Design of monopole antenna
Design of monopole antenna
(OP)
Hello
For an inverted F antenna, I know that we can modify the distance beteween the feeding line and the grounded one to modify une input impedance of the antenne and ameliorate S11.
How we can do the same thing for a monopole antenna?? how we can ameliorate the S11??
Thank you
For an inverted F antenna, I know that we can modify the distance beteween the feeding line and the grounded one to modify une input impedance of the antenne and ameliorate S11.
How we can do the same thing for a monopole antenna?? how we can ameliorate the S11??
Thank you
RE: Design of monopole antenna
Dan - Owner
http://www.Hi-TecDesigns.com
RE: Design of monopole antenna
RE: Design of monopole antenna
If the ground plane is flat, then the feedpoint Z would be about 35 ohms.
Bending the ground plane down will raise the feedpoint Z, until the extreme case where the ground plane is formed (conceptually) into the missing half of the dipole and the Z approaches the dipole Z of 70-odd ohms.
I'll see if I can find a link to a more complete explanation.
Edited to correct spillchucker.
RE: Design of monopole antenna
RE: Design of monopole antenna
http://www.radio-electronics.com/info/antennas/ver...
RE: Design of monopole antenna
For tha simulation of helical antenna connected to a pcb
https://www.google.fr/search?q=helical+antenna&...:
How we can adjust the imput impedance??
RE: Design of monopole antenna
Also, don't set your expectations too high. The system will still function even if there's a mismatch.
After that, then add series/parallel LC components to 'tune' the feedline. The normal Smith chart calculations.
You could also experiment by building a standalone dipole using two of the little helical monopoles. Thus eliminating the ground plane question. Just to better understand what you're starting with. Separating the variables.
RE: Design of monopole antenna
RE: Design of monopole antenna
RE: Design of monopole antenna
So another approach is to flatten the line by means of an antenna tuner, i.e. LC components to move the feedpoint Z around the Smith chart.
Or do what many designers of inexpensive consumer electronics do, and essentially ignore the entire issue.
RE: Design of monopole antenna
My aim is to learn how to simulation a fixed pcb+this kind of antenna but I don't know how to ameliorate the S11 because I can't add a matching components in simlation
RE: Design of monopole antenna
The point is to separate the variables. Learn what the helical monopole 'looks like' (on the Smith chart or equivalent), without being presented with a mixed-up combination view that you'll have a difficult time unpicking.
Just for laughs, build a dipole with two of your PCB counterpoise. That exercise will hopefully help to make clear that the counterpoise cannot be a complete afterthought.
If the counterpoise isn't the ideal ground plane (to mirror the monopole), then it's the other half of a badly mangled dipole.
Regarding tuning the helical monopole, what can you do? Some adjustments to the coil parameters would be equivalent to changing frequency, thus aren't very useful except as the final tuning step.
Axial mode helical antennas, where the CP RF is fired out the end, can be tuned by adding capacitance to the feedpoint by bending the first part of the coil closer to the reflector, or welding a plate onto the start of the coil.
Once you get into that sort of approach, then there are a zillion options. A sim would need to include bulk LC components, or be some fairly advanced software to model such details.