Range without shunt component in matching network

[SaiTeja]

Hello, I am designing a custom board with NRF52832 IC. I followed all PCB consideration suggested by Nordic.

This blog suggests, If using a PCB antenna, the matching network should consist of one shunt component. devzone.nordicsemi.com/.../

But I don't have VNA to measure impedance of PCB antenna.

How much range can I expect without shunt component in matching network? My requirement upto 5 meter x 5 meter

[AmbystomaLabs]

No one can say. Depending on the board, two networks that are just slapped together could have anything form perfect performance to 30 or 40 dB of loss. PCB antennae can be very difficult to design. You should at least try to spend some time in a modeling app such as the free version of Sonnet to see if your pcb antenna is vaguely close to 50 ohm at 2.45 GHz.

I have seen plenty of comments from people on this blog who chose to not spend the time on matching and end up with devices that broadcast a few feet only.

As a compromise you can put the shunt position PRECISELY where it is supposed to be and just experiment with different values from a sample kit. Assuming you put everything on the board correctly you can probably get a few meters using this approach.

Here is a Sonnet PIFA example:mobile_pifa.zip

[SaiTeja]

Thank you for your reply. I am using the MIFA refered here. www.ti.com/.../swra117d.pdf. This antenna is designed to be 50 ohm at 2.45 GHZ. Is it still necessary to use Sonnet ? By using this antenna, Can I skip shunt component?

[AmbystomaLabs]

If you copy the design FAITHFULLY without modification and you make sure to include the nRF output match EXACTLY as specified you can probably get good performance.

The shunt 1.2pF that you referred to above is part of a match for a different antenna so you do not include it. However, you still need to include the shunt cap and series inductance that is part of the nRF output match.

Even if you do all this, it still won't be perfect as your board will have a different ground plane shape/size from the TI reference design.

I should point out that you won't have any harmonic filtering, except the minor influence of the nRF output match. So, don't expect to be able to certify this with ETSI or FCC because it likely won't pass. But if it is just for experimentation then this does not matter.

[SaiTeja]

By shunt cap and series inductor that is a part of nrf output match, do you mean 0.8pF cap and 3.9 nH given in reference design? And what do you mean by ETSI or FCC . Please through some light on that.

[AmbystomaLabs]

Yes the 0.8pF and 3.9nH are part of the nRF output match and must be included. Just google FCC and ETSI they are the worlds two biggest regulatory bodies for wireless products. In any country in the world shipment/sales of wireless products is highly regulated. So if you intend to ship and sell a product you will likely need to go through one of these organizations to get approval.