NINA-B1 series - System Integration Manual
UBX-15026175 - R06
Design-in
Page 31 of 48
Table 8 summarizes the requirements for the antenna RF interface.
Item
Requirements
Remarks
Impedance
50
Ω
nominal characteristic impedance
The impedance of the antenna RF connection must match the
50
Ω
impedance of the
ANT
pin.
Frequency Range
2400 - 2500 MHz
Bluetooth low energy.
Return Loss
S
11
< -10 dB (VSWR < 2:1) recommended
S
11
< -6 dB (VSWR < 3:1) acceptable
The Return loss or the S
11
, as the VSWR, refers to the amount of
reflected power, measuring how well the primary antenna RF
connection matches the 50
Ω
characteristic impedance of the
ANT
pin.
The impedance of the antenna termination must match as much
as possible the 50
Ω
nominal impedance of the
ANT
pin over the
operating frequency range thus, maximizing the amount of the
power transferred to the antenna.
Efficiency
> -1.5 dB ( > 70% ) recommended
> -3.0 dB ( > 50% ) acceptable
The radiation efficiency is the ratio of the radiated power to the
power delivered to the antenna input; the efficiency is a measure
of how well an antenna receives or transmits.
Maximum Gain
Refer to Section 5
The maximum antenna gain must not exceed the value specified in
type approval documentation to comply with the radiation
exposure limits specified by regulatory agencies.
Table 8: Summary of antenna interface (ANT) requirements for NINA-B1
In both the cases, while selecting external or internal antennas, the following recommendations should be
observed:
•
Select antennas that provide optimal return loss (or VSWR) figure over all the operating frequencies.
•
Select antennas that provide optimal efficiency figure over all the operating frequencies.
•
Select antennas that provide appropriate gain figure (that is, combined antenna directivity and efficiency
figure) so that the electromagnetic field radiation intensity does not exceed the regulatory limits
specified in some countries (for example, by FCC in the United States).
3.2.2.1
RF Connector Design
If an external antenna is required, the designer should consider using a proper RF connector. It is the
responsibility of the designer to verify the compatibility between plugs and receptacles used in the design.
Table 9 suggests some RF connector plugs that can be used by the designers to connect RF coaxial cables based
on the declaration of the respective manufacturers. The Hirose U.FL-R-SMT RF receptacles (or similar parts)
require a suitable mated RF plug from the same connector series. Due to wide usage of this connector, several
manufacturers offer compatible equivalents.
Manufacturer
Series
Remarks
Hirose
U.FL® Ultra Small Surface Mount Coaxial Connector
Recommended
I-PEX
MHF® Micro Coaxial Connector
Tyco
UMCC® Ultra-Miniature Coax Connector
Amphenol RF
AMC® Amphenol Micro Coaxial
Lighthorse Technologies, Inc.
IPX ultra micro-miniature RF connector
Table 9: U.FL compatible plug connector
Typically, the RF plug is available as a cable assembly. Different types of cable assembly are available; the user
should select the cable assembly best suited to the application. The key characteristics are:
•
RF plug type: select U.FL or equivalent
•
Nominal impedance: 50
Ω
•
Cable thickness: Typically from 0.8 mm to 1.37 mm. Select thicker cables to minimize insertion loss.
•
Cable length: Standard length is typically 100 mm or 200 mm; custom lengths may be available on
request. Select shorter cables to minimize insertion loss.
•
RF connector on the other side of the cable: for example another U.FL (for board-to-board connection)
or SMA (for panel mounting)
