Injection transformer J2100A gain

This is a 1:1 transformer. The signal source generator is 50 Ohms and the termination is 5 Ohms. The signal generator is expecting to see 50 Ohm termination. Because it is 5 Ohms we get 2*5/(5+50)=0.182=-14.8dB.

If it were a 50 Ohm termination it would be

2*50/(50+50)=1=0dB

Thank you for your post. Let us know if the below is helpful or if you have any follow-up questions:

Variations In the Injection Transformer Frequency Response

The frequency response of the J2100A/J2101A injection transformers, and their variations, are not relevant to the transformer’s overall performance as reductions in bandwidth only result in a reduced signal being injected into the loop. This should not affect the Bode plot accuracy. This may result in increased noise, but this is not likely. There may be some confusion with the ability of the injector to inject signal into the loop with the ability of the VNA to measure the response at a particular frequency and they are only indirectly related. Certainly, the BAMP12 is available to raise the signal level injected and/or the Bode 100 software allows you to shape the injection signal to help with noise.

Some other Q&A Items:

Is this characteristic graph based on actual measurements or is it the result of a simulation?

The graphs represent actual test data measurement.

What is the unit of the vertical axis on this graph?  

dBV.

How does the gain dip affect the stability measurements?  What is the cause of this phenomenon?

This would be removed by calibration. This is the stray capacitance with the transformer leakage inductance.

Note: The J2101A indicates that the transformer has a usable range up to 45MHz. This frequency is dependent on the interconnects. So, our recommendation would be to keep your interconnects as short as possible in order to maximize the bandwidth.