The Choice of Sliding Load Positions to Improve Network Analyser Calibration

Abstract

Using a sliding load for the calibration of a network analyser a wrong choice of sliding load positions can cause an incorrect calibration and lead to errors in the corrected measurements of an unknown reflection coefficient. The frequency dependence and error sensitivity have been studied for two distributions of the sliding load positions which are both easy to use. Application formulas are presented for the sliding load used with these data point distributions.

Full Two-Port Vector-Corrected Network Analyzer in the Acoustic Domain

“…• Match: A match is provided by the sliding-load method where the load is a foam wedge free to move within a length of open waveguide. In this work five points per frequency were used, suitably selected [48,49]. Circles were then fitted to these results by the Taubin method [45,2], and the circle center was taken as the result that would have been measured had an ideal load been used.…”

“…The Match (a load with negligible reflection) is provided by a section of waveguide that contains a wedge section of foam, again using the same bolt pattern and torque. This section of foam is used as an acoustic analogue of the "Sliding Load" that was used in RF VNA calibrations and Pennington's acoustic impedance meter [48,10]. In the middle is a finite-length thru, in front of which is an inclusion in the fashion of that to be described in Fig.…”

Acoustic Vector-Corrected Impedance Meter

“…If a load is to be used as a standard, the quality of calibration depends upon the extent to which it is possible to determine the M LOAD that would result from signals b M 1 and a M 1 measured with such a perfect match presented at the measurement plane. If a load can be constructed whose residual reflection coefficient does not change with position along the waveguide, these desired measurements may be determined irrespective of the actual residual reflection coefficient with judicious choice of positions, using a mathematical process [20]. Consider the construction shown in Fig.…”