I. Introduction
Health monitoring is a key issue for any satellite application and especially for the implementation of reliable and long-life satellite-based broadcasting links. In order to provide reliable and high bit-rate broadcasting links, high-gain microwave antennas operating in -, -, -, -, or -band are used. These antennas are located on panels positioned on the external surface of the satellite. Surveying the health of these panels involves the use of sensors (e.g., for thermal or for mechanical/structural monitoring) deployed in small networks to cover the targeted surface. A very promising solution is to implement small autonomous wireless sensor networks saving the cost of deploying long wires in harsh environments. In some areas located on antenna panels of broadcasting satellites, the electric field generated by the spill-over loss of microwave antennas can reach the following maximum levels (effective values): 40 V/m in -band, 49.5 V/m in -band, 106 V/m in -band, and 127 V/m in -band. These high-frequency electromagnetic field levels are unusual for terrestrial applications, but they are available on satellites if data links are functional and can be harvested in order to power autonomous wireless sensors used for monitoring the structural health of the satellite. Moreover, the electromagnetic power radiated by microwave antennas is almost constant and consequently the dc power regulatory circuits should be minimal for harvesting systems.