Abstract-In this work, we study the reflection properties of coplanar waveguides (CPW) periodically loaded with shunt connected capacitances and periodically perturbed by varying the slot width. These structures are of interest because the low pass frequency response with spurious frequency bands, inherent to the presence of capacitors, can be improved. This is achieved through the attenuation of frequency parasitics that is obtained by the introduction of slot width modulation. Both sinusoidal and square wave patterns are considered and the effects of the relative position of reactive elements with regard to the perturbation geometry is analysed. According to coupled mode theory, the central frequencies of the rejected bands in periodic transmission media are given by the spectrum of the perturbation function. However, it is demonstrated that, due to the presence of capacitors, multiple spurious bands can be simultaneously suppressed even in the case of a singly tuned (sinusoidal) perturbation geometry. This result points out that the frequency selective behaviour associated to the presence of slot width modulation can not be interpreted in the framework of coupled mode theory, since the rejection of spurious bands in periodic loaded CPWs is not merely given by the spectrum of the perturbation geometry.
2. Fernandez, M., E. Delos, X. Melique, S. Arscott, and D. Lippens, "Monolithic coplanar transmission lines loaded by heterostructure barrier varactors for a 60 GHz tripler," IEEE Microwave and Wireless Components Letters, Vol. 11, No. 12, 498-500, 2001.
3. Barker, N. S. and G. M. Rebeiz, "Distributed MEMS truetime delay phase shifters and wide-band switches," IEEE Trans. Microwave Theory Tech., Vol. 46, No. 11, 1881-1890, 1998.
4. Borgioli, A., Y. Liu, A. S. Nagra, and R. A. York, "Low-loss distributed MEMS phase shifter," IEEE Microwave and Guided Wave Letters, Vol. 10, No. 1, 7-9, 2000.
5. Carman, E., K. Giboney, M. Case, M. Kamegawa, R. Yu, K. Abe, M. J. W. Rodwell, and J. Franklin, "28-39 GHz distributed harmonic generation on a soliton nonlinear transmission line," IEEE Microwave Guided Wave Lett., Vol. 1, 28-39, 1991.
6. Edwards, T. C. and M. B. Steer, Foundations of Interconnect and Microstrip Design, third edition, John Wiley and Sons Ltd, 2000.
7. Yang, F. R., K. P. Ma, Y. Qian, and T. Itoh, "A uniplanar compact photonic-bandgap structure and its applications for microwave circuits," IEEE Trans. Microwave Theory Tech., Vol. 47, 1999.
8. Joannopoulos, J. D., R. D. Meade, and J. N. Winn, Photonic Crystals: Molding the Flow of Light, Princeton University Press, Princeton, NJ, 1995.
9. Peral, E., J. Capmany, and J. MartÃ, "Iterative solution to the Gel' Fand-Levitan-Marchenko coupled equations and application to synthesis of fiber gratings," IEEE Journal of Quantum Electronics, Vol. 32, No. 12, 2078-2084, 1996.
10. Katsenelenbaum, B. Z. and L. Mercader, M Pereyaslavets, Vol. 44, M. Sorolla, and M. Thumm, Theory of NonuniformWave guides, Vol. 44, ser. IEE Electromagn. Waves, London, U.K. IEE Press, 1998.
11. Qian, Y., V. Radistic, and T. Itoh, Simulation and experiment of photonic band-gap structures for microstrip circuits, Proc. Asia- Pacific Microwave Conf., No. 12, 585-588, 1997.
12. Radistic, V., Y. Qian, R. Coccioli, and T. Itoh, "Novel 2- D photonic band gap structures for microstrip lines," IEEE Microwave Guided Wave Lett., Vol. 8, No. 2, 69-71, 1998.
13. Kim, T. and C. Seo, "A novel Photonic bandgap structure for low-pass filter of wide stopband," IEEE Microwave Guided Wave Lett., Vol. 10, No. 1, 13-15, 2000.
14. Akalin, T., M. A. G. Laso, T. Lopetegi, O. Vanbesien, M. Sorolla, and D. Lippens, "EBG-type microstrip filtres with one and twosided patterns," Microwave and Optical Technology Lett., Vol. 30, No. 7, 69-72, 2001.
15. Lopetegi, T., M. A. G. Laso, M. J. Erro, D. Benito, M. J. Garde, F. Falcone, and M. Sorolla, "Novel photonic bandgap microstrip structures using network topology," Microwave Opt. Tech. Lett., Vol. 25, No. 4, 33-36, 2000.
16. Lopetegi, T., M. A. G. Laso, J. Hernandez, M. Bacaicoa, D. Benito, M. J. Garde, M. Sorolla, and M. Guglielmi, "New microstrip wiggly-line filters with spurious passband suppression," IEEE Trans Microwave Theo Tech., Vol. 49, No. 9, 1593-1598, 2001.
17. Radisic, V., Y. Qian, and T. Itoh, "Broad-band power amplifier using dielectric photonic bandgap structures," IEEE Microwave Guided Wave Lett., Vol. 8, No. 1, 13-15, 1998.
18. Lee, Y-T., J-S. Lim, J-S. Park, D. Ahn, and S. Nam, "A novel phase noise reduction technique in oscillators using defected ground structure," IEEE Microwave Wireless Comp. Lett., Vol. 12, No. 2, 39-41, 2002.
19. Yun, T-Y. and K. Chang, "Uniplanar one-dimensional photonic bandgap structures and resonators," IEEE Trans. Microwave Theory Tech., Vol. 49, No. 3, 549-553, 2001.
20. Fu, Y-Q., G. H. Zhang, and N. C. Yuan, "A novel EBG coplanar waveguide," IEEE Microwave and Wireless Components Lett., Vol. 11, No. 11, 447-449, 2001.
21. Sor, J., Y. Qian, and T. Itoh, "Miniature low loss CPW periodic structure for filter applications," IEEE Trans. Microwave Theory Tech., Vol. 49, No. 12, 2336-2341, 2001.
22. Pozar, D. M., Microwave Engineering, Addison Wesley, Reading, MA, 1990.
23. Lopetegi, T., M. A. G. Laso, M. J. Erro, M. Sorolla, and M. Thumm, "Analysis and design of EBG structures for microstrip lines by using the coupled mode theory," IEEE Microwave and Wireless Components Lett., Vol. 12, No. 11, 441-443, 2002.
24. Laso, M. A. G., T. Lopetegi, M. J. Erro, D. Benito, M. J. Garde, and M. Sorolla, "Multiple-frequency tuned photonic bandgap microstrip structures," IEEE Microwave and Guided Wave Lett., Vol. 10, No. 6, 220-222, 2000.