AnsweredAssumed Answered

frequency offset

Question asked by GT32 on May 10, 2017
Latest reply on May 11, 2017 by daras

We are using a E5071C ENA and have successfully made frequency offset measurements (S21 dB) in the past on one our single conversion units.   In this configuration we used an external generator (MXG N5183B) for our LO and it was controlled via our ENA.   We now are trying to measure a double conversion box which has 2 mixers and 2 internal fixed freq LOs but we are not able to get a S21 response that looks real.   It appears that we still do not have our FOM setup correct.   We have driven the input of the box with the ENA and verified our frequency output range and direction of movement relative to our input frequency direction.  One question i have is how much latency in our box would cause the ENA Rx to not be tracking the ENA source input.  If latency is possibly our issue, are there delays that we can adjust in the ENA timing?

In our new ENA config, we are no longer using the Ext LO and it is turned off.  We have FOM turned on and are using Port 1 and Port 2.  In this config, we have our Base Freq = F1 to F2;  Port 1 is our Input and it is set up for F1 to F2.  Port 2 is set up for F3 to F4.  We verified that F3 to F4 is coming out of our box using a spec analyzer and moving in the same direction as F1 to F2.   The span of F1 to F2 = the span of F3 to F4.  We also verified the levels of the F3 to F4 signals on our spec analyzer are ~ -5 dBm which should be easily detected by the ENA.   We have tried reversing the ENA FOM Port 1 and Port 2 frequencies in case we were incorrectly mapping our ENA source freq to the ENA Rx freq.  


E5071C Settings

Avg = OFF

Smo = OFF

IFBW = 1kHz


101 pts

Sweep time = Auto (also tried 0.5s - 10s)

S21 Mag

Freq Offset Settings

    X-axis = response

    Ext Source = OFF

Trigger Settings

   Source = Internal

   Scope = Active Ch

   Low Latency = OFF (also tried ON)

Service\Overload Detect = ON (also tried OFF)



Any other things to try would be appreciated.