How Much Power Must We Extract From a Receiver Antenna to Effect Communications?

Subject to the laws of classical physics -the science that governs the design of todays wireless communication systems -there is no need to match the radiation impedance of a receiver antenna to the impedance of the front-end electronics in order to effect communications. If we dispense with a transmission line and, instead, make the front-end electronics colocated with the antenna, then a high input-impedance preamplifier can measure the open-circuit voltage directly on the antenna port while drawing negligible power. Neither Friis’ concept of noise figure, nor Shannon information theory, nor electronics technology dictates that we must extract power from an antenna. Classical physics appears not to provide a lower bound on the energy that must be extracted from the antenna for every bit of received information.