A wideband end-fire stepped slot antenna with gain enhancement and filtering capability

A wideband end-fire stepped slot antenna with gain enhancement and filtering capability is proposed. On one hand, a parasitic dipole serving as a director is introduced in the stepped slot to improve the radiation gain of the slot antenna without increasing its physical size. It is found that a gain enhancement of about 2 dB can be achieved after adopting such approach. On the other hand, an absorptive branch possessing a nearly complementary frequency response with regard to the one of the slot antenna is in-parallel loaded at the microstrip feedline. It allows the partial dissipation of the out-of-band/non-radiated RF-signal power of the antenna to attain both an RF-quasi-absorptive behaviour and filtering capability. It is found that after loading the dissipative branch, the out-of-band radiation efficiency of the slot antenna is reduced to less than 20%. The measured results of a fabricated proof-of-concept antenna prototype show a reasonable agreement with the simulated ones and verify the RF performance merits of the proposed stepped slot antenna, such as wide RF operating band covering the 3.39−4.73-GHz range, end-fire radiation with a front-to-back ratio (FBR) above 10 dB, flat radiation gain, and co-integrated filtering functionality with RF-quasi-absorptive capability.