Miniaturized, Lumped-Element Filters for Customized System-on-Package L-Band Receivers

The system-on-package (SoP) approach to design wireless front ends has proven to optimize the tradeoff between performance and size. In this paper, two new and highly compact bandpass filters are presented that show the greatest degree of miniaturization of any bandpass filters presented to date when their volume is measured in guided wavelengths. A novel packaging technique where most of the filter components are folded beneath the resonator inductors allows for this level of miniaturization. The filters are designed as lumped-element equivalent circuits and fabricated in standard low-permittivity low-temperature cofired ceramic technology that makes them suitable for embedding within a mass-producible SoP solution. In addition, electric and magnetic couplings are used to create finite transmission zeros that enhance the selectivity of these filters. The second-order filter demonstrates an insertion loss of 2.2 dB and a 3-dB bandwidth of 11% at a center frequency of 1.524 GHz. Meanwhile, the fourth-order implementation shows an insertion loss of 4.92 dB and a 3-dB bandwidth of 6.6% at a center frequency of 1.521 GHz. In both cases, the agreement between simulations and measurements is excellent. Careful analysis of individual capacitors and inductors comprising the filters is provided to explain the link between process parameters and actual measured performances.