Mobile Device Low-Power Antenna Tuner Revealed
November 10, 2011
Last week WiSpry announced the introduction of its WS2018, which it claims is the industry's lowest current consumption antenna tuner. The chip is positioned between the antenna and the front-end module of a mobile phone, matching the impedance of the antenna to that of the front-end throughout an 824-2174 MHz range. The key to the performance of WiSpry's tuners is the use of Micro-Electro-Mechanical Systems (MEMS) to switch multiple capacitors in and out of the circuit to create the values needed to match the impedance of the device and the antenna. WiSpry's manufacturing techniques are similar to those used for integrated circuits, allowing the MEMS and capacitors to be build on active CMOS silicon structures.
WiSpry's current line of tunable impedance matching networks (TIM) features capacitance values from 5 to 20 picofarads, with custom configurations up to about 30 picofarads. Proper impedance matching between the antenna and receiver front end are required to obtain the maximum power transfer (maximum sensitivity) and best noise figure performance from the receiver front end. I'm not aware of any of these circuits being used for portable TV receivers. Perhaps the cost is too high, but given the challenges of providing maximum sensitivity with small antennas in these devices, particularly at VHF, it may be worth a look.