antenna-theory.com

[scubasteve]

Hi. I was reading the page on slotted waveguide antennas here and I had questions on the circuit model.

I understand that when the slots are placed perfectly at wavelength/2 they are resonant and so the imaginary component of their impedance/admittance is 0 and consist of purely real resistance/conductance and that the distance to the shorted end of the antenna being wavelength/4 (or 3*wavelength/4 for mechanical reasons) causes it to be seen as a open circuit.

Q1. You specify an equation for waveguide wavelength for the dominant TE01 mode. However on the previous page you say the dominant mode is TE10. Why is there a discrepancy between the two pages? Is this a mistake? What is the dominant mode and if there are conditions in which it is different what are they?

Q2. You discuss how to get the input impedance once you know the slot admittance:
but how can you determine the slot admittance? Is there an analytical way to calculate this based on antenna dimensions or other parameters? Or is it expected that you simply find the value from some simulation software?

Q3. Assuming you have the slot admittance and thus the input impedance, how can you use that to actually calculate losses in the antenna? As it's purely resistive the only losses associated with this resistance should be conductive heating losses in the material itself right (ignoring possible reflection from the transmission line feeding the waveguide)? How can you determine this resistive loss? Even if you somehow determined a voltage and current as the input to the circuit(doing so may be another question entirely) what would this circuit model tell you about the losses? It would simply show all the power being consumed by the N number of slots, each slot consuming 1/N of the total power, right?

Thanks.