Lossy high frequency transmission line providing a low-pass filter characteristic

摘要

A transmission line for carrying a high frequency signal has conducting wires 15 and reference planes 13 both formed on a substrate where one or more of the following features may be arranged to provided a high frequency loss along the line. A conducting layer 17 (see also fig 5) may be formed on the conducting wires 15', such as a nickel or aluminium layer deposited by electro-plating or sputtering this relatively lower resistance material increasing losses. The wire 15 and reference planes 13 may form a co-planar transmission line (see also fig 5) with the separation D1made more narrow than D2. Widths W2 may be made more narrow that W1 possibly by forming recessed portions 153 in the wires. Roughness portions 151 be formed on one or more sided of the conducting wires, to increase losses. The substrate may be made to have a high loss tangent, such as by choosing an organic fibreglass substrate (FR4).