As mobile communication has become increasingly sophisticated, antenna tuning techniques have become more advanced. Antenna tuning involves matching the impedance of the load of the components connected to an antenna to the impedance of the antenna itself. The antenna impedance may be affected by the state of the communication device (e.g., cell phone), which can be based on a variety of factors, including the position of the communication device with respect to the user's body. When the impedance of the antenna changes, it is desirable to tune the antenna (e.g. by changing the impedance of the load) in order to keep the impedances as closely matched as possible. However, when the impedance of the load changes, the phase of the signals travelling to and from the antenna also tends to change. Unfortunately, phase changes in mobile communication signals are interpreted as meaningful data, which can degrade the reception of the signal and lead to garbled transmissions. There are certain scenarios in which impedance changes and the associated phase changes can be anticipated and tolerated by the communication system. One example is when the channel being used for communication changes. During a channel change, the transmit modulator and receive modulator generally perform a channel estimate, which is used to set up the channel for use by the communication device. Should the phase change occur before the channel estimate, or occur while the transmitter is not emitting a signal, then the phase change will have no affect on the signal received at the base station. Subsequent insertion phase changes of the channel such as those due receiver mobility and multipath channel fading are also tolerated by the receiver. However, when abrupt changes in impedance occur during the transmission of data (from antenna impedance tuning, for example), it is much more difficult for the base station receiver to react to the resulting phase shift and the quality of the received signal could be degraded.
USPTO Backgrounds
USPTO Backgrounds