A compact reconfigurable monopulse antenna with close spacing

A compact reconfigurable monopulse antenna is presented. The proposed antenna consists of two closely spaced patches, a sum-difference comparator with four PIN diodes, and an embedded inductor between the two patches. The sum-difference comparator consists of a 1-to-2 divider, two feeding lines with four PIN diodes, and the DC bias line. By controlling the states of the PIN diodes, the sum and difference beams are achieved. The embedded inductor is applied to mitigate the difference in resonant frequency at the sum and difference beams. The working mechanism of the inductor is analyzed in detail. A prototype shows that the measured overlapped −10 dB impedance covers the 3.41–3.58 GHz at the sum and difference beams. The measured gain and null depth in the broadside directions are 6.8 and −30.5 dB, respectively. The proposed monopole antenna with close space is a promising candidate for some compact systems, like unmanned aerial vehicles and mobile terminals.