Butler matrix transponder

• US 3,917,998 A
• Filed: 11/02/1973
• Issued: 11/04/1975
• Est. Priority Date: 11/02/1973
• Status: Expired due to Term

• Current Assignee: George R. Welti
• Original Assignee: George R. Welti
• Inventors: Welti, George R.
• Primary Examiner(s): Libman, George H.
• Application Number:
  US05/412,399
• Time in Patent Office: 732 Days
• Field of Search: 325/3,4,65,476 330/126 328/165
• US Class Current: 455/13.1
• CPC Class Codes: H04B 7/18515 Transmission equipment in satellites or space-based relays

Abstract

A new design for a multiple channel repeater having advantages for satellite communications systems is described. The design comprises a pair of complementary N X N Butler matrix networks that precede and follow a set of N non-linear amplifying devices. A set of filters follows the output matrix network. The phase shifts produced by the input and output matrices cause a substantial fraction of the intermodulation products to flow to output ports that are tuned to frequencies different than the intermodulation product frequencies. These intermodulation products are therefore attenuated by the output port filters and do not appear as interference. With a portion of the intermodulation products removed from the output signals, the nonlinear amplifiers can operate closer to saturation for a given output carrier-to-intermodulation ratio than a conventional transponder thereby increasing overall DC-to-RF conversion efficiency.

Claims

1. A multichannel communications transponder, comprising;

a. first phasing network means for receiving M distinct channel signals and providing N output signals where M >

OR = N, each of said N output signals consisting of a sum of all M distinct phase shifted signals divided by square root N;

b. N nonlinear amplifier means connected to receive and amplify said N output signals from said first phasing network means; and

c. second phasing network means identical to said first phasing network means and connected in mirror image fashion to receive the amplified N output signals and providing M distinct channel output signals corresponding to the originally received M distinct channel signals. j

2. A multichannel communications transponder as recited in claim 1 further comprising:

a first set of M bandpass filters tuned to said M distinct channel signals and connected to the outputs of said second phasing network means wherein intermodulation product signals produced by said N nonlinear directed to filters tuned to frequencies different from the intermodulation product frequencies by said second phasing network means.

3. A multichannel communications transponder as recited in claim 2 further comprising;

a second set of M bandpass filters tuned to the same bands as said first set and connected to the input of said first phasing network means to separate incoming signals into M distinct channels.

4. A multichannel communications transponder as recited in claim 1 wherein said first and second phasing network means are first and second Butler matrices each having N input ports and N output ports.

5. A multichannel communications transponder as recited in claim 4 wherein m<

N and the unused input ports of said first Butler matrix and the unused output ports of said second Butler matrix are terminated in matching impedances.

6. A multichannel communications transponder as recited in claim 5 wherein M 12 and N 16.

7. A multichannel communications transponder as recited in claim 4 wherein M N 4.

8. A multichannel communications transponder as recited in claim 4 further comprising:

a set of M bandpass filters tuned to said M distinct channel signals and connected to M of the output ports of said second Butler matrix, said M output ports of said second Butler matrix corresponding to the M input ports of said first Butler matrix to which the received M distinct channel signals are coupled, wherein said intermodulation product signals are directed to output ports of said second Butler matrix to which are connected filters tuned to frequencies different from the intermodulation product frequencies by said second Butler matrix.

9. A multichannel communications transponder as recited in claim 6 further comprising input means receiving twelve signals occupying contiguous frequency bands and numbered consecutively from 1 to 12 and applying those input signals to the input ports, numbered consecutively from 1 to 16, of said first Butler matrix according to the following frequency band-port assignment plan;

10. A multichannel communications transponder as recited in claim 7 further comprising input means receiving twelve signals occupying contiguous frequency bands and numbered consecutively from 1 to 4 and applying those input signals to the input ports, numbered consecutively from 1 to 4, of said first Butler matrix according to the following frequency band-port assignment plan;