Performance of a Radiation Pattern Steering On-body Gateway Antenna For On-body and Off-body Propagation

Antennas in Body Area Networks (BAN) should be designed according to the link they are expected to form. In most of the systems, an on-body gateway collects data frames from other on-body sensors and relays them to an off-body gateway, realizing two different modes of operation, on-body and off-body. For such a device, the on-body link and the off-body link have different radiation pattern requirements. Moreover the antenna should be designed taking the effects of human body being in the nearfield of the antenna on the performance into account. A planar antenna operating in the 2.4 GHz ISM band which can satisfy all requirements by radiation pattern steering with frequency is analysed here in terms of its on-body and off-body propagation performance. Analysis were performed through simulations featuring two layered numerical chest phantoms, one being cylindrical and one being flat. The effects of the antenna-body spacing are investigated through the flat phantom while the on-body and off-body propagation are investigated through the cylindrical phantom. The antenna is shown to be performing well upto 5 mm spacing. It has been proved that the antenna provides 9 dB advantage in average for the on-body link compared to the case where its off-body radiation mode is used to connect to the on-body sensor and vice versa.