TRx stacked microstrip patch antenna with high isolation

This paper presents the use of a double spur-line band rejection filter (DSL-BRF) to improve port-to-port isolation of a TRx stacked microstrip patch antenna. The simple DSL-BRF has two different sideband suppression characteristics by tuning the separation between the end points of two spur-lines. A simple TRx stacked microstrip patch antenna designed to operate at Ku-band with downlink frequency band of 12.25 ~ 12.75 GHz and uplink frequency band of 14.0 ~ 14.5 GHz had inherent isolation of 17 dB within TRx-band. Isolation performance of the antenna was improved by more than 13 dB for Rx-band and 16 dB for Tx-band after introducing DSL-BRFs into Tx- and Rx-feed networks, respectively. Because the DSL-BRFs are compatible to be embedded in 50-Ohm transmission lines, the TRx antenna with filters are remained as in same size as the antenna without filters.