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Phil Gresock, Keysight’s Radar Lead, sits down with us to discuss the basics of radar and give us a peek into the world of aerospace electronic warfare.
Agenda:
00:20 Adaptive cruise control for cars works really well.
1:00 the history of radar – the original radar display was an oscilloscope in WWII. (radar test equipment)
http://www.pearl-harbor.com/georgeelliott/scope.html
1:45 Early warning radar
2:00 The rumor that carrots are good for your eyesight was a British misinformation campaign.
2:58 The British had the “chain home radar system” all along the coast that pointed to their western front. They wanted early warning radar because they had limited defensive forces. By knowing what was coming, they could allocate defenses appropriately.
3:45 Radar originally was a defensive mechanism.
3:50 How does radar work? You send out a pulse that is modulated on a carrier frequency. If that pulse gets reflected back, we can do some math and work out how far away something is.
4:30 Typically, there’s a specific frequency used. For long range radar, like search and early warning radar, a lower frequency is used.
5:15 What does a modern radar system look like?
It depends on the application. Early warning systems are often anchored on old oil rigs. The rigs have a radome installed on them.
6:25 How does radar detect something so small and so far away? A lot of it depends on the frequencies and processing techniques you use.
6:40 There are some radar techniques you can use, for example bouncing off of the sea, the earth, the troposphere.
7:15 Radar also has some navigational benefits. For example, wind shear flying into Breckenridge airport. A change in medium is measurable.
8:10 Radars also get installed on missiles to do some last-minute corrections.
8:35 Ultimately, the goal of radar is to detect something. You’re trying to figure out range, elevation (azimuth), velocity, etc.
Different target sizes and ranges require different pulse widths, different frequencies, etc.
Azimuth is easy to determine because you know what direction your radar is pointing.
To detect velocity with radar you can use doppler shift.
10:30 Radar cross section analysis gives even more information.
11:00 There are spheres in space for radar calibration. You can send pulses to the sphere and measure what you get back.
Radar calibration sphere in low earth orbit:
http://www.dtic.mil/docs/citations/ADA532032 (for full paper, click the “full text” link)
11:40 There are also reflectors on the moon so you can use laser telescopes to measure the reflection.
Mirrors on the moon:
https://en.wikipedia.org/wiki/Lunar_Laser_Ranging_experiment
12:30 NASA put reflectors in space.
12:58 So, you send a pulse out and get a return signal, but there was a scattering effect. There are libraries for what a return pulse for different objects looks like so you can identify what you are looking at.
14:00 Radar counter intelligence techniques.
First, you have to know you are being painted by radar. Military jets have a number of antennas all around it. And, you generally know what radars are being used in a theater of operation. So, there will be a warning that will let you know you are being painted by a certain type of radar.
15:30 Get Daniel on a fighter jet
16:05 How do you stop your radar from being detected or interfered with? There are a few techniques.
Radar frequency hopping is changing the frequency used from pulse to pulse.
Radar frequency modulation changes the modulation pulse to pulse – phase shifts, amplitude changes, frequency chirps, etc.
This helps avoid detection, get better performance, or reduce susceptibility to jamming.
If you know how your radar responds to different signals, you have a lot of flexibility in what signal you use.
How do you spoof a radar? You have to know what is incident upon you and know how that will act over time. You can send out pulses advanced or lagging in time or with different Doppler shifts to give misinformation to the receiver.
You can also drown out the pulses so that your pulses get read instead of your reflections.
You have to have an intimate understanding of the radar you’re trying to defeat, a good system to handle that quickly, and good knowledge that something is actually happening.
We need radar profile flash cards.
Radar peak energies are anywhere from kilowatts to Megawatts.
21:10 A recent US Navy ship had a new hull design, and it has to turn on a beacon because it had so little reflections.
22:00 Phil thinks radars are pretty cool, and it shows up in a lot more places than you’d expect.
Radar stands for “radio detection and ranging.”
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