Two simple methods for the measurement of the dielectric permittivity of low-loss microstrip substrates

Two methods are presented for the measurement of the dielectric permittivity of low-loss microstrip substrates. It had become necessary to measure the permittivity during an investigation of attenuation in microstrip transmission lines in order to design for the required characteristic impedance. The two methods are the Reflection Cancellation Method and the Line Balancing Method. Theoretical calculations and measurement techniques for both methods are shown. The results demonstrate that the two methods (1) are accurate to within plus or minus 8%, (2) are simple to apply, (3) are not wasteful of material, and (4) can determine the permittivity associated with a specific section of microstrip.