Comparison of Injection-Locked and Coupled Oscillator Arrays for Beamforming

Injection-locked oscillator arrays (ILOAs) and coupled oscillator arrays (COAs) are analyzed using Adler's equation, and their performance to drive phased arrays for beam-steering is compared. The Monte Carlo simulation results indicate that COAs render smaller beam-pointing error when the locking range of oscillators is narrow (high Q), while ILOAs render smaller beam-pointing error when the locking range is wide (low Q). An ILOA with a frequency tripler connected to the oscillators' output is designed to increase the achievable range of inter-element phase shift, and a chip is fabricated in the TSMC 0.18- μm CMOS technology to verify the design concept, with the measured maximum phase shift around 240°.