диафрагмированные волноводные фильтры / 5b8cb2a9-231d-4b32-b483-d472e0242d21

compression. It was also demonstrated that the multiband behavior of the Koch fractal is not unique to its total self-similar fractal geometry. As a function geometry and total wire length, antennas with other geometries can exhibit similar multiband behavior independent of differences in the antenna geometry and total wire length. Finally, from a practical perspective, it should be noted that in the upper frequency bands, the operating bandwidths are very narrow and the antennas become large with respect to the operating wavelength.

REFERENCES

1.C. Puente, J. Romeu, R. Pous, X. Garcia, and F. Benitez, Fractal multiband antenna based on the Sierpinski gasket, Electron Lett 32 (1996), 1–2.

2.C. Puente, J. Claret, F. Sagues, J. Romeu, M.Q. Lopez-Salvans, and R. Pous, Multiband properties of a fractal tree antenna generated by

electrochemical deposition, Electron Lett 32 (1996), 2298 –2299.

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multiband fractal antennas, Electron Lett 37, (2001), 1150 –1151.

5. C. Puente, J. Romeu, R. Pous, J. Ramis, and A. Hijazo, Small but long Koch fractal monopole, Electron Lett 34, (1998), 9 –10.

6.C. Puente-Baliarda, J. Romeu, and A. Cardama, The Koch monopole: A small fractal antenna, IEEE Trans Antennas Propagat 48 (2000), 1773–1781.

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8.S.R. Best, On the performance properties of the Koch fractal and other bent wire monopoles, accepted for publication, IEEE Trans Antennas Propagat.

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©2002 Wiley Periodicals, Inc.

NOVEL PERIODICALLY LOADED MULTILAYER RESONATORS

Laleh Lalehparvar,1 George Goussetis,1 and Djuradj Budimir1

1 Wireless Communications Research Group

Department of Electronic Systems

University of Westminster

London, W1W 6UW, UK

Received 5 June 2002

ABSTRACT: In this paper novel 3D periodic multilayer structures are investigated in MIC technology, and a periodically loaded multilayer waveguide resonant structure is proposed. This is a very compact structure and still maintains simple fabrication process. The resonator is designed at 10 and 28 GHz. The simulated results of this resonator, which is obtained from commercial FEM software package HFSS, are confirmed by experimental results. The experiments are based on the same resonator structure, only at 10 GHz. By modifying the conventional waveguide resonator, with the proposed structure, a minimum 30% shorter resonator can be achieved, which is very important in filter applications. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 35: 374 –375, 2002; Published online in Wiley InterScience (www. interscience.wiley.com). DOI 10.1002/mop.10611

Figure 1 Configuration of the proposed periodic multilayer resonator waveguide

Key words: waveguides; resonators; multiplayer structures; periodic structures

1. INTRODUCTION

The steady growth in commercial interest in millimiter-wave and submillimiter wave applications, especially in wireless communications, security and sensory applications, and military and transport electronics, has provided a significant challenge to conventional microwave circuits and their design methodologies. Highperformance narrowband bandpass filters exhibiting high selectivity, low insertion loss, compact physical size, and low fabrication cost are important components to many microwave systems. Compact low-cost waveguide filters with high selectivity is therefore becoming an area of particular interest [1, 2].

Resonators are fundamental filter elements. They determine to a large extent the filter’s electrical and physical properties. The compactness of resonators is an important fact to consider in filter design, since a smaller-size resonator will reduce the overall size of the filters. High quality resonators are also essential for narrowband low-loss filters. This paper presents a novel compact waveguide resonator structure, which is an excellent candidate for bandpass waveguide filter elements. The proposed resonator waveguide structure is then compared to the conventional E-plane resonator in order to demonstrate the reduced size of the first. The simplicity of the physical configuration allows the commercial FEM software package (HFSS) to be used in the simulation of this novel structure. The structure is then fabricated and measurements are presented to confirm the simulation results.

Figure 2 Transmission coefficient for the novel resonator with different number of patches

Figure 3 Simulated transmission coefficient for the novel resonator at 28 GHz

2. CONFIGURATION

The proposed resonant structure, shown in Figure 1, consists of a block of dielectric, which is transveresely inserted inside a rectangular waveguide. Four transverse periodic metallic E-plane patches are present on either side of the dielectric block. The dielectric, which has r 2.2 and L 4.1 mm, supports these metallic patches. The space between the dielectric block and input and output of the waveguide is filled with air. The proposed configuration still remains simple and further minutrisation of the proposed resonator can be achieved upon use of high-permitivity, low-loss dielectric material.

The effect of number of metallic patches on the selectivity of the resonator is also investigated here. In order to do this, three resonators with almost equal metalisation area, but distributed in a different number of patches, are designed and simulated.

3. SIMULATED AND EXPERIMENTAL RESULTS

Figure 2 shows the responses for three resonators with almost equal metalisation area, but distributed in different number of patches. As shown, the selectivity is improved by increasing the number of patches. This fact is expected, since for larger number of patches, the stronger periodicity the grid has.

The simulated transmission soefficient responses of the proposed waveguide resonant structure at 28 GHz and 10 GHz are shown in Figures 3 and 4 respectively. For the validatation of the results, the novel resonator, a X-band prototype with four patches was built and tested. The resonator has been realised as a cascade of microstrip (PCB) blocks. The dielectric block is cut and mounted transversely in the waveguide housing. On either side of the block four periodic E-plane metal patches are mounted. Figure 5 shows measured transmition coefficient of the prototype at 10 GHz. There is good agreement between simulated and experimental transmition coefficients. As expected, the selectivity of the fabricated prototype is slightly worse than that of the simulated.

Figure 5 Measured transmission coefficient for the fabricated prototype at 10 GHZ

This is mainly due to inaccuracies at the mounting of the structure in the waveguide housing.

4. CONCLUSION

A compact novel periodic multilayer resonator has been presented. Its structure consists of a dielectric block, which is transversely placed inside a waveguide. The block supports periodic E-plane metallization patches. This structure results in the development of lightweight and compact filter elements. Also, a minimum 30% shorter resonator can be achieved by using this structure. This is very important for filter applications. Experimental and simulated results have been presented to verify the performance of the novel structure. The proposed resonators are excellent candidates for bandpass waveguide filters’ elements.

REFERENCES

1.C. Kyriazidou, H. Contopanagos, and N. Alexopoulos, Monolithic waveguide filters using printed photonic-bandgap materials, IEEE Trans Microwave Theory Tech MTT-49 (2001), 297–307.

2.R. Seager, J. Vardaxoglou, and D. Lockyer, Close coupled resonant aperture inserts for waveguide filtering applications, IEEE Microwave Wireless Components Lett 11 (2001), 112–114.

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8.G. Goussetis, D. Budimir, and J. Helszajn, Upper and lower bounds of 180° unit element of a ridge waveguide: Calculations and measurements, Microwave Opt Tech Lett 31 (2001), 260 –261.

© 2002 Wiley Periodicals, Inc.