Walter Toshio Iwatake

US Patent:

60384271, Mar 14, 2000

Filed:

Jun 5, 1998

Appl. No.:

9/092343

Inventors:

Rui T. Hsu - Torrance CA
David D. Bettger - Redondo Beach CA
Walter T. Iwatake - Clifton VA

Assignee:

Hughes Electronics Corporation - Los Angeles CA

International Classification:

H04B 7185
H04B 1700

US Classification:

455 121

Abstract:

The method and apparatus for determining group delay of a satellite communications channel includes a low frequency vector network analyzer and microwave swept synthesizer which together generate modulated signals. A sample of the signals transmitted to a satellite and the signals retransmitted from the satellite are compared in the network analyzer to obtain the phase of the signals. The phase of a reference signal is measured prior to and after each test frequency of the communications channel. A quasi-real time phase reference can be obtained by interpolation. Thus, the reference phase due to movement of the satellite with respect to the earth station during group delay measurement may be removed.