ELECTROMAGNETIC ENVIRONMENTAL EFFECTS

The ability of a system to operate compatibly with other systems in its intended electromagnetic environment has become a critical factor in both systems acquisition and operational planning. The Applied Engineering Division of the JSC can provide a complete environmental analysis that includes the use of worldwide frequency assignment databases, extensive equipment parameter databases, and sophisticated analysis models that can predict when, where, and how interference may occur for terrestrial, air, sea, subsurface and space-borne systems. The following analyses can be provided:

Cosite Electromagnetic Compatibility (EMC)

The dependence of modern military operations on electronic systems often means that multiple radiating and receiving equipments must be placed in close proximity, often on the same platform. This placement can lead to cosite electromagnetic interference that prevents or degrades system performance. The Applied Engineering Division has leading experts that can prevent and solve cosite problems. We utilize unique capabilities including: specialized equipment parameter databases, sophisticated antenna coupling models, and interference analysis software tools designed specifically to predict when cosite interference will occur, so effective remedial measures can be implemented.

Cosite models are used to evaluate potential high-power, non-linear effects when systems operate in proximity to each other. Cosite analyses consider the following effects:

    • Intermodulation
    • Harmonics
    • Spurious response
    • Adjacent signal
    • Component/receiver burnout
    • Case penetration
    • Receiver desensitization
    • Typical cosite platforms
    • Soldier
    • Airframe
    • Tower

Results of analysis include recommendations for ideal placement of antennas/systems and optimum frequency usage.

Intersite EMC

Intersite models are used to assess the impact of C-E equipment on other equipment within its operational environment as follows:

  • Similar to cosite EMC but radiating/transmitting and receiving device antennas are separated at greater distances and incident interference signals are typically weaker than in the cosite environment
  • Must consider interactions of all spectrum-dependent systems
  • Co-channel and adjacent signal interference are primary concerns
  • Consider effects of terrain, propagation, electromagnetic environment
  • Antenna sidelobes & backlobes
  • Computer modeling is used to assess a myriad of potential interactions
  • Include typical intersite scenarios
  • Battlefield dynamics
  • Test/demonstration
  • Interference mitigation techniques
  • Antenna placement/location & frequency management
  • Antenna design & waveform design

Radiation Hazards (RADHAZ) 

RF energy in itself can be a hazard. RADHAZ is typically mitigated by separation distance from the emitter source and there are the typical warning signs posted. The military services have established criteria to preclude hazards associated with radiated emissions from high power sources.  There are three classes of RADHAZ that we are concerned with:

  • Hazards of Electromagnetic Radiation to Personnel (HERP) is the danger to personnel from the absorption of electromagnetic energy by the human body. Personnel hazards are associated with the absorption of RF energy above certain power levels in certain frequency bands for certain lengths of time.  DoD Instruction 6055.11 defines the allowable amounts of radiation in terms of how long personnel may be exposed to RF fields of particular intensities at particular frequencies.
  • Hazards of Electromagnetic Radiation to Fuels (HERF) is the hazard associated with the possibility of igniting fuel or other volatile materials through RF energy-induced arcs or sparks. It takes a certain amount of arc energy to ignite a fuel and modern fuels like JP-5 are much safer than older fuels like JP-4. This is a major concern on an aircraft carrier due to limited separation distances. Fortunately there are many operational safeguards against this problem and we can provide appropriate recommendations.
  • Hazards of Electromagnetic Radiation to Ordnance (HERO) refers to the susceptibility of electro-explosive devices (EEDs) to RF energy. These EEDs or electrically-initiated devices (EIDs) are used to detonate explosives, launch ejection seats, cut tow cables, etc. Modern communications and radar transmitters can produce high electromagnetic environments that are potentially hazardous to ordnance. These environments can cause premature actuation of sensitive EEDs and EIDs.

The Applied Engineer Division has the knowledge, software models, and databases needed to determine susceptibility of personnel, fuels and ordnance to existing or proposed transmitters, and will provide recommendations to preclude potential hazards.