Self-Packaged Low-Loss Low-Pass Filter With Hexagonal Suspended Toroidal Inductors

This letter presents the design and analysis of the proposed hexagonal suspended toroidal inductors and the applications in a self-packaged low-loss low-pass filter (LPF). The characteristics of the proposed inductors are studied and analyzed with the developed $\pi $ -type equivalent circuit model. Compared to widely adopted spiral inductors, the proposed hexagonal suspended toroidal inductors feature improved quality factors ( $Q$ -factors) in experimental verifications. Following the developed theory and equivalent circuit model, several suspended toroidal inductors are designed and applied to a 5th-order lump self-packaged LPF. The filter achieves the passband insertion losses of < 0.49 dB and return losses of $>14.7$ dB, which demonstrate the advantages of high $Q$ -factor of the proposed inductor topology.