A transmission line based resistance compression network (TRCN) for microwave applications

Impedance matching to loads that vary with system operating point presents a significant challenge for efficient power transfer. One such load is the RF-to-dc rectifier, whose input resistance varies with rectified power. A resistance compression network (RCN) based on lumped elements was proposed to solve this problem and has demonstrated compressed impedance variation at 48 MHz [3]. At microwave frequencies, however, lumped elements become less viable and the RCN in [3] does not scale well. In this work we present a transmission line based RCN that operates at microwave frequencies. The RCN consists of two microstrip lines with unequal length. We present the theory, the design and an experimental prototype that shows the TRCN is able to compress a large load resistance variation ratio of 20:1 into a ratio of 3:1.