Mobile communication systems continue to grow in popularity and have become an integral part of both personal and business communications. Various mobile devices now incorporate Personal Digital Assistant (PDA) features such as calendars, address books, task lists, calculators, memo and writing programs, media players, games, etc. These multi-function devices usually allow electronic mail (email) messages to be sent and received wirelessly, as well as access the Internet via a cellular network and/or a wireless local area network (WLAN), for example.
Cellular devices have radio frequency (RF) processing circuits and receive or transmit radio communications signals typically using modulation schemes. In the typical device, the RF processing circuits may include a modulator, a power amplifier coupled downstream from the modulator, and an antenna coupled downstream from the power amplifier. Depending on the immediate surroundings of the cellular device, the impedance load of the antenna may vary, which can impact antenna performance.
Some cellular devices include an impedance matching device between the antenna and the power amplifier to compensate for the impedance mismatches. One drawback to this approach is that a phase change is imparted onto the transmitted signal. Depending on the wireless protocol being used, this may cause issues with the receiver device.