An efficient hybrid method is developed for calculating the coupling to a device on a printed circuit board inside a cavity. The printed circuit board is connected to a wire or cable that penetrates an aperture in the cavity enclosure. The method uses a combination of transmission-line analysis and a full-wave solver, and a decomposition of the problem into interior and exterior problems for maximum efficiency. Results are presented to verify the accuracy of the proposed method and to study the effects of cavity resonances on the coupling to a device inside the cavity.

Abstract-The generalized forward-backward and novel spectral acceleration (GFB/NSA) method is applied to capacitance extraction problems of finite planar periodic structures. In the GFB method, the interaction within a unit cell can be calculated and stored beforehand. The interactions between relatively far-separated unit cells are however calculated by the GFB/NSA method to further accelerate the calculation speed. The contributions to a receiving element on finite planar periodic structures are separated into weak and strong source contributions by an appropriate separation index, which is conveniently specified by an amount of unit cells rather than a distance. The strong source contribution is performed by the standard matrix-vector multiplication in the GFB method, while the weak source contribution is computed using the NSA algorithm. Numerical examples show comparisons of the GFB/NSA method with a commercial software, including the efficiency of the method. With the array increment in one direction, the GFB/NSA method shows O(N ) in the calculation time per iteration, while its memory requirement for a very large problem also tends to be O(N ), where N is the number of unknowns.

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A bi-characteristic-impedance transmission line (BCITL) model is used to analyze a loaded active device transmission line. The BCITL possesses lossy and nonreciprocal properties. Selection of the BCITL parameters is a key to provide correct electrical properties at its terminal. Numerical examples show that BCITL models give good agreement with the transmission matrix method.

[1] Time domain coupling from an incident plane wave pulse to a device on a printed circuit board inside of a metallic cavity enclosure is calculated and studied, using an efficient hybrid method. The cavity has an exterior feed wire that penetrates through an aperture and makes direct contact with the printed circuit board trace that leads to the device. The signal level at the input port of the device is calculated and studied. The incident electromagnetic field is assumed to be a time domain plane wave in the form of a pulse, and two pulse shapes (a Gaussian pulse and an exponentially damped sinusoidal pulse) are studied. Results show how different pulse characteristics produce different types of signals at the input to the device. The time domain results are validated by comparing with simple expressions based on the resonant frequencies and the quality factor of the cavity.Citation: Lertsirimit, C., D. R. Jackson, and D. R. Wilton (2005), Time domain coupling to a device on a printed circuit board inside a cavity, Radio Sci., 40, RS6S14,