Compact On-Chip Cul-De-Sac Mixed Topology Bandpass Filter With Extracted-Pole Unit Using TGV Technology

A compact on-chip mixed topology bandpass filter (BPF) is proposed. By virtue of a new cul-de-sac structure, this BPF realizes transmission zeros (TZs) in pairs at both high and low frequency ends simultaneously. An extracted-pole unit, which can generate two additional TZs outside the passband of the BPF, is also employed. The presence of multiple TZs can greatly improve the outband rejection performance. The proposed topology is realized using laser-induced wet etching through glass via (TGV) technology, which has merits of high precision, ease integration, and process simplification. In particular, the proposed topology can effectively reduce the filter area by 24%. The use of Metal-Insulator-Metal (MIM) capacitors and spiral inductors further reduces its size. A fabricated prototype shows the minimum in-band insertion loss is 2.49 dB and the 3-dB fractional bandwidth is 25.3%. The BPF size is 1.6 mm $\times 0.8$ mm $\times 0.35$ mm, which is only about $0.0131~\lambda _{{0}} \times 0.0065~\lambda _{{0}}$ at ${f}_{{0}} =2.45$ GHz.