Dual‐layer SIW cavity filtering antenna with a controllable radiation band and two radiation nulls

A dual‐layer substrate‐integrated‐waveguide (SIW) cavity filtering antenna with a controllable radiation band and two radiation nulls is proposed. It consists of a coaxial feeding, two SIW cavities, three metal planes and three slots. An H‐shaped slot is etched on the top plane and two rectangle slots are cut on the middle plane. A radiating mode (i.e. TE 210 mode) is excited to achieve a radiation band while two non‐radiating modes (i.e. TE 010 mode and TE 110 mode) are utilised to generate two radiation nulls. Good filtering performance including sharp sideband selectivity and high stopband suppression is achieved by these radiation nulls. Moreover, the radiation band can be independently controlled without affecting the radiation nulls. A fabricated prototype with the size of 0.58 λ 0 × 0.58 λ 0 × 0.07 λ 0 is measured. The measured centre frequency of the radiation band is at 3.49 GHz with the gain of 5.39 dBi and efficiency of 79.25%. However, the gain and efficiency of a radiation null at 3.29 GHz are −27.56 dBi and 0.07% while those of the other radiation null at 3.86 GHz are −27.29 dBi and 0.04%.