This communication presents two dual-polarized microstrip patch antenna systems based on a single radiating element with 180° ring hybrid coupler for differential feeding to achieve high interport RF isolation. One of the implemented single-layer patch antennas provides more than 67 dB isolation between transmit (Tx) and receive (Rx) ports at 2.4 GHz while the second fabricated antenna with slot coupled Tx port along with differential feeding for Rx operation provides more than 90 dB RF isolation at 2.41 GHz between dc isolated Tx–Rx ports. Moreover, the single-layer antenna provides better than 62 dB interport isolation for 10 dB-return loss impedance bandwidth (BW) of 50 MHz. Measured interport isolation for implemented antenna with slot coupled Tx port achieves around 70 and 79 dB port to port RF isolation for 50 and 20 MHz BWs, respectively, and these are the highest amounts of isolation for a single antenna to best of our knowledge. The antenna with slot coupled Tx port provides more interport RF isolation as compared to single-layer antenna due to low coupling between slot coupled and co-planar quarter-wave microstrip fed ports. Both antenna structures have the capability to remove in-band nonlinear self-interference (SI) components without complex SI cancellation circuits.

This letter presents a 2.4GHz, dual polarized microstrip patch antenna with extremely high interport isolation for shared antenna architecture based In-Band Full Duplex (IBFD) transceiver. The presented antenna configuration is based on four ports linearly polarized single radiating element with differential feeding for both transmit (Tx) and receive (Rx) operation. The double differential feeding using two identical 3dB/180° ring hybrid couplers with nice amplitude and phase balance effectively suppresses the interport RF leakage to achieve very high isolation. The prototype of proposed antenna architecture is implemented using 1.6mm thick general purpose FR-4 substrate. The implemented antenna provides more than 90dB and 80dB interport RF isolation for 20MHz and 40MHz bandwidths respectively in addition to more than 98dB port to port peak isolation when measured inside anechoic chamber. To the best of our knowledge, this is the highest amount of RF isolation reported for single; dual polarized patch antenna.

This paper presents a novel low-complexity full-duplex radio design, which only uses a single patch antenna without any duplexer or circulator for passive suppression of self-interference, and a computationally efficient technique for linear digital cancellation. The proposed full-duplex design is tested for IEEE 802.11g Wireless Standard on the WARP (v3) software-defined radio implementation platform. It is shown that this design provides a total suppression of 88 dB, which is sufficient for low-power or short-range full-duplex communication. The dual polarized slot coupled patch antenna used in our design provides an interport isolation as high as 60 dB in 2.4 GHz band. Additionally, the digital domain cancellation utilizes a frequency domain-based estimation and reconstruction approach, which not only offers up to 61% reduction in the computational complexity but also provides a 5-7 dB better digital cancellation performance in highly selective channel conditions, as compared to the time-domain-based techniques. The proposed full-duplex implementation can be easily applied in OFDM-based wireless systems, such as IEEE 802.11, which is the considered air interface in this paper.

This paper presents an in-band full duplex (IBFD) architecture, comprised of a monostatic antenna and software defined radio (SDR) implementing digital self-interference cancellation (DSIC). For this architecture, three alternative monostatic antennas with high passive suppression are integrated with a least squares linear DSIC algorithm implemented on the WARP v3 orthogonal frequency-division multiplexing based IEEE 802.11 SDR. Via detailed laboratory tests, the performance of the proposed IBFD radio architecture is investigated, considering various indoor positions and orientations for each antenna. The measurement results have been utilized to devise an analytical model for characterizing the power of the residual self-interference in the monostatic antenna IBFD radio as a function of transmit power levels. It is shown that the monostatic IBFD architecture can achieve up to almost 99 dB total cancellation, enabling medium range full duplex communication with moderate transmit power levels. Bidirectional communication is demonstrated between the two IBFD nodes with the proposed architecture, and error vector magnitude is observed as a function of increasing transmit power, i.e., SI. The throughput gain of full-duplex communication over half-duplex communication is also calculated as a function of payload size and the gain is found to be close to two for the settings used in the experiments.

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.