Compact tunable dual-channel antenna based on ferroelectric ceramics

A low-profile tunable antenna integrated in ferroelectric ceramic substrate is presented. The antenna embodies two adjacent channels into a pair of closely located slots. For frequency division duplex applications, the centre frequency and the channel separation are conveniently controlled by the embedded ferroelectric varactors, which load across the slots. The slots are excited capacitively and matched by open-ended microstrip stubs. Resistive bias networks for the varactor are integrated on the substrate. The prototype is dimensioned as 25 × 6.75 × 0.65 mm, and is mounted at the edge of a small chassis of 30 × 55 mm. The centre frequency covers from 1.47 to 1.76 GHz. The channel separation can vary from 38 to 181 MHz, which is independent of the centre frequency tuning.