Hi there,
I’m just on the beginning of a Nordic NRF52810 design. From the schematics they provide it only requires two components and an antenna. I couldn’t find an antenna specifically for this chipset but wondered if the Texas SWRA117D will do the job? The reason I ask is the pdf that describes that part has a lot more capacitors and inductors than the two on Nordics schematic.
Two components and an antenna seems to easy!
It’s very unlikely you’ll be able to pass any formal RF testing with such simple filter network.
The whitepaper claims it’s enough to match the output of IC to 50Ohm. However I yet have to see a true 50Ohm antenna - you can easily asume every physical antenna will need matching network.
If that design is for learning/testing - you can get by with these two parts and have it working.
If you want to manufacture the design and pass compliance testing - prepare to add proper antena matching network, most flexible structure would be another series-shunt-series-shunt footprints which allow you to implement both PI and T style matching filters. Series can be closed with 0R, shunt you can leave open if not used.
Hi Fred,
Understood. It’s just for a prototype. I’m also after minimal range (a meter!) using BLE, so is the compliance testing that harsh?
I’ve no idea where to start with matching but do you have a mockup of what you are suggesting? If I don’t see it visually I know what I’m like for following my assumptions and cocking it up!
Cheers, Andrew
Not sure where are you from, but in the EU the compliance requres verification of unwanted spectrum components up to tens of GHz. If it’s easy or not will depend on many factors, but to my experience it’s not as easy as the chip manufcturers would like us to believe.
Here’s the rough drawing of the general idea, you replace RM1…RM4 with proper L, C matching components.
Unused series replace with 0R, unused shunts leave empty. This way you can implement both PI style network (shunt-series-shunt) and T-style network (series-shunt-series). To properly match your antenna you’ll need VNA and handful of L&C’s.
Not enough for Bluetooth which is 2.4GHz
Does the chip not have suppression built into it? I’m happy to add those four extra components and bypass/disconnect as necessary but the Nordic datasheet doesn’t advise on anything other than the two specified. This is unlike older Ti BLE chips which have complex filtering on the datasheet.
Nordic claims these two give you matching for 50Ohm antenna. Any PCB antenna will not be true 50Ohm, and thus will require further matching.
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