Improving signal isolation in hybrid RF duplexer utilizing a band-pass filter

This study deals with a passive RF duplexer integrated with a two-notch band. To design the model, a band-pass filter is considered. Using micro-strip technology, the RF duplexer substation is simulated. It is a rectangular in parallel coupling with frequency bands of 1 and 5 GHz while existing three ports. Moreover, to enhance the impedance coefficient and decrease the admittance, the method of complementary paired resonators is taken into account. Furthermore, scattering parameters were used by the step impedance method to make an integrated monolayer substrate from signal branching in duplex mode. Thus, the band-pass filter making the frequency cut-off bands allows designing GSM-4G radars. The low cut-off microwave band is included in these bands at the 77 MHz central frequency and the second cut-off band for GSM-4G radars at the 437 MHz central frequency. The duplexer has the total dimensions of 14 mm × 99 mm and the presented RF duplexer is simulated in CST.