QUESTION

Question

Hi there,

Which antennas would you recommend? 

Use case: Deep indoor NB-IOT, think basements (smart metering project)
Bands: 5/8/20 (20 being the primary focus)
PCB dimensions: preferably 30mm wide x 100mm long. Dimensions can change slightly if there are big improvements to performance.

I'm current at the SR4L049 and SR4C033, but obviously open to any recommendation. FPC antennas are also an option.

Thank you.
Kevin

Answer 1

Hi Kevin,

I would say the best thing to do in your case is to mount an external terminal antenna to the product. Our Draco antenna would be the best to use and would mount to the upper corner of the your 30x100mm PCB. The Draco would then extend past the PCB above the device.

Using an internal FPC 35mm above the PCB would work but would be shadowed on the opposite side of the PCB so the shadowed side would then be the mounting side of the device. Our Mitis or Moseni would work for this application. You will need to ensure the FPC is at least 20mm from any metallic objects to perform sufficiently to get out of the basement.

You may try SR4L034 if you want to stay with a surface mount antenna.
I recommend using a four or more layers PCB with the top and bottom layers being ground. Try not to run long traces across the top and bottom layers as they tend to cut the ground plane short reducing the performance of the antenna.

Best regards,

Geoff Schulteis

Comments

Hi Geoff,

Thanks for the detailed response!

I'm not sure we can convince our client to use an external antenna and product height also has some restraints so the FPC option is probably also a no-go.

Let's say we have to go for a surface mount version, what PCB dimensions would you recommend? As we're currently still in the design process, we can still adjust the specs.

Thanks.

Kevin

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Hi Kevin,

I would recommend 125mm by 36mm if possible.

Best regards,

Geoff Schulteis

Answer 2

Hi Kevin, my recommendation is to put some empty PCBs with the battery and the antennas into a case and then measure them for return loss. If the return loss is ok, the next step is to measure these boards for antenna gain in three axes. If the result from two or three antennas is similar you can then select the antenna with the best price. Favourable relative. With a PCB antenna, the UFL connector on the PCB and the mounting of the antenna into the housing is added.