A Novel Duplex Antenna with Enhanced Isolation

In this letter, a duplex antenna with enhanced isolation level and similar radiation patterns is presented. The proposed duplex antenna is composed of a square patch loaded with a stub, a ground plane with two slots cut on it and the feeding network under the ground plane. The dual band radiation characteristic is achieved by adding an open stub to the square patch on the top layer of the upper substrate board. The lower band channel and the upper band channel are printed on the bottom layer of the lower substrate board. The microwave signal is coupled to the stub-loaded microstrip patch antenna through the slots on the ground plane. To improve the interchannel isolation between the transmitting and the receiving channel, an open stub is introduced in the lower band channel. The proposed antenna is simulated and fabricated. The measured impedance bandwidth of the transmitting channel and the receiving channel are 1.66-1.76 GHz (FBW=5.84%) and 2.23-2.34 GHz (FBW=4.81%). The isolation level is over 42 dB in the lower band and 48 dB in the upper band.