Apparatus for locating passive intermodulation interference sources

• US 4,648,124 A
• Filed: 04/04/1985
• Issued: 03/03/1987
• Est. Priority Date: 04/04/1985
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: United States Of America As Represented By The Secretary Of The Air Force
• Inventors: Denny, Hugh W., Warren, Walter B., Mantovani, John C.
• Primary Examiner(s): NG, JIN FAY
• Application Number:
  US06/719,792
• Time in Patent Office: 698 Days
• Field of Search: 455/19, 455/20, 455/63, 455/67, 455/295, 455/296, 367/13, 343/17.7, 324/57 N
• US Class Current: 455/67.13
• CPC Class Codes: H04B 17/20 of receivers

Abstract

An apparatus for locating passive interference sources by using a pair of different RF signals in conjunction with an acoustic signal to generate intermodulation products in metal-to-metal junctions. The acoustic tagging technique utilizes a focused, high power beam of acoustic energy to mechanically vibrate the suspected offending junction. This mechanical vibration causes the level of intermodulation products that are generated in the junction to become amplitude modulated at the frequency of the acoustic illumination. The detection of the AM sidebands with a low noise RF receiver that is tuned to a particular intermodulated component, permits the offending junction to be located.

Claims

1. An intermodulation interference locator apparatus comprising in combination:

a first RF signal means operating at a first RF frequency,

a second RF signal means operating at a second RF frequency,

a means for vibrating;

a first and second member joined together to form a metal junction, said junction being exposed to said first and second RF frequencies, said vibrating means operatively connected to said junction to produce mechanical vibrations in said junction said junction responding to said first and second RF frequencies and said mechanical vibrations by generating an intermodulation inteference signal, and,

an RF receiver means tuned to the intermodulation frequency of said first and second RF frequency, said RF receiver means receiving and detecting said intermodulation inteference signal generated by said junction, said RF receiver means providing an output signal in response to said intermodulation interference signal.

2. An intermodulation interference locator apparatus as described in claim 1 wherein said vibrating means comprises a means for generating an acoustic signal, said acoustic signal generating means to generate an acoustic wave, said acoustic wave being applied to said junction to mechanically vibrate said junction at a constant frequency, said junction responding to said acoustic wave by generating an amplitude modulated intermodulation signal which has the frequency of said mechanical vibration, said RF receiver means detecting said amplitude modulated intermodulation signal and providing an audio signal which is representative thereof.

3. An intermodulation interference locator apparatus as described in claim 2 wherein said RF receiver means includes a bandpass filter and an envelope detector means to detect said amplitude modulated intermodulation signal.

4. An intermodulation interference locator apparatus as described in claim 2 wherein said junction is one of a plurality of junctions, all of which are exposed to said first and second RF frequencies in order to identify a particular junction as the source of intermodulation interference, each junction of said plurality of junctions is separately illuminated by said acoustic wave to identify the junction that is the source of the intermodulation interference.

5. An intermodulation interference locator apparatus as described in claim 4 wherein, said plurality of junctions are formed with a metallic material to form metal-to-metal junctions.

6. An intermodulation interference locator apparatus as described in claim 1 wherein each member of said first and second member comprises a metallic material to form a metal-to-metal junction.