Title: Method of and apparatus for ground testing doppler navigation sets-a doppler radar simulator

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1. A method for testing a doppler velocity/altimeter radar with an antenna situated in an aircraft comprising the steps of:

attaching to the aircraft an anechoic chamber to absorb microwave energy, said chamber having closed sides and bottom and an open top with a plurality of parallel arranged flourescent tubes set within the chamber facing the open top so that the open top of the chamber faces the antenna;

pulsing said flourescent tubes in paralel with a direct current so that groups of ions travel in one direction through said plurality of tubes at a speed determined by the frequency of said pulsing;

transmitting microwave energy from the antenna, which energy is absorbed by the traveling groups of ions, raising said ions to a higher energy level; and

re-radiating the energy absorbed by the ions to the antenna as the ions return to their normal energy state after a delay determined by the amplitude of said direct current.

2. A doppler/range simulator for testing an aircraft doppler velocity/altimeter radar having an antenna comprising:

means for absorbing microwave energy;

a source of ionizable gas mounted within said absorbing means;

means for exciting said source of gas to create a traveling ionized field to simulate a moving target whereby energy transmitted by said antenna is absorbed by said gas and re-radiated to said antenna to provide an indication of the velocity and distance from the simulated target.

3. A doppler/range simulator as recited in claim 2 wherein said absorbing means comprises an anechoic chamber.

4. A doppler/range simulator as recited in claim 3 wherein said source of ionizable gas comprises a plurality of flourescent tubes arranged in a planar parallel array mounted within said anechoic chamber.

5. A doppler/range simulator as recited in claim 4 wherein said exciting means comprises a pulsating D.C. power supply to provide precise voltage levels and frequency levels, wherein the voltage determines the time delay between absorption and re-radiation by said ionized field to simulate target distance, and wherein the frequency of the pulses determines the speed of said field to simulate target motion.

6. A doppler/range simulator as recited in claim 5 wherein said power supply is connected to said tubes so that one end of said tubes is always positive relative to the opposite end of said tubes, and said power supply excites any pair of said tubes in phase one with the other.

7. A doppler/range simulator as recited in claim 6 wherein said simulator further comprises means for placing said simulator in proximity to said antenna so that said antenna can transmit microwave energy to, and receive microwave energy from, said flourescent tubes situated within said anechoic chamber.

8. A doppler/range simulator as recited in claim 7 wherein said anechoic chamber comprises:

an enclosure open at the top; and

a lining of microwave energy absorbent material along all sides and bottom of said enclosure.

9. A doppler/range simulator as recited in claim 8 wherein said plurality of flourescent tubes are relatively long with respect to said antenna.

10. A doppler/range simulator as recited in claim 9 wherein said placing means comprises:

a radome having a bump, said radome being mounted on said aircraft and enclosing said antenna;

a plurality of fixed hooks positioned on the sides of and around said bump; and

a plurality of swivelling hooks fitted to the exterior of said anechoic chamber suitably positioned to engage said fixed hooks on said radome whereby said simulator is securely held in proximity to said antenna so that the opening of said enclosure faces said antenna.

11. A doppler/range simulator as recited in claim 10 wherein said enclosure comprises sheet aluminum, and said lining comprises graphite-loaded sponge material.

Other info:

Inventors: Hutzelman, Robert W. (Sylmar, CA, US)
Fairbanks, Everitt E. (Arleta, CA, US)

Application Number: 499249
Filing Date: 1974-08-21
Publication_date: 1976-05-04
Assignee: The United States of America as represented by the Secretary of the Navy (Washington, DC)
Primary Class(es): 342/171 342/172
Other Classes:
US Patent Ref:

2159937	May, 1939	Zworykin	343/100.
2886811	May, 1959	Harriso, Jr.	343/100.
3024460	Mar, 1962	Dahl et al.	343/17.
3090955	May, 1963	Hubka et al.	343/17.
3225295	Dec, 1965	Altman et al.	343/17.
3622680	Nov, 1971	Palmieri	343/17.

Other Refs: 577,458

May, 1946	UK

Primary Examiner: Hubler, Malcolm F.
Assistant Examiner:
Attorney: Sciascia; R., Beers; R., Scheinbein; S.