If a TVS is used as an ESD countermeasure for a component in the vicinity of an antenna, the receiving sensitivity inevitably deteriorates due to harmonic noise during transmission.
Countermeasure and effectiveness:
We combined Murata’s LXES**A series ceramic base ESD protection device with a capacitor. As a result, no harmonic noise was generated, and moreover it was possible to implement ESD countermeasures while reducing insertion loss.
* A TVS is an ESD protection semiconductor-based device which utilizes a zener diode method. Murata calls its ceramic-based ESD protection device A-TVS (Advanced TVS).
Cause of harmonic noise generated by a TVS
When a general TVS is used, if the signal amplitude exceeds the breakdown voltage (VBR) signal by even an instant, the signal waveform will become distorted. As a result, in addition to the signal frequency, harmonic noise will occur , causing interference with other signals, and the sensitivity of the antenna will deteriorate.
Countermeasure method and effectiveness:
By combining Murata's ceramic-based ESD protection device A-TVS (LXES** A series) with a capacitor, harmonic noise is eliminated, and it is possible to perform ESD countermeasures while reducing the insertion loss.
* Murata's ceramic-based ESD protection device (LXES**A series) has low capacitance, and also has excellent ESD immunity and ESD protection performance, so it is called A-TVS (Advanced-TVS).
When an ESD countermeasure using a TVS is replaced by
Murata's A-TVS (LXES**A series) and a capacitor
As shown in the figure below, harmonic noise is eliminated, insertion loss is reduced, and ESD countermeasures can be performed.
Murata's A-TVS (LXES**A series) has a higher breakdown voltage than that of a general TVS (it exceeds the amplitude voltage of the signal). Consequently, the signal waveform has no distortion, and also harmonic noise is eliminated.
In the future, if the number of frequency bands that can be used simultaneously by using a standard such as carrier aggregation increases, harmonic noise will definitely become a major issue.
For this reason, it can be said that Murata's A-TVS (LXES** series) which is free from the problem of harmonic noise is the optimum solution for ESD protection of an RF antenna.