Basic Role of ESM System in EW Scheme, Functions, POI & Rcvr Sen

7/30/2019 Basic Role of ESM System in EW Scheme, Functions, POI & Rcvr Sen

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1. Basic role of ESM system in EW scheme? Explain with its functions, POI

and receiver sensitivity.

Answer.

1. It is one of the three Components of EW

i. Electronic Support (ES) *ESM

ii. Electronic Attack (EA) *ECM

iii. Electronic Protection (EP) *ECCM

2. Basic role of ESM:-

To search for, intercept, identify, and locate sources of intentional and

unintentional radiated electromagnetic energy. Immediate threat recognition and construction of an EOB.

Produce operational intelligence, to provide steerage for EA, and to cue

surveillance and target acquisition resources.

ES functions as collectors and processors of tactical information about an

adversary, are closely related to other intelligence functions.

3. Bloack Diagram of ESM Sysem:


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4. Major sub divisions and their functions of ESM System

SEARCH: Prior carrying out EW process, it is necessary to search for and

classify electromagnetic signals of interest.

INTERCEPT: Signals of interest, once identified in the search process, are

examined for their technical characteristics, such as bandwidth and modulation

type, as well as theircontent, which may be monitored and recorded either by

an operator or electronically.

DIRECTION FINDING (DF): The physical location of transmitters is identified by

the DF process, based on steerage provided by the search process.

ANALYSIS: Utilises the information gained from the other ES processes to

construct an EOB(Electronic order of battle)of the adversary, andattempt to infer the adversary commander's intent.

5. POI- Probablitlity Of Intercept

Key performance feature of EW surveillance and reconnaissance system.

Concept is well-summarized in a statement It tries to see and not be

seen.

This is a response to the increasing capability of modern intercept

receivers to detect and locate radar emitters, possibly leading rapidly to an

electronic attack or the physical destruction of the radar by guided

munitions or AntiRadiation Missiles.

Both Radar and Communication Signals are considered Low-probability

of-Intercept(LPI) Signals.

The LPI technique is based on the property of an emitter that due to its

low power, wide bandwidth, frequency variability and other attributes

makes radar difficult to intercept or identify by conventional passive

intercept receiver devices.

LPI signals are very broadly defined, including any feature that makes the

signal harder to detect oremitter harder to locate.

LPI Radars have some combinations of

Narrow antenna beam

Low effective radiated power

Modulation which reduces the signals delectability


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The simplest LPI feature is emission control

Reducing the transmitter power to the minimum level that will allow the

threat signal to provide an adequate SNR to the related receiver.

The lower transmitting power reduces the range at which any particular

hostile receiver can detect the transmitted signal.

In the frequency domain, the POI is PBW = BR / BT

{ Where BR= RF BW & BT= BW covered at any instant is BT,}

In the time domain, if Ta is the time during which the system fails to detect

the signal, and the total time of observation is T;

Pt = Ta / T

The overall probability of intercept is

POI = P * PBW * Pt {where P = c / t= spatial POI

c= spatial coverage in azimuth

t= total coverage.}

6. Receiver Sensitivity

Receiver sensitivity defines the minimum signal strength a receiver can receive

and still do the job it is intended to do.

i.e. A lowest signal strength can receive and still provide the properspcified output

Sensitivity is a Power level and it can also stated interms of field strength.

If the received power level is at least equal or greater than to the receiver

sensitivity, the communication link takes place over the link.

The sensitivity of receiving system defined at the output of the receiving antenna.

Three components of the receceiver sensitivity:

Thermal noise level(kTB)

The receiverv system noise figure

Signal to noise ratio

Receiver sensitivity = kTB+noise figure+required SNR

kTB=144dBm/MHz

K is Boltzmanns constant(1.38x10-23 J/0K)


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T is the operating temparature in0K(290

0K)

B is the effective receiver bandwidth(1MHz)

Noise figure: The ratio of the noise present in the reciver bandwidth to that

which would be present if only kTB were present is called the noise figure

Signal to Noise ratio: Is dependent on

The type of information carried by the signal

The type of signal modulation that carries that information

The type of processing that will be performed on the output of the reciver

The ultimate use to which the signal information will be put

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Basic Role of ESM System in EW Scheme, Functions, POI & Rcvr Sen