A 4–400 K Wide Temperature Range 2–18 GHz Reconfigurable Filter for Multifunction Applications

This article presents the world’s first 2–18 GHz reconfigurable filter capable of operating across an extended temperature range of 4–400 K, making it highly suitable for applications such as deep-space exploration, instrumentation, and electronic warfare. The proposed filter features fully digital reconfigurability, supporting high-pass, low-pass, bandpass, and all-pass responses. By integrating a tunable-zero filter architecture, the design significantly enhances frequency selectivity, while a die-package co-design approach optimizes key performance metrics such as channel isolation and out-of-band suppression. Fabricated using a 180 nm CMOS process, the filter occupies a compact chip area of $5.6\times 5$ mm² within a package size of $7.7\times 7.7$ mm². Measurement results validate a reconfigurable frequency range spanning 2–18 GHz, with insertion losses of 5–8dB and 6–8 dB in low-pass and high-pass modes, respectively, and out-of-band suppression exceeding 60 dB. In bandpass mode, the filter achieves a passband bandwidth exceeding 4 GHz and an input third-order intercept point (IIP3) of over 33 dBm. Compared to room temperature, electrical characterization over the 4–400 K temperature range shows that the insertion loss increases by approximately 4 dB at 77 K. Furthermore, when cooling from 77 to 4 K, only a slight increase in insertion loss is observed.