US 5,233,626 AGranted

Repeater diversity spread spectrum communication system

AssigneeSpace Systems/Loral, Inc.

InventorStephen A. Ames

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Abstract

A repeater diversity spread spectrum communication system provides substantially fade free communications between a transmitter (1) and a receiver (7). A transmitted signal is relayed through a plurality of linear communications repeaters (3-6) that produce copies of the transmitted signal, the copies each arriving through an independently fading signal path. The transmitter and/or the receiver may be mounted upon a mobile platform, and the plurality of repeaters may be terrestrial, or may be provided in satellites in low earth orbit or in geosynchronous earth orbit. The receiver processes the received signal copies to equalize them to one another in delay, frequency, and phase, and then combines the multiple received and equalized signal copies to produce a composite signal having a greatly reduced fading depth.

Claims20

Dependent claims

A radio frequency receiver, comprising:

means for receiving a multi-path transmitted signal comprised of a plurality of signals, each of the plurality of signals arriving at the radio frequency receiver through a separate repeater means and along a different propagation path such that each of the plurality of signals experiences a propagation delay that differs from a propagation delay of others of the plurality of signals;
means for performing a spread spectrum correlation on each of the received plurality of signals to produce at an output a plurality of correlated signals;
received signal equalizing means having an input coupled to said output of said correlation means for equalizing each of the plurality of correlated signals one to another to provide at an output a plurality of equalized correlated signals, said equalizing means including means for equalizing the propagation delay of each of the correlated signals to a largest propagation delay, means for equalizing a Doppler frequency offset of each correlated signal, and means for equalizing a phase shift of each correlated signal;
said radio frequency receiver further including
means, having an input coupled to said output of said received signal equalizing means, for combining together all equalized correlated signals to provide at an output a composite received signal.

2 more elements

A radio frequency receiver, comprising:

means for receiving n transmissions from a single transmitter, each of the n transmissions following a different propagation path, and each of the propagation paths having a different propagation path length;
n receiver channels each of which is responsive to one of the n received transmissions for acquiring and tracking an associated one of the n received transmissions;
combining means having inputs coupled to an output of each of said n receiver channels and including means for combining the output of said n receiver channels into a combined signal that is representative of the signal transmitted from the transmitter;
wherein
each of said n receiver channels includes, spread spectrum correlation means that includes means for phase locking to one of said n received transmission for recovering data symbols therefrom;
and
means, having an input coupled to an output of said phase locking means and an output coupled to one of said inputs of said combining means, for delaying the recovered data symbols with a resolution equal to a fraction of a data symbol;
and wherein said receiver further comprises,
control means having an output coupled to each of said plurality of phase locking means for specifying a phase delay thereto for causing each of said phase locking means to acquire and track a different one of said n received transmission, said control means further having an output coupled to each of said delay means for providing to each of said delay means a signal that specifies a data symbol delay period for use by each, such that the outputs of said n receiver channels that are input to said combining means are substantially equalized to one another in frequency, delay, and phase shift.

6 more elements

A communication system, comprising:

a spread spectrum transmitter means;
a spread spectrum receiver means;
and
a plurality of repeater means each of which includes means for receiving a transmission from said spread spectrum transmitter means and means for re-transmitting said received transmission for reception by said spread spectrum receiver means;
wherein said spread spectrum receiver means includes,
means for receiving a re-transmitted signal from each of said repeater means;
means for performing a spread spectrum correlation on each of the received re-transmitted signals to produce at an output a plurality of correlated signals;
received signal equalizing means having an input coupled to said output of said correlation means for equalizing each of the plurality of correlated signals one to another to provide at an output a plurality of equalized correlated signals, said equalizing means including means for equalizing a propagation delay of each of the correlated signals to a largest propagation delay, means for equalizing a Doppler frequency offset of each correlated signal, and means for equalizing a phase shift of each correlated signal;
said spread spectrum receiver means further including
means, having an input coupled to said output of said received signal equalizing means, for combining together all equalized correlated signals to provide at an output a composite received signal.

7 more elements

Dependencies are inferred from the claim text.

Facts

Application: 07/881,134Filed 11 May 1992
Granted: 3 Aug 1993
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

H04B 1/7085
Synchronisation aspects: using a code tracking loop, e.g. a delay-locked loop
H04B 1/7115
The interference being multi-path interference: constructive combining of multi-path signals, i.e. RAKE receivers
H04B 7/022
Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas: site diversity; Macro-diversity
H04B 7/0845
Weighted combining: per branch equalization, e.g. by an FIR-filter or RAKE receiver per antenna branch