PCA10031 antenna matching

RE: PCA10031 antenna matching

AmbystomaLabs — Fri, 26 Aug 2016 14:22:36 GMT

While the meander might match easily, the 51422 most likely will not. Matches go both ways.

RE: PCA10031 antenna matching

Dmitry Tarnyagin — Fri, 26 Aug 2016 13:48:04 GMT

C14/L4 resonates at > 3 GHz.

Meander antenna matches quite easy with just a single shunt, thinking 2.4GHz I see no reason of doing tricks with distributed network here. It might be a harmonics filtering network. The biggest question then is do we need to keep it this way :)..

RE: PCA10031 antenna matching

AmbystomaLabs — Fri, 26 Aug 2016 12:57:50 GMT

It is not correct that C14 and L4 would evaluate to 3nH at 2.4GHz just because mathematically it seems true. Even at a relatively low frequency such as 2.4GHz, the phase separation of R17 and the ground via placement would be very significant. As a example, it is not uncommon to see a chain of several caps in row separated by a few mm each time. While it may look like it works as one cap, it does not and this chain will very effectively transform a low impedance to a high impedance.

In the case of your matching network, since the 51422 doesn't have on chip harmonic filtering, I would guess that the intention was a match designed as a low pass network to filter harmonics. At 2.4GHz it provides a match to 50ohms for the 51422 and above 2.4GHz looks more and more like a low pass filter. In addition at 2.4GHz, C14 and L4 might just resonate becoming an open circuit then above 2.4 they become a shunt (ie, low pass network).