Daniel A Held

US Patent:

44504470, May 22, 1984

Filed:

Jul 17, 1981

Appl. No.:

6/284287

Inventors:

Howard A. Zebker - Palo Alto CA
Daniel N. Held - Altadena CA
Richard M. Goldstein - La Canada CA
Thomas C. Bickler - La Canada CA

Assignee:

The United States of America as represented by the Administrator of the
National Aeronautics and Space Administration - Washington DC

International Classification:

G01S 740

US Classification:

343 177

Abstract:

A synthetic aperture radar (SAR) target simulator for simulating the radar return, or echo, from a target seen by a SAR antenna mounted on a platform moving with respect to the target includes a first-in first-out memory (26) which has digital information clocked in at a rate related to the frequency of a transmitted radar signal and digital information clocked out with a fixed delay defining range between the SAR and the simulated target, and at a rate related to the frequency of the return signal. An rf input signal having a frequency similar to that utilized by a synthetic aperture array radar is mixed with a local oscillator (16) signal to provide a first baseband signal having a frequency considerably lower than that of the rf input signal. The first baseband signal is converted to a plurality of digital words which are clocked into the memory (26) at a rate related to the frequency of the local oscillator (16). A synthesizer (34) is locked to the local oscillator (16) and provides an output signal having a nominal frequency equal to that of the local oscillator ( 16), but altered in accordance with range changes between the SAR and the simulated target, as well as in accordance with Doppler information associated with return signals from the target.