Automatically switchable two-way rectifier

This work proposes a novel design of a modular rectifier for seamless operation in a wide range of RF received power (PRX). The solution adopts a set of rectifiers, each one optimized for a specific power range, connected in such a way that, for any incoming RF power, the most suitable one is activated, with no need for external biases to activate switches or complex control logic. Thus, the operation is fully energy-autonomous. In this work the idea is demonstrated with two rectifiers: a low-power one (RECTLOW), for the range -15 to 0 dBm and a high power one (RECTHIGH), for the range 0 to 15 dBm. Two P-HEMT-based switching circuits are located along the rectifiers RF and dc paths, respectively, and are normally OFF over the power range of -15 to 0 dBm. In such conditions the isolation between RECTLOW and RECTHIGH is about 10 dB, which allows RECTLOW to operate in its high efficiency conditions. When PRX exceeds 0 dBm, a small amount of power is leaked into RECTHIGH so that a reduced dc-voltage is available at its dc output. This voltage, by means of a limiter, controls the P-HEMPT gates, thus creating a feedback system: if PRX further increases, the P-HEMPTs are turned ON and RECTHIGH starts operating, while the path to RECTLOW is inhibited. The whole system has been tested over the entire power range and shows an RF-to-dc efficiency equivalent to the one obtained by the standalone rectifiers.