A Null Frequency Scanning Leaky-Wave Antenna

A new combline leaky-wave antenna (LWA) is proposed for null frequency scanning. The antenna contains a microstrip transmission line loaded with two groups of stubs on both sides. The two groups of stubs are placed periodically with two slightly different periods, providing two different
$n = -1$
space harmonics that contribute to two radiation beams. Then, a null pattern can be realized, in which the null appears between the two beams and scans with frequency. The working principle is investigated. The antenna is designed, fabricated, and measured. Measurement results show that the antenna has a wide null-scanning range from −38° to 40° with a null depth below −24.0 dB, in an operation band from 9.9 to 13.8 GHz.