Energy Recovery From Microstrip Passive Circuits

In this paper, the energy recovery in microstrip passive circuits from the power losses into heat is studied. For this purpose, a thermoelectric generator (TEG) based on the Seebeck effect principle is used, which converts part of the power dissipated into heat to dc electrical power. A solution integrating the TEG with the microstrip circuit is proposed, and design guidelines in order to optimize the recovered power keeping a good isolation between the RF signal and the TEG system are provided. As will be shown, under moderate applied signal powers of just 1-5 W, the levels of recovered power in microstrip passive circuits can be notable. As a demonstrator circuit, an integration device formed by an embedded microstrip bandpass filter for WiMAX applications and a TEG is designed, fabricated, and characterized (thermal and electrically). Different scenarios are considered, depending on frequency and thermal loads. For an applied inband CW input signal power of 2 W at 3.48 GHz, a recovered power of around 250 μW has been continuously supplied to the electrical load. Several aspects, such as efficiency and future improvements, are also discussed.