Poor Signal

4 months ago

Hi TP2017,

Thanks for your forum post and for your interest in our BLE solutions.

I had a look at the attached schematics and found one small mistake in the antenna matching.

The L2 is in the RFIOp line but it should be connected to the ground. Please take a look atAN-B-054: DA14585/586 Application Hardware Design Guidelinesand Figure 3: Antenna matching network ( page 9 ). The L1 inductor ( L2 in your schematic) shall be placed as close as possible to the DA14586 and connected to ground.

Additionally, what is the package of the DA14586 that you are using? WLCSP or WFN? The value of this shunt inductor depends on the package.

Additionally, the antenna marching is depended on the PCB size. You could measure the impedance of the antenna with network analyzer.

Thanks, PM_Dialog

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4 months ago

Thanks for the reply. The package is QFN40. I'll take a look at the reference AN-B-054. The size of the board is 2.9cm x 9.1cm. I'll look in to measuring the impedance with a network analyzer.

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4 months ago

I checked Figure 3 of AN-B-054. The circuit looks different than Figure 19 from AN-B-027, "Matching Components, ZOR Antenna, 1.6mm Substrate", which is the antenna we chose. It looks like the ZOR Antenna uses a different matching network than the one in AN-B-054 Figure 3.

I did notice that we should use a 3.9nH inductor vs 3.3 in our current circuit.

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4 months ago

OK. I looked at the network matching circuits shown in AN-B-054 (Figure3) and AN-B-027 (Figure 19) more closely. It looks like they are the same except the AN-B-027 doesn't show the shunt inductor (it does mention it). We assumed that the inductor was meant to be in series with the circuit when the diagram in AN-B-054 shows that it is to ground. I'm pretty sure this is the case, if you could take a look and confirm I'd be grateful.

Thanks

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