Hardware Guide

4 Circuit Design
Copyright © Fibocom Wireless Inc. 59
Table 44. Antenna performance indicators
Indicator
Description
Recommended Value
Antenna
Efficiency
Ratio of antenna radiated power to input
power.
>40% (-4 dB)
S11 or VSWR
S11 shows the matching degree of 50 Ω
impedance of the antenna, which affects the
antenna efficiency to a certain extent. The
VSWR test can be used to measure this
indicator.
<-10 dB
Polarization
type
Rotation direction of the electric field in the
maximum radiation direction of the
antenna.
Linear polarization
Radiation
pattern
Intensity of electromagnetic field in all
directions of far-field.
PIFA or IFA antenna is
recommended.
Gain and
directivity
The gain refers to the combination of
antenna efficiency and antenna directivity.
The directivity of antenna refers to the
electromagnetic field strength of
electromagnetic wave in all directions.
Gain: 2.5 dBi
Input
impedance
Ratio of voltage to current at the antenna
input end. The best situation is that the
input impedance of the antenna is pure
resistance and equal to the characteristic
impedance of the feeder. At this time, there
is no power reflection at the terminal of the
feeder, and there is no standing wave on the
feeder. The input impedance of the antenna
changes smoothly with frequency.
50Ω