Hi,

I would like to simulate a real world system I have but in CST Studio Suite  to get a better understanding of the electromagnetics behind it.

What I have is an SDR (emulating an RFID reader here with a monostatic antenna) transmitting continuous wave in the far-field, e.g. 1m away. In the near field I have two 'tags', which in this case I am modelling as simple dipoles. I would like the tags to switch their load impedances between short and open, i.e. reflecting and absorbing - which I have done using lumped elements with parameterized impedances. This will result in four possible states: (open,open), (open, short), (short, open), and (short, short) - which I simulate separately using a parameter sweep.

However, what I am struggling with is how to model the reader and the equivalent 'received' signal seen at the SDR. In reality, of course, I receive a magnitude and phase which modulates the continuous wave sent by the reader, and it is essentially the 'collided' tag responses.

The reader antenna can be anything, i.e. a dipole is ok. I want to model it as an SDR behaves, so I want to look at the received signal magnitude and phase and analyse the changes in these when the dipoles modulate their load impedance.

I would appreciate any advice how to do this! I have modelled the reader as a dipole for now (can change this to a patch later), at a distance of 0.5m from the two 'tags', and driven it with a discrete port. However, I am struggling to interpret the output results. I have looked at the discrete port (reader antenna port) voltages and these do not change with changes the tag loading. I have looked at the S11 and the results do not line up with the expected channel dictated by mutual coupling theory from Balanis.

Thanks.