A Two-Port RF Device Integrating Dual-Polarized Filtenna and Bandpass Filter Functions With Independent Reconfigurability

In this communication, a two-port RF device integrating polarization-reconfigurable dual-polarized filtenna (PRDPF) and frequency-reconfigurable bandpass filter (FRBF) functions is proposed. For the PRDPF function, a quarter-dielectric-wavelength open stub is introduced into the feedline of each port, enhancing the roll-off rate at the upper-band edge of the realized gain. A 3-D-printed polarizer is implemented over the proposed RF device to achieve polarization reconfigurability. For the FRBF realization, two resonators are connected to the feedlines, providing a filtering transmission path at the lower frequency spectrum without occupying extra area. By inserting the varactors into the filtering transmission path, the operating frequency of the filter can be tuned continuously with a constant bandwidth. Experimental results show that the device functions as a PRDPF at 3.7 GHz, and simultaneously as a FRBF at around 2.1 GHz. As for the PRDPF function, the measured average gains of 9.8 dBi and 9.5 dBic are obtained for the linearly and circularly polarized (LP and CP) states, respectively, with the out-of-band suppression levels of more than 22 dB. The measured overlapped bandwidth of impedance matching (
$\vert S_{11}\vert $
,
$\vert S_{22}\vert < -10$
dB) and axial ratio (AR) < 3 dB is 17%. With respect to the FRBF operation, three tunable operating bands with a constant bandwidth of 20% are illustrated. With the innovative reuse of the feeding network, the proposed structure provides a design method for the future communication systems with high integration level.