20 Balasubramanian and Pramanick

Figure 8. Comparison of stopband characteristics between the uniform and mixed-width filter structures; 25 and 20 mm: w1 s w5 s 9.950 mm, w2 s w4 s 6.208 mm, w3 s 5.856

mm, lR1 s lR 4 s 19.219 mm, lR 2 s lR 3 s 17.376 mm, a1 s a4 s 20 mm, a2 s a3 s 25 mm; 25 and 19 mm: w1 s w5 s 10.145, w2 s w4 s 6.222 mm, w3 s 5.768 mm, lR1 s lR 4 s 16.041

mm, lR2 s lR 3 s 22.383 mm, a1 s a4 s 25 mm, a2 s a3 s 19 mm.

quired to obtain a filter with a satisfactory performance.

The designed filters produced satisfactory performance without the application of an optimization procedure which is very time consuming. Hence, the design technique is very fast. The time required for designing a 4-pole filter was 1 min in a Sun Sparcstation-20 workstation when 50 modes are used for the characterization of the discontinuity.

4. CONCLUSIONS

A computer-aided design technique for the accurate design of H-plane bandpass filters with improved stopband performance has been developed. Improvement of the stopband behavior is possible by increasing or by using a combination of increasing and decreasing of the waveguide width within the resonator sections. The reduction of the cutoff frequency of the resonators increases the frequency spacing between the first and the second passband. Because the computeraided design procedure is based on the mode matching method, higher order mode coupling effects at all discontinuities are accurately taken into account. The examples of the H-plane waveguide bandpass filters designed with an increased-width and mixed-width waveguide section demonstrate the excellent stopband behavior of this class of filters. Postproduction tuning may

be completely eliminated as the design is accurate and the filters designed are compact in size.

ACKNOWLEDGMENTS

Financial support for this work from Natural Sciences and Engineering Research Council, Canada is gratefully acknowledged.

REFERENCES

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CAD of Tapered Wa¨eguide Bandpass Filters 21

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BIOGRAPHIES

Raju Balasubramanian received his B. E. degree in Electrical Engineering from the Government College of Technology, Coimbatore, India in 1994 and his M.Sc. degree in Electrical Engineering from the University of Saskatchewan, Saskatoon, Canada in 1997. He is currently a Senior Engineer in the Compact Software division of Ansoft Corporation.

Protap Pramanick obtained the BTechHons. degree in electronics and telecommunication engineering from the Indian Institute of Technology, Kharagpur, in 1977 and the PhD degree in microwave engineering from the Indian Institute of Technology, Kanpur, in 1982. In the same year he joined the Department of Electrical Engineering, Univer-

sity of Ottawa, Canada, as a postdoctoral fellow. In 1984 he joined the Canadian Marconi Co., Ottawa, as a senior design specialist in the Avionics Division. In April 1986, he joined Com Dev Ltd., Cambridge, Ontario. Since July, 1992 he has been working as an associate professor in the Department of Electrical Engineering, University of Saskatchewan, Saskatoon, Saskatchewan, Canada. Dr. Pramanick is the CEO of Polar Waves Consulting PWC.. PWC currently provides services to Motorola and Ericsson and many other companies. Dr. Pramanick holds several patents on filters for cellular radio and he has published extensively in the area of microwave integrated circuits. He coedited the book, E-Plane Integrated Circuits Artech House, 1987., contributed to the books, Topics in Millimeter Wa¨e Technology Academic Press, 1988., Microwa¨e Solid State Circuit Design Wiley Interscience, 1988., and Handbook of Microwa¨e Engineering

Academic Press, 1995.. He is on the editorial review board of

IEEE Transactions on Microwa¨e Theory and Techniques and the International Journal of RF and Microwa¨e Computer-Aided Engineering.