Wideband Millimeter-Wave Filtering Magnetoelectric Dipole Antenna With High Out-of-Band Suppression

Aiming at achieving wideband and filtering performance with high out-of-band suppression, this article presents a method of designing a millimeter-wave (mmWave) filtering magnetoelectric (ME) dipole antenna. Different from most previous works, antiphase electric and magnetic currents are generated simultaneously by parasitic symmetric split rings and suspended straight strips, respectively, canceling the radiation of the ME dipole in the stopband. Furthermore, the bifunctional
$\Pi $
-shaped feeding probe excites the ME dipole by capacitive coupling to realize a wide bandwidth and generates an out-of-band bandstop resonance mode to enhance the filtering performance. Therefore, multiple radiation nulls can be generated to achieve a high roll-off rate and wide stopband. The proposed antenna realizes a suppression level of over 33 dB in the stopband and an in-band efficiency of over 95%. The measured results show that the implemented
$1\times 4$
filtering array has a wide bandwidth of 21.6–31.5 GHz (37.3%). The measured average gain is about 12.9 dBi, and the out-of-band rejection level exceeds 26 dB in the stopband.