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PeterB

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About PeterB

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  1. Jlerch, the centre fed radiation pattern looks spot on, well done. The coaxial dipole pattern looks way too symmetrical in the Z-Axis. To solve that you need to place at least 3 additional lower wires to represent the coax shield (check out the link Mr RC-Cam posted above) which act like a ground plane thus approaching the pattern of a 1/4 wave monopole/unipole antenna sitting perpendicular to a ground plane. regards Peter
  2. Glad to see some experimentation Jlerch. If you remove the ground plane to simplify things, you should aim to get this toroidal shaped radiation pattern (and not a 'double doughnut'). Once you get that put the ground plane back in and you can be more confident of a realistic simulation. Let us know how you go. regards Peter
  3. Jlerch, I have 4 ideas for you to try. 1. You need to ensure the current (or voltage) sources are applied where the wires are nearly touching. It appears that you have applied one source 5% from the bottom end (E1) of wire 1, and source 2 at 5% from the far opposite end of wire 2 (i.e. 95% away from the end of wire2 closest to wire 1). I would try and apply one source at End 2 of wire 1 and the other 180deg out of phase source at End 1 of wire 2 2. There seems to be a discrepency in the View Antenna window, the XY plane is shown between the two wires, but in the Wires window, you have specified both wires to be above the XY plane (e.g. one end of wire#1 begins at 10 units above the XY plane etc) 3. Have you tried using voltage sources rather than current sources ? (set type to V rather than I) 4. Is there a ground plane ? If so , is its position causing the asymmetrical pattern ? Try removing the ground plane all-together if one exists. regards Peter
  4. Hi Ron, I had no problems being able to apply it either ! My point was that I had to trust the design had been done right rather than be able to verify the design myself with equations they (didn't) give me. Perhaps if I simulated it myself in the S/W they are advertising I could have done that too. My main thrust in this thread has been my need to go back to first principles using theory and equations to convince myself that any design I come across has a solid grounding in theory (and/or simulation as appears to be the case here). I agree with that 1st paragraph too and I might need to embark on that path to satisfy myself. regards Peter
  5. Thanks again. Yes I already listed that article in my previous post. I loved the way that article elucidated graphically for me the concept of exactly why the impedance changes as you move the probe from one edge of the patch to the other. Check out the figures under the heading Impedance Matching, and the associated text: "From the magnitude of the current and the voltage, we can conclude the impedance is minimum (theoretically zero ohms) in the middle of the patch and maximum (typically around 200 ohms, but depending on the Q of the leaky cavity) near the edges. Put differently, there is a point where the impedance is 50 ohms somewhere along the "resonant length" (x) axis of the element." regards Peter
  6. That article is a glorified advertisement for the CST MICROWAVE STUDIO product. It presents little theory, no equations and nothing about matching the impedance to 50ohms by using a probe fed rather than the standard edge fed patch design that it presents. Sorry to say but there is just NOT a lot out there for free !! regards Peter
  7. OK, thanks. The theory is out there but in text books. There is nothing substantial or in depth enough on websites. One online calculator allows you to simulate an edge fed patch but won't provide the calcs/theory to convert that to a probe fed patch as per the GPP. This paper comes close with an explanation about matching the impedance but no solid theory to follow through with. As for freeware simulation S/W. I haven't yet downloaded any but these two look promising Ansoft Designer SV and Sonnet As for a source of definitive and comprehensive theory, thankfully now Google allows us to search the university level text books which we can purchase if we need to (book content preview is understandably limited and misses pages). regards Peter
  8. Can you recommend any particular books ? Did you keep any of your design notes that we might be able to reference ? I'd like to repeat what you did for myself in order to better appreciate the method behind designing patch antennas. regards Peter
  9. Hi there Mr RC-CAM, I was unable to find any details of the theory or simulation S/W that you used to design the GPP Antenna. Would you be able to share with me/us what design tools or equations you used ? I have encountered Ansoft Designer SV and other freeware simulation tools. What did you use ? regards Peter
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