UMTS-WiFi switchable bandpass filter

Abstract

In this paper a reconfigurable bandpass filter able to switch between WiFi and UMTS transmit band standards is presented. The filter is designed in such a way that center frequency and bandwidth specifications are precisely met by defining a switchable filter topology that includes two folded resonator extensions switched by two PIN diodes. Design specifications require two center frequency states, one at 2.440 GHz with an 80 MHz bandwidth and a second center frequency state at 1.955 GHz with a 140 MHz bandwidth for the WiFi and UMTS transmit bands, respectively. Filter simulations were performed to match the required filter specifications. Measured results on the filter show a very good agreement with the simulations where a 2.428 GHz center frequency with a 71 MHz bandwidth was obtained for the WiFi state, and a 1.939 GHz center frequency with a 144 MHz bandwidth was obtained for the UMTS filter state. The simulated filter insertion losses were -3.339 and -3.796 dB for the WiFi and UMTS states, respectively. Measured insertion losses were -3.345 and -3.837 dB for the WiFi and UMTS states, respectively. The filter specifications were successfully matched with the proposed filter topology, where simulated and measured responses are in good agreement.