Compact bandwidth tunable IF filters for reconfigurable converters

Jia Ni,Petronilo Martin Iglesias,Jiasheng Hong

doi:10.1017/s1759078721000714

Abstract

AbstractThis paper aims to present some outcomes from a European Space Agency (ESA) Technology Research Programme (TRP) project on R&D of new design techniques, concepts, and filtering configurations for tunable IF (intermediate frequency) filters with a compact footprint, wide bandwidth tuning range (covering from 49 to 478 MHz at f0 = 1 GHz) as well as equivalent high-Q performance (i.e. low insertion loss variation and high selectivity by using low-Q resonators). In order to obtain a wide tuning range, the proposed filtering configuration utilizes a new tuning technique that only necessitates control of coupling values with simple DC control circuits, without the need of tuning the electrical length of resonators to avoid deviating the center frequency. Furthermore, in order to achieve the equivalent high-Q performance, a novel lossy technique by using a centrally resistor-loaded half-wavelength resonator is adopted. For the proof of concept, a six-pole prototype filter is designed, fabricated, and tested.

Highlights

Flexible satellite payloads using reconfigurable filters have found considerable interest as they have the potential to address two important areas: (a) adaptability to changing business plans via capacity re-allocation in response to traffic variability. (b) Reductions in the number of RF components needed and front-end complexity lead to reduced cost and longer lifespan
Most of the research in tunable filters has concentrated on the technology of frequency tuning or bandwidth controlling by using semiconductor, RF micro-electromechanical system devices, ferroelectric diode, p-i-n diode, silicon or GaAs varactor diodes, and so on [1,2,3,4,5,6,7,8,9]
This can be seen as an increased insertion loss in passband and a rounding of the passband edges leading to a poorer selectivity which become more pronounced in narrowband filters

Summary

Introduction

The performance of tunable filters will commonly deviate somewhat from the expected specifications or theoretical response of the ideal prototype due to the effects of limited low Q factors of tuning elements and other dissipation loss associated in the circuit. This can be seen as an increased insertion loss in passband and a rounding of the passband edges leading to a poorer selectivity which become more pronounced in narrowband filters.

Narrowband isolation

Proposed tunable IF filters

The tuning mechanism of the proposed filter

Lossy circuit technique

Pin attenuator

Conclusion