Electromagnetic compatibility (EMC) can be broadly defined as a state that exists when all devices in a system are able to function without error in their intended electromagnetic environment.
In or about 1899, the United States Navy initiated the first tests of the wireless telegraph aboard a naval ship. These tests were largely successful but presented the Navy with the problem that they were unable to operate two transmitters simultaneously.
This challenge was occasioned by the fact that the operating frequency and bandwidth of the early wireless telegraph was determined by the size, shape, and construction of the antenna.
Receiving antennas were in all times tuned to use the same frequency as the transmitting units, however, their bandwidths were difficult to control.
In effect, when the two transmitters were operated simultaneously, receivers identified the fields from both of them and the received signal was for the most part incoherent. This presented an electromagnetic compatibility problem that came to be known as the Radio Frequency Interference (RFI). Concerns over RFI (Radio Frequency Interference) grew in equal measure as the growth in Radio Communication.
Popularity of the radios and the initial EMC regulations
Giving way to provisions for different types of radio transmitters being assigned different frequency allocations and being allowed to operate at certain times in order to moderate the likelihood for Radio Frequency Interference.
The vacuum tube oscillator in 1912 and later 1918, the superheterodyne receiver is what made truly narrow band transmission and reception possible overseeing the birth of commercial radio owing to the clarity with which human speech could be relayed.
The world had now been ushered into the golden age of broadcasting and the number of radios grew exponentially compounding the challenges in the area of electromagnetic compatibility problems.
This situation prevailed until 1934 when the Federal Communications Commission (FCC) was established and commissioned to regulate U.S. interstate and foreign communication by radio, wire, and cable.
It was the regulations and licensing requirements springing from FCC that ultimately addressed the problem of radio frequency interference at that time.
EMC Technologies during and following World War II
Radio signals slowly found new markets in ships and aircraft in geographic positioning and locating (RADAR) and by the time of the second world war, a lot of radio equipment had been installed on planes and ships. Taking the EMC problem ranks higher. It is at this stage that the need for a joint Army-Navy RFI standard was realized and in 1945 JAN-I-225 was published.
Electronic devices and systems increasingly became an integral part of the social order with the growth in the reliance on personal computers, telephones, radio, and television, not to mention the fundamentally ingrained applications in defense systems among other possible systems applications. This alone justified even greater devotion and focus to solving the issue of electromagnetic compatibility.
Another milestone that was witnessed in the early days of 60’s and late 70’s beside the establishment of the organization known as the EOS/ESD (electrical overstress) Association that dealt exclusively with the susceptibility problems was the abandonment of using the term RFI for and adopted EMI or Electromagnetic Interference. This was especially advised by the fact that majority of the issues with the interface occurred at radio frequencies, this term was thought to be a more graphic nomenclature.
Two main events in the 1980’s had significant bearing and wide-ranging effects on the field of electromagnetic compatibility.
1. The introduction and proliferation of PCs and workstations.
This meant increased levels of significant sources and receptors of electromagnetic compatibility problems. Conversely, however, it also birthed the development of a variety of numerical analysis techniques that have helped solve EMC problems.
2. Revisions to Part 15 of the FCC Rules and Regulations
Successful EMC testing demonstrates a product’s compliance with EMC regulations and guarantees the same even under independent tests. For most electrical and electronic products there is always the requirement for compliance as a prerequisite to entry into the global markets.
Earlier defects in the product are detected by way of EMC Technologies during the development process and thus making it easier it is to rectify identified issues.
EMC testing procedure reduces over-engineering thereby guaranteeing that a product can confidently be compliance-tested.