Wideband Slot Array Antenna Fed by Open-Ended Rectangular Waveguide at W-Band

A wideband slot array antenna at W-band with a single-layer corporate feeding network is presented in this letter. The radiating slots are fed by open-ended rectangular waveguides to widen the impedance bandwidth instead of a commonly used coupling mechanism. A subarray of two elements placed in the H-plane is designed. In order to fit the feeding network into one layer, a compact hybrid feeding network is used, which is a combination of ridge waveguides and E-plane hollow waveguides. An 8-by-8-elements array antenna is simulated and fabricated with brass. Two metal layers are assembled by the bottom edge of the ridge waveguide to minimize the power leakage through the gap. The measured prototype achieves a relative impedance bandwidth of 35.7% with a reflection coefficient below -10 dB from 77.5 to 111.2 GHz. A peak gain of 26.8 dBi with variations within 2.5 dB is obtained. The measured radiation patterns agree with the simulations quite well, and the gain reduction remains below 1 dB in the operating range.