December 2012 Number Linearity Testing in the SureCAL Power Sensor Package FLEXIBLE STANDARDS ASSIGNMENT

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1 Overview: December 2012 Number Linearity Testing in the SureCAL Power Sensor Package This Technical Note describes linearity testing utilized in the SureCAL Power Sensor Package for power sensors operating in the +20dBm to -50dBm ranges. HARDWARE REQUIREMENTS To add functionality but still maintain maximum flexibility, three new Generic Names are added to the Flexible Standards List. The POWER METER is the power meter dedicated to the UUT sensor. This should match the assignment in POWER MONITOR #2. SIGNAL GENERATOR and STEP ATTENUATOR are unique to the linearity test and need only satisfy the requirements for frequency and power of the linearity test. USB sensors are attached to the PC USB port and the sensor s driver is assigned to the POWER METER. FLEXIBLE STANDARDS ASSIGNMENT Typical Flex Standards assignments for power sensor linearity testing

2 LINEARITY PROFILES Profiles may be used in their default state or customized and saved as your default or serial number / ID number specific in the Profile Save Options. The Linearity Profile approach allows the sensor to be tested in up to three different ranges. Note it s impossible to separate the power sensor and power meter contributions to the measured linearity error. They are combined and in essence this becomes a system test. They are combined in a worst case scenario in the default profile. Collecting Type A data for the uncertainty calculation is an editable option. Number of samples can be edited or it can also be turned off entirely. Also available is the ability to halt the test on a failure and select a retest. LINEARITY PROFILE OPTIONS EDITOR Default Profile Screen for N848x Series

3 LINEARITY PROFILE.TXT The linearity profiles are populated by the values contained in the.txt identified on the SureCAL screen. This is an example of the file used to populate the profile editor. Note: Edit the TXT using the Profile Options editor only. Sample Linearity Profile.TXT SELECTING A SIGNAL GENERATOR Most sensors will require at least +20dBm at 50MHz. Some of the pulsed sensors will require 1 GHz. A source with a high power output option is recommended. Since the signal generator has a different generic name it does not have to be the same generator as the one used for the normal cal factor testing.

4 SELECTING A STEP ATTENUATOR This is the single biggest contributor to the uncertainty. Depending on age and condition it may need to be characterized more often than a typical attenuator. The benefit to testing with the attenuator is speed. A typical sensor can be tested in less than 2 minutes. The number of characterized points is directly related to the linearity test point resolution. If an attenuator is characterized at 10 db increments the linearity test point resolution can be no greater the 10 db. If an attenuator is characterized at 5 db increments the linearity test point resolution can be no greater the 5 db. If an attenuator is characterized at 1 db increments the linearity test point resolution can be no greater the 1 db. The minimum recommended range of the attenuator characterization is 70 db. It can be less but that will have a corresponding limitation on the dynamic range that can be tested. The sample shows a characterized attenuator capable of providing up to 80dB of dynamic range. Sample Attenuator Correction File

5 PROGRAM SEQUENCE The power sensor is connected to the power meter reference and calibrated at 0dBm. USB sensors will perform their internal power reference calibration under program remote control. The source will be set to the max power level at the frequency as requested in the profile. The program will set the attenuator to achieve a reference to match the power reference calibration level. Normally this is 0dBm but a different reference power level may be selected. The test will run using the incremental settings from the profile. The reported uncertainty will include contributions from the attenuator uncertainty, Attenuator / UUT mismatch, power meter linearity and if selected, UUT repeatability. As with many other SureCAL procedures the full uncertainty budget is available for viewing and/or archiving in the SureCAL SCRATCH directory.