| With the development of wireless electronic technology,various new communication standards have been introduced one after another,which requires electronic equipment to have a variety of new functions,such as suppressing multiple single frequency points,working in multiple frequency bands,suppressing broadband interference,miniaturization.These new requirements put forward new requirements for microwave filter synthesis,and even require the filter to have the above functions at the same time.Therefore,it is of great practical significance to study new microwave planar filters with multi frequency band,wide frequency band,band notch and wide stop band.On the other hand,on the existing broadband wireless electronic equipment,the fluctuation of amplitude frequency response in the frequency band caused by electromagnetic spatial propagation and frequency response of microwave deyices is easy to lead to the distortion of received signal waveform and reduce the quality of digital signal demodulated by wireless equipment.The compensation of this wide-band amplitude frequency inconsistency needs to consume a lot of digital resources in the digital domain.The traditional microwave equalizer has a continuous periodic parasitic passband in the stopband,which affects the stopband suppression ability of the microwave front-end filter.Therefore,it is necessary to study a new microwave device,which can realize amplitude equalization and interference filtering respectively in passband and out of stopband at the same time.Based on the new requirements of modern wireless communication equipment for filters,combined with theoretical research and practical requirements,this paper studies a series of miniaturized band-notched band filters with wide stopband based on multi-resonator structure and the methods of stop band expansion,high selective microwave multi-band filters and equalization filters based on spoof surface plasmon polaritons.The main results are as follows:1.In view of the single filtering function of most existing filters,a wide stopband broadband miniaturized filter with notched bands is proposed based on the multi-resonator coupling structure.Using the resonant frequency and transmission zero of each resonator,the broadband and notch frequency of the filter can be adjusted.By setting the out of band zero position to the parasitic resonance frequency of the resonator,the upper stopband suppression range of the broadband filter is effectively increased,so that the filter has the characteristics of adjustable three notch frequency,wide upper stopband suppression range and adjustable wide band at the same time,thus a variety of filtering functions are realized.In addition,In order to further expand the upper stopband suppression range of the proposed filter,a loading structure based on groove line is proposed,which can further adjust the out of band parasitic frequency of the resonator,increase the upper stopband suppression range from 29Ghz to 32Ghz without affecting the filter notch position and working frequency band.2.Without greatly changing the coupling structure of the three notched wide upper stopband miniaturized broadband filter proposed above,a highly selective microwave triple band filter based on multi resonator structure and zero tap feeding line is proposed.Without significantly changing the resonator coupling structure of the three notched wide upper stopband broadband filter proposed above,the filtering characteristics of the device can be changed only through the coupling of different direction sources,loads and resonators,the design process between multi-notch filter and multi-band filter can be simplified.The position and width of the three bands of the filter can be adjusted independently,and there is a steep stopband interval between the frequency bands.3.In view of the problem of continuous parasitic frequency band in traditional microwave equalizer,combining the functions of microwave filter and microwave equalizer,a microwave equalization filter based on spoof surface plasmon polaritons is proposed for the first time.Both in band equalization and out of band filtering can be realized at the same time.By sputtering ITO film on flexible pet material,a flexible SSPPs unit sputtering with ITO film on single conductor central metal strip is proposed,and a flexible SSPPs equalization low-pass filter with adjustable equalization is designed by using this unit.The filter has the equalization characteristic of negative slope in the transmission passband,overcomes the periodic parasitic frequency band existing in the traditional microwave equalizer,it can compensate the amplitude difference of the working frequency band while suppressing and the out of band interference of the broadband electronic system at the same time.In addition,in order to further reduce the in band reflection coefficient of the flexible SSPPs equalization filter,a flexible SSPPs unit with single conductor rectangular grooves sputtered with ITO film is proposed,and a single conductor SSPPs flexible equalization filter is synthesized by using this unit.The measured results show that due to the sputtering of ITO film to the rectangular corrugated strip,the TEM transmission line and SSPPs unit can be better matched,and the average reflection coefficient in the passband is increased from-10dB to-13dB.4.In view of the poor localization of low-frequency electromagnetic field of single conductor SSPPs equalization filter,a SSPPs using double conductor corrugated metal strip loading with resistance based on microstrip structure is proposed,and a SSPPs equalization filter based on the SSPPs unit is designed.Compared with the single conductor SSPPs equalization filter,it has smaller reflection coefficient in the low frequency band,which increases the working bandwidth of the equalization filter in the low frequency.At the same time,the double conductor equalization filter has stronger electromagnetic field localization,which effectively reduces the circuit area of SSPPs equalization filter. |
