Study of a Reconfiguration Methodology Applied to the Development of Adjustable Microwave Planar Filters
Microwave Planar Filters, Band Pass, Band Reject, Reconfiguration, Varactor Diode, 5G New Radio.
Filters play an important role in many radio frequency (RF) and microwave applications. They are used to separate or combine different frequency bands. The electromagnetic spectrum is limited and needs to be shared, so the filters have the function of limiting and / or selecting the microwave / RF signals within the assigned spectral limits. The reconfigurable, or tunable, microwave filters have attracted a lot of attention from researchers and designers due to their emerging characteristics of improving spectral capacity and performance in current and new communication systems. This work presents a study about reconfigurable microwave planar filters. A reconfiguration methodology based on the use of semiconductor devices of the varactor diode type is proposed in order to allow the adjustment of impedances along the geometry of the filter resonator, and thus, configure the frequency response of the filtering device. The designs of three reconfigurable devices are presented, being applicable to the communication standards 5G NR sub-6 GHz, with the model 01 being a band-reject filter, and the models 02 and 03, band-pass filters. Analyzes of the equivalent circuits of the filters are developed in order to establish an understanding of their respective performances depending on the geometry and the adjustment device. The initial analyzes and simulations were performed using the equivalent circuit method and the finite element method using the Ansys HFSS software, and the equivalent model of the varactor diode was also used according to its datasheet. Preliminary results are presented, which include the response obtained through simulation and measurement of the models without the use of varactors and results with the application of the reconfiguration methodology based on the varactors. Finally, the next fundamental steps for the continuation of the research are pointed out.