Evaluating the efficiency of antennas used as sensors in microwave tissue imaging

A new method is proposed to evaluate the efficiency of antennas used in tissue microwave imaging. In this method, two identical antennas are employed, one transmitting and the other one receiving, in a setup where the scattering parameters are measured. Each antenna is considered as a two-port network and the antenna efficiency is expressed in terms of its equivalent network parameters. A signal flow graph (SFG) is developed for the two-port network formed by the two antennas and the medium between them. A system of equations is derived from the SFG and it is solved for the acquired data. This solution provides the efficiency of the antenna. The accuracy of the efficiency estimated from measured and simulated data is verified through comparison with full-wave simulations.