Use of compact LC resonant tank, resistor and frequency selective surface to construct a loaded planar dipole antenna for UWB radar and communication applications

In this letter, we incorporate a compact LC tank, chip resistors and a double-layer frequency selective surface (FSS) to construct a planar dipole antenna for UWB radar and communication systems. Two staircase rectangular antenna arms are isolated with open complementary double concentric split-hexagonal-ring resonators (LC tanks) and chip resistors for bandwidth enhancement. The overall electric size of the antenna is 0.33 λ × 0.16 λ at the lowest frequency end of the operational band. For impedance matching as well as balanced-unbalanced transition, a broadband microstrip to parallel-strip transformer (or balun) was designed as the feeding structure to the antenna. Finally, a double layer FSS is added in from the dipole to yield the in-phase reflection and consequently produce gain enhancement. The measurements show the proposed antenna operates over the frequency bandwidth of 0.65-3.8 GHz with S1 <; -10 dB and exhibits highly directive radiation patterns with smooth gains in the range of 6.2-9 dBi.