Automatic Calibration Module

Calibration

Calibration of a test setup (which includes the VNA, cables, and adapters) significantly increases the accuracy of measurements. Calibration allows for correction of errors caused by imperfections in the measurement system: system directivity, source and load match, tracking, and isolation.

Automatic calibration of VNA

The Module enables calibration in one click. The calibration is performed fully automatically, including switching between different module states, their measurements, and calibration coefficients calculation, as the software uses the data stored in the Module memory.

Calibration methods

All Modules support the following calibration methods:

•Full one-port calibration.

•One-path two-port calibration.

•Full two-port calibration.

Four-port Modules support the following additional calibration methods:

•Full three-port calibration.

•Full four-port calibration.

Full one-port calibration

The method of calibration performed for one-port reflection measurements. It ensures high accuracy.

One-path two-port calibration

The method of calibration performed for reflection and one-way transmission measurements. For example, for measuring S11 and S21 only. It ensures high accuracy for reflection measurements, and reasonable accuracy for transmission measurements.

Full two-port calibration

The method of calibration performed for full S parameter matrix measurement of a two-port DUT. This method is also known as SOLT: Short, Open, Load, Thru. It ensures high accuracy.

Full three-port calibration

The method of calibration performed for full S parameter matrix measurement of a three-port DUT. It ensures high accuracy.

Full four-port calibration

The method of calibration performed for full S parameter matrix measurement of a four-port DUT. It ensures high accuracy.

Unknown thru

The usage of a reciprocal two-port device with loss values of no more than 10 dB for full two-, three- and four-port calibration enables correction of VNA parameters for measuring parameters of non-insertion devices. Non-insertion devices are the devices that have same-gender connectors of any type, and different-gender or same-gender connectors of different types.

The Module memory stores S-parameters of the thru which are used for calibration coefficients calculation. The said parameters are not applied for the Unknown Thru algorithm.

Characterization

Characterization is a table of S-parameters of all the states of the Module switches, stored in its memory.

The Module has two memory sections. The first one is write-protected and contains factory characterization. The second memory section allows to store up to three user characterizations. Before calibration, it is possible to select factory characterization or one of the user characterizations.

Factory characterization

Factory characterization is performed during the Module manufacturing. The factory characterization data is stored in the write-protected section of the Module memory.

User characterization

The user characterization option is provided for saving new S-parameters of the Module after connecting adapters to its ports. Up to three different characterizations can be created. The user characterization can be performed using the VNA software. The characterization data is stored in the Module memory section, which can be overwritten.

Orientation

Orientation refers to the Module ports in relation to the test ports of the VNA. While the VNA ports are indicated by numbers, the Module ports are indicated by the letters A, B, C and D.

Orientation method

Manual or automatic orientation method can be selected.

Automatic orientation

For automatic orientation, the VNA software determines the Module orientation each time prior to its calibration or characterization.

Thermal compensation

Thermal compensation is a software function of S-parameters correction based on known temperature dependence data and the temperature sensor data inside the Module. Temperature dependence of each Module with factory characterization is determined during its manufacture and stored in its memory. It is possible to enable or disable thermal compensation function.

Thermal compensation of user characterization

Thermal compensation of user characterization is based on coefficients obtained during the Module manufacture. If the operating frequency range and/or the number of frequency points of the user and factory characterization are not the same, linear interpolation of thermal compensation coefficients is used for user characterization data.

Confidence check

The confidence check is a test of the current calibration, performed either by the Module, or by any other method.

The confidence check features simultaneous indication of attenuator S-parameters measured and stored in the Module memory.

Math (division) function for data and memory is used for a detailed comparison.

Operating modes

The Module is controlled using the USB interface. CMT’s VNA software or VISA library must be installed at the controlling PC. The VISA comprehensive library allows controlling measurement equipment in almost all programming languages, i.e. C/C++, Visual Basic, MATLAB, LabVIEW, etc. The Module features the USBTMC USB488 standard control protocol. The Programming Manual includes descriptions of commands used for controlling.