Transcript Radar Basics lecture (ppt)

Re-radiated
EM field ???
EM
Wave
Source
Object
uniform traveling
wave
reflected
traveling
wave
Dipole
Antenna
Generator Transmission Line
free space
wave
Continuous
Energy Density
(Standing Wave)
Reflective
Parabaloid
Power Density
decreased in this
region due to
reflection from
parabaloid.
EM
Wave
Source
𝑃𝑡 (𝑊𝑎𝑡𝑡𝑠)
Power Density
increased in this
region due to
reflection from
parabaloid.
Increase in Power
Density in a given
direction is called
GAIN, 𝐺𝑡 .
Aperture
Receiver (Rx)
(Antenna)
Detector
Object
Transmitter(Tx)
Signal
Generator
Bistatic System
Aperture
Receiver (Rx)
(Antenna)
Signal +Noise (1)
Detector
Signal post-conditioning
to enable detection
(sampling and averaging)
Signal preconditioning to
enable detection (change
frequency, amplitude, etc.)
Electronic Noise (2)
Aperture
Receiver (Rx)
Detector
(Antenna)
Circulator or Mixer
STIMULATED
Signal +Noise (1)
Signal
Generator
Transmitter(Tx)
Monostatic System
Radar Basics: Pulses and Range Gates
Ln Pr
Transmitted Pulse
Noiseless Receiver


Time
Signals and Noise
Transmitted Pulse
Ln Pr
Observed Signal
(target echo plus noise)
Time
Signal Averaging and Detection
Transmitted Pulse
Ln Pr
Observed Signal plus noise
After
Signal Averaging
(target echo plus noise)
Time
The Radar “Bright” Band
Multiple “Bright” Bands
Steradians
A Radian "cuts out" a length of a circle's
circumference equal to the radius.
A Steradian* "cuts out" an area of a
sphere equal to (radius)2.
*The name steradian is made up from the Greek stereos for
"solid" and radian. The SI Unit abbreviation is "sr".
Sphere vs Steradian
The surface area of a sphere is 4πr2.
The surface area of a steradian is just r2.
So a sphere measures 4π steradians, or about 12.57 steradians.
Likewise a steradian is 1/12.57, or about 8% of a sphere.