A six-port reflectometer calibration method using five standards is developed, and gives explicit unambiguous expressions for the calibration constants. The standards are restricted only in that their impedances may neither all have the same magnitude nor all have the same argument. The method permits exact (nonidealized) descriptions of the standards to be used, and the redundancy inherent in the analysis is utilized to reduce the problems associated with measurement noise.

An Explicit Six-Port Calibration Method Using Five Standards (Short Papers)

Microwave six-port devices have been gaining popularity in many industrial on-line microwave measurement instruments. However, the calibration of a six-port device remains a difficult task, particularly if a large dynamic range of the measurement is required. The recent development of the artificial neural network (ANN) provides a powerful tool for nonlinear approximations which can be used to calibrate the six-port devices. An industrial prototype microwave six-port instrument has been calibrated using the ANN technique, which has achieved high accuracy over a wide dynamic range.

Calibrating an industrial microwave six-port instrument using the artificial neural network technique

The authors present a novel method of calibrating the diode detectors used in six-port network analyzers, without disconnecting the diodes. The method uses only a precision variable attenuator or a power meter with no additional directional coupler. The important feature of this method is that no actual measurement of power is required to calibrate the diode detectors for six-port operation. It is very well suited to in-situ calibration of the diode detection circuits for operation of the six-port with pulse signals when the average power detected by the power meter drops to very low levels for low duty cycles. In these cases, the precision variable attenuator method is required. Measurement results are presented. >

New in-situ calibration of diode detectors used in six-port network analyzers

Reflection coefficient measurements obtained from six-port reflectometers are analyzed from a statistical and geometrical point of view. The analysis concentrates on the effect of using noisy power meters, and a simply computed, geometrically interpretable estimator of the reflection coefficient possessing certain optimality properties is derived. A suitable performance measure for this estimator is calculated for a number of different six-port designs as the true reflection coefficient ranges over the area of the Smith chart. For each design, a contour map of the measure allows for easy comparison of the designs in different regions of the Smith chart.

A Comparative Statistical Study of Some Proposed Six-Port Junction Designs

The sections in this article are


1
Microwave Radiometry

2
Microwave Spectroscopy

3
Measurement of Permittivity and Permeability

4
Time-Domain Measurements

5
Sweep Frequency Measurement of Scattering Parameters

6
Six-Port Reflectometer

7
Power Measurement

Microwave Measurement Instrumentation

A new mode of six-port operation is described, in which uncalibrated semiconductor diodes operating at a coustant level are used as power sensors. Each diode is used in turn as a leveling loop detector, and the resulting changes in source output power are measured by a single linear power meter.

P.I. Somlo

Papers

Accurate Six-Port Operation with Uncalibrated Nonlinear Diodes Digital (Short Papers)