Method for processing radio signals that are subject to unwanted change during propagation

• US 6,208,295 B1
• Filed: 01/18/2000
• Issued: 03/27/2001
• Est. Priority Date: 06/02/1995
• Status: Expired due to Term

• Current Assignee: Northrop Grumman Systems Corporation (Northrop Grumman Corporation)
• Original Assignee: TRW Inc. (Northrop Grumman Corporation)
• Inventors: Stearns, Stephen Deane, Do{haeck over (g)}an, Mithat Can
• Primary Examiner(s): Blum, Theodore M.
• Application Number:
  US09/484,564
• Time in Patent Office: 434 Days
• Field of Search: 342/378, 342/373, 342/417, 342/451, 342/361, 342/362
• US Class Current: 342/378
• 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

A method for processing received radio signals that are subject to unwanted change during propagation through the atmosphere, from a transmitter to a receiver array. The multiple signals are received as cochannel signals at the antenna array, and are processed to eliminate the effects of modification of the signals during propagation, wherein the processing step includes cumulant-based signal recovery without regard for the geometrical properties of the antenna array. In the invention as disclosed, two different information signals having two different polarization states are transmitted, and at least one of the transmitted signals is subjected to an unwanted change of its polarization state. The received signals are processed to separate and recover the two information signals without regard to their polarization states.

Claims

1. A method for processing received radio signals that are subject to unwanted change during propagation, the method comprising the steps of:

transmitting radio signals through the atmosphere;

subjecting the radio signals to modification as a result of conditions prevailing during propagation from a transmitter to an antenna array at a receiver;

receiving multiple cochannel radio signals at the antenna array; and

processing the received signals to eliminate the effects of modification of the signals during propagation, wherein the processing step includes cumulant-based signal recovery without regard for the geometrical properties of the antenna array.

2. A method as defined in claim 1, wherein:

the step of transmitting includes transmitting two different information signals having two different polarization states;

the step of subjecting the radio signals to modification includes subjecting at least one of the transmitted signals to a change of its polarization state;

the step of processing the received signals includes separating and recovering the two information signals without regard to their polarization states.