On the design of rectenna

Abstract

This paper focuses on designing a circuit that rectifies background radiation and one that is self-biasing. This circuit set-up is called a rectenna which is a special type of antenna that is used to convert radio-frequency energy into direct current electricity. A simple model of a rectenna element consists of a monopole antenna with an radio frequency(RF) diode bridge connected in series with the antenna. The bridge rectifies the ac current induced in the antenna by the electromagnetic radiation to produce dc power which is used to bias a Bipolar Junction transistor(BJT). RF sensitive/high switching diodes are usually used because they have the lowest voltage drop and highest speed and therefore have the lowest power losses due to conduction and switching. The BJT transistor has a feedback biasing and essentially amplifies the ac signal from the antenna. The amplified signal is fed into an RF diode for dc conversion. There are two stages of amplification in order to achieve a big voltage magnitude at the output that can be used to charge a device with low power ratings. Thus the idea of a cell-less power source is achieved in such implementation.