Design Of A Novel Ultra-Wideband (UWB) Bandpass Filter Based On Multi-Mode Resonators (MMR) And Defected Ground Structure (DGS)

The US Federal Communications Commission(FCC)has authorized the use of ultra wideband(UWB)technology in short distance wireless communication,and has opened the 3.1GHz~10.6GHz band as the standard band of indoor UWB system.It is free for civilian use,and has high commercial value and can be used in the Internet of things system.As an important component of the UWB system,UWB microwave filter has a key impact on the performance of the system.At the same time,there are some other narrowband communication systems in the passband of 3.1GHz~10.6GHz,which will inevitably interfere with each other between UWB communication systems.Therefore,UWB band-pass filters with notch characteristics can effectively suppress other narrowband communication systems in passband,which has become a pressing demand and has become a new research hotspot.In this paper,the design method of UWB bandpass filter,which combines multi-mode resonators with DGS,is used to effectively expand the bandpass bandwidth while ensuring the good passband characteristics.At the same time,the notch characteristics are introduced in the passband with maintaining the original passband characteristics and without increasing the additional area.The specific work is as follows:Firstly,there are several UWB bandpass filters for 3.1GHz~10.6GHz indoor UWB band based on multimode resonator designed out with the HFSS full wave simulation software.The interdigitated coupling structure combined with the defected ground structure(DGS)is used to enhance the end coupling and improve the passband characteristics.The insertion loss of the whole passband can be below 0.5d B,and the 3d B bandwidth is2.67GHz~13.68 GHz,more than 3GHz over the specified 3.1GHz~10.6GHz passband,which can more effectively utilize the existing frequency resources.The bandwidth and passband performance exceed all known UWB filters.Then,based on the previous design,a variety of different ways are used to introduce notch bands at the fixed frequency points of the passband.Based on this,several UWB bandpass filters with single fixed notch or multi fixed notches are designed.One of the most important methods is to load the DGS notch resonator and use its resonant characteristics to create notch band in the passband.Compared with the conventional microstrip linenotch resonator,it has less influence on the passband characteristics and smaller occupied area under the condition that the notch depth is less than-10 d B,which is more conducive to the miniaturization of the filter.The later design of UWB filter with adjustable notch is based on this method.Finally,by loading multiple DGS notch resonators and embedding varactors in it and adjusting the reverse bias voltage of the diode,the position of notch band can be adjusted.In the past,by loading microstrip line resonator loaded varactors,the adjustment range of notch band position is always less than 2GHz on the condition of ensuring the depth of the notch band is more than 10 d B.But the UWB filters with adjustable notch designed in this paper can ensure the notch band location can be adjusted in a wide range of 3GHz~7GHz within the passband under the condition that the notch depth is less than-10 d B.The notch band location can be adjusted flexibly to suppress the serious narrowband communication band according to the scene interference,which can meet the needs of different application scenarios.