Introduction into Theory of Direction Finding

The Direction Finding technique has existed for as long as electromagnetic waves have been known. It was Heinrich Hertz who in 1888 found out about the directivity of antennas when conducting experiments in the decimetric wave range. A specific application of this discovery for determining the direction of incidence of electromagnetic waves was proposed in 1906 in a patent obtained by Scheller on a homing Direction Finding method.

While direction finding for navigation purposes (referred to as cooperative direction finding) is becoming less important due to the availability of satellite navigation systems, there is a growing requirement for determining the location of emitters as the mobility of communications equipment increases.

Some Areas where Direction Finding can be used are:

• In radio monitoring in line with ITU guidelines
  • Searching for sources of interference W
  • Localization of non-authorized transmitters
• In security services
  • Reconnaissance of radio communications of criminal organizations
• In military intelligence
  • Detecting activities of potential enemies
  • Gaining information on enemy‘s communications order of battle
• In intelligent communications systems
  • Space division multiple access (SDMA) requiring knowledge of the direction of incident waves
• In research
  • Radioastronomy
  • Earth remote sensing