Antenna Selection

[Jeff Finkelstein]

We plan on use the ST BAL-NRF01D3 balun for a PCB with both an nRF51822 and a nRF51922 on the same PCB separated by about 4 inches.

Should we use the PCB antenna as on the reference Dongle OR Development board OR should we think about a chip antenna for best performance?

[andrew sauter]

I have similar question, but I want to use PCB antenna.

The PCA10004 and the PCA10000 are very different PCB antenna, what is tradeoff.

I am targeting 2 layer PCB, w/out impedance control.

Thanks,

[Jeff Finkelstein]

Additional information... We will be on 4 layer FR4 PCB w/o impedance control.

Does Nordic have antenna radiation patterns for both the PCA10004 and PCA10000 designs?

[FormerMember]

Hi,

You can use any of the antennas. What makes the chioce of antenna depends on the space left for the antenna on the PCB.

The PCB antenna (1/4-wavelength monopole antenna) is the largest one, and has approximately 1dB better gain than the meander antenna. This PCB antenna can be tuned two different ways:

1. The length of the antenna is approximately 25 mm. When tuning the antenna, a pi-network is used.

2. The length of the antenna is a little longer than 25 mm. When tuning the antenna, the length of the antenna is shortened until it reached a "good" length. Then a shunt component (a capasitor) is added to "move" the antenna to 50 Ohm. The tuning methods above are considered equivalent. You can read more about PCB antennas in this whitepaper.

The meander antenna (the antenna on the dongle) is smaller than the PCB antenna, and is used when there is less space available for the antenna. A meander antenna should be tuned with the same methods as the PCB antenna.

A chip antenna may be even smaller than the meander antenna, and will have to be tuned using a pi-network.

You can read more about antenna tuning in this white paper.

BR, Kristin

[Jeff Finkelstein]

Kristin,

Thanks much for the reply....

What about tuning when using the recommended ST BAL-NRF01D3 balun? Should we add provision for any discretes? If so, where?

[FormerMember]

The ST BAL-NRF01D3 balun is used for matching the chip to 50 Ohm, making a 50 Ohm point, and is not for tuning of the antenna. As the schematic shows you will, in addition to the balun, also need a capasitor for matching the chip to 50 Ohm. The tuning network for the antenna (pi-network or shunt tuning component) will be placed after this capasitor.