K-band MMIC active inductor-based bandpass filter suitable for industrial applications

The availability of integrated electronic filters for industrial applications is a missing block at microwave frequencies, in spite of the fact that filters have a crucial role in modern transceivers. This work aims to fill this gap by presenting the monolithic implementation of a high-Q active filter operating in K-band and realized by means of active inductors. The active inductor is the core of the filter and allows a fine tuning of both quality factor and frequency, while reducing the losses and increasing the selectivity; a three-cell bandpass filter is presented as a first example of application. All circuits have been designed and fabricated with a 0.1 m GaAs WIN technology. Measurements are also provided showing promising results. The inductors are stable and reproducible even when a relatively high equivalent negative resistance is obtained for loss reduction. The filter provides almost zero and constant in-band losses, a 1 dB relative bandwidth of around 7%, input and output matching better of 15 dB and a 30dB/3dB shape factor of 3.