Electric field distributions in microwave planar circuits by small coaxial probe and comparison with FDTD method

A detailed investigation of the 2D electric field distributions in bandpass filter elements that consist of microwave planar structures such as microstrip and coplanar waveguide is very useful for physical understanding, accurate and high-speed filter design and studies of electromagnetic coupling effects. By using a small electric coaxial probe, two dimensional electric field distributions for filter elements are measured. The proposed measurement system is very simple, wideband and accurate and does not required complicated system. Comparing the FDTD calculated results with measured results, the agreement is good. The upper limit of the operating frequency and the spatial resolution for the measurement system is clarified.