Mechanical Technique to Customize a Waveguide-Slot Radiating Performance

A mechanical technique to tune the radiating performance of a waveguide-fed slot is presented. Three metallic tuning screws are introduced through the bottom wall of the feeding waveguide. The field radiated by the slot is mechanically controlled with the insertion length of the tuning screws and a good input matching response is also maintained. One of the tuning screws modifies the slot coupling parameter as well as the phase of the transmitted signal, while the other pair of screws compensates the impedance mismatch introduced by the first one. A five-element traveling-wave (TW) linear array antenna has been designed and manufactured as a proof of concept to validate the performance of the tuning screws. Several improvements such as a main beam steering range of 17°, an enhancement of the antenna efficiency, the mitigation of the undesirable grating lobe appearance typical of TW air-waveguide-fed arrays, as well as the compensation of the mutual coupling effects or manufacturing tolerance errors could be experimentally achieved by using the proposed mechanism based on tuning screws.