# A Quasi-Lumped Element Tunable Bandpass Filter Based on GaAs Technology

## TL;DR

A small, tunable bandpass filter chip is developed using GaAs technology for improved frequency selectivity and performance.

## Contribution

A miniaturized tunable bandpass filter using quasi-lumped elements and PN-junction varactor diodes is proposed and experimentally validated.

## Key findings

- The filter achieves a center frequency tuning range from 5.4 to 6.2 GHz.
- The design uses a compact die area of 1.35 × 1.365 mm².
- Measured results align well with simulations, confirming the design's effectiveness.

## Abstract

This paper presents a miniaturized tunable bandpass filter chip fabricated using a gallium arsenide (GaAs) technology. In the layout design, a quasi-lumped element is utilized to replace conventional spiral inductors, complemented by on-chip PN-junction varactor diodes and Metal-Insulator-Metal (MIM) capacitors. The integration of a source-load coupling structure and grounded series LC resonators introduces three transmission zeros (TZs), enhancing the frequency selectivity. By independently tuning the coupling capacitance and the grounded series LC resonant structures, the operating frequency of the filter achieves continuous tunability. An equivalent circuit model is established to analyze the filter’s performance. For experimental verification, the proposed filter was fabricated and measured, occupying a compact die area of 1.35 × 1.365 mm2. The measured results demonstrate a center frequency tuning range from 5.4 to 6.2 GHz, showing good agreement with simulation and thus validating the proposed miniaturized continuously tunable filter.