Bandwidth enhancement of partially parallel-feeding travelling-wave array using waveguide narrow-wall cavity slot on iris in millimeter-wave band

The partially parallel-feeding traveling-wave waveguide slot array has an advantage to reduce the frequency dependence of radiation pattern and obtains broadband characteristics. However, conventional post-loaded radiating slots limit the bandwidth of the array. Therefore, the waveguide narrow-wall cavity slot on iris is proposed to extend the bandwidth of the radiating elements. 24-element two-line waveguide slot array antenna is designed in the millimeter-wave band. The bandwidth of reflection lower than -20dB for each single element was over 7GHz, then, the bandwidth of the entire array was extended to 4.3GHz in contrast to the conventional antenna with post-loaded slots 0.8GHz. The gain of the broadside direction was higher than 15dBi in 72.0-86.6GHz and the peak gain was 20.7dBi.