Transponder for use in a radio frequency communication system

• US 3,922,674 A
• Filed: 01/24/1974
• Issued: 11/25/1975
• Est. Priority Date: 01/24/1974
• Status: Expired due to Term

• Current Assignee: Gerard J. Gingras Jr, James T. Hanson
• Original Assignee: Gerard J. Gingras Jr, James T. Hanson
• Inventors: Hanson, James T., Gingras, Gerard J. Jr.
• Primary Examiner(s): Tubbesing, T. H.
• Application Number:
  US05/436,255
• Time in Patent Office: 670 Days
• Field of Search: 343/6.8R,6.5R 325/9,11,65
• US Class Current: 342/51
• CPC Class Codes: G01S 13/767 Responders; Transponders teaching or practice apparatus for gun-aiming or gun-laying using reflecting targets or active targets F41G3/26

Abstract

A transponder for use in a radio frequency communication system is disclosed wherein a received radio frequency signal is converted into an intermediate frequency signal, passed through a nonlinear network, converted into a corresponding radio frequency signal and then amplified by a radio frequency amplifier. The nonlinear network provides amplitude sensitive gain and phase adjustment to the intermediate frequency signal to compensate for the gain and phase nonlinearities in the radio frequency amplifier, thereby enabling such amplifier to operate with maximum amplification and efficiency.

Claims

1. In a radio frequency transponder wherein a received radio frequency signal is linearly amplified and then retransmitted as a radio frequency signal, such transponder including first heterodyning means for converting the received radio frequency signal to a corresponding intermediate frequency signal;

nonlinear means responsive to the amplitude of the intermediate frequency signal, for distorting such intermediate frequency signal in accordance with the amplitude of the intermediate frequency signal;

second heterodyning means for converting such distorted intermediate frequency signal to a distorted radio frequency signal; and

a nonlinear radio frequency amplifier, fed by the second heterodyning means, adapted to operate in its nonlinear region near saturation to amplify such distorted radio frequency signal into the linearly amplified and retransmitted radio frequency signal, the characteristics of the distorting means being related to the nonlinear characteristics of the nonlinear radio frequency amplifier, the improvement wherein such nonlinear means comprises;

a. an amplitude level sensitive phase shifter; and

, b. an amplitude level sensitive amplifier serially coupled to such amplitude level sensitive amplifier.

2. The improvement recited in claim 1 wherein the nonlinear radio frequency amplifier has a nonlinear gain and phase shifting characteristic and wherein the nonlinear means has a gain and phase shifting characteristic inverse to the nonlinear gain and phase characteristic of the nonlinear radio frequency amplifier.

3. The improvement recited in claim 2 wherin the amplitude sensitive phase shifter includes means for coupling the input thereof to the output thereof through at least two paths, the electrical length of such paths differing by an odd integral multiple of 90*.

4. The improvement recited in claim 3 wherein one of such paths has disposed therein an amplifier having a nonlinear gain characteristic.

5. The improvement recited in claim 4 wherein the amplifier is characterized as having a linear region and a saturation region.

6. The improvement recited in claim 2 wherein the amplitude sensitive amplifier includes means for coupling the input thereof to the output thereof through at least two paths, the electrical lengths of such paths differing by an integral multiple of 180*.

7. The improvement recited in claim 6 wherein one of such paths has disposed therein an amplifier having a nonlinear gain characteristic.

8. The improvement recited in claim 7 wherein the amplifier is characterized as having a linear region and a saturation region.