Microstrip leaky-wave antenna fed by an aperture-coupled microstrip operating at K-band is presented. Using the aperture-coupled microstrip as a feeding structure can fully exploit the wideband characteristic of the microstrip leaky-wave antenna. The dimensions of the antenna are obtained from the calculation of the propagation characteristics. Measurement shows a bandwidth of 22% for VSWR < 2:1 and a peak power gain of 12 dBi at 22 GHz for one element. Four-element array is developed with a gain of 18.7 dBi and the frequency-scanning feature is exhibited. The waveguide model is verified by measuring the 3-D radiation pattern of the microstrip leaky-wave array.

The extended version of spectral domain approach (ESDA) is applied to evaluate the scattering characteristics of discontinuities in coaxial line. Discontinuities may be in inner and/or outer conductor of coaxial line. This method secures the high accuracy by considering the singularities of fields near the conductor edge properly. The computational labor of the new method is far lighter than that of FEM, so that novel method is suitable for the time consuming iterative computation such as fitting procedure in material evaluation or optimization of antenna design.