Microhard Systems IP920, Руководство по эксплуатации

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IP920 Operating Manual: Chapter 5 Installation
45
5. Installation
The installation, removal
or maintenance of all
antenna components must
be carried out by
qualified and experienced
personnel.
5.0 Overview
The installation, removal or maintenance of all antenna
components must be carried out by qualified and
experienced personnel.
The IP920 complies with FCC part 15 at the modular level for operation in
the license-free 902-928 MHz ISM band. This chapter provides guidelines
for installing and deploying equipment which incorporates the IP920
module.
5.1 Estimating the Gain Margin
Successful communication between IP920 modules is dependent on three
main factors:
•
System Gain
•
Path Loss
•
Interference
System gain is a calculation in dB describing the performance to be
expected between a transmitter-receiver pair. The number can be calculated
based on knowledge of the equipment being deployed. The following four
factors make up a system gain calculation:
1. Transmitter power (user selectable 0, 20 to 30dBm)
2. Transmitter gain (transmitting antenna gain minus cabling loss between
the transmitting antenna and the IP920 module)
3. Receiver gain (Receiving antenna gain minus cabling loss between the
receiving antenna and the module)
4. Receiver sensitivity (Specified as -106dBm on the IP920 module)
In the following illustration, the transmitting antenna has a gain of 6 dB,
and the receiving antenna has a gain of 3 dB. The cable loss between the
module and the antenna is 2 dB on both the transmitting and receiving side.
Figure 23 Gain Calculation
The power level has been set to 30dBm (1W) on the transmitter, and the
receiver sensitivity for the IP920 is -106dBm.
System gain would be calculated to be:
30 - 2 + 6 + 3 - 2 + 106 = 143 dB.
Transmitter
30 dBm
Output Power
Receiver
Sensitivity =
-106 dBm
Cable Loss = 2 dB Cable Loss = 2 dB
Antenna Gain = 6 dB Antenna Gain = 3 dB