Axisymmetric Transformer in Glass IPD Technology and Its Application to Miniaturized On-Chip Bandpass Filters

In this letter, a miniaturized on-chip axisymmetric transformer with multi-transmission zeros (TZs) using glass-based integrated passive device (Glass IPD) technology is proposed. The proposed interwound winding transformer has two center taps. Four TZs are created by coupling capacitors and LC shunt resonators on three ports. The bandpass response is achieved by evolving the circuit structure. An on-chip prototype with a 3-dB fractional bandwidth (FBW) of 32.7% (4-4.5 GHz) is fabricated for verification purposes. In addition, a novel ultra-wideband bandpass filter (BPF) with a measured 3-dB FBW of 83.7% (4.5-9 GHz) is further designed by introducing a three-dimensional (3D) inductor, which provides a reliable solution for expanding the applications of on-chip transformer.