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A Liquid-Crystal Control, Coherent Type Optoelectronic Phased Array Antenna Beam Forming Network Using Polarization Multiplex Optical Heterodyning
IEICE TRANSACTIONS on Electronics
Publication Date: 1996/01/25
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Optomicrowave Techniques and Their Applications)
Category: Optically Controlled Beam Forming Networks
phased array antenna, beam forming network, electrically controllable birefringence mode nematic liquid-crystal cell, polarization multiplex, optical heterodyning,
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An optoelectronic beam forming network (BFN) is presented for a single beam, 3-element phased array antenna that utilizes electrically controllable birefringence mode nematic liquid-crystal cells (ECB mode NLC cells) for phase shifting and amplitude control. In the circuit, a microwave signal is carried by a pair of orthogonal linearly polarized lightwaves (signal and reference lightwaves) using the optical heterodyning technique. Birefringence of liquid-crystals is utilized to selectively control the phase of the signal and reference lightwaves. Because an interferometer is formed on a single signal path, the complexity of the optical circuit is much reduced, compared to the BFNs based on arrays of Mach-Zender interferometers. A prototype circuit is built using laser sources of 1.3 µm, and its performance experimentally examined. With small deviations among the three cells, phase shifts of up to 240 degrees are achived for MW signals from 0.9 GHz to 20 GHz with good stability; attenuation of more than 18dB is achieved. An optoelectronic technique for parallel control of amplitude and phase of MW signals was developed.