RF interference can be described as the effect of unwanted RF energy in the system under consideration manifested by degraded performance, loss of data, equipment damage, etc.
RF interference is narrowband interference affecting the electronic system, which can be considered a subsystem of EMI.
Analog circuits usually face intermodulation and demodulation effects due to RF interference.
Radiated susceptibility of amplitude modulated (AM) receivers interferes with radio reception and has always been a problem in radio communications. AM receivers are more susceptible to radio frequency interference (RFI) than frequency modulated (FM) receivers. Usually, RF interference in radio receivers is caused by transmitters that propagate signals on the same frequency or same frequency band. Cordless phones, oscillating amplifiers, and baby monitors are examples of sources that produce radio interference to AM receivers. The overloading of AM radio receivers by nearby transmitters can also create RF interference issues in radio broadcasting. Other systems that deal with electromagnetic signals are also susceptible to RF interference.
Radio Frequency Interference
The frequency range from 3 kHz up to 300 GHz is known as the radio frequency spectrum. It is a limited resource, and numerous electronic and wireless systems utilize this spectrum for various applications and services. With the proliferation of systems using radio spectrum, the stability and performance of electronic devices utilizing this spectrum are deteriorating.
The effects of undesired electromagnetic energy on electronic systems is called interference. Interference is generally categorized as electromagnetic interference (EMI) and radio frequency interference (RFI). RF interference can be described as the effect of unwanted RF energy in the system under consideration manifested by degraded performance, loss of data, equipment damage, etc.
RF interference is narrowband interference affecting the electronic system, which can be considered a subsystem of EMI. In electronic systems affected by RF interference, the RF source and receiver are physically separated, yet unwanted electromagnetic signals producing interference affect the proper functioning of the device. Electromagnetic noises get inductively coupled between the source and receiver and are called radiated emissions.
Typically, the electromagnetic coupling mechanism that produces RFI is induction. Any one component of the electronic circuit can operate as the antenna for emitting or absorbing RFI. The length of the component acting as the antenna should be at least equal to 1/20 th of the signal wavelength. With regard to the component length-wavelength relationship, high-frequency signal systems are more likely to radiate RFI than low-frequency signal systems. Cables, tall components, and apertures in the enclosures are examples of RFI antennas emitting RF noises.
Types of RF Noises
RF noises can be:
- Unintentional RF noises - These are radiated or leaked RF energy from the device that intentionally generates RF energy to use within the device. One example is RF energy emitted outside by a clock (timer) in a tablet computer.
- Intentional RF noises - Intentional RF noises are generated and emitted by devices designed for the same. One example is an unlicensed wireless baby monitor.
- Natural RF noises - Natural RF noises are either atmospheric (static) noises or cosmic noises. An example is lightning and noises produced by celestial bodies.
- Man-made RF noises - Man-made RF noises are produced by man-made systems such as power electronic systems, LEDs, computer clocks, etc. Such RF emissions are unintentional or incidental.
- Aggregate man-made RF noises - The host of intentional radiators such as harmonics, out-of-band emissions, and spurious signals from licensed and unlicensed devices forms aggregate man-made RF noises.
- Internal RF noises - RF receivers generate internal noises, and such RF interference is called internal RF noise. One example is thermal noise.
Effects of RF Interference
The effects of RF interference can be summarized as:
Interfering radio reception - RF interference hampers radio broadcasting. RF interference generated by mobile phones, portable electronics, consumer appliances, etc. is capable of interfering with the radio receivers employed for communication and navigation purposes.
Dysfunctional electronic systems - RF interference can disturb the normal operation of electronic systems.
Intermodulation and demodulation - Analog circuits usually face intermodulation and demodulation effects due to RF interference. In the case of multiple frequency RF interference, non-linearities in the circuit generate sum and difference frequencies of the fundamental components, and the harmonics, called intermodulation products, may fall within the passband of the circuit. The RF noises generated can be demodulated by active components in the circuit to produce signals within the passband of the circuit.
Data corruption - In digital circuits, RF noises can cause timing jitters and, subsequently, data corruption.
Damage of devices - The high-intensity RF noises in the vicinity of sensitive devices can produce sufficient energy that can cause permanent damage to system components and ultimately the entire system.
RF interference can disturb the functioning of sensitive devices, especially radio transmitters, radars, communication, and navigation systems. Cadence software can assist you in planning RF interference mitigation suitable for the circuit or device of interest.