chapter 1 introduction to radar - ee.fju.edu.tw

Course: Radar System Design

林昇洲博士

輔仁大學電子工程系所

Radar System Design

Chapter 1Introduction to Radar

1 - 1Chapter 1: Introduction to Radar Dr. Sheng-CHou Lin

Radar System Design

Applications of Radars

Civil Applications

•Weather Avoidance

•Navigation

•Maritime Uses

•High Resolution AreaMapping

•Sounding

•Space Flight

Military Applications

•Navigation

•Early Warning and SeeSurveillance

•Fighter/Interceptor Mission

•Air-to-Ground Operations

•Air-to-Surface NavalApplications

•Proximity Fuses

•Countermeasures


Radar System Design

SAR MAP


Radar System Design

Airbone Radar


Radar System Design

Fighter/Interceptor


Radar System Design

F-15 Multimode APG-63 Radar


Radar System Design

F-20 Multimode APG-67 Radar


Radar System Design

Phase Array Radar

愛國者飛彈射控雷達神盾雷達系統


Radar System Design

Surface-to-Air Radar


Radar System Design

Missile (AMRAAM)


Radar System Design

Missile Guidance


Radar System Design

Missile Guidance


Radar System Design

Basic Element of Radar

Transmitter

• RF amplifier• TWT

Antenna

• Parabolic Reflector• Phase-array

Receiver

• Crystal detector• RF amplifier• homodyne• Superheterodyne

Indicator

• PPI (position)• Speaker or earphone

(Doppler)

RADAR (Radio Detection and Ranging)


Radar System Design

Basic Radar Operation•Radar derives target information by correlating the received signal with the transmitted signal.

Target information Table 1-1.

Size -> strengthRange -> time delayAngular -> Antenna beamVelocity -> Doppler


Radar System Design

Radar Equation

• Transmit Power• Range• Radar Cross Section (RCS)• Frequency• Antenna Gain

- Effective ReceivingAperture (area)

- Wave length

• Other aspects for equation- Prop. Medium & Path

- Atmospheric noise

- System losses (Nonidealcomponents)

- Thermal noise

- Signal process losses(nonideal)

- Other Losses withparticular configurationsand applications

• Powerdensity atRange R


Radar System Design

Radar Cross section (RCS)


Radar System Design

Noise Factor and Noise Figure•Noise Factor: account for noise effects of the receiver

While antenna is matched to the receiver circuit, the thermal noise input tothe receiver is , ,often

. : Bandwidth

•Noise Figure: NF = 10 Log(Fn) in dB

FnSNR iSNR o

--------------------Si NiSo No----------------

No NiSo Si----------------= = = No A Fn Ni =

Ni kTB= k 1.38 10 23–=

T To 290k= = kTo 4 10 21–= B

A

FNi

Si

No A Fn Ni =

Equivalent input noise

So ASi=

Ni

Si Loss = LSo Si L=

No Ni=

kTB is the minimum level forThermal noise


Radar System Design

Maximum Detection Range

Rmax dBm

14--- Pt

dBW2 GdB 2 dBcm dBm 2 BdBMHz Fn

dBLdB

SoNo-------

min dB––– 71dB+–+ + +=


Radar System Design

Other Factors for Radar Equation

Hidden in the radar equation is the fact that the signal receivedis not fixed rather the signal is usually considered be random.

The target return is corrupted by

•Atmospheric &Thermal noise

•EMI, ECM

•Undesired returns from other targets (clutter)

•Propagation medium anomalies (irregularity)

The target RCS often changes in an unknown way due to a changeof position


Radar System Design

Radar Detection

Statistical Process

• Atmospheric, thermal noise,electromagnetic interference,background clutter, propagationmedium anomalies, electroniccountermeasures.

• Target’s RCS

Detection

• Single Pulse Probability of False Alarm• Probability of Detection• Output SNR


Radar System Design

pdf of Detection Output (No Target)

False Alarm

• SNR = 0, no Target is present• Rayleigh Distribution Approach• Threshold

• Due to Random Signals


Radar System Design

pdf of Detection Output (Target)

Probability of Detection

• SNR= 1, 2, 3... with target• Rican Distribution -> Direct ray + Rayleigh• Threshold

Maximum Detection Range

• Single Pulse Probability of FalseAlarm (Pfa)

• Probability of Detection (Pd)• Output SNR


Radar System Design

Other Factors of Pd

•Effects of unmatched receiver

— Receiver frequency response relative to a matched filter

•Effects of target signal (Steady or Fluctuating)

— Target reflexivity characteristics

•Effects of antenna pattern (scan modulation, multipath)

• Interference other than noise (clutter, electromagneticinterference, electronic countermeasures)

— Propagation medium and path

•Number of samples included in decision

— Coherent or Noncoherent

— Independent or dependent

chapter 1 introduction to radar - ee.fju.edu.tw

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