Coherent switching system for a multiple beam antenna

• US 4,882,589 A
• Filed: 12/29/1986
• Issued: 11/21/1989
• Est. Priority Date: 12/29/1986
• Status: Expired due to Term

• Current Assignee: Hughes Electronics Corporation (AT&T, Inc.)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Reisenfeld, Sam
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): SWANN, TOD R
• Application Number:
  US06/947,459
• Time in Patent Office: 1,058 Days
• Field of Search: 342/374, 342/375, 455/8, 455/10, 455/277, 455/134, 455/135
• US Class Current: 342/374
• CPC Class Codes: H01Q 3/24 varying the orientation by switching energy from one active radiating element to another, e.g. for beam switching

Abstract

A coherent multiple beam antenna switching system is disclosed. The invention is adapted for use with an antenna having a switch for directing a signal through a first feed via a first channel into a output port and for directing a signal received by a second feed into said first channel at a time T. The invention includes a power detection circuit for measuring the power in the signal in the first channel via the first feed and a controller responsive to the measured power for activating the switch prior to time T to direct the signal via the second feed and a second channel to the output port. The controller includes the capability of predicting the switching of feeds and switches in the second channel in anticipation thereof. Phase detection and correction circuits are provided for aligning the signal in the second channel with the signal in the first channel. When the signals are aligned, the channels are switched at baseband to provide for coherent switching with minimal switching transients.

Claims

1. A coherent switching system for a multiple beam antenna comprising:

first channel means connected to a first feed of said antenna, said first channel means having a first demodulator for providing a first baseband signal;

second channel means connected to a second feed of said antenna, said second channel means having a second demodulator for providing a second baseband signal;

power detection means for measuring the power of said first baseband signal;

coherent switching means responsive to said power detection means for switching from said first demodulator to said second demodulator in order to provide switching at baseband from said first baseband signal provided by said first channel to said second baseband signal provided by said second channel; and

linear predictive filter means for activating said switching means, said filter means communicatingly connected to said power detector for determining a time at which the switching will occur based on input from said power detector.

2. A coherent switching system for a multiple beam antenna comprising:

first channel means connected to a first feed of said antenna, said first channel means having a first demodulator for providing a first baseband signal and a carrier phase recovery loop for acquiring the phase of said first baseband signal;

second channel means connected to a second feed of said antenna, said second channel means having a second demodulator for providing a second baseband signal and a carrier phase recovery loop for acquiring the phase of said second baseband signal;

power detection means for measuring the power of said first baseband signal; and

coherent switching means responsive to said power detection means for switching from said first demodulator to said second demodulator in order to provide switching at baseband from said first baseband signal provided by said first channel to said second baseband signal provided by said second channel.

3. The coherent switching system of claim 2 wherein at least one of said carrier recovery loop means includes injection means for decreasing phase acquisition time of said second channel.

4. A coherent switching system for a multiple beam antenna comprising:

first channel means connected to a first feed of said antenna, said first channel means having a first demodulator for providing a first baseband signal;

second channel means connected to a second feed of said antenna, said second channel means having a second demodulator for providing a second baseband signal;

power detection means for measuring the power of said first baseband signal; and

coherent switching means responsive to said power detection means for switching from said first demodulator to said second demodulator in order to provide switching at baseband from said first baseband signal provided by said first channel to said second baseband signal provided by said second channel and including alignment means for aligning in phase said first baseband signal with said second baseband signal prior to the switching thereof.

5. The coherent switching system of claim 4 wherein said alignment means includes phase detection means for detecting phase ambiguity of said second baseband signal relative to said first baseband signal.

6. The coherent switching system of claim 5 further including an output means having phase correction means responsive to said phase detection means for correcting the phase ambiguity of said second signal relative to the phase of said first signal.