Harmonic distortion

What does Harmonic distortion mean?

Harmonic distortion is a common type of distortion That occurs when a signal contains components of frequencies that are multiples of the fundamental frequency. This distortion is caused by non-linearity in the relationship between the input and output of a system. As a Result, the output signal contains frequencies that were not present in the input signal.

Harmonic distortion is often characterized by the presence of harmonics, which are frequencies that are related to the fundamental frequency by a whole-number ratio. The most common types of harmonics are the second harmonic, which is twice the frequency of the fundamental, and the third harmonic, which is three times the frequency of the fundamental.

The amount of harmonic distortion in a signal is typically measured in terms of the Total harmonic distortion (THD). THD is calculated by taking the ratio of the sum of the powers of all harmonics to the power of the fundamental frequency. THD is typically expressed as a percentage.

Applications

Harmonic distortion is an important consideration in many applications, such as:

• Audio systems: Harmonic distortion can cause audio signals to sound muffled or harsh. In High-quality audio systems, it is important to minimize harmonic distortion to ensure that the audio signal is reproduced faithfully.
• Power systems: Harmonic distortion can cause problems in power systems, such as overheating of transformers and generators. It is important to control harmonic distortion in power systems to ensure that the system operates reliably.
• Telecommunications systems: Harmonic distortion can cause interference between different signals in telecommunications systems. It is important to control harmonic distortion in telecommunications systems to ensure that the signals are transmitted and received without interference.

History

The concept of harmonic distortion was first proposed in the early 19th century by Joseph Fourier. Fourier showed that any periodic signal can be represented as a sum of sinusoidal waves of different frequencies. This theorem is known as Fourier’s theorem.

In the late 19th century, Lord Kelvin developed a method for measuring harmonic distortion. Kelvin’s method involved using a series of filters to separate the different harmonics in a signal.

In the early 20th century, the development of the vacuum tube led to a renewed interest in harmonic distortion. Vacuum tubes are non-linear devices, which means that they can cause harmonic distortion. As a result, it was important to design vacuum tube amplifiers with low harmonic distortion.

In the mid-20th century, the development of the transistor led to a further reduction in harmonic distortion. Transistors are more linear devices than vacuum tubes, which means that they can produce less harmonic distortion.

Today, harmonic distortion is an important consideration in many different types of electronic devices. By understanding the causes and effects of harmonic distortion, engineers can design systems that minimize distortion and ensure that signals are reproduced faithfully.