Re: Looking for resources on radar.

From: George (george.l__at_cashette.com)
Date: 07/26/04 

Date: 25 Jul 2004 19:26:19 -0700

Daniel Rudy <i0n1v2a3l4i5d6d7c8r9u0d1y2e3m4a5i6l7@n0o1p2a3c4b5e6l7l8s9p0a1m2.3n4e5t6> wrote in message news:<201Lc.94146$jj6.41332@newssvr29.news.prodigy.com>...
> I've been to google, but all that I've been able to turn up is a bunch
> of companies that want to sell radar equipment. I'm thinking of using
> the 24GHz range for it. Max ranging distance is about 600 feet. If
> anyone has any design information or sources, please let me know. Thanks.

The field is huge and designs are so different that it's not really
possible to give design information without more inputs. A few
important details would help
1 What accuracy do you need?
2 How much power do you want to use?
3 How many do you want to make (is it a volume product - for how many
per year)?
4 Which countries (USA, Europe, ...) and are you concerned about
licensing?
5 Temperature range?
6 Pulse or LFM?
7 What type of antenna - narrow beam, separate Tx/Rx antennae,
di-electric rod, horn, dish, PCB patch ...?
8 Application information (reflectance of the target or target
strength)?
9 Can you use a laser rangefinder (these are cheap commercially and
may be what you need), the range is good and the beam is much tighter
requiring less processing to extract the distance information
10 Do you need polaristaion (CP or RP)
11 Is the target moving (doppler may be a concern or a measured
variable)

Some comments
24 GHz is far from trivial, both the antenna and the electronics are
difficult to design without CAD to help reduce design cycles and some
pricey measurement is required. Also the band selected places
restrictions on available bandwidths.
6GHz is much easier but still not trivial.

2.4GHz radar can be just as accurate, its just bigger and all kinds of
commercial components are available. Most design will be OK on FR4 PCB
material.

Several patents exist for radar systems of the type you seem to be
asking about, this has production/licensing implications but they
really speed up the design. Some are very old and patents are a source
of information.

There really are 3 design hurdles,
1 the microwave part (RF oscillators and their modulation)
2 the antenna and coupling to it
3 converting the speed of light signals into something you can
process

Radio approvals follow - massive headache

If you want just one or 2 then buy a commercial version and either use
the RF module inside or at least you can use the antenna.

180m is a longish range for ISM type emissions, the surface had better
be big or reflective or your antenna is going to have to be big

After all this, I agree that google and other search engines give
little useful information (unless you want a radar detector) and I
hope this thread will bring together some brains to solve some of the
design problems, one example is the genration of short pulses, less
than 1ns long needed to modulate the pulse laser or RF burst.

A starting point for your design is the radar equation, several of
these are available online but it is also the type of math that can
easily be done on paper by hand - almost in your head. You do need to
know your parameters
  Output power
  Antenna gain (size and efficiency)
  range
  target characteristics - absorbtion, reflection, amount of
scattering)
  receiver noise
Amateur radio users often have useful information and sources of parts
(also radar equation calculation examples) but their link is one way

You can of course look at available products that work over the range
required and use their specs as a starting point

Hope this helps
George

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