A Broadband Fixed-Beam Leaky-Wave Antenna

In point-to-point communication, antennas are often required to radiate a broadband signal in a specific direction. Traditional leaky-wave antennas (LWAs) have the features of low cost and high gain but also the frequency-beam-scanning property, which is not suitable for this demand. In this communication, an LWA with broadband fixed-beam property is designed in millimeter-wave band. The antenna is implemented on a ridge gap waveguide (RGW), and a series of microstrip branches are employed as phase delay lines. The working principle of the antenna is elaborated, and the main beam can be designed in any direction (including broadside and inclined angles) by selecting proper lengths for the microstrip branches. Sidelobe levels (SLLs) can be reduced by using slots with gradually changed lengths to excite the microstrip branches. Three antennas with main beam directions in 0 degrees and +/- 25 degrees are designed and measured as verifications. In the experiment, the antennas show stable radiation properties (including beam angles and realized gains) over the band from 25 to 39 GHz (a bandwidth of 43%). This LWA shows potentials in millimeter-wave broadband applications.