Silicon-integrated signal-interference dual-band bandpass filter for GNSS application

An original silicon-integrated dual-band bandpass filter for Global-Navigation-Satellite-System (GNSS) bands is presented. The engineered filtering architecture consists of a two-path signal-interference transversal filtering section (TFS) made up of a quadrature power coupler that is arranged in reflection mode. It allows a sharp-rejection dual-passband filtering response with out-of-band transmission zeros (TZs) to be obtained through constructive and destructive feedforward signal-combination effects that take place between the two electrical paths of the TFS. Furthermore, to counteract the losses inherent to the integrated lumped-element realization, compensated active inductors are used in the TFS stubs. For experimental validation, a low-noise-amplifier-(LNA)+filter module based on the conceived approach is designed with QUBIC4XI 0.25μm BiCMOS process from NXP technology, fabricated, and tested. This circuit, which operates on the two spectral bands utilized by the GNSS system (1215–1300 MHz and 1559–1610 MHz), features measured in-band power gain and noise figure respectively equal to 14 dB and 2 dB with a power consumption of 18 mW. To the best of authors' knowledge, it is believed to represent the first practical realization of a pure signal-interference dual-passband filter in integrated technology.