A circularly polarised antenna for a wireless blood-flow sensor

This paper presents a circularly polarised antenna for determining the speed of blood-flow, using Doppler effects at microwave frequencies. The structure consists of a double-feed patch antenna and a quadrature hybrid coupler in order to achieve circular polarisation and to isolate the reflected signal from the incident. The design was simulated and then fabricated. Both results were compared which showed a good agreement in terms of scattering parameters and radiation patterns.