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Unformatted text preview: ES 300 Principles of Naval Weapon Systems Problem Set 3 —AY 2011 1
NAME: ) Section: ulse RADAR.
Associated Equation 1. Comlete this table to demonstrate the differgce between the continuous wave RADAR and the Number of Duty Rmin Unique Components Component Purpose
Antennae C cle (‘tfeesazizgs
14,2457; Br
I/ . 196+ LQ€ C H +ahav1: “‘7 (a C/ 2. A RADAR transmits a 3 usec at a pulse repetition time (PRT) of 1997 usec.
a. Calculate the range resolutionvassumin g a pulse compression ratio 2 1. R , c, PW (59.295 (:13)
res / 3 Mr .92 Pct: V2 Pt _ “N
' Li 6L “‘1 —> 14— —>l 14—
pw = 3 usec PRT = 1997 usec b. Draw a picture showing how far apart two aircraft would have to be to be displayed as two separate
targets by the RADAR: AJr legit Liza's)“ ‘ ’4? H'SOM  ‘ w
6 N:tj " 5y " lie“ :1
c. Now, assume the frequency is increased over the duration of the pulse width, resulting in a pulse compression ratio of 100:1. Calculate the new range resolution ofthis RADAR. W.— ,# ~‘\ R : qgc ‘ re: we 0 PITFA L . .
PREVENTION Prmaples of Naval Weapon Systems M 5”" 3‘): [593% These terms are often confused: . , . . . Kr:
Beamwidth _ The 3. A surface ship 5 veloclty IS typically 0 — 30 knots. angular measurement a. Using a shorebased RADAR operating at 2 GHZ, calculate the range of
of the width of a Doppler shifts associated with surface ships at these speeds. + . sﬂ
transmitorreceive /\~. . \5M A (: .2 v.93 (l < — S> _ .  . : ,/———
beam. 3 eq ‘ 5
Bandwidth  The ‘ range of transmit and é— r97 “$561” + ’3'?
receive frequencies . { 1 +  Ht
inside which the 6 97‘» lamjail ' °4 A ’ 2 C10 RADAR operates' b. What is the handwidth necessary to detect these surface ships? (0 mm; A Li l7— HL 04 BM (Len—Yeregl, art 1 C: H;
J
'< ~ W burr"r (Jw_.——»~ﬁu ~ ~>‘.
~——~i—‘ ~ +
‘,‘iﬁ‘i,‘t‘i‘i‘77‘iiiz RQH .2,ooo,uoo,zoip H; 4. Your ship is on course 300° T speed 22 knots. You have an air contact on y07ﬁr Pulsed Doppler air trafﬁc control
RADAR bearing 045 °T, range 10,000 meters. The contact’s IFF transponder indicates that it is on course 180°T
with a Doppler shift of 75 Hz. Your RADAR operates at a frequency of 2.0 GHz. a. Diagram the situation, labeling LOS, cwn ship and target course/speed, 01, 02, etc: dan‘ta (7+ 3 e 8 a“? b. What is the relative velocity between your ship and the contact in the line of sight direction?
(: ﬁves ‘ A? )\ 76)(.\6§
A . :1) \/ : : ,
)\ ms R Q : (“/5 of [(+5 c. What is the target speed (knots)? b V VLD I ,_ V! CD 5 ﬁr,
Vina: V~ Luigi Y»)? a 2 cos (9 Z (0.9 ~ 92 {as (959 23 Skis Cos ( ‘1 6 '
d. Are you opening or closing the contact? . . ‘ s K x f . be/CoLUje’ A g {5 e. What is physically happening to the cairier wavelength that causes this Doppler shift? The» coax/“t, \G lore/3A3 cotmpre‘JSC/‘i #603397 ‘ v v '1 C/ WEBLINK Doppler: H0 Ore/0w “03 ‘ J re a/bc" 7
2 ll http://wwwcbu.edu/~jvarrian/aggle
ts/dopplerl/dopplerhtm ES 300 Principles of Naval Weapon Systems 5. You are ﬂying your SH60B on a surface, subsurface, search coordination (SSSC) mission in the North Arabian Gulf. You are heading 200° T at 110 knots. The E2C gives you a head’s up concerning an airborne target ﬂying
at 250 knots on bearing 090°R. Base frequency of your RADAR is 3 GHz. You estimate the contact’s course to be 1 10°T. a. Diagram and label the situation: /\: Seal ' [M ~— b. What is the speed along the line of sight in knots? VLDS : \/I (0319‘ +0\/,L C05 (91
~ {/0 (5 O} 'r 2250 as O) c. What is the expected Doppler shift?
M: ;2< m) 42572 Hz . l 6. Your aircraft is equipped with a RADAR altimeter (RADALT) which uses Frequency Modulated Continuous
Wave (FMCW) to measure the distance from the bottom of the aircraft to the ground. The carrier frequency of the transmitter is swept from 4,250 to 4,350 MHz; every 30 usec. Some time later the ﬁrst returned signal at 4,250
MHz is received while your transmitter is currently sending out a signal at 4,300 MHz. What is your current altitude? F g A 4550Mﬁl~ gisawmlp {DOMHZ
1"\’ / r 6%
7300 MHz ' 14575004”; : gC’M HZ T [)4 (ED/(ASCL:)C m S r f
u Incident Reﬂected D '6 f '
3 wave wave ._ 4 I O 0
g (delayed) Z t
§ 2  attitude
I) la =———— .—
z e y Speedoflight _, I ﬂ 6 e/b waived inﬂected m From the original transmitted waves. 1.AﬂouumMum..tmwwmmem R: C A { (3 Source: http://mwrfcom ES 300 Principles of Naval Weapon Systems 7. Use the following terms to ﬁll in these blanks:
CONTINUOUS WAVE DOPPLER SHIFT FMCW RANGE VELOCITYMS) Because a continuous wave RADAR calculates .deg from DOPPLE/Z S Ill/FT , but cannot measure range, the frequency modulated Q, My” Moo 3 w km: RADAR was created. The
FM’ CW RADAR is used to derive iﬁ MC: E information from transmitted frequency at the time the reﬂected signal is received. 8. The purpose of moving —target indicator (MTI) RADAR is to reject signals from ﬁxed or slowmoving unwanted
targets, such as buildings, hills, trees, sea and rain and retain for detection signals from moving targets such as aircraft.
a. Is an MTI function used with a basic pulse RADAR or continuous wave RADAR? Pulsed Retaich b. What information about the target does the MTI measure? \w Pornc (5"?) Ctné Moveameﬂ‘l’ (Phurt .2 v c. How is this information used to identify a moving target?
A doom?) \ AS Pkmsf, 5x“ 9+ (race. {vch p lg measure/<1, over SUL<€,S:S\V‘€, returns "there, defianccé'noiion) log+wgcyﬁ ‘HAC OJAA 9. Inverse Synthetic Aperture RADAR (ISAR) provides improved target resolution.
a. Explain what the target needs to do for this to occur: Target Must have PUMA” “0%?” CED“) bi't’cli) Yaw) b. Why must the target do this?
Paiothb MO+lU/\ arm‘k'lz’b/ iM ao)'€/ 4650‘ c. What type of target typically does this? Skies — ‘l’ea VLE’WU'HCCL Plum?) 3" 0\ clrxangn/L r/lopplc/f' Slﬂi"(+ rcél/U'are’é +0 d. What can an ISAR operator do to improve the ISAR return image? Inawﬁﬂ Uni‘ejr‘ociwoA “ilmﬁ, .)T ( )\ __,_ _ : 2 T (3—2: “a” in. (e +21%, we a, a— a _ AP
10. A search tracking Cband (f = 3000 MHz) RADAR needs to resolve targets 1 km apart (Rcross) and 15 m in range at a range of 200 km. What is the width of the mtenna to meet these parameters? >\ : tie/3:7 :  'iVl Rxoss I: Re'SclE : C .
Jij &.>:— f (300 i a) M Ravi! ES 300 Principles of Naval Weapon Systems 11. The Seasat SAR satellite operates at 1.3GHz from an orbit 800km above earth. The SAR requirement is to
achieve a resolution on the ground (Rcross) of 6m. What must be the distance traveled by the antenna? K Cross 1 E >\ 12. Consider phasedarray RADAR: 51x
02R 20‘.) :2) < :: x/ : lSﬁSl‘TM 36 365/ ~
1.3tclﬂ Lfch \ .2304 lCClﬂHﬁgqlll — sgannccl array. a. Another name for it is an e b. Explain the four advantages of a phased array (over a servomechanically steered system:) i_ IAS‘TlaNJT ECQVV\ VD St‘l’l‘pﬂ l‘V‘j ii" l3 lA 
in Very Qe/l l able, C less MUVIVJ POLF‘liT ’5 [633$ Mufﬂlmatuﬁ)
iv. M 0 FC/ lax} PA .‘l// C M ul‘i’i P I C §mrcl\€‘3/h~a(/E 3;} c. What elemental principle of how waves interact allows for phased arrays to steer a beam of
electromagnetic energy? Conﬁ(u¢+xvﬁ/ «1' ole/Sli’UC/‘l’tve, {A‘l’ar‘fﬂt’tm CC, d. If a beam must be pointed up, wave energy from the lower antenna elements must travel a greater d "u fﬁ’oun c: 1 than the energy radiating from the upper elements to arrive in phase at the same
point in space. The phasers of the lower elements must therefore A by: N C E (write in: advance or retard) the phase of their outgoing signal in order to create g Q Ki 5,: Q U Q ' I I (/5 interference and an upwardpointing beam. b (SEQ ot‘l’eS 6. Explain what parts of the phase shift formula account for differences in distance traveled by
electromagnetic waves: a c :7; e + ea; 6—1 Cl \ {élﬁbﬂ CC
f. If a required phase shift for a 6 GHz phased array RADAR element is +65 degrees:
i. How much farther must the energy from this element travel than the reference element energy? so, 5 X
",5 Fa‘l’lﬁ MP: (96° : §E§ZA>Q => AX ‘ \ titliii’)‘:7€'3ml ii. How many more wavelengths of travel does this distance equate to? , 367 AX .00? _ '
A, éeqjiCDS“ﬂ 7: ’roi‘v ES 300 Principles of Naval Weapon Systems 13. You have a planar phased array as pictured below. What is the phase shift needed for element number (2,2) in
order for it to be part of a beam with an elevation angle of 35° and an azimuth angle of negative 10°? Assume that
both the horizontal elements columns and tlg vertical elements rows are M2 apart. I Phased Array with 4x4 Elements l reference Azimuthal element number, a 4~4~ﬁf> element (0'0) 1 /\ Elevation
7+ + +5 +31+ + +:
H4 + + + Elevation element number, e Element
(21, e) = (2, 2) <— ...
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