диафрагмированные волноводные фильтры / 7ac24dac-8583-47af-9e58-830329e600de
.pdfCompact S-shaped Resonator Loaded Waveguide Bandpass Filters
N. Suntheralingam, and D. Budimir
Wireless Communications Research Group, School of Electronic Engineering, Computer Science and Informatics, University of Westminster, London,
WI W 6UW, United Kingdom E-mail: d.budimir@westminster.ac.uk
Introduction
The fast growth in commercial interest in microwave and millimeter wave systems has provided a significant challenge to conventional microwave filter and their design methodologies. High performance bandpass filters having a low insertion loss, compact size, wide stopband and a high selectivity are important for next-generation wireless and satellite communications systems. [1]-[2]. Over the past few decades all-metal inserts placed in the E-plane of a rectangular waveguide have been a sustainable solution for robust, low-cost, mass producible, low loss and high power filters at microwave and millimeter-wave frequencies. However, despite their favorable performances, the attenuation in the second stopband may often be too low and too narrow for diplexer and multiplexer applications.
In recent years, a number of approaches have been proposed in order to improve stopband performance of rectangular waveguide bandpass filters [4]-[5]. The MIT group [6]-[7] proposed the S-shaped resonators. In [8] we investigated a new class of waveguide resonator structure using S-shaped resonators. By employing S- shaped resonators we are changing cutoff frequency of the conventional waveguide resonator and achieving a higher loaded Q with shorter resonator length. This is due to the slow-wave effect; the phase velocity and the guided wavelength of the slow wave are significantly reduced relative to those of a wave propagating in a comparable homogeneous resonator structures. Hence the length of a half wavelength resonator is accordingly reduced. The proposed bandpass filter structure consists of all-metal-insert S-shaped resonators to achive low-cost, mass-producible and compact filters with improved stopband performance.
This paper therefore proposes for replacement of the conventional section of rectangular waveguide E-plane filters with the respective all- metal-insert S- shaped resonator loaded structures. These structures while improving the stopband performance and compactness, maintain the low-cost and massproducible characteristics of split-block metal insert E-plane technology.
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The electromagnetic analysis of the proposed metamaterial based S-shaped resonator loaded filter structure is conveniently based on the finite element method (HFSS™) [9]. In order to derive the design procedure for the proposed type of the filter, the propagation characteristics of the slow wave, such as the guided wavelength or phase velocity need to be determined. These in tum are determined by geometrical parameters, namely the gaps and the lengths. The gaps can be chosen arbitrarily. The periodicity lengths, together with the chosen gaps will effectively determine the wavelength; this in tum should determine the length Ires. Dimensions of the proposed filter at 9.45GHz are given in Table I. The proposed filter has its total structure length of 39 mm with Ires of 12 mm.
Parameters (mm)
Waveguide dimensions (WG16) |
22.86 * 10.16 |
Total structure |
39 |
length (~ |
|
Ires |
12 |
Metallization thickness |
0.1 |
Table I. Dimensions of the proposed filter structure
Conclusion
A novel class of E-Plane, all-metal-insert filter structure with improved stopband performance and compactness using S-shaped resonators has been proposed. The structure can be easily realized with a metal insert within a standard rectangular waveguide. The proposed waveguide bandpass filter has been designed and simulated at 9.45 GHz. The proposed structure maintains the low-cost and mass producible characteristics of E-plane filters while achieving significant size reduction.
References
[1]Vicente E. Boria and Benito Gimeno, "Waveguide Filters for Satellites" IEEE Microwave Magazine, Vo1.8, Issue 5, pp.60-70, October 2007.
[2]Ian C. Hunter, Laurent Billonet, Bernard larry, Pierre Guillon, "Microwave Filters-Applications and Technology" IEEE Trans. Microwave Theory Tech.,VoI.50, pp. 794-805, Mar. 2002.
[3]D. Budimir, "Generalized Filter Design by Computer Optimization", ISBN 0- 89006-579-9, Atrtech House Books, 1998.
[4]D. Budimir, "Optimized E-plane bandpass filters with improved stopband performance," IEEE Trans. Microwave Theory Tech., vol. 45, pp.212-220, Feb. 1997.
[5]G. Goussetis, and D. Budimir, " Compact Ridged Waveguide Filters with Improved Stopband Performance", IEEE MTT-S International Microwave Symposium, pp.953-956, June 8-13, 2003, Philadelphia, USA.
[6]Jingjing Zhang, Hongsheng Chen, Yu Luo , Linfang Shen , Lixin Ran, Jin Au Kong , "Wideband backward coupling based on anisotropic left-handed metamaterial" , Applied Physics Letters, Vol. 90 , No.4, pp. 043506 , January 2007.
[7]Hongsheng Chen , Lixin Ran , Jiangtao Huangfu , Xianmin Zhang , Kangsheng Chen , Tomasz Grzegorczyk , Jin Au Kong, "Left-handed Material Composed of Only S-shaped Resonators" , Physical Review E , Vol. 70 , No.5, pp. 1-4 ,November 2004.
[8]N. Suntheralingam, A. Shelkovnikov and D. Budimir, "Novel Millimetre Wave Metawaveguide Resonators and Filters", 37th European Microwave Conference, Munich, Germany, 8-12 October 2007.
[9]Ansoft HFSS, Ansoft Technologies, 2005