Frequency multiplication and QPSK modulation with subharmonic injection-locked active antenna

A subharmonic injection-locked oscillating antenna, operating simultaneously as a frequency doubler and as a QPSK modulator, is presented. A dual-gate MESFET is used with one of its gates integrated with a PIN diode switch controlled patch antenna and the other gate connected to a low-noise subharmonic stabilising signal. The experimental and simulation results demonstrate the possibility of the simultaneous realization of frequency multiplication by subharmonic injection locking and phase modulation through DC bias and PIN diode switch.