History

1
Introduction

• History

2
19th 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

3
History

• 1886 - 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 Maxwells thesis)
• 1900 Nikola Telsa 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

4
History (Continued)

• 1904 Christian Holsmeyer Patent issued by
  Germany and England after 1st 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
• 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

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History (Continued)

• 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!

6
History (Continued)

• 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 NRL
  pulsed a 71.3 m wavelength
• NRL transmitter located 10 km southeast of their
  laboratory and detected echos 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

7
History (Continued)

• 1918- 1923 1st 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.
• 1935 Atmospheric Scientists brought in Britian
• 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

8
History (Continued)

• 1930s 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

9
History (Continued)

• Development of Multi-Resonant Cavity Magnetron
• 1921 - High frequency oscillator
• 1924 Add split anode design allows generation
  of ultra-high frequency waves Eric Habann
• 1924 August Zacek discovers split anode
  produces considerable microwave power at
  wavelengths as short as 29 cm
• 1927 Japanese independently develop split anode
  design with microwave power at 40 cm
• 1940 Breakthrough Randall and Vooth achieve 400
  Watts of continuous power at 10 cm wavelength!
• Combined resonant cavity feature of Klystron with
  high current feature of magnetron cathode to
  create mulit-resonant cavity structure
• 1940 10 cm Radar developed by GE Research
  Laboratory in Wembley England and goes into
  operation

10
History (Continued)

• 1935-1936 Cowell and Friend detect air mass
  boundary with 5 cm radar Friend (1939) showed
  very good correlation with in situ measurements
  by aircraft
• Early 1940s Pulsed radar developed to better
  detect aircrtaft in presence of echos from sea
  and land frequency shift allows
  detectionDoppler effects rediscovered,
  polarization technologies
• 1946 - Ryde (1946) publishes work on attenuation
  and echoing properties of cloud and rain..radar
  was detecting WEATHER!

11
Types of Radars

• Monostatic vs. Bistatic
• Continuous vs. Pulsed
• Doppler

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