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Experimental study of the radarcross-section of maritime targets
P.D.L. Williams, H.D. Cramp and Kay Curtis
Indexing terms: Marine systems, Radar cross-sections, Radar systems
Abstract: A comprehensive set of results are presented for a variety of surface targets. The targets chosenrange from —40 dBm2 to + 70 dBm2 and results of the smaller ones have been compiled from trials that havetaken place over a variety of environmental conditions. These illustrate the variability experienced at sea inthe radar performance of targets, which, in a free-space environment, may exhibit neither fading nor varia-bility with the aspect viewed. The necessary statistical treatment for fading targets has been used to describethe targets examined in a manner which is directly applicable to the estimation of radar range and detectionprobabilities. Most of the results are appropriate to the bulk of marine radars using a wavelength of 3-2 cmand horizontally-polarised transmission and reception.
1 Introduction and previous work
Over 40 years ago radar was in operational use at sea.However, most of the work on radar equivalent echoingarea (r.e.a.) or radar cross-section (r.c.s.) has been in con-nection with airborne targets. The purpose of this paper isto first review some of the earlier work on the r.c.s. of mari-time targets and then to present the results of seven yearswork in this field. The paper begins by presenting theresults of extensive trials using Fibreglass buoys of in-herently low r.c.s. which were used to support reputedlynonfading targets in the form of Luneberg lenses. The nextseries of trials compared various types of passive echoenhancers that might be used to improve the radar detectionproperties of navigation buoys used by Trinity House.These same buoys were then used as targets in orthogonalpolarisation trials, and finally their short-term or pulse-to-pulse response was measured to find out more about thediffering fading characteristics of various maritime targets.
The paper then goes on to investigate and report on awide range of ships and proceeds to examine several reallysmall targets likely to be found in coastal waters in theform of floating rubbish. This rubbish creates a hazard forsmall, lightly-built craft such as hovercraft, hydrofoils andseaplanes. Examples of this floating rubbish are thenmeasured ashore in a radar anechoic chamber, and, fromtheir r.c.s. polar diagrams, peak and mean values arepresented, showing not only their specular nature but alsolow average cross-section. The paper ends by showing whatvery low r.c.s. values are presented by small yachts andpleasure cruisers and emphasises the importance of refer-ring these r.c.s. values to a suitable reference height abovethe sea: this then enables good radar range estimates to bemade from shipborne surface radars. The situation is differ-ent for airborne search radars, as their superior heightnearly always allows target height above the water to beignored in many short-range detection situations.
With these introductory remarks, various specific pointscan now be made:
(a) For all physical bodies other than a sphere, the radarcross-section of a target must be expressed in terms of a3-dimensional polar diagram with a full list of radar par-ameters used to produce such a polar diagram1"2.
I'aper T192 E, first received 13th January and in revised form 16thMarch 1978The authors are with Decca Radar Ltd., Development Laboratories,Davis Road, Chessington, Surrey KT9 ITB, England
ELECTRONIC CIRCUITS AND SYSTEMS, JULY 1978, Vol. 2, No. 4
(b) If the problem is one of small-target detection, ratherthan large-target resolution, then, with the exception oflight precipitation clutter or low-lying extended coastlines,it may be assumed that the target is small compared to theresolution, either in plan area or volume of the radar in use.
(c) For the maritime case, the movement of the ship,even during the beam dwell time of a conventional marinesearch radar coupled to the ever-varying propagation lossdue to both multipath and atmospheric effects, makes itnecessary to describe target r.c.s. by an adequate set ofstatistics.
(d) Swerling3 produced the first set of detection prob-ability curves for four different fading models following hiswork on a nonfading target, and all of these are nowavailable in a more convenient form by Mayer and Meyer.4
Historically, the earliest published but little known workfrom which an estimate of the magnitudes of radar cross-section (r.c.s.) of targets may be made goes back to thetrials of the 2 cm microwave radar carried on the Frenchliner Normandie in 1935. Examination of the records ofthe French company SFR (Society Francois RadioElectrique) gives the detection ranges of four targetstogether with the nondetection of sea clutter, from whichFig. 1 has been prepared.5 At that time, of course, neitherof the terms 'radar cross-section' or 'radar-range equation'were known, but with our present knowledge it is interest-ing to see how estimates can be made of the magnitude ofthe median r.c.s. values of four targets.
Ten years later, in 1947, Ramsey and Wilkes6 publishedtheir work on ship detection. This is one of the first papersto consider the problems of radar detection from a surfaceradar of surface targets when the normal free-space per-
2 3 4 5range, km
Fig. 1 Estimated r.c.s. of targets observed by Normandie's 1935radar
Shows likely values of a of various targets at specified ranges in trials
121
0308-6984/78/192E-0121 $1-50/0
Table 1: Parameters
Target
\ , cm
Radar height Hr, ft.
Effective targetheight Ht, ft.
Chosen effective radiusof earth, miles
of target trials carriedRamsay" before 1945
100ft yacht
10
530
22
8800
out by Wilkes and
destroyer
10
470
43
5700
formance is modified both by the earth's curvature and theLloyd's-mirror effect. The latter7 covers a point in space,and it was left to Ramsey and Wilkes to extend theargument for a target of sufficient vertical height to extendinto the vertical lobes of the pattern set up by Lloyd'smirror, so that the radar echo was produced by the cumu-lative effect of integrating all the returns from various partsof a ship and its superstructure.
In producing curves of radar received power as afunction of range, Ramsey and Wilkes still had troublefitting their curves into a Domb and Pryce model7 andfinally had to adopt different values of an effective earth'sradius. Details of two of their trials are given in Table 1,showing the large increase on even 4/3 standard earthradius used to allow for the anomalous propagationprevailing.
Early work on microwave propagation over water isreported and reviewed in Chapter 4 of Kerr8 and an impor-tant feature of this propagation work is the variability ofattenuation over water; this means that estimation oftarget r.c.s. from measurement of radar parameters andrange alone leaves errors in excess of 10 dB unless there is aprecise knowledge of the actual attenuation over the waterpath at the time and place the measurement took place.
Since Reference 8 was published in 1951, Nathanson1
has collected a little more data on ship r.c.s., the majorcontribution being from Daly of NRL whose measurementsat various elevation angles of a mine sweeper using the4FRNRL radar are tabulated on page 167 of his book,1
which also includes Russian X-band measurements on a40 ton trawler.
An examination of some of the radar literature9"12
reveals that most work has been done in the measurementof aircraft targets and spacecraft with only limited pub-lication of the r.c.s. characteristics of shipping13 in theopen literature. Wiseman,14 in reviewing the available dataon the r.c.s. of ships, perhaps is too emphatic about theproblem in stating that 'when the ship is viewed from smallelevation angles the concept of r.c.s. breaks down', but thispaper discusses some of the problems brought about by theinconsistency of different measurements.
2 Choice of method of r.c.s. measurement
It would appear that there are three broad methods tochoose from:
(a) Use of the complete radar equation with all par-ameters measured or known so that the r.c.s. of a target isexpressed in eqn. 1. For this purpose the use of a conven-tional pulse radar is assumed:
o =
where o is the actual or instantaneous r.c.s. of target, Pr isthe power received from the target, R is the range (instandard units, e.g. metres), L is the sum of all knownequipment losses (difficult to assess), Pt is the peak trans-mitter power in the pulse, G is the aerial gain (common fortransmitter and receiver), X is the operating wavelength, Fisthe propagation factor due to the Lloyd's-mirror effect andthe curved earth17 and Lp is the sum of additional propa-gation losses due to water content over the path, waveshadows etc.
Clearly, although the true radar parameters of someradar equipment might be measured to an overall accuracyof a few decibels, the losses L and Lp and the patternpropagation factor Fare much more difficult to assess.
(b) The comparison of received power from the targetbeing measured to that received from a suitable standardtarget placed nearby to the target, now all results are interms of an attenuator placed in the receiver arm of theradar.
(c) The use of scale models in some form of radar dark-room or anechoic chamber.15'16 This method, of course,subdivides into either the use of eqn. 1 to derive r.c.s.values of a model target placed on a suitable turntable toobtain a polar plot of received power, and hence r.c.s., orthe calibration of the polar diagram by substituting thetarget under test for a calibration sphere, flat plate orcorner reflector. In both cases the correct scaling factorsmust be used, including the wavelength X.An examination of the aforementioned methods leads oneto the choice of method (b), provided that facilities exist forthe observation of a wide variety of shipping from a con-venient site overlooking the sea. This method is cheaperthan the manufacture of scale models for use on a radio-modelling range15 or underwater-sonar-modelling facility,16
even accepting that the real sea trial may yield results nobetter than ±2-5 dB compared with ± 1 dB claimed by theradio-modelling facility15 for targets in free space; the latterestimate must be accompanied by all the problems ofestimating the change in r.c.s. values when the ship is float-ing in water. However, before commencing any trialsagainst shipping targets, it was felt necessary to gain someexperience in the hour-to-hour and day-to-day variability ofradar detection over water, and a set of trials carried out in1970 will now be briefly described. By repeating themeasurements on the sets of buoys many times for each ofthe separate range stations, short-term anomalies, as onebuoy heeled over due to the wind and changes its positionin the vertical lobe structure, were smoothed out.
3 First series of reflector-buoy trials
The trials were conducted to provide experience in long-term trials and enough results for sound statistical deduc-tions to be made.21
3.1 Site
The site was a coastal laboratory situated a few hundredmetres from the sea on the south-east coast of England.
3.2 Radar used
We used medium-sized X-band commercial marine radarhaving the following major parameters:
122 ELECTRONIC CIRCUITS AND SYSTEMS, JUL Y 1978, Vol. 2, No. 4
AerialA = 3-2 cmvertical beamwidth 0 = 1 5 °horizontal beamwidth 9 = 0-8°gain = 32 dB (measured)rotation speed = 20 r/minpolarisation = horizontal: linearheight: the normal tide range coupled to the use of a tele-scopic mast gave a range of aerial heights from 12 m to22 m above sea level (a.s.l.)
Transmitterpeak power Ppk
pulse characteristics:shortmediumlong
= 25 kWT
= 005 pis= 0-25 AIS
= 0-5 JUS
p.r.f2000 Hz1000 Hz1000 Hz
Receiver = linear superheti.f. bandwidth Bo = 15 or 7 MHz to suit pulse usednoise factor NF « 12 dBfitted with a calibrated i.f. attenuator in 0-1 dB steps
Display12 in p.p.i. with a wide range of range scales from 0-5 to48 nautical miles
3.3 Target buoys
Four special Fibreglass buoys were made with long polesand weights beneath them to maintain the calibrated radartargets as vertical as possible in a variety of sea states, windsand tides as experienced in winter in the English Channel.These were deployed at various ranges from 1-4 to 6nautical miles during the trials.
3.4 Radar targets
Four sets of Luneberg lenses were used having r.c.s. valuesat Jf-band of 2, 4, 6 and 10m2. Unfortunately, instead ofequatorial caps being used to give 360° azimuth cover,
polar caps were used, and three had to be mounted in eachsingle Fibreglass canister, giving 3 sectors of interferencedue to the overlap of two lens polar diagrams. For latertrials only one lens was used, and the buoy was constrainedfrom rotation by four mooring chains to present a singletarget free from interference effects, at least from the targetitself.
3.5 Residual signatures of buoys
Two of the four buoys were deployed at a range of 1-4nautical miles from the coastal radar. One had the 4 m2
target inside and the second an empty canister. Measure-ments indicated that the empty canister was 20 dB lowerthan the 4 m2 one, giving a blind median cross-section ofonly 004m2. On a separate trial the buoy and its canisterhad an r.c.s. at 3 nautical miles less than 0-1 m2, so that ther.c.s. of the buoys used for the trial was determined mainlyby the Luneberg lenses they contained.
100
20 30 40radar performance, dB
Fig. 2 Set of blip/scan curves for the 4 buoys used in the firstseries of trials
Table 2: Typical data sheet for the first series of buoy trials
DateLocation oftargets
Time
SeastateWaveheight
I ide
Wind
Sea clutter:
a) maximumb) at targets
Antenna
DisplayObserverRemarks
9th April 1970Area
Av. range
StartMidFinish
DirectionMean heightAv. SpeedDirection
RangeDirectionRangeExtensionAv. heighta.s.l.Range scalePulse lengthI.S. Bogie
W. Bay
3 n. mi.
160816291650
0-1 ftEbb15'5"5kts285°
1 n. mi.
0 n. mi.FX
20 m3 n. mi./radius0-25 jus
Batch no.4I.F. atten.
(dB)
36
33
30
27
24
21
I.F. atten.(dB) forblip-scanof:25%50%75%
% blip-scan/target
2 m2
0
0
1
654
96
2 m2
25-824-222-5
4 m2
0
0
13
5097
98
4 m2
29 027 025-4
6 m2
0
0
17
8497
99
6 m2
29-528-627-4
10m2
0
24
78
9999
100
10m2
33031 -530-1
ELECTRONIC CIRCUITS AND SYSTEMS, JULY 1978, Vol. 2, No. 4 123
3.6 Method of conducting the trial 3.7 Results
As the trial set out to produce results applicable to a marineradar using only a conventional p.p.i. and operator with noautomatic target extraction, blip/scan curves were preparedon all four targets under various conditions and ranges.Owing to the target fluctuation it was decided to use 100aerial revolutions at each attenuator setting over a range ofsystem gain to enable full detection probability curves to bedrawn from 0 to 100%. Table 2 shows a typical data sheetwhere each line entry has taken 100 aerial scans requiringan observation time of 5min. The results are shown ingraphic form in Fig. 2. At no time during the whole trialperiod from 26th February 1970 to 19th June 1970 did thesea clutter extend over the moored targets at sufficientamplitude as to obscure the targets which had already given100% detection at a lower receiver gain level.
Table 3: Comparison of results for the 4 targets deployed at 5ranges in sequence
Range a
n.mi.1-4
4-2
40CD
^ 3 5aTc 30o§ 2 5
fc 20a
w 1 5
x 10
Averageperformanceexcess
Theoreticalperformanceof the smallesttargets scaledto the 10 m2
result
Averageperformancecalculated
m'246
10
246
10
246
10
dB31 031-633-433-4
18-923-921 -126-5
170
22-223-9
2 17-14 18-26 20-2
10 220
246
10
2-67-59-4
160
dB26-529-531-233-4 - par
19-622-624-326-5 - par
170
21-723-9 - par
15-118-119-822 0 -pa r
9-112-113-8160 -pa r
dB+ 4-5+ 2-1+ 2-2
0
-0 -7+ 1-3-2 -2
0
+ 0-50
+ 20+ O-1+ 0-4
0
-6 -5- 4 - 6-4 -2
02 samples only
extrapolatedperformancebeyond 6n.mi.
"1 2 3 4 5 6 7 8 9 10range, n.mi.
Fig. 3 Detection performance for the average values of the resultsfor all targets at each of the 5 ranges at which they were successfullydeployed
3.7.1 Relative values of r.c.s. The relative r.c.s.5O values ofthe precalibrated targets are shown for each of the 5 rangesin Table 3. It will be seen that the best relationship holdsfor three targets at 4-2 nautical miles. (The 4 m2 targetbroke loose at the beginning of the trial and was finallyrecovered from Denmark!)
The average results from the median points on all theblip/scan curves are shown in Fig. 3. Superimposed on theseresults is a line corresponding to performance varying asR~4 to which the 6m2 target at short ranges correspondsbefore becoming erratic compared with the other three atthe longer ranges.
£
>
16
13
10
target height 2ma.s.1.
10 20 30 40excess performance, dB
Fig. 4 Excess performance as a function of antenna height for the10m2 target at 3 n.mi. range for all sea states prevailing
The result was obtained by taking the average performance of manytrials for four batches of results in four classes of aerial height
3.7.2 Performance change with aerial height: The expectedchange of performance as the aerial height above sea levelchanged is shown as Fig. 4. Here the target lens wasapproximately 2 m a.s.l., depending on which lens wasviewed by the radar, and a combination of tide height andtelescopic mast height produced an aerial height varyingfrom 12 m to nearly 22 m a.s.l. The change of performanceis as predicted by Domb and Pryce7 and convenientlycalculated and plotted by Denison,18 i.e. some 10 to 12 dBof improved performance as the effective aerial heightincreased by 10 m at the range of 3 nautical miles.
3.7.3 Variability of performance: The relationship of targetperformance to aerial height was not apparent by comparingthe results of just a few trials at any of the chosen ranges,but only emerged after considerable smoothing of all resultstaken at 3 nautical miles on the 10 m2 target.
The variability of results is indicated in Fig. 5, which isa collection of all the 50% blip/scan points from all the10 m2 target trials, showing the expectancy of achievingthat result again at each range based on the trials, which,of course, were spread over 6 months with a differentsample of environmental conditions at each range station.
This first series of trials perhaps puts practical maritimerange forecasting in its proper perspective. Berry19 andDenison18 both emphasise that the forecast becomesgenerally less accurate, but at the same time more pessi-
124 ELECTRONIC CIRCUITS AND SYSTEMS, JULY 1978, Vol. 2, No. 4
mistic, as the wavelength of operation drops from 30 cmto 3 cm.
These trials results represent a set of measurements re-quiring 5 min to take each point on a blip/scan curve andso approximately half an hour to complete a batch ofreadings with four targets, and represent the most heavilysmoothed trials of the three buoy trials.
cr=16°/o
extrapolatedfrom 5-6 n.mi.results
Fig. 5 Percentage probabilities of boundary conditions fordetection of 10m2 target
4 Second series of reflector-buoy trials
These were carried out in 1976 as a joint exercise betweenTrinity House and Decca Radar. The primary object was tocompare the effectiveness of various types of radar reflectorsused to improve the radar visibility of large navigationbouys. The work was first reported in October 1977.20 Aview of the 'cage'-type navigation buoy used for all these
Fig. 6 THS buoy
trials is given in Fig. 6 and the size of these steel buoys maybe judged from Fig. 7, where a 3 m tower has been added toraise the light to some 6 m a.s.l., and hence the buoys'optical horizon. Owing to the fact that all the various typesof reflector could not be deployed at the same range at thesame time for a truly comparative trial, the work had to bearranged in a number of phases. The five phases withdetails of reflectors used and results are given in Table 4.
Table 4: Organisation of trials and summary of results
Trials phase Target Target description Excess performance Target minus THSpopulation
A146
A260
B152
B232
C42
ref.
THSBBGSPCS1VBC
THSCRGSPCS1VBC
THSLLAPCS1VBC
THSLLAGCS1VBC
THSGSPGSMCS1VBC
Trinity House standard with octohedronBuoy only — no enhancementDeep corner cluster, plain metalTall channel separation buoy — see A2Coastal feature: Varne Boat Club
Main response a = 150 m2 peak valueOctohedron as THS but made in meshAs in phase A1 — opca/e = 270 m2
CS1 carried an octohedron in all trialsVarne Boat Club
As above, used as referenceLuneberg lens, a = 10 m2
Cluster of 5 corners — opeak = 35 m2
°peak ^ 1 50 m2 for X = 3-2 cmVarne Boat Club
As above for all trialsLuneberg lens, apeak should = omedian
Spiral of cubes a = 20 m2 (claimed)Main response = 1 50 m2
Varne Boat Club
As above, standard referenceDeep corner cluster in plain metalDeep corner cluster in meshThis carried the high reflectorVarne Boat Club
Mean
dB9-7
- 2 - 915-910-5
7-6
14-316-619-210-310-9
20-716-518-114-618-9
23-81 9 021-419-622-2
16-921-422-91 8 019-6
Stan. dev.(a)
dB4-92 04-44-12-9
4-74 04-15-13-8
6-15 05-86-64-4
5-83-83-94-74-4
7-15-25-75-24-1
Mean
dB—
-12-66-20-8
- 2 - 1
—2-34-9
- 4 0- 3 - 4
_
- 4 - 2- 2 - 6- 6 - 1- 1 - 8
_
- 4 - 8— 2-4-4-2
- 1 - 6
_
4-56 01-12-7
Sta. dev.(a)
dB-5-24-95-66 0
—3 04 06-64-5
—3-43-56-65-8
—3-84-57-36-1
_
5-55-5
18-57-3
ELECTRONIC CIRCUITS AND SYSTEMS, JULY 1978, Vol. 2, No. 4 125
Fig. 7 CSl buoy
Fig. 8 AP buoy
Conclusions as to which type of reflector is best aregiven in Table 5. The criteria for a radar reflector's sea-goingsuitability might have been overall size, cost or weight;hereweight is indicated, showing that the cluster of corner re-flectors, although the heaviest, is certainly not the mostefficient radar reflector; this cluster is shown as Fig. 8 andthe best reflector as Fig. 9. From earlier trials the dangersof having to split the work into a number of phases wasappreciated, but deployment of buoys in the EnglishChannel is strictly controlled and so no more than three
Fig. 9 GSP buoy
Table 5: Mean r.c.s. or a of all targets compared to weight
Order of Performancebuoy relativesuccess to t .hs .
CTso measuredand scaledto LL
CTpeakcalculatedor claimed
Weight
GSMGSPCRTHSAGAPLL
dB+ 6+ 4-7+ 2-3
0-2 -4-2 -6-4 -5
m z
112834828161510
m"270270150150
203510
kg8-66 7
1 0 012-78 0
20 06-5
buoys were allowed at any one time. Fortunately, CSl isa permanent sea mark off the Kent coast, and it, togetherwith the THS and a land target viewed over the water, wereused as control targets.
Having explained the need to run the trials in serialform, the change of propagation to the control target pro-vides an indication of the seasonal variation in propagationover the sea for the period. The average performance foreach of the three control targets, namely Standard TrinityHouse buoy (THS), high-focal-plane channel-marker buoy(CSl) and a selected land target viewed over a mainly over-water path (VBC), are plotted in Fig. 10. It will be seenhow the average of all three follow each other quite well,even though their individual results varied on a day-to-daybasis as illustrated in the sample histogram for CSl shownat three detection levels in Fig. 11. The rise in the averageradar performance corresponded to a period of exceptionallyfine and dry weather in 1976.
For the case of the Luneberg lens, the absolute radarperformance is shown at three detection levels of 75%, 50%and 25% in Fig. 11 and may be compared with theequivalent results for CSl taken over the same period. Aline joining the average of the 25%, 50% and 75% Pd foreach target shows how the CSl target corresponds to adeeper fading model than the Luneberg lens.
126 ELECTRONIC CIRCUITS AND SYSTEMS, JULY 1978, Vol. 2, No. 4
Table 6:
Reflector type
German Specktermade in mesh
German Specktermade in plain metal
Octohedronmade in mesh
Octohedron madein plain metal
AGA spiral cube
AGA pentagonalcluster of corners
Luneberg lens
Plain buoy
Buoy data with peak a/mean as o values derived from trials and calculated values of peak a
Initialsused intables
GSM
GSP
CR
THS
AGA
AP
LL
BB
Performancerelative toTHS
dB+ 6
+ 4-7
+ 2-3
ref.O
-2-4
-2-6
-4-43
- 1 2 6
PerformanceLL (direct ortransferredvia THS)
dB+ 10-4
+ 9-13
+ 6-73
+ 4-43
+ 2 03
+ 1-83
ref.O
- 8 - 2
Median r.c.s.scaledfrom LL
m 2
106
82
47
27
16
15
10
1-5
Peak almean CT50
ratio
2-5
3-3
3-2
5-4
1-25
2-3
1
?
A further conclusion to be drawn from this trial is theeffective median r.c.s. of all these reflectors compared withtheir peak values, assuming that the Luneberg lens targets,,by virtue of their 360° azimuth smooth polar diagram andbroad, smooth, elevation polar diagram, represent fade-freetargets, at least in free space. Table 6 gives the calculatedpeak-to-medium r.c.s. values of these physically small butrelatively large r.c.s. targets. The deep corner clusters,denoted as g.s.m., made of glass-reinforced plastic (g.r.p.)with a metallised mesh filling, is seen to have its mediancross-section closest to its calculated peak value. Table 7summarises the situation by comparing the two types ofcorner reflector made in either plain metal or loaded g.r.p.
The precise reason why both of the reflectors made of ametallised mesh give a better overall reflecting propertythan when made of plain sheet metal is not known, butthere can be no doubt that the rough surface presented bythe metallised mesh helps to broaden the major lobes of allthe reflectors, leaving the peak values the same.
This series of the overall trials represents results obtainedover shorter batch observation times compared to phase 1,as each point on the blip/scan curve was the result of only10 aerial scans, taking half a minute compared to the5-minute points in the first series.
1975 1976Dec. April June Sept. Nov.
1977Jan.
A l
Fig. 10 Seasonal propagation change for the control targets used
a Trinity House standard buoyb High focal plane channel marker buoyc Varne Boat Club land target
-10
-10
n
20 25
Fig. 11 Histograms of the Luneberg lens reflector
a Pd = 75%bPd = 50%cPd = 25%All phases Bl
ELECTRONIC CIRCUITS AND SYSTEMS, JULY 1978, Vol. 2, No. 4 127
Table 7: Showing the low peak to mean CT50 ratio of the bettertargets and improvement brought about by using a mesh reflector
material
Reflector Peak/mean aso
Ratio Improvementusing mesh
GSM 2-5GSP 3-3CR 3-2THS 5-4
7 "
6
5
4
3
2
1Q
-
-
-10 0 10d B
a
7 -
6
5
4
3
2
1Q
p i
-
-
-10 0 10d B
b
7
6
5
4
3
2
1
-
i~i--
i i i
-10 0 10dB
c
dB3-95-15 07-3
n
I
r
\\\\
i\rr. In
cIB+ 1-2—+ 2-3-
i n, nil
20 25
[20 25
nilrli
>0 25
Fig. 12 Histograms of the performance of CS1
a Pd = 75%bPd = 50%C x
All phases B l
5 Third series of reflector-buoy trials
These took place over the same period and with the sametargets as the second series, but from an adjacent site with anonscanning aerial which could be trained on each of themarine targets in turn.
Once more, a horizontally-polarised X-band marine-radartype of pulse transmission was used, but instrumentation torecord the individual pulse amplitude (quantised in 5 dBsteps) was available. In addition, the crosspolarised r.f. com-ponent could also be recorded at the same time. Figs. 3aand b have been specially selected, as they show that
whereas severe fading is taking place on the parallel-polarisation receiver channel from one of the targets, theorthogonally-polarised channel is returning a very steadystrong signal equal to or better than the best return in theparallel channel.
To portray a little more of the available data moreclearly, Fig. 14 shows the cumulative probability diagramsmade up from separate 1024 pulse data blocks which wererecorded sequentially over a 15min period during one dayagainst the standard Trinity House octohedron, a typegenerally deployed at sea. These data blocks (any one ofwhich might be sampled in the beam-dwell time of a
time = 0-1 s
30
20
10
t ime =0-1 sb
Fig. 13 Parallel and cross polar returns from target GSP undercalm conditions
Transmission horizontally polariseda Horizontal polarisation returnsb Vertical polarisation returns
100
enS 50c« 25a>a 0
100
f 75S 50
a 25
\
10 15 20 25 30 35dBa
10 15 20 25 30 35dBc
100
a, 75en| 50a>ii 25a>a. 0
100
* 75en2 50
a 25111a 0
\ * " " • - ^
10 15 20 25 30 35dBb
5 10 15 20 25 30 35dBd
100r
a1 50ui 25
100
* 75en
2 50Hi
a 25
\
ON10 15 20 25 30 35
dBe
10 15 20 25 30 35dBf
Fig. 14 Cumulative probability diagram for each target reachingthe signal level on the X axis
horizontally polarised returnsvertically polarised returns
128 ELECTRONIC CIRCUITS AND SYSTEMS, JULY 1978, Vol. 2, No. 4
scanning marine radar) illustrate how unpredictable theresults from a corner reflector are at sea.
It is suggested that the vast difference in data blocks,both in the parallel polarised as well as the crosspolarisedchannels, more correctly shows the short-term target-performance changes than a single cumulative probabilitydistributive diagram made up from many 1024 data pulseblocks, particularly if high detection probabilities arerequired in any one aerial sweep, i.e. the signal fade in bothchannels in Fig. 14b prohibits any decision being madeabove a detection probability of 50% in either parallel orcrosspolarised channels, even though that in the parallelreached + 30 dB.
6 Discussion on reflector-buoy trials
The trials have examined the changes of absolute radar per-formance of various enhanced targets over sampling periodsvarying from one hour to a few minutes to really fastmeasurements spaced only by milliseconds. They haveemphasised the variability not only over these differentperiods but also over daily and monthly periods, and haveTable 8: Physical data and r.c.s. of shipping
indicated that radar target cross-section measurementsrelying on a fixed propagation path loss over water willhave very poor accuracy.
They have shown how any one particular Swerlingmodel may be appropriate for a target at one time but thatmodel may be incorrect a few minutes later, and perhapsthe sea state, including direct wave obscuration betweenradar and target, is more of a dominant mechanism outsidethe range where the sea clutter itself is observed than hashitherto been noted. The presence, position and form ofthe surface evaporation duct would appear to affect surfacetarget detection as much as, if not to a greater extent than,aerial or target height themselves.
A supplementary orthogonal receiving channel recoveringthe returned target power, normally discarded in con-ventional plane-polarised radars, may provide a worthwhilemethod of combatting fading.
7 Large-ship r.c.s. trials
Having established the variability of radar performanceagainst controlled marine targets,21 it was clear that the
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ELECTRONIC CIRCUITS AND SYSTEMS, JUL Y1978, Vol. 2, No. 4 129
best metliod of obtaining reasonably accurate low-grazingangle r.c.s. data on ships was to compare the returns tothose from known calibrated targets at the same time inthe same area as the shipping passed through.
Consequently, the coastal laboratory used to carry outthe trials already described was again used with a selectionof the many ships passing each day through the EnglishChannel being chosen as targets. Each ship was trackedfrom its first detection range, plotted, and as it passed thelaboratory its photograph taken with a camera fitted witha telephoto lens. Each ship was plotted until its radardetection was no longer possible. During the ship's transitan i.f. attenuator was used to estimate its echo strength atthe 50% blip/scan ratio level and these attenuator plots areshown in a typical composite course of actual spatial plotand signal strength. During the passage of each ship thereturns from the 10 m2 calibration buoy were also measuredas well as the best estimates of the 50% blip/scan attenuationneeded for each point on each ship's transit (Fig. 15). Inthis way, the median r.c.s. of each ship could be derived interms of the control target permanently moored at 2nautical miles off the radar site. As before, the absoluteradar performance on the control target varied during thesetrials and excess performance on the buoy varied from21 dB to 43 dB, which indicated the error that would haveoccurred without the use of a control target.
10range, n.mi.
16281757
Various physical details of each ship were derived fromshipbuilders' data and other sources, so that the 18 shipsrecorded spanned a wide range from 28 ft fishing boats to800 ft tankers with gross tonnage from 5 to 45 000 tons.Table 8 gives these details together with the range ofmeasured median r.c.s. values for each ship. Each r.c.s.data bar has been annotated with the aspect, giving themaximum and minimum values, but these excluded the truebroadside 'flash', as the whole ship's length radiates thepeak of its major r.c.s. lobe back to the radar, although thiswas observed on single aerial scans from time to time andseparately when ships passed normal to the nonscanningdish aerial used in the third series of target trials alreadydescribed. In general, most of the larger ships present sucha large target r.c.s. to even a small marine radar that theirdetection at a few kilometres is no problem.
Digressing from the experimental results, consider asimple model of two theoretical targets. Examination of thevery simple diagram of Fig. 16 shows that at longer rangesthe radar performance may either be free-space limited,transition-range constrained or horizontal limited. Justbefore a ship recedes beyond the radar horizon, the effectivehighest useful target area may produce the last mile ofdetection, and by choosing the uppermost major structure,usually the top of the bridge, and calculating the best radarhorizon, namely
Rh = \-23\fh~R x 1-23 V ^
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Table 9: Details of shipping observed during trials
Max. detectionrange
c.p.a.
control' " • target
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130 ELECTRONIC CIRCUITS AND SYSTEMS, JUL Y1978, Vol. 2, No. 4
approach has been made with the actual experimentalresults and is now described.
A comparison has been made between such computationsfor the 18 selected vessels and the last or greatest detectionrange actually achieved during these trials. Table 9 and Fig.17 give this data, which is seen to provide a good guide ofdetection ranges using a medium-powered marine radarsome 30 dB up on the minimum standard set by the UKGovernment Board of Trade22 requirement, which requiresa marine radar to detect a 10 m2 target at 2 nautical mileswith a 50% probability. The '10 m2' target is a particularnavigation buoy off Portsmouth within range of the ASWEtrials site.
Several points arise from these trials in addition to theprimary data already given in Table 8. The first is the sen-sitivity to the horizontal aspect of a ship's r.c.s. (No workwas carried out at other than low-grazing angles in thevertical plane.) Secondly, the ratio of maximum to medium(median values) of r.c.s. (from 10 to 20 dB) compares withthe single polar-diagram plot given by Skolnik.13 Next arethe worthwhile results from the simple method of assessingmaximum detection range for all but the smallest vessels,and, finally, the way in which the frigate exhibits a farhigher cross-section than merchant ships of similar displace-ment or gross tonnage, most probably due to the largeamount of angular protuberances associated with warships.
The more difficult targets for merchant-marine radars todetect, particularly in sea clutter, are those very small shipsgoing down to pleasure cruisers and small 6 m (20 ft) yachtsand dinghies. In particular, the smaller boats tend toperhaps roll and pitch much more in even the slightest seaand exhibit a wide range of r.c.s. values in the vertical plane,even for one aspect. This is illustrated for the 144 ft mine
sweeper measured by NRL and shown in Table 5-5 inNathanson.1 Here the X-band horizontally-polarised resultsindicate that the r.c.s. varies from 100 m2 at depressionangles near grazing to only a few square metres at 8-7°, butthe relationship between r.c.s. and grazing angle is by nomeans smooth or free from inflections, although it mightbe construed that high-platform search radars have a moredifficult job looking for ships in sea clutter owing to theincrease of the backscatter coefficient for sea occurring atthe same time as target r.c.s. appears to diminish. Of equalimportance is the possibility that if a small boat really doeshave a median r.c.s. that drops significantly with elevationangle, then in all but the calmest seas there are now threemechanisms that make it harder to detect by radar. Theseare:
(a) The likelihood that a rolling ship will present a lowerr.c.s. profile to a surface search radar for a significantfraction of its roll period and hence present a new lowermedian value than would have been ascribed to that givenby the vertical position viewed normal to this aspect alone
(b) The ship will be obscured by intervening wavesenhanced by the search radar vessel itself being in wavetroughs for much of the time (it might be argued that ifthere were no other mechanism than target and aerialheight varying from the sea surface nominal this lattereffect would cancel, but it certainly cannot accommodatewave obscuration as well)
(c) If a higher scanner height for the search radar ischosen (and is practical), then ship r.c.s. is predicted todrop from the Daley23—Nathanson1 data, although it isuniversally agreed that the competing sea-clutter back-ground will increase, thus reducing the target to clutterratio: on the other hand, our results have shown that both
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Fig. 17 Comparison of calculated and measured maximum detection range
ELECTRONIC CIRCUITS AND SYSTEMS, JULY 1978, Vol. 2, No. 4 131
horizon range and radar-detection range is severely limitedif both target and radar are only a few metres above sealevel, unless exceptional ducting occurs.
8 Small-target trials
The work so far has shown that the radar detection ofmedium to large ships out to horizon ranges of 20 nauticalmiles is less of a problem than really small targets such asdinghies, rowing boats, life rafts and floating debris.
Accordingly, a series of trials were conducted to obtaina better estimate of r.c.s. for a selection of small targets.Calm weather had to be chosen giving flat-sea conditionsand a further small calibration target deployed near thesmall targets, which would get over the problem of radartarget height dissimilarities.
A floating sphere was chosen as the smaller calibratedtarget (a = 0-lm2). This was deployed less than a mileaway from the radar and its return power relationshipchecked with the 10 m2 Luneberg lens target mounted2 m a.s.l. and deployed at a longer range, so that both camewithin the first aerial lobe above the sea. Table 10 gives thefinal results of these static trials showing the very smallmedian r.c.s. values actually measured, and, in particular,the significant increase of 10 dB when a seagull alightedon the upturned floating log. The 14 ft dinghy was strippedof all fittings, the mast, the outboard motor etc., and itsr.c.s. was noticeably increased to around 1 m2 whenoccupied by a man standing up for a short period, whichrelates to dry-ground man measurements by Schultz et al.reported in Skolnik.24
Thus the significance of an appreciable element of thetarget being at its maximum height is well illustrated by theseagull, the man and shipping upper structures. True low-profile hulls at low-grazing angles clearly have transitionranges down to a few hundred metres, as seen by marineradars, thus making their detection much more difficultthan in the case of an airborne search radar.
The small-target trials included towing the targetsbeyond the radar-detection range, but results were socontaminated by the extra return from the wash set up,
even at very slow speeds, that they were not considered tobe other than useful in confirming the order of magnitudeof the static trials.
9 Dry land: anechoic-chamber measurements
A series of measurements of various small targets, similar tothose used in the sea trial, confirmed that their r.c.s. wasvery much as expected from simple calculations for spheres,flat plates etc., and merely endorsed the wealth of boththeoretical and experimental work carried out on variousshapes in free space.12 More interesting results wereobtained from examining the r.c.s. polar diagram of an oildrum and a wooden sleeper when each was rotated 360°in near horizontal and near vertical positions. The peakr.c.s. values for the four target conditions are given inTable 11 together with the mean value of echoing area ifthe target was rotated 360° during its radar observation.The large ratio of peak-to-mean values emphasises thespecular nature of this particular class of small targets,unlike small pieces of ice, which, owing to erosion by thesea, look and behave more like a spheroid.
Table 11: Comparison of measured r.c.s. peak values and theaverage r.c.s. for 360° rotation of each target described
Target
Oil drumnear horizontal
Oil drumnear vertical
Vertical roughwooden sleeper
Horizontalwooden sleeper
apeak
m2
27
34
12
15
CTmean
m2
0-85
3-6
0-26
0-3
Peak/mean
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9-7
16-6
16-9
10 Discussion on practical target trials
The results of the marine radar trials indicate that the r.c.s.values for the small ships and very small targets are much
Table 10: Radar cross sections of practical targets at 50% probability detection level (aso)
Sphere calibration Luneberg lens calibration
Class of r.cs.(o,n),m2
16ft log, horizontal4ft log, vertical5 gal. oil40 gal. oil drum40 gal rect. tank14ft dinghy, unmanned
28ft fishing boat1'Large ships
'Observed effect of seagull perched on log*The fishing boat had a corner reflector rigidly fixed to the mast 4 m above sea level and of peak echoing area 4m2 at X-band
132 ELECTRONIC CIRCUITS AND SYSTEMS, JULY 1978, Vol. 2, No. 4
smaller than those expected from calculations, free-spacemeasurements and current belief. These reductions arebrought about in three ways.
First, the obvious fact that a portion of all floatingtargets are submerged. Secondly, it is suggested that peakvalues of r.c.s. are often incorrectly quoted in user require-ments, leading to an apparent shortfall in radar per-formance. Finally, the very short transition ranges for thesesmall targets means that, at useful detection ranges ofseveral kilometres, the unmanned rowing boat is wellbeyond the radar transition range for a marine radar, and inaddition may well be obscured by waves for much of thetime.
Thus, apart from the problems of seeing small surfacetargets against a competing sea-clutter background,25 the
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actual physical screening of targets by intervening wavesmust make the task impossible from time to time.
Evidence of this was found in both the long series ofbuoy trials when the correlation of radar detection per-formance was examined for various sea states. This wasoriginally reported in 197021 and is now examined in adifferent manner using the results of the second series ofbuoy trials.
The use of blip/scan curves to relate detection prob-ability to relative radar performance is nearly as old asradar, and the slope of these curves was found to vary as afunction of sea state21 much more clearly than the meanradar performance at a Pd of 50%. The method used in thesecond series of trials was to look for significant inflectionsin the blip/scan curves and then relate those to the sea stateprevailing for that trial. Fig. 18 shows how the percentageof inflections for all trials increases from 20% in a calm seato over 60% for the high-sea states.
Although the number of trials taking place in high seas islimited, it is suggested that wave obscuration plays a moredominant part than variation of the target height abovewater due to buoy motion, and each inflection is caused byan obscuration lasting for several points up to the full tenor half minute needed to plot individual points on the blip/scan curves.
Figs. 19 and 20 are the blip/scan curves drawn for fivetargets in smooth and rough seas, illustrating the increase ininflections for the higher sea states.
It would be expected that the vertical polar diagram ofeach target must affect the final result. For phase Bl,Figs. 2la, b, c and d give the breakdown of inflectionsagainst sea state for the standard corner reflector (THS),Luneberg lens (LL), AGA pentagonal cluster (AP) andanother octohedron on its high tower (CS1). Althoughthere are not sufficient high-sea-state results to drawdefinite conclusions, the way the inflections increase forTHS and AP is more marked than for LL and CS1 on itstall tower, indicating that sea state, target roll, vertical polardiagram and wave obscuration all play a part in determiningthe target behaviour and fading model to be used.
100
90
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00 3 6 9 12 15 18 21 24 27 30 33 36 39 42
•° actual i.f. attenuation
Fig. 19 Blip/scan curves in smooth sea with primary data above
Numbers refer to targets in Fig. 19a
100
90
80
,_ 70
60
50
40
30
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10
9 12 15 18 21
actual i.f. attenuation
24 27 30
Fig. 20 Blip/scan curves in a rough sea with primary data above
Numbers refer to targets in Fig. 20a
ELECTRONIC CIRCUITS AND SYSTEMS, JUL Y1978, Vol. 2, No. 4 133
11 Final conclusions
All the trials carried out on buoys have demonstrated thevery variable nature of radar performance experienced overthe sea even at moderate ranges of a few nautical miles. Thesecond series of buoy trials have shown that the bestdetection is obtained with the reflectors having the highestpeak radar cross-section and that a particular set of 6 asym-metrical corners arranged in a given cluster is far moreeffective than the conventional octohedrons, especially
100 r
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a THS b LL c AP dCSl
134
when made up of a metallised mesh material embedded ing.r.p. Reputedly nonfading enhancers, such as the Luneberglens, are not suited to buoy enhancement, but they areuseful for calibration purposes.
The practical ship trials have provided a wide range ofresults for use by radar-system designers and the small-target results illustrate the problems of their detection byradar, especially in rough seas.
At low grazing angles, as seen from shipborne radar, ther.cs. of yachts and pleasure craft is often much smallerthan those results applicable to a radar mounted in anairborne platform, and indeed, as in the case of the larger
Fig. 22 28 ft fishing boat carrying a corner reflector of r.cs. =4 m2 peak
Reference height 2 m a.s.l for fishing boat and above, 0-25 m forsmaller targets
1000 r
500
400
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Fig. 23 Range of median r.cs. values for maritime targets
This is referred to as target 13 in Table 8 and text
ELECTRONIC CIRCUITS AND SYSTEMS, JUL Y1978, Vol. 2, No. 4
ships, is mainly a function of the height of their super-structure. This point is clarified in Fig. 22, in which thethree smallest ships are plotted in terms of their range ofmedian r.c.s. against their length. By running trend linesT\ and T2 back to the 4-3 m (14 ft) open boat it will beseen that the 28 ft fishing boat shown as Fig. 23 lies welloutside these lines, and its very conspicuous wheelhouseand radar reflector may well account for its high mediancross-section. The trend lines indicate that a small 20 ftyacht will have a median cross-section between 0-1 and0-3 m2 at a very low height above the water, i.e. 1 m orless, and confirms the many reports of how difficult theyare to detect by surface radar. During the last few yearsthe problem of small target detection has been made moreacute in all but the calmest seas, as most modern X-bandradars resolve individual waves at short ranges and thepeak backscatter from these may be up to 35 dB greater26
than that calculated for sea clutter using the low resolutionresults collated by Nathanson1 and appropriate to olderradars having poorer spatial resolution.
The net result is that estimates of performance againstsmall boats at sea, which have been prepared in good faithfrom standard text books, may be out by a factor of 30 to50 dB, and unless such small craft carry suitable echoenhancers as reported in this paper, their safety at sea isseverely jeopardised in conditions of poor visibility.27
12 Acknowledgments
Part of the work was supported by the US Navy SurfaceEffect Ship Project Office under contract MA 4636, andthe final series of buoy trials was carried out in conjunctionwith the Trinity House Lighthouse Service. Engineers fromboth Decca Radar and Decca Systems Study and Manage-ment (DSSM), took part in the trials activities. The dis-cussions which took place with Professor J. Croney, Prof.D.E.N. Davies, P. Wooler, M. Withers and many others aregratefully acknowledged. Finally, the constructive criticismof the referees has been of value in certain revisions of thetext.
13 References
1 NATHANSON, F.E.: 'Radar design principles' (McGraw-Hill,1969), Chap. 5
2 KELL, R.E., and ROSS, R.A.: 'Radar cross section of targets',in SKOLNIK, M.I. (Ed.): 'Radar handbook' (McGraw-Hill,1970)
3 SWERLING, P.E.: 'Probability of detection for a fluctuatingtarget', Rand. Res. Memo RM 1217, 1954, reprinted in IRETrans.
4 MAYER, D.P., and MEYER, H.A.: 'Radar target detection'(Academic Press, 1973)
5 WILLIAMS, P.D.L.: 'The detection of small, low lying, surfacetargets at sea by radar'. Ph.D. thesis, University of London, 1977
6 WILKES, M.V., and RAMSAY, J.A.: 'A theory on the per-formance of radar on ship targets'. Proceedings of the CambridgePhilosophical Society, 1947, 43, pp. 220-231
7 DOMB, C, and PRYCE, M.H.L.: 'The calculation of fieldstrengths over a spherical earth', Proc. IEE, 1947, 94, Pt. Ill,pp. 325-339
8 KERR, D.E. (Ed.): 'Propagation of short radio waves: radiationlaboratories series - Vol. 13' (McGraw-Hill, 1951)
9 BARTON, D.K.: 'Cumulative index on radar systems', IEEETrans., 1972, AES-8, (1)
10 BARTON, D.K.: 'International cumulative index on radarsystems', ibid., 1975, AES-11, (3)
11 BARTON, D.K.: 'International cumulative index on radarsystems. 1975-76 update and complete author index', ibid.,1977, AES-13, (3)
12 CORRIHER, H.A., and PVRON, B.O.: 'A bibliography ofarticles on radar reflectivity and related subjects: 1957-64',Proc. IRE, 1965, pp. 1025-64
13 SKOLNIK, M.I.: 'An empirical formula for the radar crosssection of ships at grazing incidences', IEEE Trans., 1974,AES-10
14 WISEMAN, C.H.: 'Chaff assists anti-ship missile defense',Electron. Warfare, 1977,9
15 CRAM, L.H., WOOLCOCK, S.C., and JOHNSON, R.H.: 'Radioscale modelling in support of radar system design and assessmentof performance' in 'Radar - present and future'. IEE Conf.Publ. 105, 1973, pp. 422-430
16 CRAM, L.A., and STAVELEY, J.R.: 'Recent developments inthe scale modelling of radar reflections by radar and sonarmethods' in 'Radar-77'. IEE Conf. Publ. 155, 1977, pp. 473-477
17 BLAKE, L.V.: 'Prediction of radar range' in M.I. SKOLNIK(Ed.): 'Radar handbook' (McGraw-Hill, 1970), Chap. 29
18 DENISON, E.: 'Curves relating to low angle propagation over thesea'. ASWE Technical Report TR-72-31
19 BERRY, R.E.H.: 'Radar propagation at very low altitude overthe sea' in 'Radar - present and future'. IEE Conf. Publ. 105,1973, pp. 140-145
20 WILLIAMS, P.D.L., CRAMP, H.D., and BELLION, W.E.: 'Thepassive enhancement of navigation buoys at sea. Results andanalysis of a 9-month comparative trial' in 'Radar-77'. IEEConf. Publ. 155. 1977, pp. 125-129
21 WILLIAMS, P.D.L.: 'Change of the fading characteristics ofreputed steady targets as a function of sea state in a marineenvironment', Electron. Lett., 1970, 6, pp. 853-855
22 Board of Trade: 'Marine radar performance standards'. H.M.Stationery Office, London 1957 (revised 1968)
23 DALEY, J.C.: 'Airborne radar backscatter study at four fre-quencies'. Naval Research Laboratory Letter Report, Aug.1953
24 SKOLNIK, M.I.: 'Introduction to radar systems' (McGraw-Hill,1962), pp. 49
25 WILLIAMS, P.D.L.: 'Limitations of radar techniques in thedetection of small surface targets in clutter', Radio & Electron.Eng., 1975, 45, pp. 379-389
26 LEWIS, B.L., and OLIN, I.D.: 'Some recent observations of seaspikes' in 'Radar-77'. IEE Conf. Publ. 155, 1977, pp. 115-119
27 'Using radar reflectors', Yachting Monthly, Sept. 1976
Philips David Lane Williams, M.Phil.,C.Eng., FIEE, Sen. Mem. IEEE, MRIN,was born in 1926, educated atUniversity College Nottingham andUniversity College London, served inthe Royal Navy 1943-1946, and hasbeen with Decca Radar since 1952.
ELECTRONIC CIRCUITS AND SYSTEMS, JULY 1978, Vol. 2, No. 4 135
Harry Donald Cramp was born in 1931,educated at Leicester University,served in the RAF for 3 years, and hasbeen an engineer with Decca Radarsince 1956.
Kay Curtis was born in 1915, and hasbeen with Decca Radar since 1960engaged on a variety of engineeringsupport tasks.
COMPUTER AIDED DESIGN AND MANUFACTURE OF
ELECTRONIC COMPONENTS. CIRCUITS AND SYSTEMSUniversity of Sussex: 3-5 July 1979
OrganisersThe Electronics Division of the Institution of Electrical Engineers
in assocaition with the Institute of Mathematics and its Applications,and the Institution of Electronic and Radio Engineers and with thesupport of the Convention of National Societies of ElectricalEngineers of Western Europe (EUREL).
Call for Papers
AimsThe Conference will consider advances in analysis, synthesis
modelling and simulation as applied to the design and manufactureof electronic components, circuits and systems.
It is intended to arrange informal discussion and workshopsessions in addition to the formal sessions in which papers will bepresented and discussed.
ScopeThe Organising Committee invites offers of contributions which
will cover the theoretical and practical aspects of both software andhardware developments of linear, non-linear and digital componentsand systems, in such areas as: -
A Circuit design and optimisationB Modelling and design of semiconductor devices and LSI
systemsC Layout design of integrated circuits and printed-circuit
boardsD Logic simulationE Automatic test algorithms, test evaluation and applicationsF Reliability evaluation and tolerancingG CAD system designH CAD system evaluation and performanceI Assembly, manufacture and productionJ Communication and computer system simulationK New developments with potential for industrial appli-
cations
Submission of ContributionsThose wishing to offer contributions for the programme are
asked to submit a synopsis by 6 October 1978. The synopsis, whichshould be of up to 500 words in length, should be provided insufficient detail to enable the Committee to make a proper evaluationof the contribution. It would also assist the Committee in preparingthe programme if authors would indicate on the synopsis: —•
(i) the appropriate subject designation, e.g. a contribution oncircuit design and optimisation should be marked A;
(ii) whether the contribution will describe the state-of-the-artor, if not what new developments the paper will cover;
(iii) the envisaged length of the full paper i.e. 2 or 5 pages
The authors of selected synopses will be invited to prepare finalpapers of either 2 or 5 pages in length for submission for finalassessment by 5 February 1979. Accepted papers will be printed inthe Conference Publication which will be issued in advance of theevent to all who register for the Conference.
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DeadlinesIntending authors should note the following deadline dates:
Receipt of synopses 6 October 1978
Notification to authors of provisionalacceptance of synopses November 1978
Receipt of final paper for review 5 February 1979
Working LanguageThe working language of the Conference is English and will be
used for all printed material, presentations and discussionSimultaneous interpretation will not be provided.
Equipment DisplayThe Organising Committee is considering the arrangement of a
workshop display of equipment relevant to the theme of theConference.
Those wishing to receive information on the space and facilitiesavailable for the display of equipment are asked to contact the IEEConference Department by 3 September, 1978.
VenueThe Conference will be held at the University of Sussex, where
residential accommodation will be available.
RegistrationRegistration forms and further programme details will be made
available a few months before the event and will be sent to all whocomplete and return the attached reply-form.
To: IEE CONFERENCE DEPARTMENTSAVOY PLACELONDON WC2ROBL
CADMECCS 79
Please complete or tick as appropriate:
No. of Programmes/Registration Forms required
*Title of contribution offered
*Name
*Address
•BLOCK CAPITALS PLEASE
I would be interested in receiving details on the following:
• residential accommodation
• exhibition facilities
May, 1978.
ELECTRONIC CIRCUITS AND SYSTEMS, JULY 1978, Vol. 2, No. 4
