Design of a Stacked Co-Polarized Full-Duplex Antenna with Broadside Radiation

This paper presents a co-linearly polarized (LP) stacked two-port antenna with compact size and broadside radiation patterns for in-band full-duplex (IBFD) application. The proposed IBFD antenna consists of a patch antenna and a substrate integrated waveguide (SIW) cavity-backed slot antenna (CBSA). The patch antenna and the CBSA are used as the transmitter (Tx) and receiver (Rx), respectively. The Rx is placed above the Tx for compact size. Linear polarization and broadside radiation patterns are achieved in this paper. A cavity-patch coupling (CPC) path is added for canceling the slot-patch coupling (SPC) by using four probes to connect the top layer of the SIW cavity and the metal ground. Parametric studies show that the two coupling paths can be adjusted independently. Experimental results illustrate that the measured highest isolation over 40 dB is obtained with a compact size of 30 × 30 × 4 mm3 (0.63λ0 × 0.63λ0 × 0.08λ0, λ0 is the free-space wavelength at the center frequency of about 6.29 GHz). The measured -10dB bandwidths of the Tx and Rx antennas are 430 MHz and 100 MHz, respectively. The proposed stacked IBFD antenna is validated with the merits of identical polarization, same radiation direction and compact size.