The Samsung Focus Flash is a Windows-OS smart-phone that was released last November 2011. It would be just another (good) smart-phone with Windows OS if it wasn’t because, to my knowledge, it is the first cell-phone ever to come equipped with an antenna matching network.

A matching network is a portion of the RF circuit that matches the antenna impedance to the rest of the system (typically 50 ohms). When a cell-phone antenna is tested in an anechoic chamber, it is done considering very specific user scenarios using phantom heads and hands. However, if a specific case or hand grip is not tested and this happens to be a specially bad condition for the antenna we may end up in troube. Our skin is slightly conductive so, when touching an antenna, it will slightly change its impedance and it might mess up its matching with the RF chain. If you happen to bridge with your finger two different antennas or sections of the same antenna, then is when the whole matching gets messed up and Apple goes mainstream for an actual design mistake.

Actually, anything conductive getting into the near-field of the antenna (about a fraction of the wavelength) will potentially disrupt the impedance matching. I will not go into too many details but, when an antenna is well matched most of the RF power is actually transferred and radiated from to the antenna.  But if the matching is bad the less power is transmitted/received independently of how good the signal level is. There are hundreds of examples of people showing this with an iPhone 4 in YouTube.

A tunable matching network adapts to these changes in a dynamic environment to make sure that the impedance matching of the antenna is optimum at all times. This network is intelligent enough to help the antenna to be matched to the system in any user scenario! This is when s smartphone gets really smart.

In the case of the Samsung Focus Flash, the matching network is build by an Orange County-based RF programmable solutions manufacturer, Wispry. You can read this article for more details of the A2101 tuning module based on MEMS. I am surprised that Samsung is not advertising this cool feature for their phone…I think it may be a good selling point!

Very cool stuff… the iPhone 4 might not have had all those antenna problems had it had one of this inside…

From wiSpry:

Using WiSpry’s core digital capacitor technology and tunable digital capacitor arrays (TDCA), WiSpry can support its customers with development of tunable impedance matching networks. Implementing inductors in a variety of ways, WiSpry’s front-end matching networks are capable of matching networks with up to 19:1 VSWR. TIM’s feature low voltage operation, high linearity, accuracy, and high Quality factor (Q) performance coupled and small size.
TDCA’s available for implementation into TIM’s range from standard 5pF, 10pF & 20pF arrays up to custom configurations (~30pF +) for higher capacitance values. Both series and shunt capacitors are available so that virtually any network topology can be implemented.

Teardown: Samsung Focus Flash.

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