I have a N5181A MXG feeding into a N9020A MXA. I want to change the phase of the signal and detect how long it takes from, issuing the phase change until it is detected by the MXA. This will give me the external time, so when I measure group delay in a receiver I can subtract the external time.
I am not even sure I can do this, how to do this, or if I have the right equipment or options. I am at a loss at this point.
You will want to use the IQ Analyzer mode in the MXA. The IQ Waveform measurement will allow you to capture the signal over a specified bandwidth and measurement interval. You can then trigger the measurement and acquire the signal with your phase change applied to the signal. Once you acquired the data with a READ:WAV0? you will have the IQ data of your input signal. By calculating the arctan(I/Q) you will have the relative phase of the signal to the MXA. You can then determine at what sample your phase change occurred and determine from this what time interval it occurred. You can use a simple pulse signal to determine the trigger delay needed to calibrate the system to account for cable and trigger time uncertainties.