Balance-unbalance conversion characteristics of untwisted unbalanced metallic pair lines and their application to a method for estimating equivalent ground plane

Metallic pair lines transmitting high-frequency information signals above s everal tens MHz are often used without being twisted, as flat floor cable i nstalled in buildings, ribbon-type cables installed in computer equipment, and traces in printed circuit boards. However, the conversion characteristi cs of untwisted unbalanced metallic pair lines connecting unbalanced circui ts have not been investigated over a wide range of frequencies in the MHz r egion. First, we developed a method to estimate effective power conversion factors using a cascade connection of F matrices, where the unbalance in im pedance and admittance of each pair line is distributed uniformly along the line. As a result some useful information was obtained about the balance-u nbalance conversion characteristics of the effective power which can be use d to suppress EMI phenomena in wiring, especially over several decades of h igh frequencies. Next, we attempted to apply the conversion characteristics of untwisted unbalanced pair lines obtained at frequencies below several M Hz to techniques for searching for the return circuits of conductors instal led in buildings. It was clarified experimentaly that the depth of the equi valent ground plane can be estimated by comparing the measured conversion v alues of TV feeder lines installed at the place being tested with reference values measured in advance on a copper plate.