Abstract-It is proposed that the application of defected ground structures (DGS) and electromagnetic bandgap (EBG) reduce the phase velocity, increase effective permittivity of microstrips and reduce the effective the wavelength which eventually lead to the reduction of overall length of Wilkinson power dividers. Furthermore, the adjacent strip lines may approach each other, which cause coupling problems. The undesired coupling maybe cancelled by connecting a capacitance in parallel with the isolation resistor of Wilkinson power divider. Application of DGS and EBG will not only reduce the dimensions of the divider, but also improves its scattering parameters.

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Abstract-The method of least squares (MLS) is used to develop an algorithm for the optimum design of any type of filter under any design specifications for the realization of lowpass, bandpass, highpass and bandstop characteristics. The proposed filter design method can be used for any general filter network topology, which provides high flexibility for the selection of circuit configurations suitable for any desired application. The MLS filter design procedure also incorporates source and load impedance matching, which eventually leads to the simplicity of circuits. The proposed method of filter design may be used for lowpass prototype filters or directly for bandpass, highpass or bandpass filters. Several examples of MLS filter designs are given, which compare very well with the classical methods and indicate the advantages of the proposed method of filter design. The MLS filter design may realize any frequency response characteristics, such as spurious response elimination, multiband filter realization and enhancement of some desired behaviors.

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