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Using a modulated magnetic field to transmit a signal across the air interface is an eyebrow-raising, yet viable option for an alternative low-power, low-cost communications system.

With magnetics, many of the drawbacks of traditional RF systems can be overcome. Some of these drawbacks are nulls, scattering, multipath fading, Federal Communications Commission (FCC) limits, security concerns and interference. Unlicensed RF systems such as Bluetooth and 802.11x fall in the same band. Presently, there are significant interference issues plaguing these systems because of their locations within the frequency band.

This isn't a problem in magnetic induction systems (MI) because the e-field is near-absent. MI systems are typically low power, so they can be used in most frequency bands with little interference. This has several advantages. Most notably is the ability to meet FCC limitations, particularly for short-range devices, and the ability to reuse frequencies in close proximity. For example, magnetic induction (MI) is ideal for wireless personal area network (WPAN) applications under 3 meters.

MI is a low-power technology for several reasons. It is a combination of the ability to use a lower frequency, the processing power required, design techniques, process, and transmit characteristics. A typical magnetic induction chipset may draw as little as 7 mA to transmit voice or data across a 1-meter link. RF systems would require 10 times this amount.

The ability of a magnetic communications system to operate on a carrier of 11 to 15 MHz offers tremendous advantages over a 2.4 GHz system. For instance, setting up the IF frequencies for the receiver or transmitter, or running the amplifiers requires more current at the higher frequency. An on-chip amplifier running at 2.4 GHz requires several mA of current, while an 11.5 MHz amplifier requires only a few hundred microamps. Similar current savings are typical of every block of MI systems.

The RF systems being built today are complex compared to magnetic systems. Nearly all aspects, from digitizing the receiver to channel and frequency allocation, require more processing power. This complexity requires using more complex and power-hungry processors.

Magnetic systems use design techniques that cannot be used at 2.4 GHz, resulting in less power consumption through the chain and a smaller component count.

Finally, many higher-frequency RF systems, particularly the 2.4 GHz products, require the use of more exotic semiconductor processes. The magnetic induction chipset needs only a standard (and stable) .25 µm CMOS technology. On the other hand, state-of-the-art RF companies are using silicon germanium (SiGe), BiCMOS or 0.18um CMOS processes. These exotic processes are more expensive and consume more power.

Each of these advantages adds to the incremental power savings in a magnetic induction system. Because only a few commercial RF applications require 3-meter operations (most are 10 meters or more), it is difficult to compare a 3-meter RF to a 3-meter magnetic system. For these close-proximity applications, the specification (Bluetooth for instance) still requires a minimal 10-meter operation. The RF systems designed to the 10-meter specification will draw 10-30 times more current than the magnetic system.

For devices in a personal-area network, particularly for consumer devices, price is always a tantamount concern. Consumers are usually unaware of, or apathetic about, which technology they use. They just want it to work and be affordable. It can be hard to compare cost for different technologies, unless the total solution is considered. Discussing ‘chip price’ is useless if this is only a fraction of the overall cost of building a system. For instance, Bluetooth has continuously quoted the $5 solution. However, when all is said and done, and the cost of the additional components in considered, the end cost is well above this.

Industry analysts recently cited that the cost of a two-node wireless link, using Bluetooth, is $43.24 (in 2001). The apples-to-apples cost of a magnetic system is considerably less. In medium volumes, the magnetic system requires only about 15% of the total cost for off-chip components. Therefore, this system offers chipsets at a price on the same order of magnitude of Bluetooth, while having an overall system cost well below that of the RF system's.

Furthermore, the above cost does not include manufacturing, plastic housings or batteries. It can be assumed that the manufacturing and plastics cost will be about the same regardless of technology. The battery cost, however, will vary.

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