A PHEMT frequency doubling active antenna with BPSK modulation capability

The letter presents a novel frequency doubling active antenna, based on a PHEMT device, with BPSK modulation capability. A dedicated nonlinear transistor characterization reveals the existence of two biasing regions, where the second harmonic could be generated with maximum level and phase opposition. Taking advantage of this issue, a low frequency data signal applied to the gate terminal may be used to create a BPSK modulated signal, centered at twice the carrier frequency. An adequate integration of this modulator in a dual-frequency and dual-polarization slot coupled patch, results in a compact and high performance solution. In order to characterize the integrated active radiating structure, a specific test setup was implemented in an anechoic chamber, reproducing a sort of RFID architecture.