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 0.25 mu m 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.