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Front-end module design enables MIMO market

Posted: 02 Oct 2006 ?? ?Print Version ?Bookmark and Share

Keywords:MIMO? MIMO RF? high speed network? 802.11n? 802.11a?

The implementation of multiple-input and multiple-output (MIMO) RF offers higher bandwidth and robustness. But it goes against the current wireless product trend of smaller, lower-power-consuming, lower-cost form factors. The increased performance of MIMO can be integrated easily with existing wireless products, however, to achieve economies-of-scale across product families.

But two advantages often get overshadowed by higher speeds. The specification offers a 20 percent to 30 percent range improvement over existing 802.11a/b/g standards, and provides backward-compatibility to 802.11a/b/g. Backward-compatibility allows developers to use the same equipment for residential, office and travel use. The 802.11n client card uses 802.11n where available and falls back to 802.11a/b/g for existing hotspots.

The final advantage of 802.11n over competing standards is that it uses the same 2.4GHz and 5GHz spectrum as 802.11a/b/g. This allows manufacturers to leverage economies-of-scale in processes, components and suppliers. The result is a more affordable, high-speed network.

It is important to compare apples to apples when comparing integration levels of SiGe rolls out new RF front-end module for Wi-Fi apps" target=_blank>front-end modules. Functionality sometimes gets overshadowed by headline RF features such as output power and error vector magnitude, but functionality is important for cost and critical for board space. Designers should ask these questions:

  • Are the control interfaces CMOS? If they are not, extra circuitry will be required to interface the front-end module to the IC.

  • Does the front-end module require bias voltages? If it does, this will most often require external regulators to provide the bias voltage, which are typically in the range of 2.7V to 2.9V, with additional transistor circuitry for enabling and disabling the bias voltage. Apart from the size and cost, the performance of the front-end module is directly related to the bias voltage, which changes over temperature and voltage.

Although developers may not think that current consumption and form factors are related, two of the three issues with front-end module current consumption are directly related to form factors.

Historically, current consumption was related to the issue of battery life. Product developers wanted the highest power at the lowest current consumption and were sometimes willing to accept slightly lower output power for 10 percent longer battery life. The same issue applies to MIMO applications, but on a larger scale, as there are now two complete transmit chains that are operating simultaneously.

This means that front-end module suppliers must develop even more efficient, lower-current-consuming modules to enable the MIMO market. This will become even more critical if MIMO is going to move to embedded applications with smaller batteries, such as PDAs, cellphones and gaming.

- Andrew Parolin
Director of Wireless Data Products
SiGe Semiconductor Inc.

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