introduction to radar webinar - eastern optx mwj webcast... · propagation path replicators test...

Bullock Engineering Research Copyright 2014

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Introduction to RADAR Webinar

By Scott R. Bullock

of

Besser Associates, Inc.

Sponsored by:

Eastern OptX Background

Test Solutions for: Radar Systems Transponders Altimeters

FMCW LPI

Digital Radios

Eastern OptX Background

A Veteran Owned Small Business Approved Suppler to the DoD and all Major Primes Operating in Moorestown NJ USA Since 1975. 15 Years Building Propagation Path Test Instruments. 26 Year History with Phase Noise Measurement Systems. More than 20 years of System Integration Experience. Calibration and Service Lab since 1999 currently supporting 20 year old field equipment.

Propagation Path Replicators

Propagation Path Replicators

Test Systems for Radar, Radar Ranges, and Radio Systems Operates with any signal waveform type, encryption, spread spectrum, and variable power. Uni and Bi Directional Systems High Dynamic Range (120 dB) Wide band 0.001 40 GHz Better than 1% Accuracy Replicate channel up to 200 Nautical Miles Doppler, Interferer Generation, Phase Modulator, and Multipath (fading)

Phase Noise Test Systems

Phase Noise Test Systems

6, 26, and 50 GHz Models Absolute and Residual Measurements Pulsed and CW Amplitude Noise Base Band Noise Lowest Noise Level Test Capability in the Industry (190 dBc/Hz) Single box solution

Altimeter Test Systems

Altimeter Test Systems

Universal Radar Altimeter Test System for all makes and models. For use in development, calibration, and production test application. FMCW (Swept CW. All types including constant difference frequency CDF). Compressed Pulse Radar Altimeter (CPRA, Satellite Altimeter). High Spatial Resolution Radar Altimeter (Topology Mapping). Low Probability of Intercept (LPI). Stealth altimeter for military aircraft.

Bullock Engineering Research www.BesserAssociates.com Copyright 2014

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Scott R. Bullock [email protected]

BSEE BYU, MSEE U of U, PE, 18 US Patents, 22 Trade Secrets Books & Publications

th edition http://iet.styluspub.com/Books/BookDetail.aspx?productID=395134 http://www.theiet.org/resources/books/telecom/tsddcfe.cfm

http://sci.styluspub.com/Books/BookDetail.aspx?productID=369239 http://digital-library.theiet.org/content/books/te/sbte002e

Multiple Articles in Microwaves & RF, MSN Seminars - Raytheon, L-3, Thales, MKS/ENI, CIA, Titan, Phonex, NGC, Others

Courses for Besser Associates Introduction to RADAR - http://www.besserassociates.com/outlinesOnly.asp?CTID=253 Introduction to Wireless Communications Systems - http://www.bessercourse.com/outlinesOnly.asp?CTID=235 Transceiver and Systems Design for Digital Communications - http://www.bessercourse.com/outlinesOnly.asp?CTID=208 Cognitive Radios, Networks, and Systems for Digital Communications - http://www.bessercourse.com/outlinesOnly.asp?CTID=251

College Instructor Graduate Presentation on Multiple Access to Polytechnic, Farmingdale//Brooklyn, NYAdvanced Communications, ITT Engineering 201E, PIMA

Key Designs Radar Simulator for NWS China Lake Acquisition, Target Tracking, Missile Tracking, MTI

IntegratedTopside INTOP Integrate Radar with EW, EA, Comms Radar Comms using CP-PSK Modulated Pulses for the SPY-3 Radar and PCM/PPM


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RAdio Detecting And Ranging RADAR

RADAR is a method of using electromagnetic waves to

determine the position (range and direction), velocity and identifying characteristics of targets.


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Radar Applications

Military Search and Detection Targeting and Target Tracking Missile Guidance Fire Control Acquisition, Track Airborne Intercept Ground and Battle field Surveillance Air Mapping Systems Submarine and Sub-Chasers

Commercial Weather, Navigation, Air Traffic Control Space and Range Road and Speeding Biological Research Bird and Insect Surveillance and Tracking Medical diagnosis, organ movements, water condensation in the lungs, monitor heart rate and pulmonary motion, range(distance), remote sensor of heart and respiration rates without electrodes, patient movement and falls in the homeMiniature Seeing aids, early warning collision detection and situational awareness


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Two Basic Radar Types

Pulse Radar Transmits a pulse stream with a low duty cycle Receives pulse returns from targets during the time off or dead time between pulses

Continuous Wave Radar Sends out a continuous wave signal and receives a Doppler frequency for moving targets

Bullock Engineering Research www.BesserAssociates.com

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Pulse Vs. Continuous Wave

Pulse Radar Single Antenna Determines Range & Altitude Susceptible To Jamming Physical Range Determined By Pulse Width PW and Pulse Repetition Frequency PRF Low average power Time synchronization

Continuous Wave Radar Based on Doppler Requires 2 Antennas No Range or Altitude Information High SNR More Difficult to Jam But Easily Deceived Simpler to operate, timing not required


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Pulsed Radar

Most radar systems are pulsed Transmit a pulse and then listen for received signals, or echoes Avoids problem of a sensitive receiver simultaneously operating with a high power transmitter. Transmits low duty cycle, short duration high-power RF- pulses Time synchronization between the transmitter and receiver of a radar set is required for range measurement.


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Pulse Radar Modulation

100% Amplitude Modulation AM ON/OFF keying Turn on/off a Carrier Oscillator Pulse width is how long the carrier is on Pulse Repetition Frequency is how fast the carrier is turned on


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Radar Turns on/off the Carrier Frequency

Pulse Width = 1us

Time between pulses = PRI = 7us = 1/PRF = 143 kHz

V

t

Burst of Carrier Frequency Radar burst Low duty cycle, high power Duty cycle = time on/time off * 100 a percentage Above example approx. 1/6 * 100 = 16%

carrier wave = 4MHz


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Radar Burst of Frequency Pulse Modulated On/Off Keying t

V

Oscillator

Modulator On/Off Switch

Continuous Waveform - CW

Pulse Train: PRF Radar Pulses

V

t PW

PRI = PRT

PRF = 1/PRI

t

V

PW

PRI = PRT

PRF = 1/PRI


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Pulse Characteristics

Pulses are repeated at the Pulse Repetition Frequency or PRF PRF is the number of pulses per second Pulse Repetition Indicator PRI is the time between pulses Pulse Repetition Time PRT is the same as PRI PRT = PRI = 1/PRF

Pulse Width PW - amount of time that the radar is transmitting Pulse Width (PW) determines the minimum range resolution


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Pulse Distortion

P1

PRI = 1/PRF Long P1 returns cause distortion to P2 returns

t

V

Long returns from P1 causes distortion to the returns of P2

P2


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Basic RADAR

Transmit Radar Pulse

Radar Directional Antenna

Target

Reflection off a Target


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Basic Radar Diagram

Transmitter Reflective Radar

Surface

Transmit Channel

Low Noise Receiver

Receive Channel

RADAR TARGET


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Radar Path Budget

Tracks Signal & Noise Levels from Radar to Target back to Radar Power Out (PA), Tx Losses, Channel Losses, Target Reflectivity, Channel Losses, Rx Losses, Rx Detect S/N Required S/N

Radar Budget - Allocation of Power and Noise Radar Tx PA to Radar Rx Detector (LNA) Used in Solving Tradeoffs

Size, cost, range Radar pulses are reflected off targets that are in the transmission path

Targets scatter electromagnetic energy Some of the energy is scattered back toward the radar.


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Effective Isotropic Radiated Power EIRP

EIRP = Effective Isotropic Radiated Power = RF Power * Antenna Gain

RF Power

Gain

RF Power

Target

Target

ERP = Effective Radiated Power EIRP = ERP + Gdipole (2.14dB) ERP = EIRP - Gdipole (2.14dB)


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Sun Focusing Sun Rays

To Increase Power

Focusing Radio Waves To Increase

Power

Magnifying Glass

Directional Antenna

Receiver

Focusing Increases Power To Provide Gain


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Radar Cross Section RCS

- size and ability of a target to reflect radar energy m² = Projected cross section * Reflectivity * Directivity

The target radar cross sectional area depends on:

Direction of the illuminating radar Transmitted frequency, Material types of the reflecting surface.

Difficult to estimate -sectional area theoretically

Not all reflected energy is distributed in all directions Some energy is absorbed Usually measured for accurate results


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Radar RCS Patterns

Sphere = r2

Flat Plate = 4 w2h2/

Corner Reflector = 8 w2h2 2

Similar to Antenna Gains


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Radar Transmitter Power to Target

Freespace Attenuation

Water Vapor

Rain Loss

Oxygen Absorption

Multipath Loss

EIRP

Afs = 2/(4 R)2 LAtmos Lmulti

Transmitter

Reflector Target

Pt

Gt

Power at Target = Ptarg(i) = PtGtAfs= PtGt 2

(4 R)2

Power at Target = Ptarg = PtGtAfs = PtGt 2 Includes other losses Lt (4 R)2 Lt

Lt = LAtmos * Lmulti


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Radar Received Power from Target

Afs = 2/(4 R)2 LAtmos

Lmulti


Water Vapor

Rain Loss

Oxygen Absorption

Multipath Loss

Receiver

Reflector Target

Gtarg= 4 / 2

= RCS

Gr Pr

Ptarg


Ptarg(i) 4 2 Gr 2 (4 R)2

Power received at Radar (ideal) = Pr(i) = Ptarg(i)Gtarg AfsGr =

Ptarg 4 2 Gr 2 (4 R)2 Lt

Power at Radar = Pr= PtargGtarg AfsGr = (Includes losses) Lt


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Radar Antenna Gain and Channel Losses


Water Vapor

Rain Loss

Oxygen Absorption

Multipath Loss

EIRP


Transmitter

Receiver

Reflector Target

Duplexer

Gtarg= 4 / 2

= RCS

Pt Gt 2 4 2 Gr =

( R)2 2 (4 R)2

Pt

Pr

Power at Target (Ideal) = Ptarg(i) = PtGtAfs= PtGt ( 2/(4 R)2)

Power at Radar (Ideal) = Pr(i) = Ptarg(i)Gtarg AfsGr =

Pr = One-way Loss: Lt = LAtmos * Lmulti Two-way Losses = Lt * Lt = Lt

2 = Ls

Including other losses in the path

Assume Antenna Gain Gt = Gr

PtGtGr2

3R4

PtG2 2

3R4Ls

PtGtGr c02

3f2R4 =

PtG2 c02

3f2R4Ls

=



Lmulti


Water Vapor

Rain Loss

Oxygen Absorption

Multipath Loss

Lt = LAtmos * Lmulti Gr

Gt


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Radar Example

Power at Target = Ptarg = PtGtAfs= PtGt ( 2/(4 R)2)

Pr = PtG2 2

3R4Ls

PtG2 c02

3f2R4Ls = Given: What is Pr in dBm?

f = 2.4 GHz, , = .125 Pt = 100W R = 1000m Gt = Gr = 1000 Total 2-way loss Ls = 10

= 140 m2

100(1000)2(.125)2(140)

3 (1000)4(10) Pr = =1.10235*10-8W = 1.10235*10-5mW

Prdbm = 10log(1.10235*10-5) = -49.6 dBm


Water Vapor

Rain Loss

Oxygen Absorption

Multipath Loss

EIRP


Transmitter

Receiver

Reflector Target

Duplexer

Gtarg= 4 / 2

= RCS

Gr

Pt

Pr

Gt



Lmulti


Water Vapor

Rain Loss

Oxygen Absorption

Multipath Loss



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Free Space Attenuation

Forms of free-space attenuation depends on how it is used Afs = ( /(4 R))2 will be less than 1 and multiplied Afs = ((4 R)/ )2 will be greated than 1 and divided Afs = 20log /(4 R) = will be a negative number and added Afs = 20log (4 R)/ = will be a positive number and subtracted Important to determine if it is added or subtracted to avoid mistakes

Given:

Pt = 100W = 50dBm, = .125, R = 1000m Afs = ( /(4 R))2 = 98.9 x 10-12 need to multiply: Pr = 100W * 98.9 x 10-12 = 9.89 x 10-9

Afs = ((4 R)/ )2 = 1.01065 x 1010 need to divide: Pr = 100W/(1.01065 x 1010)= 9.89 x 10-9

Afs = 20log /(4 R) = -100 dB need to sum: Pr = 50dBm + (-100dB) = -50dBm Afs = 20log (4 R)/ = 100 dB need to subtract: Pr = 50dBm - 100dB) = -50dBm


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Two-Way Radar Losses

Two-way free space loss used twice Once for the radar transmitter to target path Once for the target to radar receiver path Free Space Loss 2*Afs = 2* 20log /(4 R)

Two-way Losses in Radar in dB Atmospheric loss 2* Latmos Multipath loss 2* Lmult

T/R switch or Circulator loss 2* Ltr Antenna loss, Polarization, Mis-pointing, Radome 2* Lant Implementation loss 2*Li Losses in dB: Ltotal = 2* Latmos + 2* Lmult + 2* Ltr + 2* Lant + 2* Li


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RADAR Equation to Assess Radar Performance

P r = Radar received power P t = Radar transmitted power G t = Transmitter antenna gain G r = Receiver antenna gain G2 = Gr Gt assumes the same antenna at the radar = wavelength

R = slant range Ls = total two-way additional losses

= radar cross section of the target RCS

Log Form

Pr = PtG tG r Afs AfsGtarg1/Ls

10logPr = 10logPt + 10logG + 10logG + 10logAfs + 10logAfs + 10logGtarget - 10log(Ls)

Pr dBm = Pt dBm + 2GdB + 2Afs dB + Gtarget dB Ls dB

Pr = PtG2 2

3R4Ls

P(mW) = dBm or P(W) = dBw


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Radar Example dB

Power at Target = Ptarg = PtGtAfs= PtGt ( 2/(4 R)2)

AfsdB = 10log( 2/(4 R)2) = 20log( /(4 R) = 20log[(.125)/(4 1000)] = -100.05dB Gtarg = 10log(4 / 2) = 10log(4 /.1252) = 50.5dB

PtG2 2

3R4Ls

PtG2 c02

3f2R4Ls

=

Given: What is Pr? f = 2.4 GHz, , = .125 Pt = 100W = 50dBm R = 1000m Gt = Gr = 1000 = 30dB Total 2-way loss Ls = 10 = 10dB

= 140 m2 Pr dBm = Pt dBm + 2GdB + 2Afs dB + Gtarget dB Ls dB

Pr dBm = 50dBm + 2*30dB + 2*-100.05 dB + 50.5 dB 10dB = -49.6dBm


Water Vapor

Rain Loss

Oxygen Absorption

Multipath Loss

EIRP


Transmitter

Receiver

Reflector Target

Duplexer

Gtarg= 4 / 2

= RCS

Gr

Pt

Pr

Gt



Lmulti


Water Vapor

Rain Loss

Oxygen Absorption

Multipath Loss



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Range Determination

Range calculation uses time delay between objects Time delay is measured from source to reflector and back Time delay divided by two to calculate one way range

Sound-wave reflection

Shout in direction of a sound-reflecting object and hear the echo Calculate two-way distance using speed of sound 1125 ft/sec in air Measure two way delay of 5 seconds Range = 1125ft/sec x 5/2 = 2812ft


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Sound Wave Reflection

Hi

Hi

Determine the distance using range formula Listen to multiple echoes off difference distances

Best echo effects when the yell is short short pulse width


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Sound Wave Reflection

Hi

Hi

Determine the distance using range formula Listen to multiple echoes off difference distances

Best echo effects when the yell is short short pulse width


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Radar Range Calculation

Radar uses electromagnetic energy pulses Pulse travel at the speed of light C0 Reflects off of a surface and returns an echo back to the radar Calculates the two-way distance or slant range Slant range = line-of-sight distance from radar to target Takes in account the angle from the earth Ground range = horizontal distance from radar to target Slant range calculated using ground range and elevation Radar energy to the target drops proportional to range squared. Reflected energy to the radar drops by a factor of range squared Received power drops with the fourth power of the range

Need very large dynamic ranges in the receive signal processing

Need to detect very small signals in the presence of large interfering signals


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Slant Range

Slant Range = Rslant

Radar Directional

Antenna

Target

Ground Range = Rgnd

Elevation = EL

Rslant2 = Rgnd

2 + EL2: Rslant = (Rgnd2 + EL2)1/2

Sin = El/Rslant: Rslant = El/sin

Cos = Rgnd/Rslant: Rgnd = Rslant*cos

Given: Elevation = 5000 ft Angle = 300

Calculate Slant Range = Rslant = El/sin 5000/sin(30) = 10,000 ft What is the Ground Range = Rgnd = Rslant*cos = 10,000*cos(30) = 8660.25 ft Rslant

2 = Rgnd2 + EL2: Rgnd

= (Rslant2 - EL2) 1/2 = (10,0002 - 50002) 1/2 = 8660.25ft


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Range Calculation

Electromagnetic energy pulse travels at the speed of light C0

R = (tdelay * C0)/2 R = slant range tdelay = two way time delay Radar-Target-Radar C0 = speed of light = 3*108 m/s Given: tdelay = 1ms C0 = 3x108 m/sec Calculate Slant Range = R = (1ms * 3*108 m/s)/2 = 150km


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Radar Range Equation

Rmax = PtGtGr2 = PtGtGr c0

2 3SminLs

3f2SminLs

Double the range requires 16 times more transmit power Pt

Radar detection range = the maximum range at which a Target has a high probability of being detected by the radar

Pr = S = PtGtGr2

3R4Ls

Basic Radar Equation

R4 = PtGtGr2

3SLs

Radar Range Equation (solving for Rmax range for minimum signal Smin):


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Range Ambiguity

Caused by strong targets at a range in excess of the pulse repetition indicator or time Pulse return from the first pulse comes after the second pulse is sent This causes the range to be close instead of far away Radar does not know which pulse is being returned Large pulse amplitude and higher PRF amplifies the problem The maximum unambiguous range for given radar system can be determined by using the formula:

Rmax = (PRI T) * C0/2 PRI = pulse repetition indicator T = pulse width time C0 = speed of light

Example: PRI = 1msec, T = 1us Calculate Max unambiguous Range = (1ms 1us)*3*108/2 = 149.9km


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Range Ambiguity

P1 P2

PRI Range Ambiguities

t

V

Rmax = (PRI PW) * C0/2


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Range Ambiguity Mitigation

Decreasing the PRF reduces the range ambiguity Longer the time delay, higher free-space loss, smaller the return

Transmit different pulses at each PRF interval Higher receiver complexity Requires multiple matched filters at each range bin and at each azimuth and elevation Increases rate of the DSP required for each separate transmit pulse and matched filter pair

Requires changing the system parameters Used most often to mitigate range ambiguity Desired returns from the second pulse move with the PRF Undesired returns do not move since they are reference to the first pulse


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Minimum Detectable Range Example

P1

t

V R1 R2

R3

Minimum Detectable Range Pulse

Does not interfere with the Radar pulse

Tmin for Rmin = Pulsewidth


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Minimum Detectable Range

Radar minimum detectable range return cannot come back during the pulse width

Rmin = (T + Trecovery)*C0/2

T = Pulse width, Trecovery = time for pulse to recover

Very close range targets equivalent to the pulse width not be detected Typical value of 1 for the pulse width of short range radar corresponds to a minimum range of about 150 m Longer pulse widths have a bigger problem Typical pulse width T assuming recovery time of zero: Air-defense radar: up to 800 (Rmin = 120 km) ATC air surveillance radar: 1.5 (Rmin = 225 m)Surface movement radar: 100 ns (Rmin = 15 m)


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Plan Position Indicator (PPI)

The return is displayed on a Plan Position Indicator (PPI)

Rotating Search Radars illuminates the targets on the PPI according to the angle received Range is displayed according to the distance from the center of the PPI Uses a range gate to lock on the range of the PPI


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PPI and A-Scope Displays

N

S

00

900

1800

2700

AoA = 770

Range Gate

PPI A-Scope

Range Gate

V

t

www.BesserAssociates.com

Besser Associates ©Besser Associates, Inc. 2014 All rights reserved

Thank you for Attending !

For more information on this subject please consider attending the live Besser course, Introduction to Radar, March 2 to 4,

2015, in Costa Mesa, California. Contact Besser Associates at [email protected] or

visit us at www.BesserAssociates.com

Sponsored by: online at www.eastern-optx.com


48

Additional Slides If Needed


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Range Resolution

Range resolution - separate two equal targets at the same bearing but different ranges

Depends on the width of the transmitted pulse Types and sizes of targets Efficiency of the receiver and indicator

Pulse width is the primary factor in range resolution Able to distinguish targets separated by one-half the pulse width Basically the same as minimum detectable range Theoretical range resolution is: Sr = (c0* )/2

Sr = range resolution as a distance between the two targets c0 = speed of light = transmitters pulse width


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Pulse Compression Range Resolution

In pulse compression the range-resolution is given by the bandwidth of the transmitted pulse (Btx), not by its pulse width

Sr = > c0/2Btx

Sr = range resolution as a distance between the two targets c0 = speed of light Btx = band width of the transmitted pulse

Allows very high resolution with long pulses with a higher average power

Given: Btx = 20 MHz Calculate Range resolution Sr =


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Basic Radar Range Resolution

CW without Compression

CW without Compression

Poor Resolution

Good Resolution


52

Pulse Compression Improves Range Resolution Using Spreading Techiques

Chirped FM Compression

Phase Shift Keying PSK Compression

Good Resolution

Good Resolution

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