This document discusses communication electronic countermeasure (CECM) systems used to jam enemy communications. The objective of CECM systems is to deny information transmission over a defined area using jamming of both analog and digital modulation systems. Jamming works by transmitting radio signals that disrupt communications by decreasing the signal to noise ratio. An effective jammer must transmit at a higher power level than the enemy signal within the bandwidth of the enemy's communication link. The document describes the basic architecture of a CECM system, including a processor, exciter, power amplifier, and antennas used to generate and transmit jamming signals.

1. Communication
ECM Systems

2. OBJECTIVE
 The main objective of CECM systems is to
deny, over a defined area and by means of
jamming.
 the transportation of information performed
in
 symmetric conflicts(RF links)
 asymmetric conflicts(FM radio&anlog
and digital tv)

3.  modern communication systems use
mostly digital modulations
 but a large number of legacy
communication systems that employ
analog modulations are still available,
especially in the battlefield area.
 the architecture and jamming techniques
of CECM systems that follow, both types
of modulation are taken into account.

4. What is jamming?
 jamming is the transmission of radio
signals that disrupt communications by
decreasing the signal to noise ratio.
Basic Working Principles :
 The effectiveness of a jamming is
measured by the ratio of jammer (J) to
signal (S) power, J/S or JSR

5. • Jamming power (J) must be larger than
the transmitted signal power (S)(J/S >>1)
 The Jamming-to-Signal ratio (J/S) is usually
expressed in dB, i.e. J/S must always
remain positive in dB for effective
jamming (J/SdB > 0 dB)

6. • The jammer must transmit within the
bandwidth of the enemy communications
link
 If the enemy transmitter-receiver distance
(de) is much shorter than the jammer-
receiver distance (dj) then the enemy
transmitted power may be high enough to
over the jamming power

7. Ground vehicles:
aircrafts:

8.  They are two types of ecm:
1.RECM
2.CECM
 Radars use two way propagation
 Communications use one way
propagation

10.  the communication transmitter (Tx) and
the CECM are, respectively, at a distance
RTR and RJR from the receiver.
 The transmitted power can be
expressed as:
where PtGt = ERPt
Pt= transmitted power
Gt=antenna gain

11. ERPt=effective radiated power of
the transmitter
Gr= receiver antenna gain
The received power can be expressed as:
where PjGj = ERPj
Gr,j= receiver antenna gain in the
direction of the jammer

12. CECM ARCHITECTURE

13. Processor:
 processor manages the system resources
(power management) and is connected to
the CESM equipment, which provides
continuous monitoring of the environment
Exciter:
• Combination of synthesizer & modulator
 Synthesizer provides the carrier frequency
of the jamming signal.
 Modulator provides jamming modulations.

14. power amplifier:
 power amplifier has at least two sections,
each dedicated to a bandwidth of the
CECM
 Each section has either a number of
parallel solid-state basic power amplifiers,
usually operating in Class AB.
 Both solutions are capable of providing a
large power output

15. Antennas:
 The antenna is usually made of a couple of
log-periodic antennas capable of covering
the complete RF bandwidth from 30 to
3000 MHz.