TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
A) ELECTROMAGNETIC WAVE
Definition:
Oscillation of electrical (E) and magnetic (H) field which is perpendicular to each
other and propagates at the speed of light in free space.
B) MICROWAVE
Definition:
A microwave is a form of electromagnetic radiation / waves with frequencies that
range between 300 MHz (or 0.3 GHz) and 300 GHz (of wavelength from 1mm to 1m
long) or more.
It is name as microwaves because of their high frequencies and because of relatively
short wavelengths (wavelength = speed of light/frequency) which is speed of light =
3x108 m/s.
ELECTROMAGNETIC WAVES
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
1
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
E
Direction of travel
H
Fig 1.0 EM wave propagation
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
2
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
MICROWAVE FREQUENCY BAND
Table 1. Frequency band designation
Frequency band
Designation
Typical service
3-30 kHz
Very low frequency (VLF)
Navigation, sonar
30-300 kHz
Low frequency (LF)
Radio beacons, navigational aids
300-3,000 kHz
Medium frequency (MF)
AM broadcasting, marintime radio, Coast Guard
communication, direction finding
3-30 MHz
High frequency (HF)
Telephone, telegraph, and facsimile; shortwave
international broadcasting; amature radio; citizen's band;
ship-to-coast and ship-to-aircraft communication
30-300MHz
Very high frequency (VHF)
Television, FM broadcast, air-traffic control, police, taxicab
mobil radio, navigational aids
300-3,000MHz
Ultrahigh frequency (UHF)
Television, satellite communication, radiosonde,
surveillance radar, navigational aids
3-30 GHz
Superhigh frequency (SHF)
Airborne radar, microwave links, common- carrier land
mobile communication, satellite communication
30-300 GHz
Extreme high frequency (EHF)
Radar, experimental
Table 2. Microwave frequency band designation
Frequency
Old band designation New band designation
500-1,000 MHz
VHF
C
1-2 GHz
L
D
2-3 GHz
S
E
3-4 GHz
S
F
4-6 GHz
C
G
6-8 GHz
C
H
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
3
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
8-10 GHz
X
I
10-12.4 GHz
X
J
12.4-18 GHz
Ku
J
18-20 GHz
K
J
20-26.5 GHz
K
K
26.5-40 GHz
Ka
K
Designation
ELF extremely low frequency
SLF superlow frequency
ULF ultralow frequency
VLF very low frequency
low frequency
LF
medium frequency
MF
high frequency
HF
VHF very high frequency
UHF ultrahigh frequency
SHF superhigh frequency
EHF extremely high frequency
Frequency
3Hz to 30Hz
30Hz to 300Hz
300Hz to 3000Hz
3kHz to 30kHz
30kHz to 300kHz
300kHz to 3000kHz
3MHz to 30MHz
30MHz to 300MHz
300MHz to 3000MHz
3GHz to 30GHz
30GHz to 300GHz
Wavelength
100'000km to 10'000 km
10'000km to 1'000km
1'000km to 100km
100km to 10km
10km to 1km
1km to 100m
100m to 10m
10m to 1m
1m to 10cm
10cm to 1cm
1cm to 1mm
All frequencies (or wavelengths) of electromagnetic energy are
referred to as the electromagnetic spectrum, shown in Figure 2.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
4
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
Figure 2. Electromagnetic Spectrum
Radio waves and microwaves emitted by transmitting antennas,
illustrated in Figure 3, are one form of electromagnetic energy. They
are collectively referred to as "radiofrequency" radiation (RFR). RF
energy includes frequencies ranging from 0 to 3000 GHz.
Microwaves, very short waves of electromagnetic energy, include
frequencies ranging from around 300 megahertz (MHz) to 300
gigahertz (GHz). Microwaves are often referred to as "high frequency
(HF) radio waves." High frequency radio waves are used to transmit
information from one place to another, because microwave energy can
penetrate haze, light rain and snow, clouds, and smoke. Remote
sensing is a common application of microwaves. There are two types
of microwave remote sensing; 1) active and 2) passive.
Exposure to RF energy of sufficient intensity at frequencies between 3
kilohertz (kHz) and 300 GHz can adversely affect personnel, ordnance,
and fuel. Potential exposures of this magnitude aboard ships are
primarily
associated
with
the
operation
of
various
radars
and
communication systems
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
5
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
ELECTRIC FIELD (E)
Exist when there is a flow of electric current (movement of electrons) in a
conductor starting with negative charge and ends with positive charge.
.
++++++++++
H Field
-----------------
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
6
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
ELECTRICAL FIELD (E) BASIC CHARACTERISTICS
Fixed positive charge will repels the positive charges nearby (Fig. a).
Fixed negative charge will attracts the positive charges nearby. (Fig. b).
+
+
+
+
+
+
-
+
+
Fig. a
Fig b
+
MAGNETIC FIELD (H)
The movement of charges in a form of closed loop (starts and ends in a circle
thus it does not have a starting and ending point) (Fig c).
Right Hand Rule (RHR) is used to identify the direction of Magnetic field that
exist around the electric current.
RHR states that if the right hand thumb points in the direction of current, the
direction of Magnetic field is in the direction the curved fingers are pointed. (Fig
d).
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
7
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
arah
Fig c. Magnetic field resulting from a charge
in motion
S
Fig d Direction of magnetic
field by right-hand rule
U
Fig e. Continuous nature of magnetic lines
MAGNETIC FIELD (H) BASIC CHARACTERISTICS

Formed a close loop (no staring or ending point).

Specific direction based on right hand rule.

The field does not crossed each other.

Repels each other.

Possess a tension along its distant i.e it trys to shorten the route as
minimum as possible. (Mempunyai ketegangan (tension) disepanjang
jaraknya di mana ia cuba memendekkan laluan setakat yang mungkin).
The strength of magnetic field depends on the electric strength and its distant
from the conductor.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
8
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
METHODS TO IDENTITY THE MAGNETIC FIELD DIRECTION
i) USING COMPASS
direction
card
magnetic field
ii) RIGHT HAND RULE
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
iii) SCREW RULE
9
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
In the case of transmission and reception, both the antennas need to have the
same polarization to receive the transmitting signal.
PENGGUNAAN / KEPERLUAN GELOMBANG MIKRO DALAM SISTEM KOMUNIKASI.
 BIDANG RUANG – pemultipleksan
1. Didapati semakin tinggi frekuensi yang digunakan, semakin besar
bidangruang boleh disediakan untuk penghantaran maklumat. Ini
membolehkan penggunaan saluran yang banyak di samping
membenarkan pemancaran isyarat maklumat yang mempunyai
bidangruang yang besar seperti isyarat video.
2. Contoh : purata bidangruang yang diperlukan oleh isyarat TV ialah
6MHz. oleh itu adalah tidak praktikal untuk pancar isyarat video
pada frekuensi rendah kerana ia akan menggunakan hamper
keseluruhan daripada ruang spectrum gelombang radio.
3. Bidangruang yang besar juga untuk membenarkan pemancaran
banyak maklumat dilakukan dengan menggunakan pelbagai teknikteknik pemultipleksan disamping membenarkan perhubungan data
kerana ia memerlukan bidangruang yang besar.
4. Ciri-ciri yang menyebabkan penggunaan gelombang mikro meluas
ialah panjang gelombang, frekuensi tinggi, bidang ruang yang
besar (maklumat dihantar dengan banyak menggunakan kaedah
pemutipleksan, perhubungan data, kurang hangar)
 MEMPERBAIKI PENGARAHAN ANTENA
Panjang gelombang () yang kecil membolehkan pembinaan antenna
yang tinggi gandaan dan dapat memberikan ruang sinaran yang sempit,
seterusnya menghasilkan pengarahan yang baik.
Bermakna tenaga dapat ditumpukan kepada keluasan yang kecil.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
10
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
Contoh :penggunaan di dalam ketuhar gelombang mikro, radar dan lainlain.
Kelebihannya ialah penjimatan kos pembinaan antenna, gandaan antenna
adalah tinggi dan sudut kembangan/lebar alur kecil.
 KEBOLEHARAPAN
Penerimaan isyarat bertambah jelas kerana kesan pudaran adalah kurang
pada frekuensi gelombang mikro.Ini adalah disebabkan oleh perambatan
tenaga yang berlaku secara garis-nampak (dapat menjimatkan kuasa
pemancar kepada penerima) daripada pemancar kepada penerima.
 LEBIH EKONOMI
Kuasa yang lebih kecil diperlukan oleh pemancar dan penerima pada
frekuensi gelombang mikro jika dibandingkan dengan gelombang pendek.
KELEMAHAN GELOMBANG MIKRO

Memerlukan stesen pengulang yang banyak.

Panjang gelombang yang kecil dan litarnya yang padat menyebabkan ia
tidak sesuai untuk digunakan bagi tujuan ketenteraan.

Tenaga gelombang mikro menghasilkan kesan pemanasan contohnya
microwave.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
11
TOPIC 1: MICROWAVE FUNDAMENTALS
1.2
MICROWAVE DEVICES (EP603)
UNDERSTAND THE HAZARD OF ELECTROMAGNETIC RADIATION.
Excessive levels of exposure to RFR can result in adverse acute
(immediate) effects on people such as involuntary muscle contractions
(electro stimulation), electrical shocks/burns (from touching metal
objects in RFR fields), and excessive heating of tissue (thermal
damage). High-level electromagnetic energy produced by RFR can also
induce electrical currents or voltages that may cause premature
activation of Electro-Explosive Devices (EEDs) and electrical arcs that
may ignite flammable materials. Modern communication and radar
transmitters aboard Navy ships can produce high-intensity Radio
Frequency Radiation (RFR) environments that are potentially
hazardous to 1) operating and maintenance personnel, 2) ordnance
and fuels and, 3) associated equipment. The type of biological effect
on humans from RFR depends on the frequency of the electromagnetic
wave (see Background section for more information). The severity of
the biological effect depends on the intensity (strength) of the RFR.
Biological effects that result from heating of tissue by RF energy are
often referred to as "thermal" effects. Exposure to very high levels of
RF radiation can be harmful due to the ability of RF energy to heat
biological tissue. In a healthy human body, the thermo-regulatory
system will cope with the absorbed heat until it reaches the point at
which it cannot maintain a stable body core temperature. Beyond this
point the body may experience hyperthermia (heat exhaustion) and/or
irreversible damage to human tissue if the cell temperature reaches
about 43 degrees Celsius. There is a higher risk of heat damage for
organs that have poor temperature control, such as the lens of the eye
and the testes. The amount of absorbed energy to produce thermal
stress is affected by the health of the individual (some medical
conditions and medications may affect thermoregulation),
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
12
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
environmental conditions (higher ambient temperature and relative
humidity make it harder for the body to release heat), and physical
activity (strenuous work can raise rectal temperature by itself).
Radiated energy can also result in high levels of induced and contact
current through the body when in close proximity to high-power RF
transmitting antennas. The biological hazards associated with
electromagnetic radiation, established by the Institute of Electrical and
Electronics Engineers (IEEE) C95.1 Standards Committee and adopted
by the Tri-Service Electromagnetic Radiation Panel, is in DODINST
6055.11, Protection of DoD Personnel from Exposure to
Radiofrequency Radiation and Military Exempt Lasers.
In addition to personnel concerns, RF fields may generate induced
currents or voltages that could cause premature activation of electroexplosive devices in ordnance, equipment interference or sparks, and
arcs that may ignite flammable materials and fuels.
1.2.1 3 MAIN CATAGORIES OF EM RADIATION HAZARD (RADHAZ):
i) Hazard of Electromagnetic Radiation to Personnel (HERP)
ii) Hazard of Electromagnetic Radiation to Ordnance (HERO)
iii) Hazard of Electromagnetic Radiation to Fuel (HERF)
HAZARD OF ELECTROMAGNETIC RADIATION TO PERSONNEL
(HERP)
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
13
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
Effects only possible at ten times the permissible exposure limit
 Heating of the body
 Cataracts
 Fertility
 Shocks or burns
 (developing foetus is at no greater risk than mother)
Radar and communication systems, which use high-power RF transmitters and high-gain
antennas represent a biological hazard to personnel working on, or in the vicinity of,
these systems. The detrimental effects of overexposure to RFR are associated with an
increase in overall body temperature or a temperature rise in specific organs of the body.
High-level electromagnetic energy can also induce electrical currents or voltages that
may cause shocks and burns. An RF burn is the result of RF current flow through that
portion of the body in direct contact with a conductive object (in which an RF voltage has
been induced) or at the site of a spark discharge (no direct contact with a conductive
object).
The use of HF transmitters (1 kilowatt and up) and the complicated structure and rigging
aboard ship, especially cargo ships, has increased the probability of voltages being
induced on various objects. The handling of metallic cargo lines while shipboard HF
transmitters are radiating can be hazardous to ship’s personnel. On numerous occasions,
RF voltages have been encountered on items such as crane hooks, running rigging,
booms, missile launchers, and parked aircraft. These voltages, which may be sufficient to
cause injury, are induced on the metallic items by radiation from nearby transmitting
antennas.
The danger of HERP occurs because the body absorbs radiation and significant internal
heating may occur without the individuals knowledge because the body does not have
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
14
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
internal sensation of heat, and tissue damage may occur before the excess heat can be
dissipated.
Two maximum hazard limits are defined;
1) Controlled Environments - where personnel are aware of the potential danger of RF
exposure concurrently with employment, or exposure which may occur due to incidental
transient passage through an area, and;
2) Uncontrolled Environments - A lower maximum level where there is no expectation
that higher levels should be encountered, such as living quarters
Hazards of Electromagnetic Radiation to Ordnance (HERO):
Premature activation of electro-explosive devices
High intensity RFR fields produced by modern radio and radar transmitting equipment
can cause sensitive electrically initiated devices (EIDs) classically known as electroexplosive devices (EEDs), contained in ordnance systems to actuate prematurely.
RFR energy may enter an ordnance item through a hole or crack in its skin or through
firing leads, wires, and so on. In general, electrically initiated ordnance systems are most
susceptible during assembly, disassembly, loading, unloading, and handling in RFR
electromagnetic fields. The potential dangers to ordnance and fuels are obvious because
there could be an explosive chain reaction.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
15
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
The potential dangers to ordnance and fuels are obvious because there could be an
explosive "chain reaction" by exploding; consequently, these limits are generally lower
than personnel limits.
There are three HERO categories.
The HERO limit 2 is for HERO "unsafe" or "unreliable" explosive devices with exposed
wires arranged in optimum (most susceptible) receiving orientation.
This usually occurs during the assembly/disassembly of ordnance, but also applies to
new/untested ordnance until proven "safe" or "susceptible."
The HERO limit 1 is for HERO susceptible ordnance fully assembled undergoing normal
handling and loading operations. HERO safe ordnance requires no RF radiation
precautions. A list of which specific ordnance (by NALC) falls into each category can be
found in OP 3565 along with specific frequency restrictions for each piece of ordnance.
For example, all missiles of one variety are susceptible (HERO 1 limits), while another
missile has both susceptible and safe variants (with no RADHAZ limits).
Other ordnance may be HERO unsafe (HERO 2 limits)
3. Hazards of Electromagnetic Radiation to Fuel (HERF): Fuel vapors can be ignited
by RF induced arcs during fuel handling operations close to high powered radar and radio
transmitting antennas. For example, many ships carry at least one helicopter or have the
ability to refuel a helicopter and, therefore, carry fuel to support helo operations
HERF precautions are of more general concern to fuel truck operators. However, some
general guidelines include:
 Do not energize a transmitter (radar/comm) on an aircraft or motor vehicle being
fueled or on an adjacent aircraft or vehicle.
 Do not make or break any electrical, ground wire, or tie down connector while
fueling.
 Radars capable of illuminating fueling areas with a peak power density of 5
W/cm2 should be shut off.
 For shore stations, antennas radiating 250 watts or less should be installed at least
50 ft from fueling areas (at sea 500 watts is the relaxed requirement).
 For antennas which radiate more than 250 watts, the power density at 50 ft from
the fueling operation should not be greater than the equivalent power density of a
250 watt transmitter located at 50 ft.
1.2.2 STATE THE RADIATION HAZARD LIMIT FOR PUBLIC
EXPOSURE
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
16
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
These Personnel Exposure Limits (PELs) are based on a safety factor of ten times the
Specific Absorption Rate (SAR) which might cause bodily harm. The term PEL is
equivalent to the terms "Maximum Permissible Exposure (MPE)" and "Radio Frequency
Protection Guides (RFPG)" in other publications.
There are several exceptions to the maximum limits in Figures 2 and 3 (in some cases
higher levels are permitted):
 High Power Microwave (HPM) system exposure in a controlled environment,
which has a single pulse or multiple pulses lasting less than 10 seconds, has a
higher peak E-Field limit of 200 kV/m.
 EMP Simulation Systems in a controlled environment for personnel who are
exposed to broad-band (0.1MHz to 300 GHz) RF are limited to a higher peak EField of 100 kV/m.
 The given limits are also increased for pulsed RF fields. In this case the peak
power density per pulse for pulse durations < 100 msec and no more than 5 pulses
in the period is increased to: PELPulse = PEL x TAVG/ 5 x Pulse Width, and the
peak E-field is increased to 100 kV/m. If there are more than 5 pulses or they are
greater then 100 msec, a time averaged PD should not exceed that shown in
Figure 3.
 A rotating or scanning beam likewise reduces the hazard, so although an on-axis
hazard might exist, there may be none with a moving beam. The power density
may be approximated with: PDscan = PDfixed (2 x Beam Width / scan angle)
 Many other special limitations also apply, such as higher limits for partial body
exposure,
The PELs listed in Figures 2 and 3 were selected for an average RF exposure time at
various frequencies. In a controlled environment, this averaging time was selected as 6
minutes for 0.003 to 15,000 MHz. If the exposure time is less than 6 minutes, then the
level may be increased accordingly.
Similar time weighted averages apply to uncontrolled environments, but it varies enough
with frequency.
Special training is required for individuals who work in areas which emit RF levels which
exceed the uncontrolled levels. Warning signs are also required in areas which exceed
either the controlled or uncontrolled limits.
Although E-Field, H-Field, and power density can be mathematically converted in a farfield plane wave environment, the relations provided earlier do not apply in the near field,
consequently the E- or H-field strength must be measured independently below 100
MHz. It should be noted that for lower frequency HERO limits are listed as peak E-field
values, whereas lower RF limits on HERP are in average (RMS) E-field values. Upper
frequency restrictions are based on average (RMS) values of power density in both
regulations except for certain circumstances.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
17
TOPIC 1: MICROWAVE FUNDAMENTALS
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
MICROWAVE DEVICES (EP603)
18
TOPIC 1: MICROWAVE FUNDAMENTALS
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
MICROWAVE DEVICES (EP603)
19
TOPIC 1: MICROWAVE FUNDAMENTALS



MICROWAVE DEVICES (EP603)
Exposure limits are specific for locations that are defined as either controlled
or uncontrolled environments.
Controlled environments are areas where exposure may be incurred by
personnel who are aware of the potential for RF exposure as a result of
employment or duties; by individuals who knowingly enter areas where higher
RF levels can reasonably be anticipated to exist; and by exposure to transient
passage through such areas.
Uncontrolled environments generally nclude public areas, living quarters and
work places where there is no expectation that igher RF levels should be
encountered.
Herp
"restricted" limit is for individuals more than 55" tall because they have more body mass.
In other words, all people may be exposed to the lower limit, but only persons taller than
55" may be exposed to the higher limit of 10 mW/cm2
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
20
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
1.2.3 EXPLAIN THE RADIATION PROTECTION TO BE PRACTICED.
Hazards of Electromagnetic Radiation to Personnel (HERP)
Adequate protection measures or appropriate operational restrictions has to be considered
to maintain personnel exposures within the exposure limit.
ENGINEERING CONTROLS:
Engineering controls that should be kept in mind by the designer include:
• Properly design and install shielding material on RF energy sources. Such as bonding,
grounding, shielding, and the use of nonmetallic materials to reduce Electromagnetic
Interference and to protect personnel from electrical shock.
• Design devices which produce high levels of stray RF radiation so that they can be
operated remotely.
• Use nonmetallic materials where RF burn-hazards are a problem.
• Electrically ground and/or insulate metallic structures producing contact shocks.
• Rotate antennas to make it less likely that sufficient energy will be transmitted to cause
an adverse effect to personnel, ordnance, and fuel because the rotation reduces the time of
exposure to any single location. Place the antenna at a greater height, pointing it at a
greater elevation angle, and blank the signal while the energy may be directed in the path
of a ship structure to further reduce the potential for adverse effects.
• Install safety disconnect switches for all rotatable antennas (except submarine and
ECM antennas) to disable antenna rotation and equipment radiation prior to personnel
entering the antenna swing circle. Lockout devices for disconnect switches will prevent
inadvertent activation and save manhours used to perform maintenance procedures.
• Coordinate with other system designers and installers to avoid undesired interaction
between ship systems.
ADMINISTRATIVE CONTROLS:
Administrative controls are related to procedures, which the designer is responsible for
establishing and must also be linked to Human Systems Integration (see the Human
Factors Engineering section of this website).
• Use physical barriers (such as fences, warning signs, lights, or alarms) that identify the
radiation-control area at its perimeters and access routes to preclude individuals from RF
radiation exposure.
• Keep radar beams pointed away from personnel working areas. Aircraft using highpower radars will be parked (or the antennas oriented) so that beams are directed away
from work areas.
• Maximize the distance between the worker and the source of RF energy emission.
• Tune the equipment electronically to minimize the stray power emitted.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
21
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
• Operate transmitters at reduced power.
• Restrict simultaneous use of certain combinations of antennas, frequencies, and cargo
handling equipment.
• Develop standard operating procedures (SOPs) to inform those who use the system
about RF control procedures.
• Provide RF safety and health training to ensure that all ship personnel understand the
RF hazards to which they may be exposed and the means by which the hazards are
controlled.
• Ensure that radiation hazard (RADHAZ) warning signs are properly posted and
boundary lines are established in accordance with the ship's current RADHAZ
certification.
• Ensure that required tags are installed properly and observed when working on radar
antennas.
• Working aloft, especially near shipboard antennas, presents special considerations and
procedures for safety.
PERSONAL PROTECTION:
When exposures cannot be reduced by engineering and administrative control methods,
RFR protective suits, including head and eye protection, can be used. (protective
equipment, such as electrically insulated gloves and shoes for protection against electrical
shock or RF burn, or for insulation from the ground plane.)
Suits should be tested to ensure that they reduce worker exposure to levels below the
occupational exposure limits and that they do not pose any safety hazards (e.g.,
overheating, shocks, or fire).
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
22
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
HAZARDS OF ELECTROMAGNETIC RADIATION TO ORDNANCE (HERO)
For most ordnance, a HERO problem is inevitable unless the designer recognizes the
possible hazards and organizes all phases of the ship’s development so that the hazard is
precluded in the initial design. Retrofitting after a HERO problem is discovered at some
later stage of development is, at best, expensive and time consuming and often detracts
from the tactical reliability of the ordnance. Impacts on war-fighting performance and
acquisition program cost and schedule can be significant.
• Engineering Controls: There are four basic approaches to solving the HERO problem:
1. Continuous RF Shield: This approach consists of enclosing all EID’s and their firing
circuits (including all power sources, transmission lines, and switching and arming
devices) within a continuous electromagnetic interference (EMI) shield or “conductive
box.” Use of a conductive box requires that proposed design techniques and fabrication
methods will ensure that the electromagnetic environments (EME) cannot penetrate into
the shielded area. This concept is illustrated in Figure 4 and requires that the integrity of
the RF shield be designed and maintained throughout the life cycle of the system.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
23
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
2. Shielded Compartments and Interconnections: Another method to exclude RF
energy from coupling into ordnance is to compartmentalize the system into shielded
subsystems connected with RF-shielded or protected interconnects as shown in Figure 5.
This technique requires that the RF shielding integrity of each subsystem and of each
interconnection be designed so that the EME cannot couple into the system at any point.
3. EMI Filtering: Most ordnance requires breaking electrical connections when the parts
of the system are physically separated. Thus, it is often impossible or impractical to keep
all conductors within one continuous shield. Therefore, EM energy must be excluded by
some other method. It can be excluded from a shielded enclosure at a connector by means
of an EMI filter (a low-pass filter). The proper use of a filter is illustrated in Figure 6.
4. RF Arcing Protection: The design of circuits associated with systems that have
electrical connections exposed to the EME is very important. RF arcs can occur when
connectors are mated and unmated, especially for ordnance that may be attached to very
large structures or host platforms that are exposed to high-frequency environments. These
arcs can generate EM energy throughout the RF spectrum, including low-frequency
components that are in the same band as the firing signal, and will even pass through a
filter if one is installed. A break in the firing circuit between the arc point and the EID
until after the connection is made will circumvent this problem because a direct current
path is necessary for an arc to occur. This technique is illustrated in Figure 7.
• Administrative Controls: HERO reduction techniques vary depending on
susceptibility of the ordnance involved and frequencies and power density of radiation
involved. Ship's personnel can cope with HERO restrictions by:
 Reducing power output of the transmitting antenna,
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
24
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
 Increasing the distance between ordnance and the transmitting antenna,
 Performing tasks in shielded areas.
HAZARDS OF ELECTROMAGNETIC RADIATION TO FUEL (HERF)
RF induced arcs can ignite fuel vapors during fuel handling operations close to highpowered radar and radio transmitting antennas. Personnel handling fuels afloat should be
aware of this potential hazard.
The probability of ignition during normal fueling procedures is reduced by the following
methods:
• Using less volatile fuels.
• Introducing pressurized fueling systems on aircraft.
• Locating transmitting antennas away from fueling stations and
vents. (specifies the safe distances from radiating sources at which
fueling operations may be conducted.)
• Securing all transmitting antennas located within the quadrant of the ship in which
fueling is being conducted.
• Ensuring RADHAZ cutouts for microwave radiators are not overridden during fueling,
which could result in the illumination of fueling areas.
• Avoiding energizing any transmitter (radar or communications) on the aircraft or motor
vehicle being fueled or on adjacent aircraft or motor vehicles.
Avoiding making or breaking any electrical, static ground wire, tie-down connection, or
any other metallic connection to the aircraft or motor vehicle while it is being fueled;
making the connections before fueling commences; and breaking them afterwards.
CONCLUSION
Radio Frequency Radiation can be potentially hazardous to 1) operating and maintenance
personnel, 2) ordnance and fuels, and 3) associated equipment. Radio Frequency
radiation hazards can be reduced by properly designing and installing shielding material
on RF energy sources. Radar and communication systems aboard ships should be
designed and installed for safe operation and maintenance to avoid shock, RF burn, and
fall hazards.
Ship and weapon designers should recognize the possible electromagnetic radiation
hazards to ship personnel, ordnance, and fuels and organize all phases of the development
so that these hazards are precluded or minimized in the initial ship design.
Incorporating electromagnetic radiation hazard protection during the planning and design
phases of any new ship acquisition decreases operation and maintenance costs compared
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
25
TOPIC 1: MICROWAVE FUNDAMENTALS
MICROWAVE DEVICES (EP603)
to the cost of retrofitting an already built system. The Acquisition Program Manager’s
participation in system safety working groups and other Integrated Process Teams (IPTs)
supports efficient communication on all system safety issues. Early and continued
coordination with other system designers and installers is essential to avoiding undesired
interaction between systems and to developing common control and display and
operational processes.
PREPARED BY : ROHANA BT. IBRAHIM
POLIMAS
DECEMBER 2012 SESSION
26