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Helical Resonator

Posted Feb 18, 2020, 7:00 a.m. EST RF & Microwave Engineering 1 Reply

Pedram Yaghoubi
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Hi, I am looking for possible resonances of a helical resonator in a copper cylinder. Here I attached my file. By using eigenfrequency study in the RF package and setting up reasonable boundary conditions, I received 66 MHz as the lowest eigenfrequency. But I know from my geometry it should be around 25 MHz. What can be the problem?

1 Reply Last Post Feb 19, 2020, 3:22 a.m. EST
Joydip Nandi
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Posted: 4 years ago Feb 19, 2020, 3:22 a.m. EST

Hi pedram,

As i am unable to see your mph file, i can't investigate the exact glitch. Probable solution I may suggest and that you have to check in your model. Here, I am also attaching one model.

  1. Geometry: You should take outer shield as a solid domain and surface of this domain will be acting as a outer shield of the resonator Here you have to check the short end of helix properly connected with the outer shield. So, you just select the one end of the helix and do the extrude operation. Then make union operation to the helix domain and shiled. Then do delete operation to the extra domain of extruded portion.
  2. select the air domain only for domain 1.
  3. put all surface as the conducting copper boundary. (this will be required when you will use IBC boundary conditions)
  4. put EMW domain only for domain 1 as shown in attached file.
  5. As you are not interested about quality factor then stick to PEC boundary conditions to save computation time. Otherwise You can use IBC conditions.
  6. Now add the study of eigen frequency search.
  7. Put the nearest number around where eigen frequency will be searched. You can select the search method ** closest in absolute value.**

hope that will solve the problem. Please see the attached file also

Hi pedram, As i am unable to see your mph file, i can't investigate the exact glitch. Probable solution I may suggest and that you have to check in your model. Here, I am also attaching one model. 1. Geometry: You should take outer shield as a solid domain and surface of this domain will be acting as a outer shield of the resonator Here you have to check the short end of helix properly connected with the outer shield. So, you just select the one end of the helix and do the **extrude** operation. Then make **union** operation to the helix domain and shiled. Then do **delete** operation to the extra domain of extruded portion. 2. select the air domain only for domain 1. 3. put all surface as the conducting copper boundary. (this will be required when you will use IBC boundary conditions) 4. put EMW domain only for domain 1 as shown in attached file. 5. As you are not interested about quality factor then stick to PEC boundary conditions to save computation time. Otherwise You can use IBC conditions. 6. Now add the study of eigen frequency search. 7. Put the nearest number around where eigen frequency will be searched. You can select the search method ** closest in absolute value.** hope that will solve the problem. Please see the attached file also

Attachments:

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