Errors in measurements of linewidth of single-crystal ferrites due to nonideal microwave components

A brief description is given of a recently published method for measuring the linewidth of single-crystal ferrites. A theoretical analysis is made of the errors caused by the deviation from the ideal of two of the components in the test apparatus. These deviations include a VSWR greater than unity due to the input isolator and the finite directivity of the directional coupler. The range of possible error is given as a function of the degree of deviation from the ideal, and of the reflection coefficient due to the ferrite sample at resonance. A range of possible errors is given, since the actual error will also depend on the phase angle between the spurious signal generated by the deviation from the ideal and the proper signal. This phase angle is a function of geometry and can be different in different test setups. Experimental data support the theoretical analysis. With precision commercial equipment the measurement error is small. Thus if the VSWR due to the input isolator does not exceed 1.1, and the directivity of the directional coupler is 40 dB or more, the maximum error will be ±3 percent.