HFSS - can I obtain the total radiated power (over 4 pi steradians) ?

I've tried to simulate an antennna consisting of a small slot in the braid. The peak gain is about -50 dBi (very small), but the magnitude of S12 is around 0.3 dB, which suggests to me more power is being lost than is actually being radiated. This seems a bit odd, as I would have expected far less than 0.3 dB loss if the peak gain is only -50 dBi. But I'd like to try to add up all the power radiated, which should hopefully match that loss between the input and output of the coax.

So can I get a figure (in Watts) for the total power radiated by integrating the power density over 4 pi steradians?

I suspect the disparity from S21 and the gain might be the S-parameters are not sufficiently accurate as there is so little radiation. The boundary probably radiates a significant amount when the slot in the coax is lambda/10 or lambda/100 long.

Yes, you can use the fields calculator or generate the radiated power from a report once you have solved the model.

With the fields calculator follow these steps:
1. Copy the Vector_RealPoynting Named Expression onto the stack.
2. Under Input click the Geometry Button, Find the Surface (NOT VOLUME) that corresponds to your radiation box.
3. Click the Normal Button under Vector, this will produce a normal vector for the surface.
4. Click the Integration curly S symbol under Scalar, this will produce the integration of the real poynting vector with the surface.
5. Click Eval this will produce the results.

To generate the result using a report follow these steps:
1. Go to HFSS->Results->Create Far Field Report->Data Table
2. Select the range of Theta and Phi you would like (check Families tab for Phi range), and frequency if you did a frequency sweep. These Theta and Phi come from the Infinite Sphere Radiation that you have to specify.
3. Select Antenna Params under Category, Then RadiatedPower Quantity and function <none>
4. Click New Report to generate a data table displaying the radiated power.

Thank you, that is most helpful. I will try them when I next use HFSS.

I'm unable to edit the original post of mine (not sure why), but to save any confusion, the setup was a piece of coax, with waveports at each end. A section of the braid was removed from the coax, so it acted as a small leaky feeder antenna. One can probalby work that out from the description, if you read it all, but I did not write it very clearly