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A Varactor-Based Very Compact Tunable Filter with Wide Tuning Range for 4G and Sub-6 GHz 5G Communications
Yasir I A Al-Yasir1, Naser Ojaroudi Parchin1, Yuxiang Tu1
1Faculty of Engineering and Informatics, University of Bradford, Bradford BD7 1DP, UK.
Sensors (Basel, Switzerland)
|August 23, 2020
Summary
This study presents a compact reconfigurable microstrip filter for 4G and 5G systems, tunable from 2.5 to 3.8 GHz. The filter achieves excellent performance using a novel hybrid co-simulation method.
Area of Science:
- RF and Microwave Engineering
- Wireless Communication Systems
- Filter Design
Background:
- Reconfigurable filters are crucial for modern wireless systems like 4G and 5G, enabling adaptability across various frequencies.
- Existing designs often face challenges with size, tunability, and performance trade-offs.
- Compact and efficient tunable filters are needed to support the increasing demand for flexible wireless communication.
Purpose of the Study:
- To introduce a novel, compact microstrip reconfigurable filter for 4G and sub-6 GHz 5G applications.
- To demonstrate a new hybrid co-simulation method for designing and optimizing reconfigurable filters.
- To achieve wide frequency tuning range (2.5–3.8 GHz) with excellent performance metrics.
Main Methods:
- Design of a microstrip filter utilizing three coupled line resonators with λ/4 open-circuited stubs.
- Tuning the center frequency by adjusting coupling coefficients between resonators.
- Utilizing varactor diodes and a biasing circuit for electrical tunability.
- Employing a hybrid co-simulation technique combining CST Microwave Studio (MWS) and CST Design Studio (DS) with SPICE models for active components.
Main Results:
- Achieved a tunable frequency range from 2.5 to 3.8 GHz.
- Maintained an impedance bandwidth between 95 and 115 MHz.
- Measured return loss exceeded 17 dB, and insertion loss remained below 1 dB.
- Fabricated filter on Rogers RO3010 material in a compact size of 13 × 8 × 0.81 mm³.
- Demonstrated excellent agreement between simulation and measurement results.
Conclusions:
- The proposed hybrid co-simulation method effectively designs and optimizes compact reconfigurable microstrip filters.
- The developed filter meets the stringent requirements for 4G and 5G wireless systems.
- The compact size and wide tunability make this filter suitable for integration into modern mobile devices and communication infrastructure.
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