P.B. Katehi

Frequency-Dependent Characteristics of Microstrip Discontinuities in Millimeter-Wave Integrated Circuits

A theoretical approach for the representation of microstrip discontinuities by equivalent circuits with frequency-dependent parameters is presented. The model accounts accurately for the substrate presence and associated surface-wave effects, strip finite thickness, and radiation losses. The method can also be applied for the solution of microstrip components in the millimeter frequency range.

On the modeling of electromagnetically coupled microstrip antennas--The printed strip dipole

A generalized solution for a class of printed circuit antennas excited by a strip transmission line is presented. The strip transmission line may be embedded inside or printed on the substrate. As an example, microstrip dipoles electromagnetically coupled (Parasitically excited) to embedded strip transmission line have been analyzed accurately, and design graphs are provided for a specific substrate material. These graphs permit the establishment of a design procedure which yields the microstrip dipole length, overlap, offset, and substrate thickness with the goal of a desired input match for a given substrate material. The method accounts for conductor thickness and for arbitrary substrate parameter. Comparison with experiment shows excellent agreement.

Study of a novel planar transmission line

A new type of monolithic planar transmission line, the microshield line, is proposed. This line can operate without the need for via-holes or the use of air-bridges for ground equalization. Furthermore, it has shown the tendency to radiate less than the conventional microstrip or coplanar waveguide (CPW) and can provide a wide range of impedances due to the many available parameters for design. The space domain integral equation method is used to analyze four different discontinuities of the proposed type. A comparison to conventional CPW with respect to radiation shows very good performance.<<ETX>>

Characterization of microstrip discontinuities on multilayer dielectric substrates including radiation losses

A two-dimensional space-domain method-of-moments treatment of open microstrip discontinuities on multi-dielectric-layer substrates is presented. The full-wave analysis accounts for electromagnetic coupling, radiation, and all substrate effects. The technique is utilized to characterize commonly used discontinuities on one and two dielectric layers, and numerical results for step, corner, and T-junction discontinuities are included. On the microstrip conductors, both current components are expanded by rooftop basis functions. Once the current distribution is evaluated, transmission line theory is used to determine the network parameters. Numerical results from this technique demonstrate excellent agreement with measurement and the spectral-domain technique in the case of single dielectric layers. >

A generalized method for analyzing shielded thin microstrip discontinuities

An integral equation method for the accurate full-wave analysis of shielded thin microstrip discontinuities is described. The integral equation is derived by applying the reciprocity theorem and then solved by the method of moments. In this derivation, a coaxial aperture is modeled with an equivalent magnetic current and is used as the excitation mechanism for generating the microstrip currents. Computational aspects of the method have been explored extensively. A summary of some of the more interesting conclusions is included. >

Real axis integration of Sommerfeld integrals with applications to printed circuit antennas

Printed circuit antennas are becoming an integral part of imaging arrays in microwave, millimeter, and submillimeter wave frequencies. The electrical characteristics of such antennas can be analyzed by solving integral equations of the Fredholm first kind. The kernel involves Sommerfeld integrals which are particularly difficult to solve when source and field points lie on an electrical discontinuity, as it occurs in the determination of the characteristics of printed circuit antennas. An analytic‐numeric real axis integration technique has been developed for such integrals and it is combined with piece‐wise sinusoidal expansions to solve the Fredholm integral equation for the unknown current density.

An integral equation method for the evaluation of conductor and dielectric losses in high-frequency interconnects

An integral equation method is developed to solve for the complex propagation constant in multilayer planar structures with an arbitrary number of strip conductors on different levels. Both dielectric losses in the substrate layers and conductor losses in the strips and ground plane are considered. The Greens function included in the integral equation is derived by using a generalized impedance boundary formulation. The microstrip ohmic losses are evaluated by using an equivalent frequency-dependent impedance surface which is derived by solving for the fields inside the conductors. This impedance surface replaces the conducting strips and takes into account the thickness and skin effect of the strips at high frequencies. The effects of various parameters such as frequency, thickness of the lines, and substrate surface roughness on the complex propagation constant are investigated. Results are presented for single strips, coupled lines, and two-level interconnects. Good agreement with data available in the literature is shown. >

A bandwidth enhancement method for microstrip antennas

Bandwidth enhancement methods for electromagnetically coupled microstrip dipoles are discussed. It is demonstrated that if parasitic metallic strips are incorporated in the structure either co-planar and parallel to the embedded microstrip transmission line open end, or between the transmission line and the microstrip dipole, then substantial bandwidth enhancement results. Experimental verification of this model is introduced for a bandwidth definition based on the frequency range which satisfies a voltage standing-wave ratio (VSWR) \bar{E} - and \bar{H} -plane patterns verify the theoretical model which accounts for radiation from the microstrip dipole, the parasitics, and the transmission line.

Shielding effects in microstrip discontinuities

As an application of the theoretical method described in a companion paper L.P. Dunleavy and P.B. Katehi (ibid., vol.36, no.12, p.1758-66, 1988), numerical and measured results for open-end and series gap discontinuities and a coupled line filter are presented. Comparisons are also made to predictions obtained with commercially available CAD packages. The results verify the accuracy of the theoretical method and demonstrate the effects of shielding on discontinuity behavior. The experimental techniques used, which involve the through-short-delay de-embedding approach, are explained. >

A generalized method for the evaluation of mutual coupling in microstrip arrays

An analytical method for the evaluation of mutual coupling in microstrip arrays is discussed. The elements of the array are excited by microstriplines printed on or embedded in the substrate. As an example, the mutual coupling between microstrip dipoles electromagnetically coupled to embedded strip transmission lines is evaluated accurately. The presented method is valid in the millimeter range as weft as at microwave frequencies and does not have any substrate limitations. Also, it accounts for conductor thickness and surface wave excitation. Comparison with experimental results shows excellent agreement.