986-05-01), Langewellpott
patent: 4608701 (1986-08-01), Burgers et al.
patent: 4800390 (1989-01-01), Searle
patent: 5081643 (1992-01-01), Schilling
patent: 5101501 (1992-03-01), Gilhousen et al.
patent: 5107273 (1992-04-01), Roberts
patent: 5109390 (1992-04-01), Gilhousen et al.
patent: 5248982 (1993-09-01), Reinhardt et al.
patent: 5260968 (1993-11-01), Gardner et al.
patent: 5422908 (1995-06-01), Schilling
patent: 5425059 (1995-06-01), Tsujimoto
patent: 0531028 (1993-03-01), None
patent: 9210890 (1992-06-01), None
Data Communication, Networks and Systems, Howard W. Sams & Co., 1987, pp. 343-352.
Digital Communications With Space Applications, S.W. Golomb et al., Prentice-Hall, Inc., 1964, pp. 45-64.
InterDigital Technology Corporation
Le Amanda T.
Volpe and Koenig P.C.
LandOfFree
Phased array spread spectrum system and method5 does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Phased array spread spectrum system and method5, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Phased array spread spectrum system and method5 will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2533838