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Changing my PCB Antenna to a whip antenna

 
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JeanMichelCorde
Antenna-Theory.com Newbie


Joined: 31 Oct 2014
Posts: 2

PostPosted: Thu Nov 20, 2014 3:13 pm    Post subject: Changing my PCB Antenna to a whip antenna Reply with quote

Hello,

I am working on a 868 MHz pcb antenna prototype on a microcontroller and I would like to change it to a whip antenna of the same frequency.
I am really new to antennas Shocked , I am not expecting for a full explanation on how to change my antenna. I just would like to know if someone here has already tried to do it and could guide me.
For instance do I need to first contact a company or is there ways to do a simulation of the performances myself?

Thank you

Kinds Regards
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E Kafeman
Antenna Theory Regular


Joined: 04 Feb 2013
Posts: 24
Location: Sweden

PostPosted: Thu Nov 20, 2014 11:48 pm    Post subject: Reply with quote

If there already is an internal antenna, do it most likely also have some kind of impedance matching circuit at PCB.
That circuit must be modified to fit your external antenna impedance.
For a whip antenna (monopole), its impedance is depending on placement and size relative your PCB ground plane.
Designing impedance matching circuit is a relative complicated procedure as it requires both some antenna knowledge and good tools, such as a vector network analyzer to measure actual impedances.

If optimal performance not is needed can it be enough if RF stage manufacturer have a proposed general matching circuit design.

For even less performance, just replace internal antenna with a 0.25 wavelength wire. As an external antenna can be given a better radiation position can it still be an improvement compared with an internal antenna.

Here is an example how an internal 2.4 GHz antenna is impedance matched with aid of a VNA and a software suited for impedance matching.
Procedure is similar for an external antenna.
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