диафрагмированные волноводные фильтры / 6f4fa70b-7207-4711-a4f5-dc737b60e305

Figure 5 Measured radiation patterns of the cylindrical triangular microstrip antenna at resonance; antenna parameters are the same as given in Figure 3. a. E-plane pattern, b. H-plane pattern

3. RESULTS AND CONCLUSIONS

Figure 2 shows the calculated and measured input impedance of a triangular microstrip patch antenna on a ground cylinder of radius a s 15 cm. Good agreement between theory and experiment is obtained. The results for the antennas with different cylinder radii are presented in Figure 3. It is seen that the resonant frequency increases with decreasing cylinder radius; however, the resonant input resistance decreases when the cylinder radius is decreased.

For the radiation pattern, the calculated results are shown in Figure 4. Results indicate that, with decreasing cylinder radius, the radiation pattern is slightly broadened, and the radiation in the backward direction is increased. For comparison the measured radiation patterns of the cylindrical triangular microstrip patch antenna are presented in Figure 5. Because the patch antenna in the experiment is mounted on a finite-length ground cylinder and the measurement accuracy for the relatively weak radiated field in the lower hemisphere is limited, only the radiation pattern in the upper hemisphere is measured and plotted in Figure 5. From the results it can be seen that the calculated data generally agree with measured data.

In conclusion, a full-wave analysis of a cylindrical triangular microstrip patch antenna excited at its fundamental mode has been studied. Curvature effects on the antenna characteristics have been analyzed. An experiment has also been conducted, and theoretical results are verified by the measured data.

REFERENCES

1.J. S. Dahele, R. J. Mitchell, K. M. Luk, and K. F. Lee, ‘‘Effect of Curvature on Characteristics of Rectangular Patch Antenna,’’ Electron. Lett., Vol. 23, 1987, pp. 748]749.

2.T. M. Habashy, S. M. Ali, and J. A. Kong, ‘‘Input Impedance and Radiation Pattern of Cylindrical-Rectangular and Wraparound

Microstrip Antennas,’’ IEEE Trans. Antennas Propagat., Vol. AP38, 1990, pp. 722]731.

3.S. Y. Ke and K. L. Wong, ‘‘Input Impedance of a Probe-Fed

Superstrate-Loaded Cylindrical-Rectangular M icrostrip Antenna,’’ Microwa¨e Opt. Technol. Lett., Vol. 7, 1994, pp. 232]236.

4.K. M. Luk and K. F. Lee, ‘‘Characteristics of the Cylindrical-Cir- cular Patch Antenna,’’ IEEE Trans. Antennas Propagat., Vol. AP-38, 1990, pp. 1119]1123.

5.K. L. Wong, C. Y. Huang, and Y. H. Liu, ‘‘Generalized Trans-

mission Line Model for Cylindrical-Circular Microstrip Antennas,’’ Microwa¨e Opt. Technol. Lett., Vol. 8, 1995, pp. 63]68.

6.H. D. Chen and K. L. Wong, ‘‘Input Impedance and Radiation

Pattern of a Probe-Fed Cylindrical Annular-Ring Microstrip Antenna,’’ Microwa¨e Opt. Technol. Lett., Vol. 8, 1995, pp. 152]156.

7.J. Helszajn and D. S. James, ‘‘Planar Triangular Resonators with Magnetic Walls,’’ IEEE Trans. Microwa¨e Theory Tech., Vol. 26, 1978, pp. 95]100.

8.H. R. Hassani and D. Mirshekar, ‘‘Analysis of Triangular Patch Antennas Including Radome Effects,’’ IEE Proc. Pt. H, Vol. 139, 1992, pp. 251]256.

9.K. L. Wong, Y. T. Cheng, and J. S. Row, ‘‘Resonance in a

Superstrate-Loaded Cylindrical-Rectangular Microstrip Structure,’’ IEEE Trans. Microwa¨e Theory Tech., Vol. 41, 1993, pp. 814]819.

10.S. Y. Ke and K. L. Wong, ‘‘Full-Wave Analysis of Mutual

Coupling Between Cylindrical-Rectangular M icrostrip Antennas,’’ Microwa¨e Opt. Technol. Lett., Vol. 7, 1994, pp. 419]421.

Q 1997 John Wiley & Sons, Inc.

CCC 0895-2477r97

OPTIMIZATION-ORIENTED DESIGN OF COPLANAR WAVEGUIDE BANDPASS FILTERS

D. Budimir1 and I. D. Robertson1

1 Communications Research Group

Department of Electronic and Electrical Engineering

King’s College

University of London, Strand

London WC2R 2LS, United Kingdom

Recei¨ed 3 December 1996

ABSTRACT: The design of CPW bandpass filters with electromagnetic simulations dri¨en indirectly by an equal ripple based optimizer is presented. This ¨ector procedure has se¨eral ad¨antages o¨er the general-purpose optimization routines pre¨iously applied to the design of CPW filters. The filter, which employs three resonators with a combina- tion of both edge and end coupling, has a center frequency of 23 GHz with a 1.8-GHz bandwidth and a measured insertion loss of only y3.5 dB. Q 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 15: 52]54, 1997.

Key words: microwa¨e filters; CPW transmission lines; microwa¨e inte- grated circuits

I. INTRODUCTION

Simulation software packages such as Touchstone, Super Compact, or MrFILTER provide different methods for optimization of filter elements. These methods are for general applications and do not provide the results that are required in the specific area of microwave filters. The approach presented here Figure 1. requires less frequency sampling than previous methods. This method optimizes the passband of a

filter with respect to the Chebyshev or minimax. criteria. This relates directly to the way filters are fabricated in practice. General-purpose optimization techniques w1x may not be able to satisfy filter specifications, and may even converge to local minima.

II. NUMERICAL AND EXPERIMENTAL RESULTS

In order to illustrate the new approach, a three-resonator edge-end coupled CPW bandpass filter has been designedsee Figure 2.. The filter can be described by five parameters: gaps SA, SB. and lengths L1, L2, LA., as marked in Figure 2. We used equal ripple optimization with L1, L2, LA, and SB as variables for the filter, with SA fixed at 0.074 mm. The optimization variables before and after optimization are listed in Table 1. Figure 3 dashed line. shows the calculated passband return loss of both filters with the use of the approximate method. This approximate design was used as a starting point for equal ripple optimization. The passband return loss calculated with the use of the filter dimensions obtained on convergence are shown in the same figure solid line.. For the electromagnetic analysis of the CPW discontinuities, em Sonnet. w4x was used throughout the optimization. The filter was designed to illustrate the accuracy of the developed method. Figure 4 solid line. shows the calculated insertion loss of the final design of the filter. Also included in this figure dashed line. is a plot of the measured insertion loss of the fabricated design. Across the passband the final measured insertion loss is better than y3.5 dB. Part of the increased insertion loss may be attributed to the dimensional variations in the layout that occur when the gold is etched. The designed filter was fabricated with the use of CPW transmission lines on an alumina substrate. The thickness and dielectric constant of the substrate are 0.635 and 9.9 mm, respectively. A very good agreement between theory and experiment was observed. The filter was tested with the use

TABLE 1 Parameter Values for the CPW Bandpass Filter Before and After Optimization

Figure 4 Measured dashed line. and calculated solid line. insertion loss of the filter

of a Cascade wafer probe connected to a HP8510 network analyzer.

III. CONCLUSIONS

A computer-aided design procedure for the accurate design of CPW bandpass filters has been developed. An equal ripple approach to optimization is adopted. This approach has the following advantages over the general-purpose optimization techniques adopted previously:

1.The problem of local minima does not arise.

2.Optimization is carried out with respect to the Chebyshev or minimax. criteria.

3.Less frequency sampling and therefore less calculation of the S parameters of the CPW discontinuities is required.

4.Optimization is usually only required for the passband.

The electromagnetic analysis of the discontinuities in CPW bandpass filters presented in this article has been performed with the use of em Sonnet..

ACKNOWLEDGMENT

The support provided by the EPSRC UK is gratefully acknowledged.

REFERENCES

1.J. W. Bandler and S. H. Chen, ‘‘Circuit Optimization: The State of the Art,’’ IEEE Trans. Microwa¨e Theory Tech., Vol. MTT-36, 1988, pp. 424]443.

2.V. Postoyalko and D. Budimir, ‘‘Design of Waveguide E-Plane

Filters with All-Metal Inserts by Equal-Ripple Optimization,’’

IEEE Trans. Microwa¨e Theory Tech., Vol. MTT-42, Feb. 1994, pp. 217]222.

3.D. Budimir, Software Package DBFILTER, London, 1996.

4.em User’s Manual, Sonnet Software, Liverpool, NY, May 1992.

Q 1997 John Wiley & Sons, Inc.

CCC 0895-2477r97

APPLICATION OF COORDINATE-FREE EFFECTIVE MEDIUM THEORY TO PERIODICALLY PLANE-STRATIFIED ANISOTROPIC MEDIA

A. V. Lavrinenko1 and V. V. Zhilko1

1 Department of Theoretical Physics

Belorussian State University

4 Scoriny Avenue

Minsk 220050

Recei¨ed 17 October 1996

ABSTRACT: The effecti¨e tensors of permitti¨ity and permeability for multilayer anisotropic media are obtained. All expressions are written in a direct coordinate-free manner. The theory is illustrated by examples with particular systems of layers. Complete agreement with formulas obtained by other methods is shown. Q 1997 John Wiley & Sons, Inc.

Microwave Opt Technol Lett 15: 54]57, 1997.

Key words: effecti¨e medium; anisotropic medium; periodic medium; electromagnetic wa¨e propagation