Modeling a coaxial colinear antenna
时间：04-07
整理：3721RD
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I'm looking to model coaxial colinear antennas, like this sort of thing
Build A 9dB, 70cm Collinear Antenna
These were to the best of my knowledge first described in a paper by Wheeler
"A VERTICAL ANTENNA MADE OF TRANSPOSED SECTIONS OF COAXIAL CABLE"
in 1956
IEEE Xplore - A vertical antenna made of transposed sections of coaxial cable
though Wheeler's paper mentions a patent 17 years earlier, so it seems this antenna has been around a very long time. They are often called CoCo antennas.
As far as I can tell, programs like NEC based on the thin wire approximation wont work as they can't handle the two different dielectrics. I have thought of trying to model it as air-spaced line, but I'm not sure if that is possible either, as I think making the outer conductor a fine mesh might start running into limitations of that model, as the wires will need to be very short to form the outer conductor.
I did think of trying this in MMANA-GAL, and got as far as to start writing a C program to compute the location of the wires, but have not pursued this any more, as I'm not convinced it is worth the effort.
Has anyone written any software for this, or has anyone got any examples for either FEKO, CST, HFSS, ADS or other commercial software?
I've been doing some reading about EM software lately, and have read that the only method where it is practical to write ones own software from scratch is the Finite Difference Time Domain (FDTD), and then only for restricted problems. Well, the FDTD approach would work here I think, and one could probably write the code to do it. But if there's a model around for one of the commercial packages, I'll take that approach.
I've wondered if there's an advantage to using a cable with a large velocity factor, so the element lengths become much closer to a half-wave in free space. That's why the use of air-spaced line looks attractive from a electrical point of view, but mechanically it is much more difficult.
Dave
Build A 9dB, 70cm Collinear Antenna
These were to the best of my knowledge first described in a paper by Wheeler
"A VERTICAL ANTENNA MADE OF TRANSPOSED SECTIONS OF COAXIAL CABLE"
in 1956
IEEE Xplore - A vertical antenna made of transposed sections of coaxial cable
though Wheeler's paper mentions a patent 17 years earlier, so it seems this antenna has been around a very long time. They are often called CoCo antennas.
As far as I can tell, programs like NEC based on the thin wire approximation wont work as they can't handle the two different dielectrics. I have thought of trying to model it as air-spaced line, but I'm not sure if that is possible either, as I think making the outer conductor a fine mesh might start running into limitations of that model, as the wires will need to be very short to form the outer conductor.
I did think of trying this in MMANA-GAL, and got as far as to start writing a C program to compute the location of the wires, but have not pursued this any more, as I'm not convinced it is worth the effort.
Has anyone written any software for this, or has anyone got any examples for either FEKO, CST, HFSS, ADS or other commercial software?
I've been doing some reading about EM software lately, and have read that the only method where it is practical to write ones own software from scratch is the Finite Difference Time Domain (FDTD), and then only for restricted problems. Well, the FDTD approach would work here I think, and one could probably write the code to do it. But if there's a model around for one of the commercial packages, I'll take that approach.
I've wondered if there's an advantage to using a cable with a large velocity factor, so the element lengths become much closer to a half-wave in free space. That's why the use of air-spaced line looks attractive from a electrical point of view, but mechanically it is much more difficult.
Dave