Portable wireless devices, such as smart phones and tablets, have antennas incorporated into their industrial designs. These antennas can be multi-band, operating on multiple frequency bands such as in the range of 700 MHz to 2690 MHz. It is expected that many more frequency bands will be implemented in portable devices in order to ease the capacity congestion of the wireless cellular frequency bands Impedance matching over a large range of Radio Frequency (RF) bandwidth becomes increasingly more challenging as the number of supported bands increases.
Tunable components present a viable approach to antenna system design, which is ever more complex due to the growing list of operating frequencies and the increasing diversity and use cases of portable wireless devices. A primary application of such elements is in tunable matching networks, to compensate the power loss associated with the time-varying impedance mismatch in different operation modes of the device. In case of a wireless handheld device, the antenna impedance as seen by the transceiver varies when the user takes his device out of holster, sends a text message, watches a video, answers a phone call, and so on. A matching network can be tuned in an effort to reduce these impedance variations seen by the transceiver and hence improve the antenna performance.
Tunable components can be configured in various configurations utilizing various components, such as capacitive elements. Charging and discharging times of the capacitive elements can be directly related to performance of the tunable components.