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adam.stroz
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Custom PCB antenna question.

Hello, 

I have a question about design a custom PCB for DA14531. I created a pcb with ZOR Antenna, for 1,6  mm Substrate (from your doc. AN-B-027). And i place a output PI filter (C4,C2,C3 on screenshot) close to the DA14531 RF pin. And my question is, it is correct to connect antenna directly to PI filter out (C4 on PCB)? Do i need a microstrip line? Is my desing correct? 

  
Device: 
PM_Dialog
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Hi adam.stroz,

Hi adam.stroz,

Thanks for your question. Let me check it and I’ll get back to you.

Thanks, PM_Dialog

PM_Dialog
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Hi adam.stroz,

Hi adam.stroz,

Apologies for the delay. I’ve escalated this to the RF Team internally to check the antenna and the layout. I’ll let you know ASAP with our comments.

Thanks, PM_Dialog

PM_Dialog
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Hi adam.stroz,

Hi adam.stroz,

A ZOR antenna needs a matching, so we are assuming the pi-structure is not the filter we suggest in AN-B-075 but the antenna matching? The line between the output of the pi and the antenna feeding point is very short, so the mismatch will be compensated by the antenna matching.

Are the structures above the antenna conductive? This would impact the antenna efficiency.

Thanks, PM_Dialog

adam.stroz
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Hello,

Hello,

So, the L2 C3 C4 is antenna matching circuit? Value for these elements from AN-B-027 are correct (C3,C4 = 2p2 L2=1,5n)?

What do you mean by "Are the structures above the antenna conductive?"

My PCB is round, next to the antenna there are two holes (no tinning and copper) below the antenna is a polygon layer (top and bottom) connected to GND. Antenna is created directly from your dxf file.
Description in attachment.

Attachment: 
adam.stroz
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I have an additional question, 

do I need a coil with inductance 3n3 placed in series at the RFout pin (before the matching circuit)?

  
MHv_Dialog
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Yes, we recommend following

Yes, we recommend following the schematic for the DA14531 USB development kit: https://www.dialog-semiconductor.com/sites/default/files/da14531-devkt-b-usb_vc3_376-13-d-sch.pdf

/MHv

adam.stroz
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Hello,

Hello,

Thanks for answers, but according to  DA14531 USB development kit schematics. I need only Z7 coil (without Z6, Z8 Z5 elements)? What is the function of Z5, Z6, Z7, Z8 element circuit? 

MHv_Dialog
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Some extra filtering was

Some extra filtering was needed to acheive world wide RF certifications

/MHv

PM_Dialog
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Hi adam.stroz,

Hi adam.stroz,

Please find below some extra inputs from our RF Team:

The values for the antenna matching circuit are depending on the ground, size of the PCB and housing. On our test board we used a parallel 2.2pF capacitor, a serial 1.5nH inductor and did not populate the parallel capacitor close to the antenna. A different board might need a different matching. That can be checked with a network analyzer as soon as the board is ready.

We were not aware that this (please find attached) is a round PCB and wondered if the dark red structure above the antenna is a conductive layer. If this is just empty space everything is fine.

Thanks, PM_Dialog

Attachment: 
adam.stroz
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Hello,

Hello,

Thanks for answer. Yes, red structure above antenna is empty space.