Excitation of leaky modes on multilayer stripline structures

A quasi-analytical method for calculating the excitation of leaky modes on multilayer stripline structures by a finite source is presented in this paper. Simple sources such as an infinitesimal dipole near the conducting strip or a delta-gap feed on the conducting strip of the transmission line are considered. The method uses a numerically constructed Green's function for the source in the presence of the conducting strip, which is calculated from Fourier transform theory in terms of a one-dimensional Green's function for a line source in the presence of the conducting strip. The numerical Green's function involves a one-dimensional integration in the longitudinal wavenumber plane. The residue contributions from the poles of the Green's function define the excitation amplitudes of the leaky and bound modes that exist on the structure. The numerical Green's function is also used to numerically calculate the complete current on the strip excited by the source. The correlation between the leaky-mode current and the complete current is used to define the extent of the physical meaning of the leaky mode. The generalized pencil of functions (GPOF) method is used to study this correlation by resolving the complete current on the strip into exponential waves, which are then compared with the current of the leaky mode. The physical meaning of the leaky modes is also analytically examined by consideration of the branch cuts in the longitudinal wavenumber plane for the numerical Green's function integration. A "path consistency condition" is established as a necessary condition for the physical meaning of the leaky mode.

[1]  Tapan K. Sarkar,et al.  Time-domain measurements with the Hewlett-Packard network analyzer HP 8510 using the matrix pencil method , 1991 .

[2]  H. Shigesawa,et al.  Conductor-backed slot line and coplanar waveguide: dangers and full-wave analyses , 1988, 1988., IEEE MTT-S International Microwave Symposium Digest.

[3]  David R. Jackson,et al.  Leakage of the dominant mode on stripline with a small air gap , 1995 .

[4]  David R. Jackson,et al.  Radiation from one-dimensional dielectric leaky-wave antennas , 1995 .

[5]  T. Tamir,et al.  GUIDED COMPLEX WAVES: PART I. FIELDS AT AN INTERFACE , 1963 .

[6]  Mikio Tsuji,et al.  The nature of the spectral gap between bound and leaky solutions when dielectric loss is present in printed-circuit lines , 1993 .

[7]  Rolf H. Jansen,et al.  Spectral Domain Investigation of Surface Wave Excitation and Radiation by Microstrip Lines and Microstrip Disk Resonators , 1983, 1983 13th European Microwave Conference.

[8]  Mikio Tsuji,et al.  Theory and experiments of simultaneous propagation of both bound and leaky dominant modes on conductor-backed coplanar strips , 1993, 1993 23rd European Microwave Conference.

[10]  Krzysztof A. Michalski,et al.  Rigorous analysis of open microstrip lines of arbitrary cross-section in bound and leaky regimes , 1989 .

[11]  David R. Jackson,et al.  Proper and improper dominant mode solutions for a stripline with an air gap , 1993 .

[12]  Mikio Tsuji,et al.  Dominant mode power leakage from printed‐circuit waveguides , 1991 .

[13]  M. Kahrizi,et al.  Accurate de-embedding procedure for characterizing discontinuities , 1992 .

[14]  Dennis P. Nyquist,et al.  Discrete Higher-Order Leaky-Wave Modes and the Continuous Spectrum of Stripline , 1995 .

[15]  A. A. Oliner,et al.  The Nature of the Leakage from Higher Modes on Microstrip Line , 1986, 1986 IEEE MTT-S International Microwave Symposium Digest.

[16]  D. M. Pozar,et al.  Full-wave spectral-domain computation of material, radiation, and guided wave losses in infinite multilayered printed transmission lines , 1991 .

[17]  T. Sarkar,et al.  Using the matrix pencil method to estimate the parameters of a sum of complex exponentials , 1995 .

[18]  D. Jackson,et al.  The effect of substrate anisotropy on the dominant-mode leakage from stripline with an air gap , 1995, Proceedings of 1995 IEEE MTT-S International Microwave Symposium.

[19]  R. Marqués,et al.  Integral representation of spatial Green's function and spectral domain analysis of leaky covered strip-like lines , 1995 .

[20]  A. A. Oliner,et al.  Guided complex waves. Part 2: Relation to radiation patterns , 1963 .

[21]  Mikio Tsuji,et al.  Printed-circuit waveguides with anisotropic substrates: a new leakage effect , 1989, IEEE MTT-S International Microwave Symposium Digest.

[22]  Tapan K. Sarkar,et al.  Matrix pencil method for estimating parameters of exponentially damped/undamped sinusoids in noise , 1990, IEEE Trans. Acoust. Speech Signal Process..

[23]  David R. Jackson,et al.  Existence of a leaky dominant mode on microstrip line with an isotropic substrate: theory and measurement , 1993, 1993 IEEE MTT-S International Microwave Symposium Digest.

[24]  D. P. Nyquist,et al.  Identification of propagation regimes on integrated microstrip transmission lines , 1993 .

[25]  Y. Hua,et al.  Generalized pencil-of-function method for extracting poles of an EM system from its transient response , 1989 .