How to avoid antenna desense using integrated common-mode filters in industrial automation and computer applications

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Parts of sound radiation occurs in industrial automation and computer applications due to high-speed data links including switches and displays. For industrial applications to perform correctly, electromagnetic interference (EMI) must be limited and often requires reinforced shielding.


To guarantee a high level of signal integrity, STMicroelectronics ECMF™ technology filters interference coming from common-mode noise generated by high-speed datalinks. In addition to ensuring compliance with international EMC standards, our portfolio of common-mode filters with integrated ESD protection (ECMF) prevents ESD issues for a wide range of interface speeds.

Antenna desense: a persistent global issue

When the frequency of nearby noise interferes with the transmission of RF signals, this is known as antenna desensitization or desense. The receiver loses sensitivity, which causes it to miss some or all of the data sent in the transmission. Noise from high-speed datalinks including USB4, USB 3.2, and HDMI 2.1 as well as DisplayPort 2.1 for displays can, for example, disturb the performance of Wi-Fi 6, Wi-Fi 6E or Bluetooth modules.

Antenna desense and RF interference affects a wide variety of products in industrial and consumer applications, which significantly degrades system performance and can also damage your brand. Engineers are aware of this, but it can be difficult to solve this issue.

How ECMF technology can secure Wi-Fi 6, Wi-Fi 6E and Bluetooth transmissions in industrial applications

ECMF™ technology is an integrated solution that combines a common mode filter with ESD protection optimized with low clamping voltage. Thanks to this silicon-based technology, ST proposes very small devices with very high inductive impedance for an improved common-mode rejection ratio (CMRR) compared to passive technologies.

Additionally, to address PCB layout constraints in industrial applications, ST's most recent ECMF filters with a 10.7 GHz differential bandwidth are available in a QFN-10L package for the 4-line ECMF4-40A100N10 and a QFN-6L package for the 2-line ECMF2-40A100N6.

How it works

High-speed datalinks use differential signaling to transmit data. The two signals of a differential pair (D+ and D–) have the same magnitude, but the opposite phase. For this type of signaling, there are two possible modes: differential mode and common mode.

In differential mode, the signals flow between the source and the load with opposite phase, while common mode signals flow with the same phase. Ideally, the transmitted data is sent in differential mode while the common mode signal is zero.

Unfortunately, some unwanted noise can occur when signals of a different pair are not exactly in opposite phase, or when there is coupled noise on each line of a differential pair. This noise generates radiation through the cable or flex assemblies.

To improve the robustness and resolve antenna issues for RF communication, especially in industrial applications, a common mode filter and ESD protection are required. This also helps systems pass ESD and EMC compliance tests.

The challenge in selecting the correct ECMF device is to find the best trade-off between an efficient common-mode filter to clean the radiation noise and a high-bandwidth differential filter to avoid filtering out the useful datalink signals.

ECMF Filtering behavior

How ECMF can add value to your industrial computer and measurement equipment?

In the industrial market, the trend today is to transmit even larger amounts of data between systems as well as the increase in size and resolution of displays. This has led to the development of standards with higher data-transmission rates associated with connectors including USB-C with USB4 and HDMI with HDMI 2.1. Moreover, the latest trends in Industry 4.0 call for a reduction in the size and power consumption of systems. A smaller size means an increased risk of internal noise radiation in industrial systems.

To limit EMI and antenna desense issues, our silicon-based ECMF™ technology is optimized to meet the challenges of industrial applications in full compliance with ESD IEC 61000-4-2 and EMC IEC 61000-4-3 standards.

Our most recent ECMF filters with a 10.7 GHz differential bandwidth include the 4-line ECMF4-40A100N10 in a QFN-10L package and the 2-line ECMF2-40A100N6 in a QFN-6L package.

ECMF2 40A100N6ECMF4 40 A100N10