Modern isolation of dual-band proximity coupled microstrip antenna front-end transceiver

This paper presents a high port isolation for dual-band of frequency orthogonally polarized proximity coupled rectangular microstrip patch antenna. This is achieved by placing a lowpass filter (LPF) at the transmitting port of antenna for suppressing the higher order harmonic frequency components generated by the integrated power amplifier and a bandstop filter (BSF) at the receiving port of antenna for passing the desired frequency band signal (2.0 GHz band signal) and filter out/ suppression of unwanted transmitting frequency band signal (2.5 GHz band signal) at Rx port. The filters were designed utilizing two different shapes of defected ground structure (DGS) units placed underneath the microstrip feeding lines. Parametric study for the DGS units is presented. A design formula for the 3dB cut off frequency for both DGS units is given. The simulated and measured results for LPF and BSF filters are presented. Finally, the measured and the simulated results of the proposed dual frequency proximity coupled patch antenna shows a high port isolation than the conventional dual frequency proximity coupled patch antenna by about 20 dB.