Design Of The Ultra-Wideband Bandpass Filter With Notch Band

As one of the most important components of ultra-wideband system,the performance of ultra-wideband filter determines the performance of the whole UMB system.Nowadays,there are some bands that have been occupied in the ultra-wideband band.The signals of these bands overlap with the ultra-wideband system,which will cause some interference to the UWB system.The notch UWB filter has a good suppression effect on the interference,so this filter has become one of the research goals of many scholars and research institutions.The filter,which has high performance,compact structure,flexible notch and low cost,has become the main pursuit and goal of us.Nowadays,there are many ways to implement notch bands.For example:(1)an opencircuit stub with a fixed length embedded in a resonator.(2)coupled resonator with notch characteristics.(3)a Comple-mentary Split Ring Resonators etched on a metal ground.(4)add open stubs to feeder line to realize asymmetrical input/output structure.(5)generated by the resonator itself,etc.Based on this,four notch UWB filters with excellent performance are simulated and fabricated in this paper.The specific work is as follows:(1)A single-notch UWB band-pass filter based on CSRR structure is designed.Firstly,a UWB filter based on SIR structure is designed.Secondly,in order to suppress the existing communication band in the pass band,an asymmetric input / output structure is realized by loading an unsymmetrical input / output structure on the feeder lines,and the adjustable notch frequency is studied.Then by etching the spur line on the resonator to introduce the transmission zero at the high frequency,and by etching the L-shaped slot,the clutter frequency point in the stop band is suppressed to a great extent,and the ultra-wide stopband characteristic is realized.Finally,a single notch UWB filter with compact structure,excellent performance and ultra-wide stopband is obtained by simulation and optimization with electromagnetic simulation software.(2)A single notch UWB filter based on asymmetric feed structure is designed.Firstly,a UWB filter based on the SIR structure is designed,but the resonance point at the low frequency is not obvious,the resonance point at the low frequency is improved by the addition of the T-shaped stub.Then the UWB band-pass filter is realized by the introduction of strong coupling.It meets the requirements of miniaturization,and the in-band flatness is excellent.Then,the asymmetric input-output structure is realized by adding a pair of open-circuit stubs to the coupling line,and the required notch frequency band is introduced.The resonant frequency of the notch band varies with the physical size of the additional open-circuit stubs.Finally,the electromagnetic simulation and optimization are applied to obtain a single-notch UWB filter with excellent performance,compact structure and wide stop bandwidth.(3)Two multi-notchs UWB bandpass filters are designed.Firstly,a UWB filter based on stub-loaded SIR resonator is designed.Its structure is compact and pass band selectivity is good.Secondly,in order to suppress the interference signals in the pass band,two different notch structures are introduced,that is,folding T-type resonator to realize 8GHz notch frequency band and folding U-type resonator to realize 5.8GHz notch frequency band,respectively.Through the simulation and optimization of electromagnetic simulation software,a double notchs UWB filter is designed.Finally,based on the double notch UWB filter,the third notch structure,I-shaped resonator,is introduced to realize the 6.8Gz notch.The three notch structures suppress the interference of three different frequency signals respectively.Through the simulation and optimization of electromagnetic simulation software,a three notchs UWB filter is realized.Three notch bands are adjusted independently and not affected by each other.