Method and apparatus for complex phase equalization for use in a communication system

• US 6,215,983 B1
• Filed: 01/18/2000
• Issued: 04/10/2001
• Est. Priority Date: 06/02/1995
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: TRW Limited (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Inventors: Dogan, Mithat Can, Stearns, Stephen Deane
• Primary Examiner(s): Hunter, Daniel
• Assistant Examiner(s): Nguyen, Thuan T.
• Application Number:
  US09/483,905
• Time in Patent Office: 448 Days
• Field of Search: 455/63, 455/60, 455/67.3, 455/205, 455/67.6, 455/202, 455/203, 455/206, 455/296, 455/302, 455/303, 455/304, 455/324, 375/324, 375/325, 375/340
• US Class Current: 455/63.1
• CPC Class Codes: G01S 3/74 Multi-channel systems specially adapted for direction-finding, i.e. having a single antenna system capable of giving simultaneous indications of the directions of different signals systems in which the directions of different signals are determined sequentially and displayed simultaneously G01S3/04, G01S3/14
• CPC Class Codes: H04B 7/0857 using maximum ratio combining techniques, e.g. signal-to- interference ratio [SIR], received signal strenght indication [RSS]
• CPC Class Codes: H04B 7/086 using weights depending on external parameters, e.g. direction of arrival [DOA], predetermined weights or beamforming
• CPC Class Codes: H04L 25/03993 Noise whitening

Abstract

Method and apparatus for complex phase equalization in a communication system. The method includes receiving and downconverting a two-dimensional communication signal to generate in-phase (I) and quadrature (Q) components that have been phase-rotated by an unknown amount during propagation from a transmitter, and then processing the I and Q signals in a cumulant recovery processing system to obtain phase correction of the I and Q signals prior to demodulation. The final step is demodulating the two-dimensional communication signal. Phase correction is effected without regard to modulation type and independently of the demodulating step.

Claims

1. A method of complex phase equalization for use in a communication system using two-dimensional signal constellations, the method comprising the steps of:

receiving and downconverting a two-dimensional communication signal, to generate in-phase (I) and quadrature (Q) components that have been phase-rotated by an unknown amount during propagation from a transmitter;

processing the I and Q signals in a cumulant recovery (CURE) processing system, to obtain phase correction of the I and Q signals prior to signal demodulation; and

demodulating the two-dimensional communication signal after the foregoing processing step, wherein phase correction is effected without regard to modulation type and independently of the step of demodulating.

2. Complex phase equalizer apparatus for use in a communication system using two-dimensional signal constellations, the apparatus comprising:

a receiver for receiving a two-dimensional communication signal and generating in-phase (l) and quadrature (Q) components, wherein the I and Q components are subject to phase rotation by an unknown angle;

a cumulant recovery (CURE) processing system connected to receive the I and Q components from the receiver wherein the I and Q signals received by the CURE processing system are each a linear combination of two independent source signals, which are the I and Q signals prior to phase rotation, and wherein the CURE processing system derives the two independent source signals and effectively compensates for the phase rotation of the I and Q signals; and

a demodulator connected to receive phase-corrected I and Q signals from the CURE processing system, wherein the CURE processing system effects phase correction of the communication signals prior to demodulation and independently of the demodulation type and the demodulation process.