Unknown Thru Calibration

• Overview

• Procedure

Other topics about Advanced Calibration

Overview

Unknown Thru Cal is the preferred THRU method of calibrating the ENA to measure a non-insertable device. The major benefits of using a unknown Thru calibration are:

• It is easy to perform.

• Provides better accuracy than Defined Thru and is usually better than Adapter Removal.

• Does not rely on the existing standard definitions that may no longer be accurate.

• Causes minimal cable movement if the THRU standard has the same footprint as the DUT. In fact, the DUT can often be treated as the THRU standard.

The Thru must satisfy the following requirements:

1. Thru must be Reciprocal (with S21 and S12 equal) in nature. It should have a consistent behavior, independent of the direction from which it is used.

2. The electrical length of the Thru should be known at an accuracy of ±1 /4 of the wavelength.

3. Unknown Thru is NOT supported during the TRL calibration.

Procedure

To measure the nominal electrical delay of the Unknown Thru standard:

1. With port 1 configured, perform a simple S11 response calibration at port 1 by using a short circuit
   
   Press Cal > Calibrate > Response (Short) > Short

2. Connect the Unknown Thru standard to port 1 and terminate the standard with a short circuit.

3. Measure the electrical delay of the Unknown Thru standard
   
   Press Cal > Port Extensions > Auto Port Extension > Measure SHORT > Port 1
   
   The electrical delay is automatically measured and can be confirmed.
   
   Press Cal > Port Extensions > Extension Port 1 {Value}

4. If there is an offset in the short circuit used to terminate the Unknown Thru standard, remember to subtract its electrical length from the measurement result.

To perform the unknown Thru Calibration, follow the procedure below:

1. Press Cal key, then click Calkit.

2. Select the desired calibration kit (e.g. 85033D or User Kit)

3. Press Cal > Modify Calkit > Define STDs > No Name > Label

4. Type a name for unknown Thru Cal standard e.g. {Unknown Thru1}

   • By changing the label to a different name (e.g. Unknown Thru1), the 'No Name' standard will adopt to the specified new name.

5. Press Cal > Modify Calkit > Define STDs > {Defined Name} > STD Type > Unknown Thru

6. Click Offset Delay, then enter the approximate offset delay value of the unknown Thru standard.

7. Press Cal > Modify Calkit > Specify CLSs > Thru > Set All > {Defined Name}

   1. Different Unknown Thru can be used for different ports.

8. Press Cal > Calibrate > n-Port Cal (n>1) > Transmission > {Defined Name} to execute mechanical Unknown Thru calibration.

9. Complete Reflection, and Isolation (optional) calibration for n full port Cal.