True Time Delay Beamforming
Final rept. Feb 1992-Feb 1994
ESSEX CORP COLUMBIA MD
Pagination or Media Count:
Wide aperture arrays for transmitting and receiving wideband signals suffer beam broadening when steered away from the array normal using phase delays between the array elements. This beam dispersion is eliminated if time delays instead of phase shifts are used between antenna array elements. This report represents the results of a project to demonstrate the proof-of-principle of an acousto-optic signal processing concept that generates and controls, with a single tone, the set of time delays required for linear antenna array beamforming. This acousto-optic concept allows an array to scan a beam rapidly over a continuum of angles. In the approach described in this report, the time delays between elements are generated by using an acousto-optic Bragg cell as a continuous delay line, and indirectly tapping selected points in the Bragg cell to the output. This optical tapping is controlled with a second Bragg cell and other standard passive optical elements. Included in this concept is a passive optical element to ensure that the phase shifts of the carrier of the time delayed signals will be correct at the RF of the array. The time-delay controller also provides the proper relative phases between the carriers of the time delayed signals at the RF of the antenna array. A proof-of-principle breadboard of the time delay controller was assembled. Its of the demonstration of the breadboard are described.
- Acoustooptic and Optoacoustic Devices