Resonator-Loaded Waveguide Notch Filters with Broad Tuning Range and Additive-Manufacturing-Based Operating Frequency Adjustment Procedure

Abstract

This article presents a new class of ring-resonator-loaded waveguide notch filters with a broad tuning range, low cost, and improved performance. The proposed approach employs a complementary asymmetric split-ring resonator coupled to a microstrip transmission line and excited in a rectangular waveguide. An equivalent circuit model is proposed to explain the working principle of the proposed notch filter. The adjustment of the operating frequency is based on the additive manufacturing of a metallic copper patch allocated on the microstrip transmission line, which enables extensive tuning capabilities and consistent performance with minimum variations across the tuning window. For demonstration purposes, a filter employing a WR-28 waveguide and photolithography-manufactured resonator is prototyped and experimentally validated. The measured results indicate a broad 8 GHz tuning range with a consistent insertion loss, ranging from 23.4 to 31.4 GHz. An inverse regression model is constructed using measurement data obtained for tuning patches of various sizes, which allows for determining the relationships between the operating frequency and the copper patch size. The resulting calibration curve enables rapid filter tuning to the required frequency by inserting metallic patches of the model-predicted size.

Three-Dimensional Meso-Structure-Based Model for Evaluating the Complex Permittivity of Asphalt Concrete

“…The asphalt content and aggregate gradation in these specimens were ke As shown in Figure 11a, the real part of the complex permittivity tends to be smaller when more coarse aggregates are replaced with fine aggregates. The main reason for this trend is that the absorption and loss capacity of coarse aggregates are stronger than those of fine aggregates, which is consistent with the findings reported in the previous literature [36]. At the same time, Figure 11b shows that the increase in fine aggregate content could also decrease the imaginary part of the complex permittivity.…”

High-Precision Calculation Using the Method of Analytical Regularization for the Cut-Off Wave Numbers for Waveguides of Arbitrary Cross Sections with Inner Conductors

“…After substituting (22) in ( 18) and (19), we arrive at the final form of the equations to be solved, being a coupled ISLAE where the index m runs over m = 1, 2, 3, . .…”

“…The three requirements outlined above are important in practical applications. An example occurs in the publication [22] in which the design of a class of ring-resonator-loaded waveguide notch filters depends upon an accurate determination of the cut-off wavenumbers in the waveguide. Recognizing the practical significance of the calculations, appearing in numerous publications, of cut-off wavenumbers for waveguides with variously shaped outer and inner conductors, there is a need to develop a universal and accurate instrument for providing the ultimate estimate of the correctness of such calculations.…”

Establishment and Application of Recursive Digital Processing Algorithm with Difference Analysis-Based Parameter Setting and Difference Feedback

“…2 filters [7], notch filters [8], etc. ), adaptive filters [9], wavelet transforms [10], Empirical Mode Decomposition [11], methods based on neural networks [12], and machine learning algorithms [13,14].…”