Direct-coupled waveguide filters for the lower gigahertz frequency range

Abstract

An analysis method based on the coupled-integral-equations technique (CIET) and the mode-matching technique (MMT) is presented for the design of a variety of directcoupled waveguide filters suitable for applications in the lower gigahertz frequency range. The method is verified by comparison with data obtained through other numerical techniques and measurements. With reference to standard waveguide filters, the issues of filter miniaturization and stopband extension toward higher frequency bands are investigated. For given frequency specifications in the 2-GHz frequency range, examples of rectangular coaxial waveguide filters, ridge waveguide filters, ridge waveguide filters including coupling irises and T-septum waveguide filters are presented. It is demonstrated that the rectangular/square coaxial waveguide filter achieves the highest degree of miniaturization, but that ridge and, especially, T-septum waveguide filter technology is advantageous with respect to stopband performance toward higher frequencies. In particular, a T-septum filter centered at 2.155 GHz is shown to block the entire frequency range up to 7.5 GHz. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12: 217-225, 2002.

Classical eigenvalue mode‐spectrum analysis of multiple‐ridged rectangular and circular waveguides for the design of narrowband waveguide components

“…Such cases have always caused problems in mode-search algorithms that require a system determinant to vanish, e.g. [3][4][5][6][7][8][9][10][11][12][13].…”

“…Such cross sections typically include a variety of ridges in either rectangular enclosure, e.g. multiple-ridged waveguides [1][2][3][4][5][6], T-septum waveguides [6][7][8][9], L-shaped waveguides [10], trough waveguides [11], or in circular housings, e.g. multiple-ridged circular waveguides [1,5,[12][13][14][15], and corrugated circular waveguides [16,17].…”

“…[3][4][5][6][7][8][9][10][11][12][13]15], which leads to a singular-value problem requiring the system determinant or, alternatively, the smallest singular value to vanish [9]. However, this method has several disadvantages.…”

Broadband rectangular‐to‐ridge‐to‐T‐septum waveguide transformers

“…The final design step consists of two stages in which an MMT routine similar to that of [13] and an optimization strategy [15] are used. In the first optimization run, only the section lengths are optimized.…”

“…For given constant ridge s and T-septum thickness t, the gap width g (for a ridged section) and the width w (for a T-septum waveguide section) are designed to match the individual section's impedances. This is performed with a 2D routine based on the modematching technique (MMT) and subdomain basis functions [13]. As long as the impedance can be achieved with g i Ն g Nϩ1 , the respective section will be a ridge waveguide.…”