48 V Power System for Distributed Antennae

December 19, 2016

As the mobile phone market has matured and smartphones have become an indispensable part of daily life so our expectations for fast, reliable data access have escalated.  We expect to be connected reliably inside buildings, in car parks, in underground tunnels and even in escalators.  Mobile phone coverage depends on line-of-sight to the base station, but building metalwork and local radio frequency noise from HVAC motors and other equipment can screen or interfere with these signals when we are inside buildings.

One of our customers provides very low profile, physically small, remote distributed antennas that can be fitted unobtrusively inside buildings.  To ease installation these are powered from the existing ethernet cabling (PoE) and must operate at high ambient temperatures, typically exceeding 55°C (within cupboards etc), and they themselves must generate very low conducted and radiated electromagnetic interference to avoid masking the smartphone signals.

The power supply solution developed took the 48 V PoE input, filtered it, isolated it (to minimize noise further)  reduced and regulated it to 10 V at 30 W.  Using the QPI-12LZ filter dramatically reduced the profile of the filter to below 5 mm above the printed circuit board and provided excellent conducted noise suppression.  The PI3105 isolated DC-DC converter module selected was just 6.7 mm high and had a footprint of just 22 x 16.5 mm.

The availability of a standard, low profile filter dramatically reduced development time and sped the approval process.  This solution is now successfully in mass production.

Distributed Antennae Power Chain

Distributed Antennae Power Chain

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