OPTICAL SYNCHRONIZATION OF MILLIMETER-WAVE OSCILLATORS FOR DISTRIBUTED ARCHITECTURES

Future generations of communication and surveillance platforms will be based on large-aperture phased array antennas composed of many active-MMIC-based transmit/receive modules. This paper concerns the phase and frequency coherency of these modules. A review of various methods of phase and frequency synchronization of active modules is presented, and particular emphasis is placed on the synchronization of oscillators through the use of an indirect subharmonic optical injection locking technique. In this approach, the nonlinear behavior of both large-signal modulated laser diodes and solid-state oscillators is exploited to extend the bandwidth of the synchronizing link to the millimeter-wave frequency range. Experimental results of the phase and frequency coherency of two 21.5 GHz FET oscillators are also reported here. Optimum performance has been achieved at a subharmonic factor of 1/4, with a locking range of 84 MHz and a phase noise degradation of only 14 dB. The phase coherency measurement of two injection-locked oscillators points to a phase shift, which is introduced as a result of the frequency detuning between the slave and master oscillator signals. A scheme to correct for this phase error is also presented. © 1990 IEEE