A design of waveguide elliptic filter based on resonant diaphragms with a complex aperture

Abstract

A novel approach to the synthesis of waveguide band-pass elliptic filters on the transverse metal resonant diaphragms with the complex aperture is proposed.The aperture of the diaphragm is considered to be a rectangular window with two L-shaped metal ridges. For the complex conductivity of the diaphragm, we solve the corresponding electrodynamic problem. We also construct and investigate an equivalent circuit of the resonant diaphragm containing a series-parallel LC circuit. The geometry of the diaphragm aperture is found to be corresponding to the parameters of the equivalent circuit. We construct a third-order elliptic filter and provide a computer simulation of the diaphragms satisfying the amplitude-frequency characteristics of its resonators. We show that some resonators can be located on one complex resonant diaphragm, which then reduces the length of the filter. The band-pass filter for a rectangular waveguide WR137 is developed and manufactured. The central frequency of the filter is 6.6 GHz, the passband width 7.5 % with return loss of −20 dB, and the total length is 34 mm. KEYWORDS circuit theory, complex aperture, computer simulation, diaphragm resonators, electrodynamic analysis, elliptic filter, microwave waveguide Int J Circ Theor Appl. 2019;47:55-64.wileyonlinelibrary.com/journal/cta

Inline Waveguide Filter With Transmission Zeros Using a Modified-T-Shaped-Post Coupling Inverter

“…Transmission zeros (TZs) are commonly exploited to increase the selectivity in bandpass filters, and they can be realized by cross couplings between nonadjacent resonators [1]- [3], by overmoded resonant cavities [4]- [6], or by frequency-variant couplings (FVCs). In waveguides, a FVC could be implemented by means of different structures, such as a single partial-height metallic post [7]- [10], a pair of closely-spaced posts [11], [12], a series or shunt stub [13], [14], or with more-complex resonant diaphrams [15]- [20]. Various synthesis procedures to design filters with FVCs have been reported in the technical literature [21]- [23].…”

A multi-function resonator based on an asymmetric tri-post rectangular waveguide section

“…Moreover, a sequence of the singlets acting as a doublet was reported in [11] as well. Later, a pseudoelliptic filter realized on the pairs of L–shaped inserts in a rectangular waveguide and in a substrate-integrated waveguide was reported in [13, 14]. In according to the nonresonating node approach proposed by Amari and Rosenberg [15, 16], a two-post-based resonator exploits the fundamental nonresonating mode bypass coupling from a source to a load in order to generate a TZ.…”

Compact Quasi-Elliptic-Type Inline Waveguide Bandpass Filters With Nonlinear Frequency-Variant Coupling Inverters

“…FVCs are commonly exploited to generate extra TZs in the stopband region of the bandpass filter while also providing the required inter-resonator coupling levels. Various methods have been proposed in the technical literature to implement and synthesize dispersive couplings for different technologies [6]- [15]. Nevertheless, in most of these approaches, each dispersive coupling produces one single TZ in the filter stopband due to its specific type of frequency-variation pattern.…”

“…Nevertheless, in most of these approaches, each dispersive coupling produces one single TZ in the filter stopband due to its specific type of frequency-variation pattern. In the case of waveguides, this frequency-variant coupling is implemented via an inverter in the form of a series- [16] or shunt-type stub [17], a single or double partial-height post [16], [18], [19], or a resonant diaphragm [6], [19]- [21]. Assuming that the coupling coefficient is a linear function of frequency, the coupling matrix of the filter can be synthesised by solving an inverse structured generalized eigenvalue problem [8], [22].…”