Causes of small bandwidth of chip antenna

RE: Causes of small bandwidth of chip antenna

RalfA — Fri, 11 Jul 2025 14:07:59 GMT

[quote userid="2125" url="~/f/nordic-q-a/122897/causes-of-small-bandwidth-of-chip-antenna/542265"]It depends a bit on the size of the PCB, but a via every 5 to 10 mm in a grid across the whole PCB, plus one at every grounded component will do fine.[/quote]

Ah, okay. I used a via spacing of 0.75mm in the BLE area, especially from the BalUn to the tuning network and the antenna. Dedicated vias are also used further away from that area, but not in a grid - will do that.

Regards

RE: Causes of small bandwidth of chip antenna

ketiljo — Fri, 11 Jul 2025 14:00:50 GMT

[quote user="RalfA"]This is already done in the new layout, especially using the 1st inner layer as GND. Regarding the vias for connecting the layers together, is it enough to use those vias in the area of the BLE circuit/antenna or is it needed to do it on the whole contour of the GND polygons?[/quote]

It depends a bit on the size of the PCB, but a via every 5 to 10 mm in a grid across the whole PCB, plus one at every grounded component will do fine.

RE: Causes of small bandwidth of chip antenna

RalfA — Fri, 11 Jul 2025 13:49:55 GMT

Hello ketiljo,

thank you for your answer.

[quote userid="2125" url="~/f/nordic-q-a/122897/causes-of-small-bandwidth-of-chip-antenna/542262"]If the antenna is side mounted, it can't be corner mounted and you have to find another antenna. [/quote]

Okay, so there's no way to use the 2450AT18D0100.

[quote userid="2125" url="~/f/nordic-q-a/122897/causes-of-small-bandwidth-of-chip-antenna/542262"]A good ground plane is key for good antenna gain. Use one of the inner planes for ground, first inner plane preferably. Use plenty of vias to connect all ground planes together. [/quote]

This is already done in the new layout, especially using the 1st inner layer as GND. Regarding the vias for connecting the layers together, is it enough to use those vias in the area of the BLE circuit/antenna or is it needed to do it on the whole contour of the GND polygons?

Regards

RE: Causes of small bandwidth of chip antenna

ketiljo — Fri, 11 Jul 2025 13:39:21 GMT

When you are designing in a chip antenna, the layout, placement and clearance to ground is critical. The cavity in the ground plane around some antennas are part of the design so make sure you follow the datasheet exactly here.

If the antenna is side mounted, it can't be corner mounted and you have to find another antenna.

A good ground plane is key for good antenna gain. Use one of the inner planes for ground, first inner plane preferably. Use plenty of vias to connect all ground planes together.