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Miniature CMOS stacked spiral-coupled directional coupler with 67-dB isolation and 0.8-dB insertion loss, IEEE Electron Device Lett 33 (2012), 919-921.ABSTRACT: In-band full duplex (IBFD) wireless communication operation can be realized by suppressing the self-interference at the receiver that is caused by coupling of radio frequency (RF) power from its own transmitter. In case of analog/RF domain self-interference cancellations techniques, most of the reported systems require transceivers with multiple transmit and receive antennas in order to achieve sufficient isolation. We have designed a dual port orthogonal polarized single patch antenna without a circulator/duplexer for IBFD communication, which uses external feed forward loop for self-interference cancellation in RF domain. The implemented antenna provides 47.5 dB interport isolation without feed forward loop and 73.5 dB isolation between transmit and receive ports at 2.4 GHz when external feed forward loop is activated. In both cases, the interport isolation is better than 40 dB for 24 MHz antenna 10 dB input impedance bandwidth. The peak isolation operating frequency can be adjusted by changing the loop attenuation and phase shift to operate antenna at any frequency within 24 MHz antenna 10 dB input impedance bandwidth. The interport isolation measurement results with peak isolation at lower cutoff and upper cutoff frequencies of antenna input impedance bandwidth adjusted through loop tuning are also presented.