Hfss rectangular waveguide Problem

when I model rectangular waveguide with copper walls and plotting attenution vs frequency it gives zero after cuttoff frequency

did u define air inside of your wave guide????

So what's the problem. After the cutoff frequency, you should have complete transmission or zero attenuation (Like a High pass filter).

Hi

I design the 1st order high pass filter for the with cutoff frequency 100 HZ and gain 100. My filter passes all the frequencies above 100 hz but when frequency goes above 1.3 Khz output goes in attenuation.Its tried every thing to increase the attenuation but same result found.Please tell me how i can increase this attenuation from 1.3khz to 10 khz.

What size waveguide are you using? To my knowledge, nobody ever uses waveguide at frequencies in the range 100 Hz to 10 kHz. It would need to be absolutely huge. I forget the width/height/frequency relationships, but the width and height are of the order of λ/2. So for 1 kHz, you are looking at a waveguide with a hieght of around 75 km.

HFSS is not designed for such low frequencies.