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ABSTRACT: This article outlined several optimization techniques applied in different steps of the synthesis of filters and multiplexers. The importance of the subject has been appreciated by more and more researchers and engineers in this community. As it is impossible to cover all technologies available, the objective here is to provoke a broader thinking beyond basic filter synthesis. Established computer-aided design methodology is a true blend of both synthesis and optimization. In most cases, to meet a set of well thought-out specifications, the science of filter synthesis and trade-off applies. In other cases, the optimization of design is an art which creates opportunities and new possibilities.
IEEE Microwave Magazine 11/2011; · 2.11 Impact Factor
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ABSTRACT: In this paper, the performance improvements and limitations of the enhanced microwave multiplexer are thoroughly studied for applications in communications satellites considering in-band flatness of gain and group delay, out-of-band rejection, temperature stability and insertion loss. The overall performance of the enhanced multiplexer with M<sup>th</sup> order channel filters is similar to conventional design with M+1<sup>th</sup> order channel filters. It is shown that the difference in the coefficients of thermal expansion of the materials for the channel filters and the manifold has an effect on the multiplexer temperature stability. Impact of channel filter resonator Q factor and fractional bandwidth on the passband insertion loss is also demonstrated using different designs.
Microwave Symposium Digest (MTT), 2011 IEEE MTT-S International; 07/2011
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ABSTRACT: A new approach for designing a microwave multiplexing network is presented in order to improve channel performance. Through design and optimization of the connecting transmission line structure, the new approach ensures that an extra pole is formed in the passband of each channel. The channel filter order is therefore increased by one without additional resonators. Significant improvement in the performance of the multiplexer is achieved without the penalty of increased size or weight of the hardware, which is extremely important for applications in communication satellite. Simulation and measurement results are used to demonstrate the feasibility of such enhanced microwave multiplexing networks.
IEEE Transactions on Microwave Theory and Techniques 03/2011; · 1.85 Impact Factor
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ABSTRACT: In this paper, a novel true inline configuration for cross-coupled coaxial cavity filters is presented, which is characterized by a simple and compact structure, improved performance, and good tunability. Instead of using folded structures, dedicated coupling probes, or extra cavities, as required by conventional techniques, cross coupling is realized by changing the orientation of selected resonators. Sequential coupling between adjacent resonators and cross coupling between nonadjacent resonators are effectively controlled by introducing small metal plates at different locations. A six-pole bandpass filter with two transmission zeros was built and tested. The measurement and simulation results agree very well, demonstrating feasibility of the inline filter configuration. It enables compact design with improved resonator Q compared to conventional combline filters. Furthermore, cross coupling can be readily adjusted using tuning elements.
IEEE Transactions on Microwave Theory and Techniques 01/2010; · 1.85 Impact Factor
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ABSTRACT: This paper presents new ideas for the design and implementation of microwave filters with single and dual stopbands. They can be realized with waveguide, coaxial, dielectric resonators, or in a planar technology. The new methods represent an advance over present methods in that the resonators are direct coupled, thus avoiding the need for transmission line phase lengths between resonator stubs that tend to degrade performance due to their dispersion and are difficult to adjust during tuning. Three bandstop (BS) configurations are presented. The first will accommodate even or odd characteristics and also asymmetric responses, although some negative or diagonal cross-couplings will be needed. The second resembles the cul-de-sac configuration for bandpass filters and needs no diagonal or negative couplings even for asymmetric characteristics. The third is an application of the cul-de-sac synthesis technique to dual-band bandstop (DBBS) filters. All these BS designs are very similar to regular bandpass filters in their design and realization. The design of a DBBS filter is presented and compared with an equivalent bandpass filter to demonstrate its advantages. Finally, the simulated and measured results of a fourth-degree BS filter design in the novel cul-de-sac configuration are presented.
IEEE Transactions on Microwave Theory and Techniques 12/2005; · 1.85 Impact Factor
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ABSTRACT: This paper presents some ideas for the design and implementation of microwave bandstop filters realized with waveguide, coaxial, dielectric resonators, or in a planar technology. The new methods represent an advance over present methods in that the resonators are direct-coupled, thus avoiding the need for transmission line phase lengths between resonator stubs which tend to degrade performance due to their dispersion, and are difficult to adjust during tuning. Two bandstop configurations are presented, both of which are very similar to regular bandpass filters in their design and realization. The first accommodates even or odd characteristics and also asymmetric responses, although some negative or diagonal cross-couplings are needed. The second resembles the cul-de-sac configuration for bandpass filters, and needs no diagonal or negative couplings even for asymmetric characteristics. A simulation of a 4<sup>th</sup> degree design in this configuration is included, and a practical model in waveguide is in the course of being tuned and measured.
Microwave Symposium Digest, 2005 IEEE MTT-S International; 07/2005
