Analysis of RF‐DC Rectifier Input Impedance for the Appropriate Design of Matching Network for Wireless RF Energy Harvesters

The environmental radio frequency (RF) energy is used as an alternate solution of power for the easily accessible and non-accessible (hazardous) wireless sensor nodes. To convert available RF energy into direct current, rectifiers are needed. The matching network is required to match antenna impedance and rectifier input impedance. The design of matching circuit depends on the input impedance of rectifier. Rectifier circuit is non-linear in nature as diodes and MOSFETs are used for rectification. Therefore, input impedance is a function of various parameters like frequency, input power and output load. Consequently, matching network circuit design will change and maximum energy cannot be harvested from the incoming power as received power is very low. So in this chapter, a study of input impedance of RF-DC rectifier with non-linear Schottky diode model has been carried out on CADENCE virtuoso software at three different frequencies, viz . 930 MHz, 2.45 GHz and 3.5 GHz. This work demonstrates a change in input impedance of RF-DC rectifier from 5.991-j345.25 Ω to 5.987-j71.48 Ω as frequency increases from 930 MHz to 3.5 GHz. With output load resistance, input impedance shows very large variations at lower frequency range and small variations at high frequency range.