Laminated Glass-Based, Compact Inline Stepped-Impedance Resonator Bandpass Filters for 5G New Radio Modules

Abstract

Miniaturization of millimeter-wave (mm-wave) filters relies on innovative designs that require fine lines and spacings. These designs drive the need for precision fabrication that cannot be achieved with traditional laminates or cofired ceramics. This gives unique performance justification to glass substrate technologies for future integrated mm-wave components because of both superior performance and 3– $5\times $ reduction in volume. In this letter, laminated glass-based compact inline stepped-impedance resonator (SIR) filters are presented for 5G new radio (NR) modules. The frequency bands of interest are 5G NR bands: n257 and n260. The filters are designed using microstrip transmission lines with the fourth-order quasi-elliptic response with skew-symmetric feed. The enhanced transition responses of these filters provide transmission zeros (TZs) on either side of the passband. When these filters are designed for mm-wave applications, their dependence on the accuracy of metal patterns increases significantly due to narrow linewidth and spacing requirements to realize moderate fractional bandwidths. Two inline SIR filters are fabricated using a large-area, panel-compatible semiadditive patterning (SAP) process on precision redistribution layers (RDLs) of a laminated glass substrate stack up. The sensitivity of these filters to the dimensional variations of patterned copper is analyzed, and the discrepancy between simulated and measured response of the filters is studied by performing postfabrication simulations.