Contactless PIM Measurement Method Using Balanced Stripline

This paper introduces a new contactless measurement method using a balanced stripline to evaluate the PIM performance of copper-clad laminates. Unlike methods that use unbalanced microstrip lines, this approach eliminates the influence of physical ground plane dimensions. We present an evaluation method using traveling waves based on conventional PIM measurement and a method using standing waves that does not require a matched termination. Experimental results using a nickel-strip line as a PIM source on a copper-clad laminate show that the standing wave method achieves the same sensitivity as the traveling wave method with much lower applied power. A simulation using an equivalent circuit with lumped elements and the harmonic-balance method is also presented to show the relationship between the two measurement methods.