A wideband capacitively fed suspended plate antenna for wearable wireless sensors

A suspended shorted patch capacitively fed using an inverted L-shape feed is a compact antenna for wearable wireless sensors. A short microstrip line was printed on the sensor PCB to connect the antenna to a transceiver chip. The shorting of the suspended patch was done using printed silver ink on the side wall of a 22mm × 6mm × 6mm block of polycarbonate plastic that suspends the mounted patch. Based on the required bandwidth, the height of the plastic block can be decreased to 2 mm. The simulated 10 dB bandwidth of the antenna, was 98% (2.2 GHz-6.44 GHz) for a 6 mm high polycarbonate block. The size of the sensor including the elevated antenna was 35mm × 22mm × 9mm. The antenna features an upward directional radiation pattern which decreases the electromagnetic coupling between the human body and the antenna. The simulated total radiation efficiency of antenna is more than 90% in free space which drops to 70% at 2.4 GHz and 80% at 5.8 GHz when the sensor is located next to a voxel model of the human body and simulated maximum gain of antenna was 2.3 dBi at 2.4 GHz, 3.5 dBi at 3.5 GHz and 4.6 dBi at 5.8 GHz respectively.