Communications: directive radio wave systems and devices (e.g. – Directive – Including a steerable array
Patent
1992-10-01
1993-12-28
Issing, Gregory C.
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a steerable array
342372, 359173, 359191, 359238, 385 7, H01Q 322, H04B 1012, G02F 107
Patent
active
052743810
ABSTRACT:
A liquid crystal and acousto-optic based control system for phased array antennas provides independent control of scanning along two axes of the antenna. The optical control system includes a laser source providing polarized laser beams processed in an in-line interferometric optical architecture that uses two acousto-optic deflectors (AODs) driven by separate sidebands of a microwave signal that is a mixture of a drive frequency corresponding to the desired carrier frequency and a variable control frequency for determining a selected sideband frequency. The AODs and associated polarization rotators generate a plurality of optical signal pairs, each pair having one first order positive doppler shifted light beam deflected by a first sideband drive signal and one first order negative doppler shifted light beam deflected by a second sideband drive signal, the positive and negative doppler shifted beams being respectively orthogonally linearly polarized and traveling along almost collinear paths. A further optical phase delay is introduced in a predetermined one of the light beams in each optical signal pair via electrical control of an array of liquid crystal pixels in a spatial light modulator (SLM). After passing through the SLM, orthogonally-polarized light beams in each pair are combined; this signal is then used via heterodyne detection by a respective photodiode to generate an electrical output signal.
REFERENCES:
patent: 5117239 (1992-05-01), Riza
patent: 5187487 (1993-02-01), Riza
patent: 5191339 (1993-03-01), Riza
Nabeel A. Riza, An Acoustooptic Phased Array Antenna Beamformer With Independent Phase and Carrier Control Using Single Sideband Signals, IEEE Photonics Technology Letters, vol. 4, No. 2, Feb. 1992.
T. Day et al., Active Frequency Stabilization of a 1.062 .mu.m, Nd:GGG, Diode-Laser-Pumped Nonplanar Ring Oscillator to Less Than 3 Hz of Relative Linewidth, Optics Letters, Feb. 15, 1990, vol. 15, No. 4.
Riza, "Acoust-optic Control of Phased Array Antennas", May 1990, GE Technical Information Series.
Checkovich Paul
General Electric Co.
Issing Gregory C.
Young Stephen A.
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