Characterisation of an aperture-stacked patch antenna for ultra-wideband wearable radio systems

This work presents, for the first time, the time-domain characteristics of an aperture-stacked patch antenna (ASPA) for ultra-wideband (UWB) wearable devices. The methodology of antennas characterisation for UWB radio systems is also outlined. The antenna operates within the 3-6 GHz frequency band. Time-and frequency-domain characteristics of this antenna are presented in transmission mode (Tx), receiving mode (Rx) and for 2-antenna (Tx-Rx) system. The pulse driving the antenna has duration of 0.65 ns. In the Tx mode, pulses radiated in different directions of the H-plane have very similar shapes. Fidelity factors are as high as 91.6-99.9%. For 2-antenna system, pulses received in normal and end-fire-like directions have the fidelity of 69.5%. As it was found, antenna does not behave ´reciprocal´ comparing Tx and Rx modes. For normal propagation direction, radiated pulse is the 2^nd derivative of the input waveform, but in the RX mode, received pulse is the 1^st derivative of the incident plane wave. This antenna can be used for transmission of short-pulses, even 0.65-1 ns in duration. It is also small (planar dimensions 32/19mm) and compact. Microstrip configuration allows further integration of active devices on the same board. Taking into account above results we can say that ASPA is a good candidate for UWB noninvasive wireless body area network (WBAN) applications.