Honeywell XYR301E, Руководство пользователя

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XYR301E Wireless Ethernet User Manual
Page 20 April 2012
Antenna Diversity
One reason to use multi antennas is because of local radio licensing regulations. All countries have a limit on the
amount of transmitted power and radiated power from the antenna. In the US this is 630 milliwatts transmit power and
4 watts EIRP (Effective Isotropic Radiated Power). In a normal system if a high gain antenna is used it improves the
receive signal as well as boosting the transmit signal and possibly pushing it over the EIRP regulation limit. Using
Antenna diversity we can use two antennas, one for receive and the other for transmit. The receive antenna has no
regulatory limits as it does not radiate power so any gain antenna can be used. To calculate the transmit antenna limit
see the examples below. Example If using the XYR301-E in the US the maximum radio transmit power level will be
630mA which will allow up to 4 watts EIRP, what this means is that we can add a gain of approximately 10dB
(including cable loss) without infringing the EIRP. This is calculated by using the general rule of thumb when working
with dB and Power which is doubling the power is a 3dB gain. If using 10m (33ft) of Cellfoil coax cable
(approximately 3dB of loss) and an 8 dBi Antenna this would equate to approximately 5dB of gain, well below our
10dB limit. If using 20m (66ft) of Cellfoil coax cable (approximately 6dB of loss) and a 15 dBi Antenna this would
equate to approximately 9dB of gain, which is also below our 10dB limit. Another application where antenna diversity
may be needed is in industrial plants and factories installations which can suffer from
―
multi-path fading
∥
effects
where multiple reflected radio signals adversely affect the signal strength. In a
―
static
∥
installation, where the radio
path is not changing, moving an antenna to the position of maximum signal solves this problem. However where the
radio path changes because the XYR301-E is mounted on moving equipment, or if there is moving equipment in the
area, then the solution is to use two antennas. Because the two connectors are separated, the RF signal at each
connector will be different in the presence of multi-path fading. The XYR301-E unit will automatically select the
higher RF signal provided RX diversity has been enabled on radio Config page. See Section 3.9
―
Advanced Radio
Configuration for details of configuring Antenna Diversity
Bench test and Demo System setup
Care must be taken with placement of antenna in relation to the radios and the other antennas. Strong radio signals can
saturate the receiver, hindering the overall radio communications.
When setting up a Benchtest/Demo or a short range system the following considerations should be taken into account
for optimum radio performance and reduced signal saturation.

If using Demo Whip antennas (WL-DG900-1 and WL-WH900-SMA) it is recommended that only the Access
Point be fitted with an antenna.

If using Demo Whip antennas on each end, 20dB coax attenuator must be connected in-line with the coax
cable.

If using Demo Whip antennas, modules and antennas must be kept a suitable distance from each other. Check
the receive signal strength on the “Connectivity page” of the module and ensure the level is not greater than -
45dB
Demo Whip antennas should not be used in the final installation as the maximum performance of the modem cannot be
guaranteed.
If using a DG-900 antenna, it is better to keep the antennas at least 3ft (1m) away from the module so as to limit RF
saturation.
Plant and factory installations
Another application where antenna diversity may be needed is in industrial plants and factories installations which can
suffer from
―
multi-path fading effects where multiple reflected radio signals adversely affect the signal strength. In a
―
static installation, where the radio path is not changing, moving an antenna to the position of maximum signal solves
this problem. However where the radio path changes because the XYR301-E is mounted on moving equipment, or if
there is moving equipment in the area, then the solution is to use two antennas. Because the two connectors are
separated, the RF signal at each connector will be different in the presence of multi-path fading. The XYR301-E unit
will automatically select the higher RF signal provided RX diversity has been enabled on radio Config page.