Lecture 1 INTRODUCTION. Dr. Aamer Iqbal Bhatti. Radar Signal Processing 1. Dr. Aamer Iqbal Bhatti

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1 Lecture 1 INTRODUCTION 1

2 Radar Introduction. A brief history. Simplified Radar Block Diagram. Two basic Radar Types. Radar Wave Modulation. 2

RADAR The term radar is an acronym for the phrase RAdio Detection And Ranging It is used to describe systems that use electromagnetic energy to detect distant objects and possibly determine

3 RADAR The term radar is an acronym for the phrase RAdio Detection And Ranging It is used to describe systems that use electromagnetic energy to detect distant objects and possibly determine other characteristics such as direction and range This is accomplished by illuminating a volume of space with electromagnetic energy and sensing the energy reflected by objects in that space. 3

Radar: Acronym for Radio Detection and Ranging Radar is a remote sensing technique: Capable of gathering information about objects located at remote distances from the sensing device.

4 Radar: Acronym for Radio Detection and Ranging Radar is a remote sensing technique: Capable of gathering information about objects located at remote distances from the sensing device. Two distinguishing characteristics: 1. Employs EM waves that fall into the microwave portion of the electromagnetic spectrum (1 mm < l < 75 cm) 2. Active technique: radiation is emitted by radar radiation scattered by objects is detected by radar. 4

5 Why microwaves? Microwaves can penetrate haze, fog and snow readily, and rain and hail less readily, so radar can see through these conditions. An elementary radar system 5

6 A short history of RADAR (19 th Century) EM radiation propagating through atmosphere can be reflected, scattered or transmitted at reduced speed Development of radio technologies bring these effects to light Realization that information buried in these effects 6

7 Heinrich Hertz discovers wave form of EM radiation EM waves can be reflected by certain objects Proves electrical wave identical to optical wave (James Clerk Maxwell s thesis) 1900 Nikola Tesla said in Century Magazine when we make sound wave we can hear echo likewise electrical waves also bounce off an object and the echo potentially can tell us the distance and velocity of that object 7

8 Early 1900s Development of pulsed technology Under development for detection of submarines using acoustic waves in WWI. EM waves needed new technologies in short wave generation Christian Holsmeyer Patent issued by Germany and England after 1 st recorded demonstration of detection of objects by radio Public demonstration 18 May, 1904 of detection of ships passing under bridge through beam of radio waves 8

9 1922 Important studies on propagation of radio waves by Gugliemo Macroni lead to advances in electromagnetic detection 1922 Navy testing high frequency radio transmission across Potomac river interrupted by passing wooden ship the Dorchester Researchers Albert Hoyt Taylor and Leo C. Young noticed this and suggested that these interruptions be used to detect ships in the night. Later, in 1934 Young and Taylor have similar experience with passing aircraft! 9

10 1925 First pulsed device making ranging possible 1925 G. Briet and M Tuve (Dept. of Terrestrial Magnetism of the Carnegie Institution) demonstrate first ranging In cooperation with radio engineers of the US (Naval Research Labs) NRL pulsed a 71.3 m wavelength NRL transmitter was located 10 km southeast of their laboratory and detected echoes 150 km from above Was this first radar??? Yes: because they detected No: because reflection height a function of wavelength and not well defined position of an object 10

11 st real attempts to measure Ionosphere heights by pulsed radar British physicist W. F. G. Swann came to Univ. of Minnesota where Breit was Assistant Professor and Tuve was Research Fellow. They were unsuccessful but their work led to later work. 11

12 History (Continued) 1935 Atmospheric Scientists brought in Britain CSSAD Committee for the Scientific Survey of Air Defense approached Robert A. Watson Watt about use of radio waves to find aircraft Watt was pioneering detection of thunderstorms by detecting radio emissions of lightning Inquiry triggered Watson-Watt and Collegue A. F. Wilkns to propose a radar system to detect local aircraft 5 months later Watson-Watt demonstrate radio detection and ranging of aircraft led to a radar network that provided British early detection of approaching German aircraft 12

13 1930 s Development inus, Germany, England, Italy, France, Holland, Japan and Hungry 1936 April 28 - NRL first definitive detection and ranging of aircraft 14 December Us Army Signal Corp locate airplane by pulse method 13

14 History (Continued) The single most important step in bringing microwave radars was the development of MAGNETRON in By 1941, US had produced about 100 models of early warning radars. World war II changed the world. And after that following radars started to made o Tracker radars o Airborne radars o VHF radars o Fire control radars 14

15 Recent Developments Microwave electronically steered Radars antennas. Phase stable and gridded microwave transmitter amplifiers. Multimodal Radars. Digital computer signal processing. Pulse compression. Fast Fourier Transforms. Synthetic aperture Radars (SAR). Sophisticated smoothing and prediction algorithms. Low observable targets. 15

16 Modern radars Modes of AN/APG-77 AN/APG-77 Installed in Raptor 22 16

17 Different Radar Tasks Detecting and locating ships and land features for ship collision avoidance. Navigating aircrafts and ships in bad weather or at night. Measuring altitude above the surface for aircraft and missile navigation. Detecting and locating severe weather for ground, ship and aviation safety and comfort. Mapping land and sea area from aircraft and spacecraft. Detecting ground moving vehicles such as tanks for defense purposes Precisely measuring distances for land surveying. Detecting and measuring objects under the ground surface. 17

18 Radar Simplified Block Diagram Transmitter/ Modulator Freq gen. Timing control Duplexer Receiver Signal processor Data Proc. displays 18

19 Block Diagram Modules Frequency generation and timing control: This block generates the frequencies and synchronization signals required by the system. Transmitter: It generates the radio signal which is used to illuminate the target from which the echo is derived. Modulator: This function controls the transmitter in pulsed systems, turning it on and off to form the pulse. In CW radars it provides the modulation used by some to find target range. Duplexer: The duplexer switches the antenna of monostatic single antenna system between the transmitter and the receiver. 19

20 Block Diagram Modules Antenna: The antenna concentrates the illumination signal into a narrow beam radiated in a single preferred direction, intercept the target echo signals from this same preferred direction and matches the system impedances those of the propagation medium. Antenna Controller: The antenna controller positions the antenna beam to the defined azimuth and elevation angles and reports these angles to the system controller and data processor. Receiver: The receiver amplifies the echo signals to a level sufficient for later system components, such as signal processor. 20

21 Block Diagram Modules Signal Processor: This function process the target echoes and interfering signals to increase the target echo signal level and suppress the interference, thereby increasing the signal to interference ratio. Data Processor: The data processor stores and processes the location of detected targets. Displays: The displays put the information in a form useable to radar operators and others, such as air traffic controller and weapon system operators and supervisors. 21

22 Pulsed RADAR Concept 22

23 Two Basic Radar Types Pulse Transmission Continuous Wave 23

24 PULSED RADAR Pulse - RADAR transmits a series of pulses separated by non-transmission intervals during which the radar listens for a return CW RADAR Continuous Wave - Constantly emitting radar. Relative motion of either the radar or the target is required to indicate target position. Frequency shift. 24

25 Pulse Radar Components Synchronizer Transmitter Power Supply Duplexer ANT. Display Unit Receiver Antenna Control 25

26 Continuous Wave Radar Employs continual RADAR transmission Separate transmit and receive antennas Relies on the DOPPLER SHIFT 26

27 Doppler Frequency Shifts Motion Away: Echo Frequency Decreases Motion Towards: Echo Frequency Increases 27

28 Pulse Vs. Continuous Wave Pulse Echo Single Antenna Gives Range, usually Alt. as well Susceptible To Jamming Physical Range Determined By PW and PRF. Continuous Wave Requires 2 Antennae Range or Alt. Info High SNR More Difficult to Jam But Easily Deceived Amp can be tuned to look for expected frequencies 28

29 RADAR Wave Modulation Amplitude Modulation o Vary the amplitude of the carrier sine wave Frequency Modulation o Vary the frequency of the carrier sine wave Pulse-Amplitude Modulation o Vary the amplitude of the pulses Pulse-Frequency Modulation o Vary the Frequency at which the pulses occur 29

RADAR DEVELOPMENT BASIC CONCEPT OF RADAR WAS DEMONSTRATED BY HEINRICH. HERTZ VERIFIED THE MAXWELL RADAR.

RADAR DEVELOPMENT BASIC CONCEPT OF RADAR WAS DEMONSTRATED BY HEINRICH. HERTZ VERIFIED THE MAXWELL RADAR. 1 RADAR 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