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Radar Many in a series of McGourty-Rideout Productions

What is Radar? RADAR (Radio Detection And Ranging) is a way to detect and study far off targets by transmitting a radio pulse in the direction of the target and observing the reflection of the wave. It’s basically radio echo

RADAR RA dio D etection A nd R anging Radar observables: Target range Target angles (azimuth & elevation) Target size (radar cross section) Target speed (Doppler) Target features (imaging) Antenna Transmitted Pulse Target Cross Section Propagation Reflected Pulse (“echo”)

### Slide 4:

Radar Frequency Bands Frequency Wavelength 1 mm 1 km 1 m 1 m m 1 nm 1 MHz 1 GHz IR UV 10 9 Hz 0 1 2 3 4 5 6 7 8 9 10 11 12 30 20 10 8 6 5 4 3 9 7 Allocated Frequency (GHz) Wavelength (cm) X-Band C-Band S-Band L-Band UHF VHF Visible 10 12 Hz Ku K Ka W

### The Range:

The Range Distance from the radar Measured from time delay between transmitted pulse and returned signal received

### The Range:

The Range Remember, in general v=d/t and d=vt The range is just a distance Since radio waves travel at the speed of light (v = c = 300,000 km/sec ) range = c • time/2 Why divided by 2?

### The Range:

The Range The “2” is because the measured time is for a round trip to and from the target. To determine the range, you only want the time to the object, so you take half!

Radar Range Measurement Transmitted Pulse Reflected Pulse Range Target Target range = c t 2 where c = speed of light t = round trip time

### Atmospheric Effects:

Atmospheric Effects

### Slide 11:

Atmospheric attenuation Reflection off of earth’s surface Over-the-horizon diffraction Atmospheric refraction Radar beams can be attenuated, reflected and bent by the environment

Radar The range and the direction of the target determine its location, which is what is needed for many radar applications such as air traffic control .

### How Strong Is It?:

How Strong Is It? The strength of the received echo can also be measured This will vary with the distance of the target, its size, its shape and its composition

### Types and Uses of Radar :

Types and Uses of Radar Search radars scan a large area with pulses of short radio waves Targeting radars use the same principle but scan a smaller area more often Navigational radars are like search radar, but use short waves that reflect off hard surfaces. They are used on commercial ships and long-distance commercial aircraft

### Types and Uses of Radar:

Types and Uses of Radar Mapping radar scans a large regions for remote sensing and geography applications Wearable radar which is used to help the visually impaired Air traffic control uses radar to reflect echoes off of aircraft Weather radar uses radar to reflect echoes off of clouds

### Types and Uses of Radar:

Types and Uses of Radar Weather radars use radio waves with horizontal, dual (horizontal and vertical), or circular polarization Some weather radars use the Doppler effect to measure wind speeds

Incoherent Scatter Radar- A Radar Application Used to study the Earth's ionosphere and its interactions with the upper atmosphere, the magnetosphere, and the solar wind

### Incoherent Scatter Echo:

Incoherent Scatter Echo Electrons in ionosphere are radar targets These electrons can scatter radio waves