диафрагмированные волноводные фильтры / 4a45b95b-c7d2-4e73-8f0e-06816709ad5f

Waveguide Filters Based on Conventional and Complementary Split Ring Resonators for Microwave and Millimetre-wave Wireless Applications

Suntheralingam Niranchanan, Djuradj Budimir and F. Kamal Wireless Communications Research Group, University of Westminster 115 New Cavendish Street, London, W1W 6UW, UK

Introduction

Modern ways of research and development in telecommunications today are led by customer demands for mobile, robust and convenient information services at any place and at any time. As a result in microwave systems, mass production suited low-cost passive devices are widely required in order to build the essential components of the communication systems. High performance narrow-band bandpass filters having a low insertion loss, compact size, wide stopband and a high selectivity are important for next-generation wireless systems. At present most filters at microwave and mm-wave frequencies are produced either in waveguide (air-filled metal pipe, dielectric-filled or micromachined air-filled) with high associated machining costs, image guide and nonradiative dielectric guide with high associated loss [1,2,3]) or using dielectric resonators although they are less compatible with modern MMIC technology, especially when one is concerned about convenient and efficient integration with active devices or using planar technologies (microstrip, suspended substrate stripline and coplanar waveguide) [4,5].

Over the past few decades rectangular waveguides have been a sustainable solution used to design robust, low loss and high power circuits at microwave and millimeter-wave frequencies. In the filter structures, which are viable to meet requirements of the modern technology [1], reduction of the physical size has become one of the primary goals. Recently proposed concepts of left-handed medium (LHM) have become the subject of extensive investigations due their capability to provide novel unconventional properties to different propagation media [2]-[4]. This approach makes use of the left-handed medium created by a novel type of resonance elements, Split Ring Resonators (SRRs), in combination with the thin metal wireline [4]. These are printed on the dielectric slab, which is then inserted into the plane of symmetry of the rectangular waveguide. These structures are able to alter the electromagnetic boundary conditions of the surface and prohibit propagation of signal in a certain frequency band. Thus, the traditional miniaturization techniques, which commonly employ dielectric-filled waveguides with standard dimensions bound to the wavelength (λ), may be enhanced to achieve more compact high-performance waveguide components.

This paper demonstrates the use of the left-handed properties imposed by SRRs in order to achieve miniaturization of rectangular waveguide filters. Analysis and design of the SRR-loaded bandpass filters are presented. Simulated results demonstrate feasibility of the proposed structures.

Proposed Filter Structures

The proposed metawaveguide SRR filter structures are shown in Figure 1. These SRR-loaded waveguide bandpass filters are realized as a cascade of the resonator unit cells. The transmission line is loaded with the slab of a composite material, which conveniently facilitates both split ring resonators with the metal septa on the top of the plane. Three different configurations are designed and the simulated results are given below. In the filter1 the SRRs are etched on both sides of the dielectric block and filter2 is single sided and the it is a Complementary Split Ring Resonator (CSRR) configuration, both are characterised by the following parameters. The dielectric which has relative dielectric permittivity of 2.2, thickness of 1.0 mm supports this SRR and metallisation thickness of 0.0017 mm. Standard rectangular waveguide (WG-16: a = 22.86 mm, b = 10.16 mm) has been used as a housing to fit a 1.0 mm thick dielectric slab. In filters3&4 the standard rectangular waveguide (WG-25: a=3.759 mm, b=1.88 mm) has been used as a housing to fit 0.510 mm thick three dielectric slabs two of them for the walls of the waveguide and the other in the middle for filter3 and two dielectric slabs of the same thickness for the walls and metal septa in the middle for filter4. As shown in the Figure 1, the rings are etched both in the side walls and in one side of the middle dielectric.

Filter4 configuration

Filter3 configuration

Fig. 1. Configurations of the proposed waveguide filter structures

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Table I. Dimensions of the SRR-loaded bandpass filter configurations

Simulation Results

In order to validate the argument made these filter structures has been designed and simulated. Figures 2 and 3 show the simulated S-parameter responses in X-Band for the filter configurations 1 and 2 respectively. The simulated return loss and insertion loss of the proposed waveguide filter3 at 59 GHz and filter4 at 65 GHz are shown in Figures 4 and 5, respectively.

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Conclusion

Four different novel split ring resonator (SRR) loaded rectangular waveguide bandpass filter structures have been presented. Configurations for the filters1&2 are simulated at X–band and filters3&4 at V-band. These kind of band pass filters are expected to find applications particularly in the mm-wave, submm-wave and terahertz range circuits, e.g. in highly selective diplexers and multiplexers.

References:

[1]V. Postoyalko, and D. Budimir, "Design of Waveguide E-plane Filters with All-Metal Inserts by EqualRipple Optimization," IEEE Trans. Microwave Theory & Tech., vol. MTT-42, pp. 217-222, February 1994

[2]V. G. Veselago, “The electrodynamics of substances with simultaneously negative values of ε and μ,” Soviet Phys. Uspekhi, vol. 10, no. 4, pp. 509-514, Jan.-Feb. 1968

[3]J.B. Pendry, A.J. Holden, D.J. Robbins, and W.J. Stewart, “Magnetism from conductors and enhanced nonlinear phenomena,” IEEE Trans. Microwave Theory & Tech., vol. 47, no. 11, pp. 2075-2084, November 1999

[4]D. R. Smith, W. J. Padilla, D. C. Vier, S. C. Nemat-Nasser, and S. Schultz, “Composite medium with simultaneously negative permeability and permittivity,” Phys. Rev. Lett., vol. 84, pp. 4184-4187, May 2000

[5]A. Shelkovnikov, N. Suntheralingam, and D. Budimir, "Novel SRR Loaded Waveguide Bandstop Filters," IEEE AP-S/URSI Int. Symp., Albuquerque, USA,July 2006

[6]D. Budimir, "EPFIL-Waveguide E-plane Filter Design", Software and User Manual, ISBN 1-58053-083- 4, Artech House Books, 1999

[7]Ansoft HFSS, v.9.0, 2004

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