RoadMAPS Overview
2-18
RoadMAPS User’s Manual
Antenna and Duplexer
The RoadMAPS antenna, used for both transmission and recep-
tion, is connected to both the RF receiver and the RF transmitter
subsystems by way of the duplexer, and performs at an operating
temperature from -40
°
C to +85
°
C.
The antenna is made of a corrosion-free material that is tolerant to
ultra-violet exposure. It has a magnetic base and is capable of
staying in place at speeds of up to 70 m.p.h.
The antenna is stored in the RoadMAPS Unit carrying case when
not in use.
The antenna will provide nominally 6 dB of gain in the horizontal
plane and will have a cable of optimized length between the Road-
MAPS unit (duplexer/lightening arrestor) and the antenna itself.
The antenna cable will be terminated with an N-type connector.
The return loss at the end of the cable will be below -15 dB at both
transmitting band and the receiving band. The lightening arrestor
will not introduce more than 0.2 dB losses in any of the operating
bands.
The duplexer, as explained previously, ensures that the receiving
band is passed from the antenna to the RF receiver and the trans-
mitting signal is passed from the RF transmitter to the antenna. It
is also the sybsystem that provides the separation between the RF
receiver and the RF transmitter, allowing the two to operate
simultaneously. The duplexer is designed to be a high quality, low
insertion loss, high attenuation device. In the following paragraph,
the term “band” refers to 910-920 MHz in receive mode and 951-
962 MHz in transmit mode.
The duplexer’s insertion losses in the 915 MHz band or the 956
MHz band will be no more than 0.5dB. The attenuation of the
transmitting band at the RF receiver’s input will be a minimum of
60dB, and the return losses in any of the 3 RF ports will be below -
15dB.
While the antenna is designed to stay in place at speeds of up to 70 m.p.h., the system
is only capable of taking reads in a drive-by mode of up to 30 m.p.h.
Содержание RoadMAPS
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