This slide provides a background on the function of a coupler in a typical wireless application. Any handset or wireless device consists of a RF chipset, a PA and a matching circuit. The PA transmits an RF signal from the RF chipset, through the antenna. A typical wireless device in the market can transmit up to 900 mW – 1 W of power. Without a coupler at the output of the PA (at the input of antenna), a change in antenna impedance will result in power being reflected back into the PA causing less power to be transmitted from antenna. In order to meet operator requirements, the PA will try to pump more power out of the antenna, resulting in higher current draw and in extreme conditions, damage to the circuit. Therefore a coupler is implemented between the PA and antenna, to detect any power reflections and dynamically adjust the gain of the PA, avoiding excessive current draw and protect sensitive components in the circuit.