Design Of Microstrip Tunable Balanced Filtering Power Divider

In recent years,the rapid development of the wireless communication industry has brought rapid changes to people's lives and also brought new challenges to the development of microwave devices.The traditional power divider has a narrow working band and poor selectivity.By integrating the filter into the power divider,the selection performance can be improved.The correct design can achieve a wide working bandwidth,while achieving good frequency selectivity and matching characteristics.At the same time,in order to adapt to the development of the miniaturization and high anti-interference of microwave devices,balanced tunable devices came into being.The emergence of balanced tunable devices,while solving the problem of high interference and multi-channel,also correspondingly reduces the volume of the entire communication system.In recent years,many power dividers with integrated filtering response have been proposed,which are called filtering power dividers,but there are few researches on balanced tunable filtering power dividers.This paper has studied and designed two tunable filtering power dividers and a dual-band balanced tunable bandpass filter.The main contents are as follows:(1)A tunable filtering power divider with good filtering characteristics based on the stepped impedance resonator is designed.In order to achieve wide stop band performance,the input end is loaded with a ?/4 open stub.In order to achieve reconfiguration,four varactor diodes are loaded on the external resonator.In addition,by applying source and load coupling on each path of the power division network,a pair of transmission zeros that can effectively improve passband selectivity is generated.The center frequency of this design can be reconstructed from 3.0 to 3.5GHz while maintaining a constant absolute bandwidth of450 MHz.(2)A balanced tunable filtering power divider is designed based on the stub loaded resonator,which realizes the differential mode passband with high selectivity and isolation.U-shaped microstrip-slotline feeding network can be used to achieve independent broadband commonmode rejection greater than 40 d B.Six varactor diodes are loaded on the resonator to realize tunable center frequency and bandwidth.By changing the voltage across the varactor diodes,the tunable center frequency of 3.2?3.75 GHz and the reconfiguration of the fractional bandwidth 12.1%?17.6% can be realized.(3)Based on the step impedance resonator and the stub loaded resonator,a balanced dual band pass filter with high selectivity and low insertion loss is designed.The balanced microstrip-slot line transition structure can achieve broadband common mode rejection,and the rejection is independent of the differential mode response,which greatly simplifies the design process.Six varactor diodes are loaded to the resonator to achieve reconfiguration.The center frequency and bandwidth of the balanced dual-band band pass filter are quasiindependently tunable.The tunable ranges of the center frequencies of the two passbands are 2.48?2.85 GHz and 3.6?3.95 GHz,and the tunable ranges of the fractional bandwidth are20.16%?7.02% and 11.11%?14.29%.This article has already studied the balanced tunable filtering power divider,but it is only for single band.In order to meet the development of the communication system,further research will be carried out on the multi-band balanced tunable filtering power divider.