A Unidirectional, Printed Antenna With High Interport Isolation Over Wider Bandwidth for 2.4 GHz Full Duplex Applications

This work presents a dual-polarized, proximity-fed bistatic antenna system with comparatively wideband self-interference cancellation (SIC) performance for 2.4 GHz single-channel full-duplex (SCFD) or in-band full-duplex (IBFD) wireless applications. The presented antenna system is comprised of two closely spaced (spatial separation of
$\lambda _{\mathrm {o}}$
/4) proximity-fed patches with dual-polarized characteristics for transmit (T
_x
) and receive (R
_x
) modes. The proximity feeding offers comparatively wider impedance bandwidths (BWs) for both T
_x
and R
_x
ports. The T
_x
mode is excited through a single-port proximity-fed square patch, whereas the R
_x
mode operation is realized through a differentially driven proximity-fed dual-port patch. The compact structure for the presented antenna is realized through the vias interconnection of R
_x
ports of patch and differential feeding circuit. The implemented antenna prototype characterizes better than 87 dB peak interport decoupling, and the experimental results demonstrate higher than 80 dB interport isolation over the entire 10 dB return-loss impedance BW of 120 MHz for the presented antenna. Furthermore, the recorded results provide better than 6 dBi gains with higher than 75% peak radiation efficiencies for both T
_x
and R
_x
modes. In addition, the measured cross-polarization levels are more than 30 and 42 dB below the respective T
_x
and R
_x
co-polarization levels. The contributions of this work are the demonstration of a compact, dual-port antenna with comparatively wider impedance and isolation BWs along with low cross-polarization characteristics for both modes without compromising the radiation performance and electrical size of the proximity-fed printed patch antenna.