Radiation from Wires and Loops: Understanding Current Loops

Radiation from Wires and Loops: Understanding Current Loops

Introduction

Current loops are often employed in electronics due to their ability to create small magnetic fields, which can interact with surrounding wires or printed circuit boards (PCBs). This interaction may lead to radiation emission, which is a concern for workers handling these components or devices containing them. To understand this phenomenon better, we'll delve into the fundamentals of current loops, the electromagnetic interference they produce, and its implications.

Fundamentals of Current Loops

A current loop consists of two wires connected by a choke coil inductor, which acts as a low-pass filter. It's designed to pass DC voltage while blocking AC voltages above a certain frequency. When a voltage is applied across the wire pair, current flows through them initially. However, it gets choked off after a short distance because of the high resistance induced by the choke coil.

Electromagnetic Interference

When alternating current (AC) passes through a wire, it generates a magnetic field around the wire. If the wire is part of a closed loop, the magnetic field forms toroids centered at each point in the loop. As the current changes direction, the magnetic field reverses its direction, creating eddy currents within any conductive objects nearby, like the PCB. These eddy currents generate counter eddy currents, which heat up the conducting material and emit radiofrequency (RF) energy.

The RF energy emitted depends on several factors such as the loop size, the number of turns in the loop, the current flowing in the loop, and the properties of the conductive material being used. Moreover, the proximity of nearby wires or components influences the amount of radiation emitted as well.

Implications

Electromagnetic radiation produced by current loops may have significant consequences when using electronic equipment. For instance, radiated emissions from a signal line may interfere with other lines, leading to signal degradation or even equipment malfunction. Radiated emissions from power supply lines may cause problems similar to EMI, disrupting sensitive electronics.

In case you work with PCBs or other equipment containing current loops, it is essential to consider shielding techniques to minimize the effects of electromagnetic radiation. Shielded cables and ground planes can help contain the RF energy generated by current loops and reduce its potential impact on sensitive systems.

Conclusion

Understanding the relationship between current loops, electromagnetic radiation, and electromagnetic interference is crucial for designing effective shielding methods and minimizing the negative impacts of current loops on electronics. While circuits employing current loops offer convenience and efficiency, engineers must prioritize safety measures to protect against potentially harmful RF emissions.