4.7 Antenna Design
1) Antenna Efficiency
Antenna efficiency is the ratio of antenna input power to radiated power. Due to the antenna’s return loss,
material loss, and coupling loss, the radiated power is always lower than the input power. Antenna
efficiency > 40% (-4dB) is recommended.
2) S11 or VSWR
S11 indicates the matching degree of the antenna’s 50Ω impedance, which affects the antenna efficiency
to a certain extent. This indicator can be measured using VSWR test. S11 < -10dB is recommended.
3) Polarization
Polarization is the rotation direction of the electric field in the maximum radiation direction of the antenna.
Linear polarization is recommended.
4) Radiation Pattern
Radiation pattern refers to the antenna’s electromagnetic field strength in the far field in all directions.
Half-wave dipole antenna is the most suitable terminal antenna. For built-in antenna, PIFA antennas or
IFA antennas are recommended:
Antenna area: 6mm high x 10mm wide x 100mm long.
Antenna radiation direction: Omni_directI/Onal (omnidirectional).
5) Gain and Directivity
Antenna directivity refers to the electromagnetic field strength of electromagnetic wave in all directions.
Gain is a collection of antenna benefits and antenna directivity.
Recommended antenna gain ≤ 2.5dBi.
6) Interference
In addition to the antenna performance, other interferences on the PCB also may affect the performance
of the module. In order to ensure the high performance of the module, interference must be controlled.
Suggestions: For example, LCD, CP, FPC routing, audio circuit, power supply should be as far from the
antenna as possible, and make the appropriate isolation and shielding, or filtering on the path.
7) Antenna Index Requirements
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