VNA Matching

[Matt9999]

Hello, I want to check the component alignment on the layout.

My layout is different than the reference.

Where should I connect the VNA?

Can I calibrate it on the PCB?

[Matt9999]

Which components are responsible for matching to 50ohm.NRF51822 QFAC

[Asbjørn]

Hello Mateusz,

Can't really use and base this on VNA measurements alone as you won't see the actual output power and attenuation of the harmonics. You do need a spectrum analyzer to look at the output power and harmonics to do this, especially since you've gone for a layout that is different from the reference. You would attach a 50Ohm cable to the same point as you have marked with VNA and measure towards the chip. Disconnect the antenna from the measurement.

It's not possible to say exactly which component you would need to change to get this right, but the inductor across ANT1 and ANT2 along with the C8 and L2 would often be our starting point.

Best regards

Asbjørn