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Home > Archive > Electrical code Compliance > July 2005 > FCC Regulations and Transmission Legality
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FCC Regulations and Transmission Legality
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| Scotty OpAmp 2005-07-04, 6:25 pm |
| Hello All,
For my senior design project, our group is building a radar gun to
measure the speed of moving objects. I am trying to find information
pertaining to the frequency bands and power that we can use. We are
looking for something around 3 Ghz so that the doppler shift is large
enough to not be effected by the phase noise, but small enough so that
we can use our lab equipiment to analyze it. If anyone can recommed a
good site, or a specific article in the FCC regulations, I would
greatly appreciate it. Thanks
-S.O.
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| Ed Price 2005-07-04, 6:25 pm |
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"Scotty OpAmp" <scotty_opamp@hotmail.com> wrote in message
news:1120490575.366105.283550@g47g2000cwa.googlegroups.com...
quote:
> Hello All,
>
> For my senior design project, our group is building a radar gun to
> measure the speed of moving objects. I am trying to find information
> pertaining to the frequency bands and power that we can use. We are
> looking for something around 3 Ghz so that the doppler shift is large
> enough to not be effected by the phase noise, but small enough so that
> we can use our lab equipiment to analyze it. If anyone can recommed a
> good site, or a specific article in the FCC regulations, I would
> greatly appreciate it. Thanks
>
> -S.O.
>
Consider 2450 MHz, an Industrial, Scientific & Medical (ISM) frequency. Look
at 47 CFR 18 for ISM guidance. Look at 47 CFR 15 for Low Power emitters.
What you are proposing is an intentional emitter, but you may be able to
find an allowance for a sufficiently low-power emitter, especially if you
put it on an ISM frequency. The 2450 MHz band is already carrying microwave
oven leakage, Zigby links and a ton of other junk. You may have problems
from these other emitters though. I suppose you could get an old oven
magnetron to run CW (with a redesigned power supply), but minimum operating
power might be rather high. Voltages, currents and RF power are all at a
non-beginner hazard level.
Next choice would be to consider the X-band. Old police Doppler radars
started in the X-band, at 10.525 GHz. I think that too is an ISM frequency.
There are several bands designated for vehicular radars, for speed
measurement, traffic control and anti-collision uses. I think there's
another vehicular band around 37 GHz. Take a look at 47 CFR 2 for frequency
allocations in the USA. The X-band is popular because there's lot's of
surplus hardware around, and high-gain, very directional antennas are
reasonably portable. You can likely make a milliwatt-level CW signal source
quite easily.
I examined a military intrusion detection system a log time ago that used
low-power 60 MHz, extremely stable CW emitters located throughout a
protected area. Even a slow-moving human body would produce enough Doppler
shift for the sensor's narrow-band receiver to detect the small shift and
report the intruder.
I would suggest some ARRL books, like the general Handbook and the UHF
Experimenter's Manual. That's a good start, and if you are a ham, then there
are some legal frequencies available to you that are also suitable for
Doppler experimentation.
You should also consider other forms of Doppler-shifted energy. Could you do
the job with audio waves or ultrasonic energy? Also, if the project is to
measure an object's velocity instead of demonstrating Doppler Theory, then
how about pulsed energy with round-trip timing?
--
Ed
WB6WSN
El Cajon, CA USA
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