A broadband beam-fixed planar-array antenna using slot pair and conductive bar at millimeter-wave frequencies

This paper presents a broadband millimeter-wave planar-array antenna that uses a slot pair and crossing conductive bar. The antenna is fed by a waveguide feed network in the E-plane to reduce the feed-line loss and a microstrip-feed network in the H-plane in order to decrease fabrication costs. The waveguide and microstrip are coupled through the slot pair, which is placed a quarter guided-wavelength distance apart, so that the reflected waves from the slots cancel each other. As a result, the antenna exhibits very broadband characteristics. The conductive bar is laid above the slots to increase the coupling. Results from simulation and measurement of the fabricated antenna show the reflection bandwidth to be more than 7.1% of the 40.5-43.5-GHz frequency range. The antenna also has fixed beams, low side-lobe levels (SLLs) at all frequencies of interest, and a high gain of 28.1 dBi at 41.5 GHz.