What is nRF51 DK antenna's name or Application Note?

[mahmoud.tolba]

Hi Nordic Community,

Could you please tell me what is the antenna reference design used in the nRF51 DK? and why a lot of BLE development boards (like Redbear BLE shield) use this type of antenna instead of using the Inverted-F Antenna(IFA)?

A lot of articles I have read saying that IFA has the best efficiency (around 80%) if you have a free space in the PCB, So I just wanted to compare the antenna used in the nRF51 DK and the IFA with respect to size, performance, development cost, tuning cost and time to market.

Waiting to hear from you :)

[FormerMember]

The antenna on the nRF51 DK is a quarter-wavelength monopole antenna, and it is described in this whitepaper.

An inverted-F antenna (IFA) is a quarter-wavelength monopole antenna (1/4-wavelength antenna ) where the additional"F"-part represents a tuning component. For a regular 1/4-wavelength antenna that tuning component is the physical parallel component nearest the antenna.

The value of the tuning component has to be found during tuning, because the antenna impedance depends among other of the environment of the antenna; two identical 1/4-wavelength antennas may require different values of the tuning component because they are used in different designs, different housing, and different environments. Therefore, it is a lot easier to tune a "regular" 1/4-wavelength antenna than an IFA antenna. Theoretically, you would need to adjust the "F"-part of the antenna for the various tuning measurements.