Radar

• MTI Radar


  Moving Target Indicator Radar

  
• Advanced Radars

  • Perform multiple functions like determination of range, velocity of targets, Doppler shift and identification of friends from foe and fire control, weather forecasting etc. at a function of a microsecond

  
• Block Diagram of MTI Radar


  1. Transmitter

  2. Receiver

  3. Delay Line Canceller

  4. Display

  
• Principle of Operation of MTI Radar

  1. Transmit pulse

  2. Receive echo

  3. Delay line canceller removes stationary clutter

  4. Display moving targets

  
• Delay Line Canceller (DLC)

  Removes stationary clutter by subtracting a delayed version of the signal from the current signal

  
• Double Delay Line Canceller

  Uses two delay lines to improve clutter cancellation

  
• Blind Speeds


  Speeds at which moving targets are not detected due to the radar's pulse repetition frequency

  
• Methods of Reduction of Effect of Blind Speed

  1. Staggered PRF

  2. Jittered PRF

  3. Multiple PRF
• Types of MTI Radars

  • Area MTI Radar
  • Coherent MTI Radar
  • Non-coherent MTI Radar
  • Airborne Moving Target Indicator (AMTI) Radar
  • Digital MTI (DMTI) Radar

  
• Area MTI Radar

  • Covers a wide area to detect moving targets

  
• Coherent MTI Radar


  • Uses a coherent reference signal to detect Doppler shifts

  
• Non-coherent MTI Radar


  • Does not use a coherent reference signal

  
• Airborne Moving Target Indicator (AMTI) Radar


  • Detects moving targets from an airborne platform

  
• Digital MTI (DMTI) Radar


  • Uses digital signal processing techniques for clutter cancellation

  
• Response of MTI to Moving Objects

  Moving targets are detected while stationary clutter is removed

  
• Points to Remember about MTI Radar

  
• Signals of MTI Radar


  • Successive sweeps on an A-scope display
  • Superposition of these signals showing moving targets

  
• Basic delay line canceller block diagram


  • Effect of DLC on the signal

  
• MST Radar

  Moving Scatter Target Radar

  
• SAR Radar


  Synthetic Aperture Radar

  
• LIDAR


  Light Detection and Ranging - measures distance by emitting light and detecting the reflected signal

  
• Phase Shifter


  A device that can change the phase of a signal, often used in radar systems
• Length of the synthesis antenna


  The length of the antenna used in a synthetic aperture radar
• Diode phase shifter


  A phase shifter that uses diodes to change the phase of a signal
• PIN diode


  A type of diode used in phase shifters and other microwave circuits
• Pulse Doppler Radar


  A radar that extracts the Doppler frequency shift to detect moving targets in the presence of clutter

  
• Types of Pulse Doppler Radar


  • High-prf pulse Doppler radar
  • Medium-prf pulse Doppler radar

  
• Range Gated Doppler Filters


  1. Quantize the range into small intervals

  2. Apply narrow band filters to each range gate

  3. Eliminate collapsing loss and preserve range resolution
• Digital Signal Processing in MTI Radar

  1. Split IF signal into I and Q channels

  2. Sample and store in memory

  3. Subtract current sweep from previous sweep

  4. Combine I and Q outputs

  
• Blind Phase


  Phase relationship between the radar signal and the Doppler signal that can cause complete loss of the target signal

  
• Advantages of digital processing over analog delay lines in MTI radar