Radar uses a transmitter to illuminate a target with a signal. The receiver then detects the echo reflected signal which allows the radar to calculate the distance to the target using the time elapsed and velocity of the signal. A radar system includes a transmitter, receiver, antenna, duplexer, power supply, and data processing unit to determine bearing, range and speed information of targets which is plotted and can be tracked over time. Identification systems like IFF interrogate aircraft and receive reply signals to identify friendly aircraft using different modes like coded mission numbers or air traffic control assigned identification codes.

2. Radar transmitter illuminates the target with
a signal
Reflected signal (Echo) picked up by
Radar receiver
Radar Principle

3. Distance=Velocity x (Time/2)
Radar Principle

4. Synchronizer Transmitter
Display Unit Receiver
Power
Supply
ANT.
Duplexer
Antenna Control
Data Processing unit
/ Signal Processor
Radar Block Diagram

5. RADAR DATA
Plot
• Depneds on received echo
• Bearing and range information, radial speed
• Coordinates
Track
• Processed Plots
• Heading, georef position,
track number, identification
Plot history
to initiate
track

6. IFF
Identification of Friend or Foe
Secondary Surveillance Radar (SSR)
Ground IFF transmits or challenges aircraft
Aircraft give reply signal

7. IFF MODES
Mode 1 – provides 2-digit mission code. (military only – can
be changed in flight)
Mode 2 – provides 4-digit unit code. (military only – can't be
changed in flight)
Mode 3/A – provides a 4-digit identification code for the
aircraft, assigned by the air traffic controller. (military and
civilian)
Mode 4 – provides a 3-pulse reply to crypto coded challenge.
(military only)
Mode S – selective mode