7 posts / 0 new
Last post
daniel59
Offline
Last seen: 11 hours 2 min ago
Joined: 2016-01-08 04:34
Why my bluetooth signal is bad?

Hi,

I use a a ceramic chip antenna, RFANT3216120A5T by Walsin, connect to DA14580 with a 6.8nH inductor and 50 ohm Impedance Transmission Line according to RFANT3216120A5T datasheet, and a 3.9nH inductor according to AN-B-018 section 3.7.

My board can only be detected in about 2 meters distance.

Is there anything I forget to place on the board?

Daniel

Device: 
SDK: 
MT_dialog
Online
Last seen: 1 min 35 sec ago
Staff
Joined: 2015-06-08 11:34
Hi daniel59,

Hi daniel59,

The range of a device (antenna) depends on multiple factors, impedance matching, placement on the PCB, trace length, etc, even not proper soldering on a ceramic antenna on the PCB can cause range issues. You can have a look at the IoT reference design documents, the IoT uses a Ceramic Antenna and use this as a reference.

Thanks MT_dialog

daniel59
Offline
Last seen: 11 hours 2 min ago
Joined: 2016-01-08 04:34
Hi MT_dialog,

Hi MT_dialog,

I find the IoT project use a Pi matching, without the 3.9nH inductor. It's different from AN-B-018 section 3.7. Why?

Daniel

MT_dialog
Online
Last seen: 1 min 35 sec ago
Staff
Joined: 2015-06-08 11:34
Hi daniel59,

Hi daniel59,

Because it uses a different antenna, the AN-B-018 document deals mostly with PCB antennas and not ceramic antennas. Apparently there was no need for additional matching on IoT and thats why they didn't place that inductor. I suppose that the improvement with the additional inductor was minor.

Thanks MT_dialog

daniel59
Offline
Last seen: 11 hours 2 min ago
Joined: 2016-01-08 04:34
Hi MT_dialog,

Hi MT_dialog,

I found the note on the antenna datasheet....it said "The antenna matching network values here are used when antenna is mounted on evaluation board"......

I think maybe this is my problem....

So how can I calculate the matching component for my board? Is there any online RF calculator recommanded?

Daniel

MT_dialog
Online
Last seen: 1 min 35 sec ago
Staff
Joined: 2015-06-08 11:34
Hi daniel59,

Hi daniel59,

When knowing the antenna impedance (this should be measured in the full application with plastics using a network analyser), and knowing that the RFIO of the 580 is 50 Ohm, one can calculate the required values for a PI-network matching filter. After doing so you should repeat the measurement and the result should be close to 50 Ohm. You will be able to find a tool for determining the matching components parts in the following link http://www.fritz.dellsperger.net/smith.html.

Thanks MT_dialog

daniel59
Offline
Last seen: 11 hours 2 min ago
Joined: 2016-01-08 04:34
Hi MT_dialog,

Hi MT_dialog,

If I have antenna s-parameter file, like Johanson's antenna 2450AT07A0100, do I still need the network analyser? or I can pick one with 2.44Ghz frequency into the smith chart from .s1p file?

Daniel