Research And Design Of Millimeter Wave Microstrip Filter

The millimeter wave is an electromagnetic wave with frequency of 30GHz to 300GHz in vacuum,and its corresponding working wavelength is 10 mm to 1 mm,which has the advantages of wide bandwidth and high data transmission rate.With the development of 5G communication technology,the world has conducted close research on related millimeter wave technology.As a key passive component of millimeter wave communication and radar systems,filters are mainly used for band selection and filtering out clutter interference.Among them,the microstrip filter has the advantages of compact structure,easy integration and light weight,and has high research and engineering value.Based on the above scientific research and industrial background,this paper studies and designs three millimeter-wave microstrip filters.The main research contents are as follows:Firstly,the development process of the filter,the current situation and challenges are introduced.The basic theory and design method of the filter are studied and elaborated,including the impedance resonator theory and the odd-even mode analysis method?Based on the theoretical research,a single-passband filter was designed according to the requirements of project.The central frequency of the filter is at 32.92GHz,the relative bandwidth is 8.3%,the in-band insertion loss is less than 1.45dB,and the return loss is greater than 20.85dB.The advantage is that a new structure combining a double U-shaped feedline and a dual-mode stepped impedance-loaded resonator improves the suppression of stopband at the left side of the passband,and introduces more zeros at the right side of the passband.The bandwidth of stopband at both sides of the passband reaches 9GHz or higher,whose suppression are greater than 20dB,the structure is simple and compact,so it has great practical value.In the following work,this paper designed a broadband filter with a central frequency of 25.8GHz,the relative bandwidth of passband is 19%,the in-band insertion loss is less than 0.27dB and the return loss in the passband is greater than 13.1dB.The advantage is that the 3dB bandwidth reaches 25.2%.There are 2 transmission zeros near the passband,and the bandwidth of stopband at the lower frequency is 9.42GHz whose suppression is greater than 20dB,which is compact.Finally,a new four-mode resonator was studied and a dual-band filter was designed.The central frequency of the first passband of the filter is 20.61GHz,the relative bandwidth is 4.2%,the in-band insertion loss is less than 2.17dB,and the return loss is greater than 10.6dB.The central frequency of the second passband is 29.57GHz,the relative bandwidth is 9.4%,the in-band insertion loss is less than 2.26dB,and the return loss is greater than 12dB.The advantage is that the structure is compact,the size is only0.31?_g(9)0.24?_g,there are 4 transmission zeros near the passband,the bandwidth of stopband reaches 19.83GHz whose suppression is greater than 25.47dB,and the bandwidth of stopband reaches 30.38GHz whose suppression is greater than 16.1dB.