Matching network for nRF24L01+, balun, PA and PCB ant

[Joe Wright]

So I was thinking of having the following:

1. nRF24L01+
2. to balun (e.g., Johanson 2450BM14A0002 or Anaren BD2425NnRF)
3. to PA/LNA RFX2401C
4. to PCB antenna

If I'm willing to manually trim the PCB antenna trace a bit at a time, do I need any additional tuning? Would that be a pi network and where would it go? Between 1 and 2, 2 and 3, 3 and 4? Or just a shunt capacitor between 3 and 4?

The circuit is going in a custom racket handle prototype and, although at the open end, will be surrounded on 3 sides by PLA and fiberglass/epoxy matrix, have other components (couple of chips and small lipo) at other end of pcb, as well being affected by a hand holding the racket.

I don't have access to a network analyser so will be labouriously doing multiple packet testing in various configurations, while making any adjustments as needed. Therefore I want to minimise the amount of components to change.

Also, reference PCB designs are available for 1, 2 and 4 or 1, 3 and 4. To have all 4 elements should I place the PA inputs where the antenna is placed in the balun pcb reference?

Many thanks, Joe

[FormerMember]

1) If tuning the antenna by cutting it's length, you will only need one component in the antenna tuning network, and that is shunt capacitor. The shunt capacitor will be placed as close to the antenna as possible, between 3 and 4.

2) The PA/LNA should be placed in the 50 Ohm reference point, between the balun and the shunt antenna tuning capacitor. The PA/LNA can be placed "as close as possible" to the balun. If there is a distance between the balun and the PA/LNA, the transmission line between the two should be a 50 Ohm transmission line. In that case, the width of the transmission line can be calculated using appCAD (co-planar waveguide).

[Joe Wright]

Awesome, thanks