Ferrite bead filter for power over coax

April 17, 2019 //By Nick Flaherty
Murata's filter ferrite bead is designed for high frequency, high current automotive applications
Murata has launched a series of ferrite beads specifically designed for automotive networks using Power over Coax (PoC), supporting currents up to 1400 mA and frequencies up to 1GHz.

The BLM18DN_SH series uses an internal electrode developed by Murata that limits the size to 1.6 mm x 0.8 mm (1608) while offering a maximum DC resistance of 0.12 Ohm and maximum rated current of 1400 mA while supporting frequencies at 1GHz. This is the first product to offer this performance in a compact size for power over coax designs. 

As vehicles become more complex and sophisticated and especially as a result of increased image sensing, data communication needs within vehicles have increased significantly. Multiple protocols exists including CAN, LIN, FlexRay and Ethernet and the wiring, along with the associated power cabling, has increased in weight to the point it is now an issue. The transition towards PoC is addressing this by transmitting data on a single coaxial cable that is also able to carry the power.

However, systems such as Advanced Driver Assistance Systems (ADAS) and In-Vehicle Infotainment (IVI) use a 1.5 GHz band GPS signal that creates noise that can significantly affect data transmission at 2.4 GHz. To resolve this, a high impedance noise filter that can carry large currents and remain effective into the GHz band is needed. Murata’s existing BLM18GG series supports the frequency range required but is limited to 200 mA making it unsuitable for PoC implementations. 

The four devices in the new series are aimed at the Bias Tee circuits required for PoC implementation and applications which will need the capability of wide frequency coverage and ability to operate at temperatures up to 125ºC. The devices are AEC-Q200 compliant for automotive designs.


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