Practical Synthesis of Compact Strip Filters in the Range 430 MHz - 15 GHz

Abstract

The paper describes practical experience in the selection and synthesis of convenient to manufacture and compact bandwidth-missing strip filters with a high level of frequency selectivity for different frequency bands, located in the range of frequencies from 430 MHz to 15 GHz. As a result, the properties of six different variants of strip-bandwidth filters with different types of topology were synthesized, modeled, manufactured and practically investigated. They are: the third-order multi-resonator filter with a central frequency of 437 MHz and a relative bandwidth of less than 10 %; the two-layer second-order filter for a central frequency of 440 MHz with a band of 20 % and a sixth order filter for a central frequency of 610 MHz with a 30 % band, as well as the three-layer fourth order filter for a central frequency of 1.22 GHz with a 30 % band; the cascading structure of the two lattice filters for a central frequency of 2.44 GHz with a relative band of 30 %; and the filter on parallel-coupled semi-wave micro-strip resonators for a central frequency of 14.8 GHz with a relative band of less than 10 %. The results are presented in the form of amplitude-frequency filter characteristics, through which their main selective properties are assessed: the width of the work bandwidth at -3 dB and the amount of losses within it, as well as the levels of suppression in the side bands of the barrier and the width of the high-frequency barrier band extending to the second bandwidth of the filter. The high efficiency and acceptability of modeling for the initial parametric synthesis of filters has been confirmed. AWR Design Environment is used to do this, taking into account the experience of setting it up for practical production. And measurements of filter characteristics are made on the vector analyzers of the chains of National Instruments and Rohde&Schwarz. Relatively new reduced filters for low-frequency microwaves are practically worked out, which are up to 7 times smaller than filters ( l /4). The results are not limited to specific manufactured filters, as they can be summarized for other central frequencies by corresponding changes in the size of the structures in proportion to the change in the wavelength of ultrahigh frequencies.