Tunable harmonic re-radiator for sensing applications

A tunable harmonic re-radiator using meandered shorted patch antennas is designed for wireless sensing applications. The device operates by receiving an interrogation signal and re-transmitting the (modulated) second harmonic. Tunability is achieved by integrating a varactor diode into the input matching network, providing the means for modulating the retransmitted harmonic. Special emphasis has been placed on developing electrically small antennas to significantly reduce the overall footprint without compromising efficiency. The re-radiator measures 22 mm times 8.8 mm and has a measured conversion efficiency of 1.3% at a doubler input power of only 18 muW.