| How Radar Works |
Radar stands for radio detection and ranging.
Radar was used first used on ships to detect icebergs and other obstacles. The
most common radar transmits a train of narrow, rectangular-shape pulses
modulating a sinewave carrier. The echo signal is returned and evaluated on a
cathode ray tube, CRT. Distance is measured by the time it takes the pulse to
travel to and from the target.
A continuous waveform, CW, radar can also be used. This radar shows the
doppler frequency shift to measure the velocity of a target.
Most radars operate at frequencies from
about 220 MHz to 35 GHz. However, some radars have operated as high as 5 MHz
and others at 94 GHz. Knowing the frequency the wave length is
determined by dividing the frequency in MHz into 300 to give the wave length
in meters. Usually the higher the frequency, the sharper the return signal and
the more accuracy can be obtained in determining distance and location.
Standard Radar Frequencies and Wave Length
|
| Band designation |
Wave length |
Frequency range |
Application |
| HF (high frequency) Decametric |
100 - 10 m |
3-30 MHz |
Radio, broadcast |
| VHF (very high frequency) Metric |
10 - 1 m |
30-300 MHz |
Radio, TV |
| UHF (ultra high frequency) Decimeter |
1m - 30 cm |
300-1000 MHz |
RADAR, TV |
|
| L, microwave region |
30 - 15 cm
|
1000-2000 MHz |
RADAR, TV |
| S, microwave |
15 - 7.5 cm |
2000-4000 MHz |
RADAR |
| C, microwave |
7.5 - 3.8 cm |
4000-8000 MHz |
RADAR |
| X, microwave |
3.8 - 2.5 cm |
8000-12,000 MHz |
RADAR |
|
| Ku, microwave |
2.5 - 1.7 cm |
12-18 GHz |
RADAR |
| K, microwave |
1.7 - 1.1 cm |
18-27 GHz |
RADAR |
| Ka, extremely high frequency |
11 - 7.5 mm |
27-40 GHz |
RADAR |
| mm, extremely high frequency |
7.5 - 1 mm |
40-300 GHz |
|
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Computer Classes and Books:
Two Computer Courses are available on CD-ROM disks
that are intended to provide a basic understanding of the subjects of radar
and microwave tubes. Many explanations of various items are presented with
animations to best describe the subject material. Test questions are available
with scoring to assist in learning the subject matter. Available from CDtechware.
One is How to Speak Radar and the other is Fundamentals of Microwave
Tubes. Both are published by Arnold Acker who worked for over 30 years at
Varian Brothers. Mr. Acker has taught many classes on radar so he has a good
feeling and understanding of how to explain this most interesting topic. Mr.
Acker at CDtechware can be reached at 209-847-2304 or e-mail address: arnacker@jps.net. |
A good book on radar is "Introduction to Radar
Systems" by Merrill I. Skolnik. This book, in its second edition, is
published by Mc GrawHill and can be purchased from Borders.
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