N723-EA Hardware User Guide
Chapter 5 Application Interfaces
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Schematic Design Guidelines:
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Element components in the above figures are capacitors, inductors, and 0 Ω resistors. Place
these RLC components as close to the antenna interface as possible.
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If static electricity is introduced at the antenna, it is recommended that electrostatic protection be
added. You can use a TVS tube with ultra-low junction capacitance. It is recommended that you
use a TVS tube with a junction capacitance less than 0.5pF. In addition, you must ensure that
the reverse breakdown voltage of the TVS tube is greater than 10V. TVS tubes with a reverse
breakdown voltage of 15V or more are recommended.
PCB Design Guidelines:
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Lay copper foil around the RF connector. Dig as many ground holes as possible on the copper to
ensure 50 Ω impedance in the trace.
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The trace between the pin and the antenna connector should be as short as possible. Control
the trace impedance to 50 Ω.
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If you adopt an SMA connector, a big RF solder pad might result in great parasitic capacitance,
which will affect the antenna performance. Remove the copper on the first and fourth layers or all
layers of a multiple-layer PCB under the RF solder pad.
Figure 5-35
Recommended RF PCB design
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A reasonable distance should be kept between ANT_MAIN and ANT_DIV to avoid mutual
interference that may affect reception performance.
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On the PCB, keep the RF signals and components far away from high-speed circuits, power
supplies, transformers, great inductors, the clock, etc.
5.6.2
Antenna Assembling
The antenna used by the module must comply with the mobile device standard. The standing wave
ratio should be between 1.1 and 1.5, and the input impedance should be 50 Ω. Requirements for
antenna gain vary according to the application environment. In general, the greater the in-band gain
and the smaller the out-of-band gain, the better the performance of the antenna.
Antenna interfaces can be connected to a rubber ducky antenna, magnet antenna, or embedded