Table of Contents
Advertisement
Observe the following recommendations while selecting external or internal antennas:
• Select antennas that provide optimal return loss or Voltage Standing Wave Ratio (VSWR) over all
the operating frequencies.
• Select antennas that provide optimal efficiency over all operating frequencies.
• Select antennas with the appropriate gain and that provide the appropriate gain (antenna
efficiency x directivity) characteristics so the electromagnetic field radiation intensity does not
exceed the regulatory limits specified in some countries. For example, the limits defined by the 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 6
suggests several 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
Hirose
I-PEX
Tyco
Amphenol RF
Table 6: 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
• 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)
Consider that SMT connectors are typically rated for a limited number of insertion cycles.
Additionally, the RF coaxial cable may be relatively fragile compared to other types of cables. To
increase application ruggedness, connect U.FL connector to a more robust connector such as SMA
fixed on panel.
☞
A de-facto standard for SMA connectors implies the usage of reverse polarity connectors
(RP-SMA) on Wi-Fi and Bluetooth
replace the antenna with higher gain versions and exceed regulatory limits.
The following recommendations apply for proper layout of the connector:
• Strictly follow the connector manufacturer's recommended layout:
SMA Pin-Through-Hole connectors require GND keep-out (that is, clearance, a void area) on all
o
the layers around the central pin up to annular pads of the four GND posts.
U.FL. surface mounted connectors require no conductive traces (that is, clearance, a void area)
o
in the area below the connector between the GND land pads.
UBX-22005601 - R04
C1-Public
NORA-W10 series - System integration manual
Series
U.FL® Ultra Small Surface Mount
Coaxial Connector
MHF® Micro Coaxial Connector
UMCC® Ultra-Miniature Coax Connector
AMC® Amphenol Micro Coaxial
®
end products to increase the difficulty for the end user to
Design-in
Remarks
Recommended
Page 22 of 56
Advertisement
Table of Contents
