Wideband/Dual-Band Dielectric Filtering Inverted-L Antenna With Reflective and Quasi-Reflectionless Radiation Nulls

A class of dielectric filtering inverted-L antenna with reflective- and quasi-reflectionless-type radiation nulls is proposed to achieve wideband or dual-band operation. To this aim, a dual-function dissipative branch is exploited, which is in-parallel loaded at the feedline of the microstrip-fed dielectric inverted-L antenna. This absorptive branch, which is terminated in a grounded resistor, exhibits a quasi-complementary frequency response with regard to the one of the antenna. In this manner, it can mostly absorb the out-of-band RF-signal power not radiated by the antenna, hence creating quasi-reflectionless-type radiation nulls. Furthermore, the loaded branch can also generate a notch band giving rise to a reflective-type radiation null, which comes determined by the length of the branch and it is independent of the quasi-reflectionless radiation nulls. Thus, by controlling the spectral location of the notch band out of or within the operational frequency band of the dielectric inverted-L antenna, wideband or dual-band operational capabilities can be functionalized into it. For experimental-validation purposes, proof-of-concept prototypes for the two devised wideband and dual-band antenna approaches are designed, manufactured, and characterized. The measured results are in reasonably-close agreement with the simulated ones. The measured fractional impedance bandwidths of the two antenna prototypes are 28.3% (wideband one), 3.1% and 4.2% (dual-band one), respectively.