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What is Radio Frequency Interference - RFI

Radio frequency interference abbreviated as RFI is also called as Electromagnetic interference (EMI). It is defined as a disturbance that arises in electrical circuit either by electromagnetic conduction or radiation released from any of the external source. The effective performance of the electrical circuit is limited or say degraded by the disturbance in form of interruption or blockage. The source could be any could be of any thing; it can be an artificial object or natural one that carries quickly varying electrical currents. Examples are electrical circuit, the sun or the northern light. RFI, though to a minimum extent can affect AM and FM radio, cell phone and television reception. It can be deliberately used for radio jamming in form of electronic warfare and can be accidentally used as a consequence of spurious emissions through intermodulation products.

Historical background

In the earlier days of radio communication, the negative effects of interference have been felt from intentional and unintentional transmission and apparently the need was to manage the radio frequency spectrum. A meeting of the IEC i.e. International Electrotechnical Commission in Paris endorsed the International Special Committee in Radio Interference that there should be a set up to manage and deal with problems caused by the EMI. They have grown over decades and has formed basis of world’s EMC regulation now. FCC in the USA imposed legal limits on electromagnetic emissions from all the digital equipment in 1979 because of the huge amount of increase in the digital systems that were meddling with wired and radio communication. In the middle of 1980s, “new approach” directives were adopted by the European Member states with the purpose of standardizing technical requirements for products and it was the first time that there was a legal prerequisite on immunity and emissions on the apparatus. To give products a known level of immunity, there may be additional costs but the positive part is increases their perceived quality.

Types of Rfi:

EMI or RFI has two forms narrowband and the other is broadband. The difference between the two is that when interferences occurs from desired transmission of the data for example radio and TV stations, cell phones etc. is called narrowband and broadband interferences occurs when sudden frequencies radio emitter waves interfere.. Electric power transmission lines, electric motors, thermostats, bug zappers and like are included in this category. One of the characteristic of broadband RFI is its incapacity to filter it efficiently after entering the receiver chain.

Causes of RFI:
RFI is one of the wide ranges of complaints handled by FCC and is no doubt difficult to track down. The reason is that the devices which uses radio frequency as part of their operation and to process their working can be the cause of radio frequency interference. The interference is transmitted through air in the form of radio waves or can also be conducted through power lines. Communication equipment like computers, microwave ovens, aquariums, lighting systems and like can cause the interference naturally. So we can say that it is not necessary that interference is initiated with our neon signs and may not even be our business in causing the problem.

How it can be Reduced or Minimized?
There are some of the significant means of minimizing radio frequency interference and they are

By using bypass or “decoupling” capacitors on each active device, it is connected across the power supply.
Using series resistors and VCC filtering, high speed signals can be controlled
The last remedy after using all the techniques failed is Shielding. The failure is because of the additional expense of radio frequency gaskets and the like.