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Got negative gain in design circular patch antenna in HFSS. I found It's because my antenna is not radiating despite good matching. Please help?

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Apr 19, 2022
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Hi everyone,
I have designed a circular patch antenna array in HFSS 2018.2 environment working at the ISM band. I got negative gain(-10.6dBi) and realized gain(-10dBi) in my design at operating frequency. After analysis I found that their radiation efficiency is very less means the antenna is not radiating. Further, I plot the matching parameter to see whether the matching is good or not. I found matching is already good. I have used microstrip feed. Please help me to get positive gain. I have attached my HFSS file here. Please help me to get positive gain(dBi) and make the antenna radiate?


  • Circular_Patch_Array.rar
    85.7 KB · Views: 94

If matching is good and gain is low, you have too much loss in the antenna. This could be metal loss, substrate loss or both.

(If your antenna structure is unusual, you might have created a lossy resonator that doesn't radiate.)
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- Remove all the PEC vias (cylinders) that you put around the patches and you will get about 15dB more realized gain. I don't know why you put them in place anyway. Beware, the S11 will change when you do this opperation and have to change the frequency in Analysis/Setup 1 and also in the plot families sweep.
- You will get more gain if place all four patches in the same position (polarization). Now you have two elements in V and two in H polarization.
- At 2.4GHz, you will get more gain if use a better substrate than the cheap FR4. For example Rogers 4003.

i can not help at all with HFSS.
but consider this, you could make an "antenna" out of an sma connector with a 50 ohm resistor chip soldered on.

the impedance match will be EXCELLENT.
but it will not radiate anything.

Antennas can have the same effect. Lets say you have a lossy material making up the antenna, and you need some sort of big standing wave/resonance to make it might appear to be matched, but also is radiating since it is just turning your RF power into heat

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