Automatic Transformation of Curved-to-Flat Calibration Lines by a Normalizer

In high-accuracy swept-frequency insertion-loss testing, antenna-pattern measurement, and many other applications, significant measurement-system output variations are caused by the system itself. These variations can be recorded and subtracted from the measurement results to provide the required accuracy generally by recording system calibration lines with attenuation standards in the test position and reading the measurement results against these calibration lines. However, the procedure is tedious, costly, and does not lend itself to automation. The linearizer is a device for storing the system calibration and correcting for it before displaying the results. With no loss in accuracy, it provides an output curve that can be read on an ordinary rectilinear graph, used to actuate GO-NO GO switches, or automaticaly compare a test piece against a standard. Details of operation and some performance data are given for a particular analog-type linearizer and associated swept-frequency measurement system for insertion-loss or scattering coefficients. The linearizer can readily display a scale of 0.02 dB/inch with adequate stability and reproducibility. Two such linearizers can be used together to display two components of a vector or phase and amplitude, etc. Other applications are discussed and several possible approaches to an ideal system shown.