
SmartSensor 105
10.0 Data Buering. The RVSD shall store, in non-volatile
memory, at least 2,400 interval data packets with the maxi-
mum number of lanes congured.
11.0 Radar Design.
11.1 Frequency Stability. The circuitry shall be void of
any manual tuning elements that could lead to human
error and degraded performance over time.
All transmit modulated signals shall be generated by
means of digital circuitry, such as a direct digital synthe-
sizer, that is referenced to a frequency source that is at
least 50 parts per million (ppm) stable over the specied
temperature range, and ages less than 6 ppm per year.
Any upconversion of a digitally generated modulated
signal shall preserve the phase stability and frequency
stability inherent in the digitally generated signal.
This specication ensures that, during operation, the RVSD
strictly conforms to FCC requirements and that the radar signal
quality is maintained for precise algorithmic quality. Analog
and microwave components within an RVSD have character-
istics that change with temperature variations and age. If the
output transmit signal is not referenced to a stable frequency
source, then the RVSD is likely to experience unacceptable
frequency variations which may cause it to transmit out of its
FCC allocated band and thus will be non-compliant with FCC
regulations.
The RVSD shall not rely on temperature compensation
circuitry to maintain transmit frequency stability.
Temperature-based compensation techniques have been shown
to be insucient to ensure transmit frequency stability. One
reason this type of technique is not sucient is that it does not
compensate for frequency variations due to component aging.
The bandwidth of the transmit signal of the RVSD shall
not vary by more than 1% under all specied operating
conditions and over the expected life of the RVSD.
The bandwidth of an RVSD directly aects the measured range
of a vehicle. A change in bandwidth causes a direct error in the
measured range, i.e., a 5% change in bandwidth would cause a
range error of 10 ft. (3 m) for a vehicle at 200 ft. (61 m). If the
bandwidth changes by more than 1% due to seasonal tempera-
ture variations and component aging, then the RVSD will need
to be frequently recongured to maintain the specied accuracy.
11.2 Antenna Design. The RVSD antennae shall be de-
signed on printed circuit boards.
Printed circuit board antennae eliminate the need for RF con-
nectors and cabling that result in decreased reliability. Printed
circuit antennae are less prone to physical damage due to their
extremely low mass.
The vertical beam width of the RVSD at the 6dB points of
the two-way paern shall be 65 degrees or greater.
This enables the RVSD to provide simultaneous detection from
a lane located at the minimum oset and a lane located at the
maximum range. The vertical beam width of an RVSD deter-
mines the eld of view in which it can detect trac. If the eld
of view is smaller than the distance between the minimum oset
and the farthest range, then the RVSD will be unable to detect
vehicles over the entire range. A vertical beam width of less than
65 degrees will not allow an RVSD, mounted at a typical height
of 17 ft. (5.2 m), to simultaneously detect and report informa-
tion when the lanes are positioned from the minimum oset of 9
ft. (2.7 m) to the maximum range of 200 ft. (61 m).
The horizontal beam width of the RVSD at the 6dB points
of the two-way paern shall be 11 degrees or less.
A narrow horizontal beam width allows the RVSD to resolve ve-
hicles at the farthest ranges. If the horizontal beam width is too
large, a trailing vehicle may be merged with the vehicle in front.
The sidelobes in the RVSD two-way antenna paern shall
be -40dB or less.
Low sidelobes ensure that the performance from the antenna
beam widths is fully achieved.
11.3 RF Channels. The RVSD shall provide at least 4 RF
channels so that multiple units can be mounted in the
same vicinity without causing interference between them.
12.0 Conguration.
12.1 Auto-conguration. The RVSD shall have a method
for automatically dening trac lanes or detection zones
without requiring user intervention. This auto-cong-
uration process shall execute on a processor internal to
the RVSD and shall not require an external PC or other
processor.
The auto-conguration process shall automatically dene
trac lanes or detection zones by detecting the relative
position of vehicles within the RVSD’s eld of view.
The RVSD shall include a transceiver capable of detect-
ing multiple vehicles present within its eld of view. The
RVSD shall also include a processor or computer with
executable instructions that estimates the position of each
of the vehicles, records the position of the vehicles, gener-
ates a probability density function estimation from each
position of the vehicles, and denes trac lanes from that
probability density function estimation. The probability
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