A Multiband Filter for Multistandards Wireless Communications Receivers

Abstract

A new topology for a multiband filter suitable for multistandard and multiband mobile terminals is proposed. This filter named MultiCrossed Open Stubs (MCOS) is based on the wideband Quarter-Wave Short Circuited Stubs (QWSCS) topology and consists of open stubs connected together with the main transmission line via a~multicross junction. This technique allows division the wide bandpass response into several subbands by means of open stub transmission zeros. Full synthesis of the MCOS filter using ABCD matrices and its application to GSM, GPS, UMTS, LTE, and Wi-Fi standards using FR4 microstrip technology are presented. Scattering (S) parameters simulations and measurements show good agreement according to standard specifications in terms of center frequencies and bandwidths. The achievable return losses for all bands are higher than 10dB, and transmission losses are between 3.9,dB and 6 dB. The proposed multiband filter topology is well suited for the implementation of reconfigurable multiband filters.