JMA 51 Radar Recommendations

8/11/2019 JMA 51 Radar Recommendations

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Recommendations

Possible replacement parts

1. Receiver2. Transmitter line modulator, how flexible?can create a multi pulse width modulator using a

different architecture in order to switch to different PRF and PW.

For the weather radar to detect different objects with varying sizes, with a good resolutionof the object, the pulse width (PW) and pulse repetition frequency (PRF) of the

transitter should be adjusted!

"he #$%&' weather radar uses a line&type pulser which produces pulses with a pea of

up to *+! "he advantage of line type pulsers is their efficiency and saller for factor

and weight copared to hard tube pulsers! -ut they have a disadvantage of having a fi.ed

pulse width which liits their application! /f we want to change the application of the

radar, the transitted pulse ust have a different PW and PRF!

"he pulse width of the line type pulser depends on the Pulse&foring 0etwor which is a

transission line with luped paraeters, as discussed in the anual! "he PF0 is one of

the parts of the "ransitter that could be changed in order to provide the weather radar a

different purpose to detect objects saller than rain clouds with a high resolution!

%nother solution to that could be done is to build a variable pulse width odulator as

discussed in 12well, 3! 45, Radar transitters6! 7hown below are the different circuit

configurations that could be done to have a variable pulse width odulator

"he configuration shown ipleents the line type odulator with two switches! 7

operates lie the usual switch in line type pulser! 8n the other hand, 7* enables the

odulator to achieve varying pulse widths by terinating the output pulse before the PF0

copletely discharges and dissipates it to another resistor or load!


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7iilar to the first configuration, the first switch, 7, operates lie the noral switch

found in line type pulsers but in this configuration, the e.cess energy that won9t be use to produce

the output pulse is returned to the power supply through a coupling transforer, therefore

increasing the efficiency of this configuration copared to the first configuration!

/n the third configuration, the energy is returned to the power supply using a coupling

transforer, "! When 7* closes, the pulse is terinated and the voltage across the PF0 is

reversed: this voltage reversal is coupled to the power supply through "! "he losses incurred in

this configuration is less than the losses fro the second configuration through the careful designof the transforer " to iniize fringing and air gap losses!

Discrete components, ma not be directl compatible. !ourced directl from the manufacturer."ustom#made

$. Power !uppl the efficiency of the power supply is good e.cept the ' ;


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%. &ntire power suppl there are off#the#shelf replacements especiall for the $ phase '(R and

)P!. The PD* is +ood as it is for its specific use.

Possible Reuse1. "an the R" weather radar, as it is, be used to detect somethin+ else?

To answer that, we first explain how a radar ac-uires detection.

"an ou -uantif clutter suppression?

R"! of some tar+ets


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1/ 0&" 2$ &dition 1.3 2334#12

To compute for the reflected power, the radar ran+e e-uation is used, ta5in+ into account the free#space

path loss 2/. Ductin+ conse-uences not et accounted for see 'ppendix/.

6here

and

7or !89'! ships +reater than :33 and :333;T,


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The R" radar sensitivit is #113 d*m. Thus, a :33+t ship will not be above the radar receiversensitivit until it is approximatel :5m awa from the radar. 9i5ewise, a :333+t ship will not be above

the sensitivit until it is approximatel 13.:5m awa from the radar. Dependin+ on the threshold for

detection, both ships can either be seen< or unseen. 0f it was seen, it can be detectedpracticall motionless compared to weather activit, ie, wind speeds, rou+h seas, the R"

radar@s movin+ tar+et indicator >AT0 al+orithm mi+ht consider it as clutter and not a tar+et. '")D!P


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'ir search radar#

2D >'BG!P!#"1.2:3#1.$:3 :335 1u#%u

23, 33,

13331:$3HG$.:H

antenna,

transmitter,

receiver,'"),D!P

'ir search Radar#

$D>'BG!P!#'$.%$#$.:: :35

1u or

2u:33#1333

1,2,$,: or

131.1HG$.:H

antenna,transmitter,

receiver,'"),D!P

'ir traffic controlsstem>'BG"PB

1

2.4#2.C 1:5 3.:u#1u

C33 or1:33

132HG1.:H#$.3H

'pproach searchradar sstem for

aircraft

landin+>'BG7PB#2

2.44:#2.C :335 3.u 1233 1: and $33.::HG%H

"lose support

control for

bombin+missions>aircraft

+uide and missile

trac5er>'BGA!I#1'

2.4#2.C 2:35 3.u %13 3#232H>conical

;round

penetratin+ radar3.$#1 3.331#1

133p#

13n1335#13A# #

antenna,

transmitter,receiver, D!P

a. "han+es to the ma+netron have to be made coherent to enable Doppler capabilit BoteJ define

Doppler capabilit and wh it is needed refer to section.. of the manual document/. Pulsed or7A"6? 't lower power, $26 >chec5 ma+netron specs. "han+e or ma5e transmit power variable.

"han+e or ma5e pulse width and pulse repetition fre-uenc variable>TF0! P'RT '9R&'DK

D0!")!!&D 0B TF& "F'B;&! 0B TR'B!A0TT&R !&"T08B. 'dd recommendationshow>ma+netron phase loc5in+.

Document ma+netron operation

/n order to enable doppler capability to the #$%&' radar, the transitted signal ust be

coherent in order to deterine the phase difference and frequency difference of the transitted

and received signals! %s discussed above(docuentation of agnetron operation), the phase of

the output signal of the agnetron differs every pulse! Fortunately, a ethod called agnetron

injection locing can be used to loc the starting phase of a agnetron!

%n e.ternally injected RF signal is injected to the agnetron9s output signal through a circulator!

"he level of the injection signal depends on the spectral bandwidth of the agnetron, typically at

< to *


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/n the paper of (7later, #!, "he Phasing of $agnetrons, 4;+) agnetron phase locing was

e.plained! =sing atheatical odels of agnetron, it was e.plained that the injection signal

fro a stable oscillator is equivalent to an e.ternal adittance whose phase depends on the phase

difference between the stable oscillator and the agnetron! "he agnetron will loc to the

injected signal such that the resulting reactance of the injected signal would pull the agnetron

frequency to equal the frequency of the injected signal! /f the frequency difference is not that

great and there is enough power fro the injection signal, frequency pulling will occur and

locing would tae place! "he article states that phase locing is not iediate as in the case of

frequency locing and for pulsed agnetrons, phase locing ay occur before the pulse reaches

its pea since the tie it taes to phase loc is generally shorter than pulses used in pulsed

agnetrons!

7hown below is the test setup done to an >&band networ with the agnetron pea output power

of *'< W(noinal)! RF signal fro stable oscillator with a ;


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"he disadvantage of injection locing is the need for a stable oscillator with high output power

and a circulator that can accoodate high power pulses!

b. "han+es to the receiver architecturec. "han+es to si+nal processin+ compare output, sampled from the field

d. Tabletop radar

'rchitecture1


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R7 receiver specs

#sensitivit

#+ain#B7 >approximate

"an we provide overall specs, includin+ si+nal processin+?#ran+e >"6, =ust compute in terms of transmit power

#velocit#velocit resolution

#displa instantaneous velocit measurement

'rchitecture 2


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To upscaleJ

1. power amplifier

$/ Belander, '. Toth#Pal, L., MAodular sstem desi+n for a new !#band marine radar,M Radar

"onference # !urveillance for a !afer 6orld, 233C. R'D'R. 0nternational , vol., no., pp.1,:, 12#1 8ct.233C.

2. antenna optionsJ monostatic, bistaticbistatic better isolation

tx antenna monopole

rx antenna phased arra

monostatic phased arra


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%/ Ponsford, '.A. !ev+i, 9. "han, F."., M'n inte+rated maritime surveillance sstem based on hi+h#

fre-uenc surface#wave radars. 2. 8perational status and sstem performance,M 'ntennas and

Propa+ation Aa+aEine, 0&&& , vol.%$, no.:, pp.:2,$, 8ct 2331

'ppendix Ductin+ conse-uences 2/


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JMA 51 Radar Recommendations

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