Electromagnetic Interference

Electromagnetic Interference(EMI) is the interference caused in an electrical path or electrical device due to an external source such as lightning, solar storms, and solar flares. Have you ever experienced some unwanted noise, while communicating through mobile phones? This unwanted noise is caused because of Electromagnetic Interference. In this article we are going to learn what is electromagnetic interference with Some Examples Next we will go through how it evolves, its effect, its properties of electromagnetic Interference, advantages and disadvantages of electromagnetic interference. So it is basically an unwanted noise in the electric circuit by an outside source.

Electromagnetic Interference is also called as radio frequency interference as it is also a subset of electrical noise on the EMI spectrum and it disrupts the radio frequency system.

What is Electromagnetic Interference (EMI)?

Electromagnetic Interference is unwanted interference caused in an electrical path or electrical device due to an external source. Electromagnetic Interference causes degradation in the performance of electrical devices. EMI is the coupling of signals from one system to another. This external source can be both natural and man-made source. Electromagnetic Interference is also known as Radio frequency interference. Electromagnetic Interference is caused in an electrical circuit when an electric current is disrupted by an external source. This usually occurs when the electronic device is exposed to the electromagnetic field , also because of electricity and magnetism it occurs. It is a transient disturbance which occurs at the place where source emits the short duration of pulse energy .

Electromagnetic Interference in Two Pairing Cables

Examples of Electromagnetic Interference

The Electromagnetic Interference an be Man-Made or Synthetic. The Following are Some of the Example of the Electromagnetic Interference

• CrossTalk: When The Signal from one Telephone Line is Mixed with Another Nearby Line, Causing Interference and Compromising in call quality.
• Medical Equipment Interference: Using of Electronic Devices like Mobile Phones, Which are used near the Sensitive Medical Equipments can lead to improper Functioning of Equipments.
• WiFi Signal Disruption: When Cordless Phones which are used in the Same Frequency of WiFi can lead to disruption of WiFi which leads to Reduction of WiFi Strength and Slower Internet Connections.

Cause and Effect of Electromagnetic Interference

There are some list of Cause and Effect of Electromagnetic Interference given below :

Cause of EMI

• The main factor which causes Electromagnetic Interference is from any external source including both man-made and natural source.
• EMI occurs when there is interference between electricity and magnetism. Natural sources which cause EMI are lightning, solar storms, rain, cosmic rays and solar flames.
• Man-made sources which causes EMI are electrical sources or external radio sources.
• When electric current flows through any wire it generates magnetic field around it, and conversely a moving magnetic field produces electrical current around it.

Effects of EMI

One of most common effect caused by EMI is disruption in mobile networking while communicating with other. Effects of EMI is very dangerous on human beings. EMI can affect medical devices which contain electrical components and electrical circuits. EMI sometimes lead to damage in electrical devices and causes malfunction in it. Some effects of EMI are listed below :

• EMI causes cancer in human body.
• EMI causes bad effects on human brain and human body.
• EMI sometime leads to heavy injury or sometimes lead to death of a patient.
• EMI causes damage to electrical devices present in hospitals.

Classification of Electromagnetic Interference

There are different types of Electromagnetic Interference based on the sources from which is generated. Some of its types are:

• Conducted EMI (Intentional EMI)
• Radiated EMI (unintentional EMI)
• Intra-system EMI
• Inter-system EMI
• Coupled EMI

Conducted EMI (Intentional EMI)

Conducted EMI occurs when there is a direct path from source to receiver. Some common examples of conducted EMI include power cables and electrical interconnection cabling. It occurs in two modes, common and differential. Some sources of conducted EMI includes electrical motors, DC converters, thermostatically controlled appliances, micro-controllers and ethernet traffic. It is used to emit the electromagnetic energy that is in radars and so on.

Radiated EMI (unintentional EMI)

Radiated EMI does not require any physical contact. Radiated EMI travels through air. These emission occurs when devices produce unintentional electromagnetic energy in the form of an electrical field. Some sources of radiated EMI includes radar systems, electrical motors, switch-mode power supplies, power transmission lines and telecommunications equipment. There are two types of Radiated EMI:

• Narrowband EMI
• Broadband EMI

Narrowband EMI : This type of EMI affects communication devices such as radios, televisions, and smartphones. This type of EMI happens over a discrete frequency. Narrowband EMI affects only a specific radio frequency and is commonly from a radio transmitter. Mobile phones are one of the cases of its effects.

Broadband EMI : This type of EMI causes permanent damage to devices and is always a matter of concern. Broadband EMI affects a large portion of the radio spectrum at many frequencies and is commonly caused by malfunctioning equipment.

Intra-System EMI

Intra-system EMI occurs between two elements in the same system. When interference produced within a system goes to couple the signal from the source of the interference and the electronic system itself. One real-life example of Intra-system EMI which occurs between radar transmitters and radar receivers.

Inter-system EMI

Inter-system EMI occurs between two different system (devices). This occurs when EMI generated within one system affects the performance of another system under different control users. One real-life example of inter-system EMI which occurs between computer and television.

Coupled EMI

Coupled EMI happens when the source and receiver are not connected electrically but enough close together for generating EMI. Coupled EMI can be further classified in two types on the basis of transmittance:

• Magnetically Coupled EMI
• Capacitively Coupled EMI

Magnetically Coupled EMI : It generates when a conductor’s magnetic field induces an unwanted current in a conductor placed near to it. One real-life example is the hum sound heard in a audio cable when a power cable and an audio cable are near to each other.

Capacitively Coupled EMI : The voltage variations and coupling capacitance between the source and receiver induces unintentional currents in the target, generates capacitively-coupled EMI in the target. Capacitively coupled EMI happens when the conductors are kept close together.

Characteristics of Electromagnetic Interference

• EMI usually come from high-power radio, electrical sources. Even mobile phone, which we use regularly is also one of the source of EMI.
• EMI occurs when received energy causes the receptor to act in abnormal manner. It is one of the reason of poor performance of electrical devices.
• Electromagnetic Interference is classified into further types on the basis of transmittance and devices in which it occurs.
• Electromagnetic Interference causes unwanted noise inside devices or sometimes causes malfunctioning of system.
• The transfer of energy between different system occur through radiation and conduction. EMI is the result of electromagnetic emissions.
• There are three elements involved in EMI which are source, coupling medium and receiver. Source is the emitter part, and receiver is the victim part.
• So this replaces the current and then radiates the RF spectrum respectively.

EMI Coupling Mechanisms

The EMI can be coupled from source to receiver in different ways. EMI coupling mechanisms describe the way EMI travels from source to receiver or victim device. The coupling path differs in each EMI coupling mechanism, and it is important to understand EMI traveling paths. Electromagnetic disturbances are transmitted from source to the receiver/victim through a variety of means, such as a common conducting path, mutual inductance or capacitance, or air or vacuum. EMI coupling mechanism can classified into four types, i.e.,

• Conductive Coupling
• Capacitive Coupling
• Inductive Coupling
• Radiated Coupling

EMI Coupling Modes

The four types of Coupling Mechanism are mentioned below:

Conductive Coupling

Conductive coupling refers to the process of energy transfer between two independent metallic objects that is facilitated by their direct physical contact. The process primarily involves the transfer of electrical and electrochemical energy to reduce the occurrence of corrosion on one or both of the metallic objects that are present.

Capacitive Coupling

Capacitive coupling is the transfer of alternating electrical signals or energy from one segment of a circuit to the other using a capacitor. The coupling provides a medium for the AC signals while blocking the DC energy. The capacitive coupling or DC blocking may be intentional, either for analog, digital and gimmick loop applications or unintentional as in the case of parasitic capacitive coupling.

Inductive Coupling

When the EMI from a source couples to a target over the magnetic field, then the coupling is said to be as inductive coupling. Inductive coupling utilizes the principle of electromagnetic induction to induce currents in the target due to the varying magnetic field between the source and receiver. The intensity of the coupling voltage is dependent on the current variations and mutual inductance between the source and receiver.

Radiated Coupling

When the source and receiver are separated physically from each other then the EMI travels via air or vacuum to reach the receiver. The electromagnetic interference is radiated in this type of EMI coupling. Radiated EMI mostly comprises higher-frequency signals in the microwave frequency range. Radiated EMI is also known as radio frequency interference (RFI).

How is EMI transmitted ?

The source of EMI can be both natural and man-made. EMI can be transmitted through two main modes of action one is conducted means and other is radiated. Conducted types involve noise that passes through a conductor into or out of a device, while radiated noise is received or transmitted wirelessly. At lower frequency , unwanted noise travel through conducted means. At higher frequency noise travel through radiated means. Sometimes it is also possible that EMI occurred through radiated means appear to happen through conducted means.

Two Main Modes of EMI Transmission are:

• Conducted means of EMI
• Radiated Means of EM

Conducted means of EMI

Interference transferred from a source to a receiver along a direct path is called conducted EMI. Conducted EMI is caused by physical contact. This method requires a physical conduction between source and receiver so it transfers electromagnetic emissions to connected equipment. Common paths for conducted emissions include power cables and electrical interconnection cabling. Conducted EMI also occur through parasitic capacitance.

Radiated Means of EMI

Radiated EMI requires no physical contact. Radiated EMI travels through the air instead. These emissions happen when devices produce intentional or unintentional electromagnetic energy in the form of an electrical field. Damage from EMI-radiated emissions occurs through induction. Radiated emissions spread outward, sometimes traveling long distances. Depending on their proximity and severity, they can have unwanted impacts on receiving devices located within the vicinity. These electrical emissions can also interfere with the source device operation if they overwhelm the circuitry.

Techniques to Control Electromagnetic Interference

There are some technique available to reduce the effect of EMI or for controlling EMI. Some of them are:

• Grounding
• Shielding
• Filtering

Grounding

Grounding is similar to earthing. Grounding protects the entire power system from poor performance or malfunctioning. The one side of live wire is connected to electrical appliances and other side is inserted into ground to avoid overloading and other accidents. An electrical conductive path is introduced in this between electrical and electronic system and a reference point – basically it is the connection made to the earth.

Shielding

For reducing the effect of EMI, EMI shielding is done. EMI shielding is method of creating a barrier that prevents leakage of strong electromagnetic fields that can interfere with electrical devices and signals. EMI shielding is done to isolate the electromagnetic field source or as an enclosure of the device that needs protection. It contains radiation in the source and consist of a circuit as well. So small radiation ends up by penetrating the shield if it is not so thick .

Filtering

EMI filters are an effective way to protect devices against the harmful impacts of electromagnetic interference. EMI filtering is also known as EMI suppression filters. EMI filters are attached to devices or circuits and it can suppress electromagnetic noise transmitted through conduction. These filters remove any unwanted current conducted through wires and cables.

Advantages and Disadvantages of Electromagnetic Interference

There are some list of Advantages and disadvantages of Electromagnetic Interference given below :

Advantages of EMI

EMI is also useful at many places. For performing some activities it is used intentionally. Few of its advantages are listed below:

• EMI is considered as important while designing electronics and circuit boards.
• EMI is necessary for modern high-speed devices.
• EMI is used for radio jamming for emergency purposes.

Disadvantages of EMI

EMI has negative impact on both human beings and electrical devices. Few disadvantages of EMI are listed below :

• EMI causes malfunction of electrical devices and sometime stops its functioning.
• EMI prevent the proper use of the radio frequency spectrum.
• EMI have direct effect on human tissue.
• EMI sometimes lead to EMI cancer in human beings.

Applications of Electromagnetic Interference

EMI has various application in security , medical , aerospace industry and in vehicular control system. Some of its application are listed below :

• EMI has ability to disrupt connection, malfunction devices, cause loss of data, because of this EMI can be used for security and cyber purpose by every developing countries.
• EMI can be used intentionally for radio jamming, as in electronic warfare.
• EMI can be used to block connections of missiles and rockets.
• EMI can save any country from heavy air and water attack by jamming its connection from where it is operated.
• It is used in military and electrical components such as inductors , transformers , motors etc.

Conclusion

From above discussion it is concluded that EMI is threat to human development. It is necessary to prevent unnecessary occurrence of unwanted noise as it can cause loss of signal, malfunction of device, changed behavior of devices. The best way to prevent EMI is to use good quality electronics equipment. EMI Shielding in electronic devices and equipment is the use of manufacturing techniques and materials to protect signals from being disrupted by external electromagnetic signals as well as preventing generated signals from interfering with surrounding components. There are three techniques of controlling Electromagnetic Interference grounding, shielding and filtering. Electromagnetic shielding is one of most famous method for reducing the effect of EMI and thus stops the phenomenon that results into the radiation of electrical signals into the places which there presence is undesirable.

FAQs on Electromagnetic Interference

How does EMI occur ?

Electromagnetic Interference (EMI) occurs when unwanted electromagnetic signals disrupt the normal operation of electronic devices or systems. There are various mechanisms through which EMI can occur:

Sometimes we hear an unwanted noise while talking with another person through mobile phones. It is caused due to.

Electromagnetic Interference is the reason when hear an unwanted noise while talking with another person through mobile phones. It creates an unwanted noise because of any external source.

How can EMI be tested and measured ?

Testing and measuring Electromagnetic Interference (EMI) is crucial to ensure that electronic devices and systems comply with electromagnetic compatibility (EMC) standards. Here are some common methods and tools used for testing and measuring EMI:

• Spectrum Analyzer
• EMI Receiver
• Oscilloscope
• Network Analyzer