An optically driven phased array antenna utilizing heterodyne techniques

An optically driven phased array antenna system that utilizes heterodyne techniques to generate the microwave carrier frequency and phases is proposed. The heterodyning at each antenna element requires three injection-locked lasers. The microwave carrier frequency is determined by the order of the modulated sideband used in the injection-locking scheme. A design is also presented for an integrated optical fast Fourier transform (FFT). This device can perform the necessary phase processing for both beam steering and detection-of-arrival angle. Recent results on the noise properties of injection-locked semiconductor lasers are applied to the proposed antenna system. The effect of noise on the gain, signal-to-noise ratio, and the bandwidth of the antenna system is examined. It is shown that the performance degradation of the system, due to the noise in the lasers, is minimal, and therefore the bandwidth promise of optical drive could well be achieved with the use of heterodyne laser locking techniques.>