Study on energy recovery from substrate integrated waveguide circuits

In this work, the energy recovery in microwave passive circuits from the power losses into heat is studied. For this purpose, a thermo-electric 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 a substrate integrated waveguide (SIW) circuit is proposed, and design guidelines in order to optimize the recovered power are provided. As will be shown, under moderate applied signal powers of just 1-5 W, the levels of recovered power in SIW passive circuits can be notable. As a demonstrator circuit, an integration device formed by an X-band SIW bandpass filter 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 9.68 GHz, a recovered power of around 310 μW has been continuously supplied to the electrical load. Several aspects such as efficiency and future improvements are also discussed.