Calibration Types
The two-port ACM allows the Analyzer software to perform one-path two-port, full one-port or full two-port calibration. The four-port ACM additionally allows performing full three/four-port calibration. Calibration is performed with the click of a button.
Characterization
Characterization is a table of S-parameters for all the states of the ACM switches, stored in the ACM memory. There are two types of characterization: user characterization and factory characterization. The ACM 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. Factory characterization or any of the user characterizations stored in the ACM memory can be selected before calibration. The user characterization option is provided for saving new S-parameters of the ACM after connecting adapters to the ACM ports.
The software allows to perform a user characterization and save the data to the ACM with the click of a button. To do this, the Analyzer test ports should be calibrated in configuration compatible with the ACM ports.
Automatic Orientation
Orientation means relating the ACM ports to the test ports of the Analyzer. While the Analyzer test ports are indicated by numbers, the ACM ports are indicated by the letters A and B for two-port ACM, and A, B, C, D for four-port ACM.
Orientation can be defined either manually or automatically. In the case of automatic orientation, the Analyzer software determines the ACM orientation each time prior to its calibration or characterization.
Unknown Thru
The Thru implemented by the electronic switches inside the ACM introduces losses. That is why the exact parameters of the Thru should be known, or an Unknown Thru algorithm should be used to achieve the specified calibration accuracy. The software allows to use both options. The ACM memory stores S-parameters of the Thru, which are used to compute calibration coefficients. If an Unknown Thru algorithm is applied, such parameters are disregarded.
Thermal Compensation
The most accurate calibration is achieved if the ACM temperature is equal to the temperature at which it was characterized. When this temperature changes, certain ACM state parameters may deviate from the parameters stored in the memory. This results in reduction of the ACM calibration accuracy.
To compensate for the thermal error, the ACM features thermal compensation function. Thermal compensation is a software function of the ACM S-parameter correction based on its temperature dependence and the data from the temperature sensor inside the ACM. The temperature dependence of each ACM is determined at the factory and saved into its memory.
Thermal compensation can be enabled or disabled.
Confidence Check
The ACM also implements an additional state — an attenuator, which is not used in calibration. The attenuator is used to check the current calibration performed by ACM or any other method. This is called a confidence check.
In the confidence check mode, the factory measurement of the attenuator is loaded into the memory trace, which may be compared to the measurement being performed by the active trace. The two traces may be compared, and their differences may be evaluated to determine the accuracy of the calibration performed.
For a detailed comparison, the math (division) function can be used for data and memory.
