Research On An Adjustable Dual-band Pass Filter And Its Application In GNSS Systems

In recent years,with the development of communication technology,the GNSS receiving system obtains more and more attention.Not only miniaturization and low cost,but also compatibility of multiple systems is required.As the front-end components of the receiver,the study of electronic tuning filter with high speed,good frequency selectivity and miniaturization has important theoretical significance and application value.This paper discusses the design of tunable dual-band bandpass filters loaded with varactors,and studies the application of the tunable filter in GNSS system.Specific content is as follows:A novel tunable dual-band bandpass filter with two independently adjustable bandwidthes is studied.The single band bandpass filter is designed by using of the open-stub loaded E-type resonator.The n-type feed network is put forward to enchance the coupling.Then,we change the length of equivalent electric to change the difference of the two resonant frequencies by tuning the varactors on the open stubs of the resonator.Thus the two bandwidthes of the filter can be tuned independently.A new type of dual-band bandpass filter with two independently adjustable frequencies is studied.This paper proposed a new kind of four-mode resonator based on the open-stub loaded resonator.On this basis,a dual-band bandpass filter is designed,which adopts the interdigital coupling feed.Then the frequencies are adjustable independently,in the form of changing four resonant frequencies by tuning the varactors loaded on the open stubs of the resonator.A new type of bandwidth and frequency independently adjustable dual-band bandpass filter is proposed in this chapter.A novel kind of four-mode resonator is designed based on the short-circuit stub loaded resonator.And this four-mode resonator and interdigital coupling feed are adopted to form a dual-band bandpass filter.In the end,the bandwidth and frequency of the filter can be tuned independently by tuning the varactors on the open sutbs and short stubs respectively.Finally,a GNSS receiver system is built and tested.A broadband circularly polarized antenna and a wideband low noise amplifier are designed,which form the GNSS receiver system with tunable filter and GPS receiver.The experimental results show that the system can impletment the search function successfully,which shows the importance and effectiveness of the tunable dual-band bandpass filter.