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Spectrum and Electromagnetics 101

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Spectrum and Electromagnetics 101

This section contains background and basic educational information on Spectrum Supportability (SS) and electromagnetic environmental effects (E3) issues, some introductory technical material on each and the importance of considering each early in the development and acquisition of systems.  These resources provide acquisition professionals an overview of the technical aspects of spectrum supportability and E3 considerations in military weapons system procurement.

Program management must address SS and E3 throughout the system life cycle when developing an electronic system that will operate compatibly in its fielded environment and must ensure that EMC and SS are designed into the system.  Numerous DoD agencies and organizations can assist the program office with E3 matters.

Definitions

  • Electromagnetic Environmental Effects (E3):   The impact of the electromagnetic environment upon the operational capability of military forces, equipment, systems, and platforms. Also called E3. (JP 3-13.1).  [From: Department of Defense Dictionary of Military and Associated Terms,  (August 2021)]
  • Electromagnetic Compatibility:  The ability of systems, equipment, and devices that use the electromagnetic spectrum to operate in their intended environments without causing or suffering unacceptable or unintentional degradation because of electromagnetic radiation or response. Also called EMC. [From: Department of Defense Dictionary of Military and Associated Terms,  (August 2021)]
  • Electromagnetic Spectrum Management:  Planning, coordinating, and managing use of the electromagnetic spectrum through operational, engineering, and administrative procedures.  [From: Department of Defense Dictionary of Military and Associated Terms,  (August 2021)]
  • Spectrum Supportability:  the assessment as to whether the electromagnetic spectrum necessary to support equipment is available for use by the system.  The assessment requires, at a minimum, receipt of equipment spectrum certification, reasonable assurance of the availability of sufficient frequencies for operation from host nations, and a consideration of Electromagnetic Compatibility (EMC).   [Guidance for these requirements is found in DodiInstruction 4650.01].
  • Objective for E3 Control:  The objective of establishing E3 control requirements in the acquisition process is to ensure that DoD equipment, subsystems, and systems are designed to be self-compatible and operate compatibly in the operational electromagnetic environment.  To be effective, the program manager should establish E3 control requirements early in the acquisition process to ensure compatibility with co-located equipment, subsystems, and equipment, and with the applicable external electromagnetic environment. [excerpt from DAG Guidebook]
  • E3 Testing:  E3 can adversely affect the operational effectiveness of military forces, equipment, systems, and platforms. Today's increasingly complex military EM environment is congested and this is coupled with a reduction of spectrum allocation for exclusive military use. The mix of DoD-developed and commercial-off-the-shelf (COTS) electronic equipment increases the importance of the need for effectively managing E3 and spectrum usage in the battle space. It is the responsibility of the program manager (PM) to ensure, and the responsibility of the Developmental and Operational Test Agencies (D&OTA) to validate, the readiness of systems to be fielded into this environment. Historically, failure to verify equipment/platform EMC in the item's intended operational electromagnetic environment have caused costly program delays and reduced operational effectiveness. [excerpt from DAG Guidebook]

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ELF Radio Spectrum Microwaves Terahertz   Infrared   Visible   Ultraviolet   X-Rays       Gamma Rays
3-30 Hz SLF*: 30-300 Hz 300 GHz -300 MHz 300 GHz-3 THz   Far Infrared: 300 GHz-30 THz   790 to 405 THz   30 PHz - 790 THz
 30 PHz-30 EHz     More than 10 EHz
ULF*: 300-3000 Hz
  Mid-Infrared: 30-120 THz   8 × 1014 to 3 × 1016 Hz
VLF*: 3-30 kHz
  Near-Infrared: 120-400 THz
LF*: 30-300 kHz
MF*: 300-3000 kHz
HF*: 3-30 MHz
VHF*: 30-300 MHz
UHF*: 300-3000 MHz
SHF*: 3-30 GHz
EHF*: 30-300 GHz

* Super Low Frequency (SLF)   Ultra-Low Frequency (ULF)  Very-Low Frequency (VLF)  Low Frequency (LF)   Medium Frequency (MF)   High Frequency (HF)   Very-High Frequency (VHF)   Ultra-High Frequency (UHF)

  Super-High Frequency (SHF)   Extremely-High Frequency (EHF)   ExaHertz (EHz)



The types of electromagnetic radiation are broadly classified into the following classes:

  • Gamma radiation:  penetrating EM radiation arising from the radioactive decay of the atomic nuclei. It consists of the shortest wavelength EM waves thereby imparting the highest photon energy. 
  • X-ray radiation: a high energy EM wave with a very short wavelength that is able to penetrate and pass through many materials such as clothing, body tissue, and internal organs.
  • Ultraviolet radiation: a band of the EM spectrum with wavelength from 10 nm to 400 nm, shorter than visible light but longer than X-rays.
  • Visible radiation:  a form of EM radiation that is visible to most human eyes
  • Infrared radiation:  known as Infrared and is a region of the EM radiation spectrum where wavelengths range from about 700 nanometers (nm) to 1 millimeter (mm). 
  • Terahertz (THz) radiation: sometimes known as the submillimeter band, consists of EM waves from 0.1 - 30 THz. One THz is 1012 Hz or 1000 GHz. Wavelengths of radiation in the terahertz band range from 1 mm to 0.1 mm. 
  • Microwave radiation: EM radiation between radio waves having frequencies between 300 megahertz (MHz) and 300 gigahertz (GHz) and wavelengths between 1 meter and 1 millimeter.
  • Radio waves: are a type of EM radiation with wavelengths in the EM spectrum longer than infrared light and is used in communications like mobile phones, radio and television 


What is a decibel or dB?

The decibel (dB) is a logarithmic unit that indicates the ratio of a physical quantity (usually power or intensity) relative to a specified or implied reference level. A ratio in decibels is ten times the logarithm to base 10 of the ratio of two power quantities. The decibel is often used to express power or amplitude ratios (gains), in preference to arithmetic ratios or percentages. One advantage is that the total decibel gain of a series of components (e.g., amplifiers) can be calculated simply by summing the decibel gains of the individual components. Similarly, in telecommunications, decibels denote signal gain or loss from a transmitter to a receiver through some medium (free space, waveguide, coax, fiber optics, etc.) using a link budget. The decibel unit can also be combined with a suffix to create an absolute unit of electric power. For example, it can be combined with "m" for "milliwatt" to produce the "dBm". 0 dBm equals one milliwatt, and 1 dBm is one decibel greater (about 1.259 mW).



The following table describes some of the Image removed.various modulation types with the principle advantages, disadvantages and uses.

Kind Description/Advantages Disadvantages Uses
Amplitude Modulation - double side band plus carrier (AM) The amplitude of the carrier signal is varied in accordance with the instantaneous amplitude of the modulating signal. Simplifies receiver; preserves the waveform of message.  Analog. Doubles bandwidth occupancy; Requires extra signal power. Radio broadcasting, telephony, telegraphy, telemetering.
Single-sideband, suppressed carrier (SSB) Saves bandwidth occupancy; Conserves signal power. SSB transmitters are generally designed to minimize the amplitude of the carrier signal and when the carrier is removed from the transmitted signal, it is called suppressed-carrier SSB. Analog. Unable to handle relatively low frequencies; adds inherent delay; waveform of wanted message is not preserved. Long distance telephony and telegraphy over land and submarine cables.  History - SSB entered commercial service on January 7, 1927 on a transatlantic radiotelephone circuit between New York and London England. The high power SSB transmitters were located at Rocky Point, New York and Rugby, England. The receivers were located in extremely quiet areas.
​Amplitude Shift Keying
 ​A form of AM that represents digital data as variations in the amplitude of a carrier wave - the binary symbol 1 is represented by transmitting a fixed-amplitude carrier wave and fixed frequency for a bit duration of T seconds. If the signal value is 1 then the carrier signal will be transmitted; otherwise, a signal value of 0 will be transmitted.
 ​ASK is sensitive to atmospheric noise, distortions, propagation conditions. Can be transmitted over fiber optic cable.
 ASK was used at radio frequencies to transmit Morse code and was referred to as continuous wave (CW) operation
Angle Modulation - Narrow band Constant signal power Extra bandwidth occupancy Telecommunications, particularly broad-band carrier and TV over microwave radi
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