2 Electronic Support

Question 1

ESM receivers are used for _____ reaction.

Answer 1

Real-time

Question 2

ES Receivers may be devided into two categories:

Answer 2

Threat Warning Receiver (TWR) and;
Reconaissance/Surveillance Receivers

Question 3

What is a Threat Warning Receiver (TWR)?

Answer 3

Provides threat warning over a preset frequency range in real time. It gives you advanced warning that a threat is present.

Question 4

TWR is _____ sensitivity.

Answer 4

Low

Question 5

What is a Reconnaissance/Surveillance Receiver?

Answer 5

Have higher sensitivity and direction finding accuracy to measure more radar parameters. Can be real time or long analysis.

Question 6

Reconnaissance/Surveillance Receivers are _______ sensitivty.

Answer 6

High

Question 7

What are the four functions of an Electronic Support system?

Answer 7

Reception - radar pusle is intercepted and detected
Measurement - signal parameters are measured
Recognition - compare against library
Display / Report - to operator and CCS

Question 8

What are three domains which ES systems must operate?

Answer 8

Signal Domain
Temporal Domain
Spatial Domain

Question 9

Signal Domain

Answer 9

Receiver polarization and frequency must match

Question 10

Temporal Domain

Answer 10

Receiver must be operating at the same time as the radar system transmits energy.

Question 11

Spatial Domain

Answer 11

Antennas must be able to receive energy from the direction of the transmission

Question 12

What are the performance requirements of ES systems?

Answer 12

Frequency coverage
Sensitivity and selectivity
Dynamic range
Bearing and elevation coverage
Quick Analysis Time

Question 13

For a receiver to intercept a signal it must _____ and then ______

Answer 13

Cover the frequency band

Be tuned to the correct frequency of the transmitter

Question 14

Sensitivity refers to the ability to ______

Answer 14

detect signals in noise (SNR)

Question 15

A wide bandwidth _____ sensitivity.

Answer 15

Reduces

Question 16

What is selectivity?

Answer 16

The ability to select a certain range of frequencies and reject all others.

Question 17

Selectivity is _______ proportional to bandwidth.
A selective receiver is ______ sensitive.

Answer 17

Inversely
More

Remember sensitivity is inversely proportional to bandwidth.

Question 18

If a receiver is very selective, it has ________ probablity of intercept.

Answer 18

Reduced.

Selectivity is the ability to select a certain range of frequencies and reject all others. It will not be able to cover a wide range all at once but it can cover one narrow range very well.

Question 19

What is Dynamic Range?

Answer 19

Ability to process very weak and very strong signals equally well.

Question 20

What is Analysis Time?

Answer 20

The period of time required for reliable target identification.

Question 21

What are two factors which limit sensitivyt of the receiver?

Answer 21

Noise Figure
Noise Bandwidth

Question 22

What is dwell time?

Answer 22

After a receiver detects a signal, such as a radar pulse, there is a short period of time during which other pulses will be missed.

Question 23

What is Range Advantage?

Answer 23

Ratio of the distance where an ESM receiver can detect a radar to the distance a radar can detect the ESM receiver’s platform.

Question 24

What is Probability of Intercept

Answer 24

A qualitative measurement of probability of intercept based on time, frequency, direction

Question 25

How do you calculate the number of sweeps required for a certain POI?

Answer 25

Question 26

What are the 4 types of ES Receivers?

Answer 26

Direct Detection or Crystal Video Superheterodyne Instantaneous Frequency Measurement Compressive

Question 27

Direct Detection: Crystal Video Receiver

Answer 27

Extracts the signal from the carrier wave but removes frequency and phase information. It simply tells you there is a threat. It has a very wide BW though, giving it a high POI.

Question 28

Direct Detection: Scanning Crystal Video Receiver

Answer 28

Adds an electronically scanning narrowband microwave filter before the detector. This provides some frequency measurement by increasing selectivity but it decreases the probability of intercept and it is still low sensitivity.

Question 29

Direct Detection: Multi-Channel Crystal Video Receiver

Answer 29

A combination of basic crystal detectors, each tuned to a different band of frequencies. This allows frequency measurement, Improved sensitivity because each detector is over a narrower BW. Imrpoved POI Faster than the scanning crystal receiver.

Question 30

Superheterodyne Receiver

Answer 30

High sensitivity and selectivity Low POI

Question 31

Superhet: Automatic Tuning Superhet Receiver

Answer 31

**automatically** variable local oscillator frequency. So the LO will automatically sweep over a range of IFs. The conventional will require an operator to change the IF. Results in very high sensitivity. Higher POI over conventional superhet.

Question 32

Superhet: Channelized Superhet Receiver

Answer 32

One LO and a number of IF amplifiers that together covera wide bandwidth. Improved sensitivity, POI,

Question 33

Instantaneous Frequency Measurement (IFM) Receiver

Answer 33

A bank of frequency discriminators. Each discriminator in series makes progressively more precise measurements. You can create a parallel array of these discriminators and sum them together progressively more precise to create a digital IFM system.

Question 34

What are the limitations of IFM?

Answer 34

Processing time Low sensitivity High POI

Question 35

Compressive Receiver

Answer 35

Uses an automatic tuning superheterodyne receiver to sweep frequencies with the LO. The signals are multiplied with a delay filter which delays the signal proportional to its frequency. This time delay then corresponds to a frequency. Its another way of differentiating multiple frequency signals without a FFT. High POI High sensitivity Multiple simultaneous signal handling Good frequency resolution

Question 36

Phase Comparison Array

Answer 36

Measures the phase difference to determine direction

Question 37

Simultaneous Amplitude Comparison

Answer 37

Compares relative amplitude from different directions to determine strongest direction. This is used because at radar frequencies, you cannot use Adcock array.

Question 38

Steerable Direction Antenna

Answer 38

Rotating antenna which indicates its bearing info when the return is strongest. Low POI

Question 39

Four basic actions of recognition

Answer 39

Pulse Sorting PRI Analysis Scan Analysis Emitter Comparison

Question 40

What is Pulse Sorting?

Answer 40

Determining which incoming pulse is which.

Question 41

How do we describe a signal when Pulse Sorting?

Answer 41

AOA Frequency Duration TOA Amplitude Each pulse is represetned as 80 to 100 bit description

Question 42

What are 3 methods of direction finding?

Answer 42

Time Difference of Arrival Angle of Arrival Frequency DIfference of Arrival (doppler)

Question 43

Define Quick Analysis Time

Answer 43

The ability of an ESM system to process and analyze EM signals to extract useful information about targets.

Question 44

What is a threat library? What is it used for? How is it generated?

Answer 44

Threat library is a collection of information used to identify and classify targets based on their EM emissions. Information is gathered and analyzed and added to the threat libary for future deployements.

Question 45

What factors affect receiver sensitivity

Question 46

Draw a superheterodyne receiver

Answer 46