Symmetric stripline duplexer

Abstract

The compact duplexer using the symmetric stripline and containing the fifth-order comb filters in transmit channel TX (2300–2370 MHz) and receive channel RX (2510–2580 MHz) is constructed, and the characteristics of obtained duplexer are measured. This duplexer is built using dielectric material Al2O3 (Alumina, polikor) with high thermal conductivity that makes it possible to use the operating power of 10 W at small dimensions 57´11.8´4 mm. The losses in bandpass of TX and RX filters did not exceed 3 dB during the filter attenuation at adjacent channel frequencies of no less than 60 dB. It is shown that the selection of the width of metallized strip at the base of quarter-wave resonators makes it possible to change the duplexer width for attaining the required value. The circuit of coupling of resonators with loads used in this design made it possible to obtain a sufficiently high level of isolation from each other for RX and TX channels of duplexer. This level does not exceed 60 dB. The finite thickness of internal conductors of stripline amounting to 16 mm is taken into account while building the duplexer that results in good agreement between the simulation and measurement results.