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In this letter, high-selective bandpass filters, in the printed ridge gap waveguide technology, are presented. The filters are designed to perform 4.68% fractional bandwidth at center frequency $f_{0}$ = 24.78 GHz. In the proposed filters, to obtain high selectivity, a cross-coupling between the nonadjacent resonators and also a coupling between the input and output ports to create an extra pair of transmission zeros in the transfer function of the filters are used. Finally, the filters are fabricated, and their scattering parameters are measured to verify the simulation results. [ABSTRACT FROM AUTHOR]

The Crank-Nicolson finite-difference timedomain (CN-FDTD) method is used for the linear analysis of a field-effect transistor (FET) based on the distributed model, wherein the FET is considered as an active multiconductor transmission line (AMCTL). The telegrapher's equations governing the AMCTL are derived and discretized by the CN-FDTD method. The results are compared with measurements and the leapfrog (LF)-FDTD method. Unconditional stability of the CN scheme is investigated. Agreement with measured results is preserved in an acceptable level even by increasing the time step-size by a factor of 1500 to that of the LF-FDTD method. [ABSTRACT FROM AUTHOR]

The Crank–Nicolson (CN) version of the finite-difference time-domain (FDTD) method is applied to the analysis of multiconductor transmission lines (MCTLs). Stability and dispersion issues are investigated for different cases, including single and multiconductor lossless and lossy lines. It is shown that for MCTLs, stability of the CN-FDTD method is conditioned by the structure of coupling matrices. Sufficient conditions for unconditional stability are derived. Four practical problems are analyzed using the CN-FDTD method and the results are compared to measurements and Leap-Frog method. For the first three cases, it is observed that using the CN method, the Courant number can be increased by the factor of 50 with good agreement with measurement results. [ABSTRACT FROM PUBLISHER]