A novel wafer level integrated low-insertion-loss filter working at 1.8 GHz (DCS LPF) with suspended inductors and patterned ground shields on the lossy silicon substrate is fabricated. Thick BCB interlayer is used as the supporting dielectric, and the backside cavity on Si wafer is formed by using a two-step back-etching process. The influence of patterned ground shields on the Q factor of the suspended inductors and the influence of low-resistivity silicon on the insertion loss of filters are analyzed by EM simulation. The fabricated 2.7 nH inductor has a maximum Q factor of 49 at 8.2 GHz and high Q factors more than 22 in the broadband frequency range from 1 GHz to 10 GHz. And the realized LPF in DCS band has the insertion loss of 0.35 dB and return loss of more than 15.5 dB at the pass band, with the second harmonic rejection being 23 dB and the third harmonic rejection being 38 dB respectively.
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