Engineering 101

Compact power designed for a low profile antenna array

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As the mobile phone market has matured and smartphones have become an indispensable part of daily life, people’s expectations for fast, reliable data access have escalated.

Users now expect to be connected reliably wherever they are, whether inside buildings, in car parks, in underground tunnels and even in elevators.

While users want 100% coverage with no blind spots, architects and building owners want the equipment to be invisible.

To be able to conceal systems, they must be small, typically with a very low profile.

One customer developed a distributed antenna system that was required to have a height of less than 25mm to enable un­obtrusive fitting inside buildings.

The power solution for the antennae had to generate very low conducted and radiated electromagnetic interference to maximize effective signal range.

The requirement for quiet operation meant that forced air cooling with fan could not be used, demanding high efficiencies to enable conduction cooling.

The solution

A complete solution was developed based on a PFM Isolated AC/DC converter (9.4mm high) and its companion AC input front-end module (AIM).

These power components are housed in Vicor VIA Packaging Technology, an electrically and thermally-adept solution that enables high power density with a height of just 9.3mm.

The PFM and AIM take a universal AC mains voltage of 85-265V, and convert it directly to a 24V hub voltage, which was used to power three rails.

Two of the rails used ZVS Buck Regulators, one providing a regulated 24V and the other a regulated 5V.

Packaged in an LGA SIP, these ZVS Buck Regulators are just  2.56mm high, and require minimal additional external components.

The third rail, which required more power, utilized a PRM regulator to boost the voltage to 48V with a VTM current multiplier.

Both of these components are 6.73mm high, and the VTM provides the isolation required by the load.

The outcome

With such low profile power components, the customer was able to achieve their design goals and create a product that could easily be hidden, yet provided the coverage that consumers demanded.

Although height was the most challenging requirement, in applications such as these power density is also critical.

All five power components used in the design are among the industry’s highest density as well as providing the lowest profile.

The power components used are also very high efficiency, particularly the PRM/VTM and ZVS regulators, which not only eliminated the need for fans, but also reduced the requirements for conduction cooling, further minimizing the form factor.

The complete portfolio of scalable power components, from the source to the point of load, provides upgrade capability to the antenna, without the need for an expensive redesign.

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Source Vicor

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