If communication waves from cellular or Wi-Fi sources interfere with and intrude into microphone lines for smartphones or other devices, some of their components will become noise components in audible bands known as "TDMA noise", and may be emitted from speakers as unpleasant sound. Countermeasures which implement combinations of TDK's noise suppression filters and ESD Notch Filters can not only demonstrate outstanding effectiveness at suppressing TDMA noise with no effect on signals, but can also provide a variety of other benefits such as improving cellular or Wi-Fi communication reception sensitivity, and providing countermeasures against ESD (electrostatic discharge).

Class-D amplifiers, which are used in devices such as smartphones and audio equipment, have the advantages of being compact and highly efficient, but crucially require countermeasures against noise generated by their high-speed switching. TDK has an extensive lineup of products which can provide effective noise countermeasures while ensuring high sound quality and without affecting signals. This article describes the applications and effectiveness of these products in speaker lines for various devices which use Class-D amplifiers.

Ensure voice quality, Prevent degradation of reception sensitivity (self-poisoning), Suppress harmonic distortion in Class-D amplifiers in Noise Suppression Filters for Audio Lines

TDK has developed TCM0403R common mode filters, which have realized a significant size reduction compared to the existing thin-film common mode filters. This size reduction was made possible through the application of unique thin-film processing techniques, developed for HDD heads. These filters are ideal as a noise suppression measure in mobile devices such as smartphones and tablets, for which conservation of space is demanded.