An Adapter Removal Calibration Method to Measure 50-ohm to 75-ohm Devices.

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Presented below are two methods of making this measurement. Both approaches utilize 50Ω to 75Ω adapters as the adapter removal technique.

• The first approach, "Method 1", employs a 50Ω to 75Ω mechanical adapter as the adapter to be removed. The mechanical adapter is a Keysight part number 1250-0597.
• The second approach, "Method 2", utilizes a 50Ω to 75Ω minimum loss pad as the adapter to be removed. The minimum loss pad is a Keysight part number 11852B option 004.

Regardless of the approach, the following procedures apply.

WARNING!
DO NOT MIX a 50Ω N-type connector directly with a 75Ω N-type connector. Due to the physical structure of N-type 50Ω and N-type 75Ω connectors there are inherent risk when interconnecting.

Inadvertent mating of a 50Ω N-type male connector to 75Ω N-type female connector WILL PERMANENTLY DAMAGE the 75Ω N-female pins.

Conversely, interconnecting any 75Ω N-type male connector to a 50Ω N-type female connector WILL result in a NON MECHANICAL connection. Damage should not occur. However the RF energy is simply "coupled" between the connections due to the lack of mechanical compatibility.

Refer to Figure 1 for images of various 50Ω and 75Ω N-type male and female connectors.

Refer to Figure 2 for an image of a 75Ω N-female damaged by mating with a 50Ω N-type male.

Connections:

• Connect an 11857D 7mm-7mm test port cable assembly to PORT 2 of the 8753ES network analyzer (this is one cable assembly of the Keysight 11857D test port cable pair).
• Next attach a 7mm N-type 50Ω male adapter to the end of the 7mm cable assembly.

• Perform a full 2-port calibration with the 85032B cal kit (N-type 50Ω).
• Save this calibration to the 3.5" internal floppy disk.
• Move the 11852B Option 004 minimum loss pad back to the port 1 adapter as noted below (see image below):

• Perform a full 2-port calibration with the 85036B cal kit (N-type 75Ω).
• Save this calibration to the same 3.5" internal floppy disk used in the previous step.
• To the adapter listed above, connect a standard (non-option 004) 50Ω to 75Ω minimum loss pad (11852B).
• Directly on PORT 1 of the 8753ES attach a 7mm to N-type 50Ω female adapter (Keysight part numbers: 1524A or; 85054-60001 or; 85054-60001).

Note: The device under test (DUT) was another Keysight 11852B 50Ω to 75Ω minimum loss pad.

Adapter Removal Calibration Procedure:

• Connect the 50Ω to 75Ω adapter to the cable/adapter assembly configured above (Connections section). Note: that if using Method 1 (via the mechanical adapter) then the adapter has a delay of 139ps. If using Method 2 (minimum loss pad), the delay is 216ps.
• Via the analyzers front panel keys select CAL, MORE, ADAPTER REMOVAL, RECALL CAL SETS, from the file selection list on the internal floppy select (highlight) the first stored calibration kit and execute a RECALL CAL PORT 1, repeat the processes selecting (highlight) the second stored calibration kit and execute a RECALL CAL PORT 2, RETURN, ADAPTER DELAY (enter the delay of the adapter used, if via the 1250-0597 mechanical adapter then enter 139ps, if via the 11852B minimum loss pad then enter 216ps), REMOVE ADAPTER.

Results:

Using either the mechanical adapter (Method 1) or the 11852B minimum loss pad (Method 2) for the adapter resulted in excellent measurements results. Return loss measurements for S11 and S22 were on the order of 36 dB worst case at the 2 GHz stop frequency.