Electronics > RF, Microwave, Ham Radio

Cut steps when tuning a 2.4g meander antenna length.

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Psi:
When cutting a 2.4ghz meander antenna shorter and shorter to tune the length, how much length should I be cutting/grinding off each time to avoid missing a good antenna length?  eg 1mm? less?

I'm using this coil layout, except without the exact FR4 edge positioning that they spec.
Also I have a longer feed line to the antenna, 4mm or so surrounded by GND plane and via stitching.
https://www.st.com/resource/en/application_note/an5129-low-cost-pcb-antenna-for-24ghz-radio-meander-design-for-stm32wb-series-stmicroelectronics.pdf

geggi1:
1mm is almost 1% of a full wavelength and that will give a big difference in in the resonant point of the antenna.
I would recommend to trim as short lengths as possible.

Another way to get it into resonance is to use a trimmer cap in the matching capacitors see page 4.
Option one is to use one trimmer capacitor 60pF or something and trim for the highest output.
Option two is to use a fixed 120pF and a trimmer at the same size, trim for the highest output.
The last potion is to play around with fixed caps.

Psi:
Is it better to do length tuning with the RX or TX antenna?

coppercone2:
do strokes of a file

geggi1:

--- Quote from: Psi on May 22, 2023, 12:00:39 pm ---Is it better to do length tuning with the RX or TX antenna?

--- End quote ---

Normaly it is better to tun the lenght but on higher frequencies it is hard because just tiny changes will give large changes resonant frequency.
One way to get around this is to make the antenna wide band to simplifie the tuning.

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