In this paper spatial-band pass filters consisting of frequency selective surfaces (FSSs) are designed in order to realize both the desired transfer function of the filter in the frequency domain and drastic size reduction. Each FSS is made of aperture elements and patch elements. In this design method, the shape of each FSS is designed by a genetic algorithm (GA) so that the resonant curve of each FSS fits to the resonant curve which can be obtained from an equivalent circuit approach. By locating these designed FSSs at the intervals of quarter wavelength a spatial band pass filter is realized. Furthermore, a technique which controls the frequency response of each FSS has been applied to reduce the longitudinal size of filter. By this technique the FSSs are located at the intervals which are much shorter than a quarter wavelength, keeping the desired transfer function. Through a designed example it is shown that the half longitudinal length of a typical spatial filter can be obtained without any additional structure. Magnetic type spectral domain dyadic Green's functions are derived, and the characteristics of a spatial band-pass filter are calculated by means of the coupled magnetic filed integral equation which accurately takes higher order mode interactions. Derived linear matrix equations are solved using method of moment (MoM). The effectiveness of the proposed structure and its performance are verified and validated by designing and simulating an equal ripple spatial band pass filter at X-band.
2. Kern, D. J. and D. H. Werner, "A genetic algorithm approach to the design of ultra-thin electromagnetic band-gap absorbers," Microwave Opt. Technol. Lett., Vol. 38, No. 1, 61-64, Jul. 2003.
3. Kern, D. J., D. H. Werner, M. J. Wilhelm, and K. H. Church, "Genetically engineered multi-band high impedance frequency selective surfaces," Microwave Opt. Technol. Lett., Vol. 38, No. 5, 400-403, Sep. 2003.
4. Chen, C., "Scattering by a two-dimensional periodic array of ducting plates," IEEE Tran. Antennas Propagation, Vol. 18, 660-665, Sep. 1970.
5. Abbaspou, A., K. Sarabandi, and G. M. Rebeiz, "Antenna-filter-an-antenna arrays as a class of band pass frequency selective surfaces," IEEE Trans. Microw. Theory Tech., Vol. 52, No. 8, 1781-1789, Aug. 2004.
6. Pous, R. and D. M. Pozar, "A frequency-selective surface using aperture coupled micro-strip patches," IEEE Trans. Antennas Propagation, Vol. 39, No. 12, 1763-1769, Dec. 1991.
7. Ohira, M., H. Deguchi, M. Tsuji, and H. Shigesawa, "Multi band single-layer frequency selective surface designed by combination of genetic algorithm and geometry-refinement technique," IEEE Trans. Microw. Theory Tech., Vol. 52, No. 11, 2925-2931, Nov. 2004.
8. Zhang, Y. L., W. Hong, K. Wu, J. X. Chen, and H. J. Tang, "Novel substrate integrated waveguide cavity filter with defected ground structure," IEEE Trans. Microw. Theory Tech., Vol. 53, No. 4, 1280-1287, Apr. 2005.
9. Hao, Z. C., W. Hong, J. X. Chen, X. P. Chen, and K. Wu, "Compact super wide band pass substrate integrated waveguide filters ," IEEE Trans. Microw. Theory Tech., Vol. 53, No. 9, 2968-2977, Sep. 2005.
10. Luo, G. Q., W. Hong, H. J. Tang, and K. Wu, "High performance frequency selective surface using cascading substrate integrated waveguide cavities," IEEE Microwave and Wireless Components Letters, Vol. 16, No. 12, Dec. 2006.
11. Yakovlev, A. B., A. I. Khalil, C. W. Hicks, A. Mortazawi, and M. B. Steer, "The generalized scattering matrix of closely spaced strip and slot layers in waveguide," IEEE Trans. Microw. Theory Tech., Vol. 48, No. 1, 126-137, Jan. 2000.
12. Hill, A. and V. K. Tripathi, "An efficient algorithm for the three-dimen-sional analysis of passive microstrip components and discontinuities for microwave and millimeter-wave integrated circuits," IEEE Trans. Microw. Theory Tech., Vol. 39, No. 1, 83-91, Jan. 1991.
13. Ohira, M., H. Deguchi, M. Tsuji, and H. Shigesawa, "Novel waveguide filters with multiple attenuation poles using dual-behavior resonance of frequency-selective surfaces," IEEE Trans. Microw. Theory Tech., Vol. 53, No. 11, 3320-3326, Nov. 2005.
14. Itoh, T., "Spectral domain immitance approach for dispersion characteristics of generalized printed transmission lines ," IEEE Trans. Microw. Theory Tech., Vol. 28, No. 11, 733-736, Jul. 1980.
15. Schmidt, L. P. and T. Itoh, "Spectral domain analysis of dominant and higher order modes in fin-lines," IEEE Trans. Microw. Theory Tech., Vol. 28, No. 11, 981-985, Sep. 1980.
16. Chan, C. H., K. T. Ng, and A. B. Kouki, "A mixed spectral-domain approach for dispersion analysis of suspended planar transmission lines with pedestals ," IEEE Trans. Microw. Theory Tech., Vol. 37, No. 11, 1716-1723, Sep. 1989.
17. Amari, S., J. Bornemann, and R. Vahldieck, "Fast and accurate analysis of waveguide filters by the coupled integral equations technique ," IEEE Trans. Microw. Theory Tech., Vol. 45, No. 9, Sep. 1997.
18. HFSS Release 10.0, Ansoft Corp., 2003.