NINA-B1 series - System Integration Manual
UBX-15026175 - R06
Design-in
Page 30 of 48
Figure 11: Example of RF trace and ground design from LILY-W1 Evaluation Kit (EVK)
3.2.2
Antenna design (NINA-B111 only)
Designers must take care of the antennas from all perspective at the beginning of the design phase when the
physical dimensions of the application board are under analysis/decision as the RF compliance of the device
integrating NINA-B1 module with all the applicable required certification schemes heavily depends on the
radiating performance of the antennas. The designer is encouraged to consider one of the u-blox suggested
antenna part numbers and follow the layout requirements.
•
External antennas such as linear monopole:
o
External antennas basically do not imply physical restriction to the design of the PCB where the
module is mounted.
o
The radiation performance mainly depends on the antennas. It is required to select antennas with
optimal radiating performance in the operating bands.
o
RF cables should be carefully selected with minimum insertion losses. Additional insertion loss will
be introduced by low quality or long cable. Large insertion loss reduces radiation performance.
o
A high quality 50
Ω
coaxial connector provides proper PCB-to-RF-cable transition.
•
Integrated antennas such as patch-like antennas:
o
Internal integrated antennas imply physical restriction to the PCB design:
Integrated antenna excites RF currents on its counterpoise, typically the PCB ground plane of the
device that becomes part of the antenna; its dimension defines the minimum frequency that can be
radiated. Therefore, the ground plane can be reduced down to a minimum size that should be
similar to the quarter of the wavelength of the minimum frequency that has to be radiated, given
that the orientation of the ground plane related to the antenna element must be considered.
The RF isolation between antennas in the system has to be as high as possible and the correlation
between the 3D radiation patterns of the two antennas has to be as low as possible. In general, an
RF separation of at least a quarter wavelength between the two antennas is required to achieve a
maximum isolation and low pattern correlation; increased separation should be considered if
possible, to maximize the performance and fulfil the requirements in Table 8.
As numerical example, the physical restriction to the PCB design can be considered as shown
below:
Frequency = 2.4 GHz
Wavelength = 12.5 cm
Quarter wavelength = 3.125 cm
1
o
Radiation performance depends on the whole product and antenna system design, including
product mechanical design and usage. Antennas should be selected with optimal radiating
performance in the operating bands according to the mechanical specifications of the PCB and the
whole product.
1
Wavelength referred to a signal propagating over the air.
