GNSS LNA-filter module using BAW CRF filters

Abstract

Recently, a new standard has been proposed to augment the performance of future Global Positioning System (GPS) receivers, and is generally referred to as the Global Navigation Satellite System (GNSS) band. By also requiring differential signals from the output of the filter to the cell phone receiver, further performance improvements can be obtained. To accommodate the new GNSS specifications and to provide single-ended to differential (SE-DE) mode conversion, new filter designs are required. In this work, we describe a two-stage, SE-DE filter design for GNSS that is based on coupled resonator filter (CRF) technology. The design provides insertion loss better than -2.5 dB over a frequency range greater than 56 MHz. Out-of-band rejection is greater than 40 dB from DC to 6 GHz, and better than 60 dB below 2 GHz. As a stand-alone filter, excellent phase and amplitude balance are achieved without the need for external inductors. In a frontend module consisting of the filter and an Avago LNA, we have measured >;13 dB gain over the GNSS band. The module also shows excellent rejection and true differential output equivalent to surface acoustic wave filter solutions.