Investigating power amplifier behavior in User Equipment terminals

Sammanfattning: In this thesis work, experiments have been carried out to study the behavior of radio frequency power amplifier which is the one of the largest power consumers in a user equipment which is a mobile phone in this case. A CMW-500 which is a Rohde and Schwarz equipment has been used to emulate the base station. A user equipment has been chosen that operates in accordance with cat12 LTE. The input path of the power amplifier from the device driver has been surgically intruded to introduce signals of interest. The design of the experimental set up has been challenging. Introducing signals of interest to measure linearity and third order modulation products, with the user equipment being connected to the CMW-500, took lot of planning and preparation. A very high frequency switch has been introduced to switch between the input signals from the device driver and the signals introduced for the purpose of the experiments. The switch also has a low insertion loss. Efforts have also been made to check that the signals introduced into the input of the power amplifier are of the same level as the input signal to the power amplifier from the device drivers. So, additional attenuators and amplifiers have also been introduced in a manner that the noise figure is as low as possible. Experiments have been conducted to understand the linearity characteristics and efficiency of the power amplifier. After conducting the experiments, it has been observed that because of varying supply voltage it is very difficult to understand the behavior of the amplifier in a high-power mode. The measurements made for measuring efficiency of power amplifiers clearly showed that the power amplifier behaves in 2 power modes: a low power mode with constant supply power and a high-power mode where envelope tracking sets in and the supply voltage varies. The specifications of the power amplifier read that the behaviour of the power amplifier is controlled digitally. So, while conducting experiments, there has almost been no control over the mode in which the power amplifier would operate.