SIW Sub-Array Antenna With High Isolation Offering Dual-Polarized Monopulse Patterns

A high isolation antenna is presented which offers dual-polarization monopulse beam patterns, making the design suitable for polarization diverse or full-duplex (FD) systems. The single-layer structure is defined by a network of 2-D sub-arrays oriented in a cross-shape configuration using series-fed slots in substrate integrated waveguide (SIW) technology. Also, the proposed design exploits dual-differential feeding to achieve a -10 dB impedance matching bandwidth (BW) from 23.2 GHz to 25.4 GHz, and measured isolation values are more than 70 dB (peaking to about 90 dB) over this same operating range. Realized gain values are 13 dBi (and above) while cross-polarization values are less than 35 dB below the beam maximum. The novelty in the design can be defined by the inclusion of a simple SIW isolation element at the center of the antenna structure. This provides enhanced isolation and enables co-location for the vertical and horizontal SIW sub-array branches, and this simple and low-profile arrangement supports efficient dual-linear polarized radiation. To the best knowledge of the authors, no similar 2-D planar antenna design has been previously reported offering high isolation in the K-band and which can offer sum and difference beam patterns in the far-field (FF). Some applications include monopulse tracking setups for communications as well as in-band FD systems which require dual-polarization at microwave and millimeter-wave frequencies.