Problem with a jumping port Zo
时间：03-22
整理：3721RD
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Hi, I am encountering a problem when simulating a microstrip line feed rectangular microstrip antenna in HFSS. I wonder if anyone met the similar problem before or possibly has an explanation for it.
I am feeding my rectangular microstrip antenna with a section of microstrip line, and I set the waveport at the end of the feed line, which touches one face of my radiation boundary. The size of the waveport has been chosen to cover all the fringing field while kept at a reasonable size to ensure waveport solution accuray. I assigned an integration line on the waveport pointing vertically from the feed line to the ground plane, and the default characteristic Zo was left at Zpi. Because my structure is symmetric, I cut it into half and assigned a perfect H plane in the middle, and the impedance multiplier was set to be 0.5.
The interesting problem I found is as I change my microstrip antenna geometry, even not touch my feed line section, the port solution gives different port Zo constantly. i.e. Zo could jump from 75 ohms to 101 ohms, if I just changed the depths of the notch, where the feed line contacts the antenna. I also found that it seemed like Zpv gave more stable results than Zpi. But I thought Zpi was more acceptable since power and current are always defiend. And since I need to obtaine the input impedance of the antenna by applying the de-embedding process along the feed line, the jumping Zo is not acceptable. Would anyone give me some suggestions?
Thanks a lot,
Ying
I am feeding my rectangular microstrip antenna with a section of microstrip line, and I set the waveport at the end of the feed line, which touches one face of my radiation boundary. The size of the waveport has been chosen to cover all the fringing field while kept at a reasonable size to ensure waveport solution accuray. I assigned an integration line on the waveport pointing vertically from the feed line to the ground plane, and the default characteristic Zo was left at Zpi. Because my structure is symmetric, I cut it into half and assigned a perfect H plane in the middle, and the impedance multiplier was set to be 0.5.
The interesting problem I found is as I change my microstrip antenna geometry, even not touch my feed line section, the port solution gives different port Zo constantly. i.e. Zo could jump from 75 ohms to 101 ohms, if I just changed the depths of the notch, where the feed line contacts the antenna. I also found that it seemed like Zpv gave more stable results than Zpi. But I thought Zpi was more acceptable since power and current are always defiend. And since I need to obtaine the input impedance of the antenna by applying the de-embedding process along the feed line, the jumping Zo is not acceptable. Would anyone give me some suggestions?
Thanks a lot,
Ying