Dimensioning

Algorithm

Engineering

Aerospace engineering

Bandwidth (computing)

Filtering theory

Low-pass filter

Cascade

Coupling (piping)

Telecommunications

Computer science

Prototype filter

Chemical engineering

Filter (signal processing)

Mechanical engineering

Insertion loss

Physics

Waveguide

Mathematics

Optics

Waveguide filter

Electronic engineering

Resonator

Block (permutation group theory)

Geometry

Topology (electrical circuits)

Network synthesis filters

Filter design

Optoelectronics

Computer vision

Electrical engineering

IEEE Transactions on Microwave Theory and Techniques

In this article, we introduce a synthesis-based design approach for waveguide filters, including singlets. As is known, a singlet block comprises one resonator coupled to source and load plus an additional coupling between source and load. In this way, a pole-zero pair is produced, thus allowing the introduction of a transmission zero in the frequency response. Structure making that uses cascaded singlets (especially implemented in waveguide technology) has been successfully used to realize compact and quasi-in-line pseudoelliptic filters. The design of this configuration suffers, however, from a severe drawback; while an isolated singlet can be exactly synthesized, when these blocks are put in cascade, nonresonating nodes (NRNs) are required to allow the cascade connection. Consequently, the resulting topology includes both cross couplings and NRNs, for which no exact synthesis solution is till now available (all the design solutions proposed in the literature are based on optimization). The new design procedure here proposed overcomes this drawback, allowing the synthesis of the equivalent circuit of the cascaded-singlet topology. Once this circuit is obtained, the dimensioning of the singlets can be carried out by exploiting a full-wave simulator according to the procedure described in the article. The proposed design approach allows a very accurate initial dimensioning of the filter, which represents an excellent starting point for final adjustments/optimizations. A detailed design example is presented in the article showing how to practically implement the novel procedure. This new approach is also experimentally validated by a waveguide filter prototype, previously designed by optimization and fabricated. It is shown how this filter can be redesigned with the novel procedure, obtaining very similar physical dimensions in a noticeably shorter time.

Design of Waveguide Filters With Cascaded Singlets Through a Synthesis-Based Approach