Wireless communication systems have been facing a steadily growing demand for higher data rates. Since, the radio spectrum is a limited resource, systems with multiple antennas can be utilized as a way to increase spectral efficiency. In a transmitter, the use of several parallel transmit paths and antennas increases system complexity and cost. Cost-efficient solutions, which employ active antenna arrays, are therefore preferred. However, such solutions are vulnerable to crosstalk due to mutual coupling between the antennas, and antenna mismatches. Combined with the nonlinear behavior of the power amplifiers, these effects cause nonlinear distortion. Since nonlinear distortion deteriorates the quality of the transmitted signal, it can prevent the transmitter from meeting standard requirements and fulfilling spectrum regulations. Analysis, assessment and, if necessary, compensation of nonlinear distortion are therefore essential for the design of multi-antenna transmitters.
In this seminar, a technique for modeling and predicting nonlinear distortion in multi-antenna transmitters is presented. With this technique, the output of every path of an arbitrarily sized transmitter, as well as the radiated far-field, can be predicted with only low computational effort. The technique connects models of the individually characterized transmitter components, rather than modeling the complete multi-antenna transmitter. Hence, it can be used to investigate and compare the effects of different power amplifier and antenna array designs at early design stages without complicated and expensive experiments.
Furthermore, a digital predistortion technique for compensating nonlinear distortion in multi-antenna transmitters is presented. Digital predistortion is commonly used in transmitters to pre-compensate for undesired nonlinear hardware effects. Existing predistortion techniques are either unsuitable for transmitters with more than one transmit path, or require highly complex multi-input predistorter functions, which makes them infeasible. The proposed solution combines a linear function block with dual-input predistorters, which reduces the complexity compared to other techniques.
Room HC2, Hörsalsvägen 14
23 March, 2017, 10:00
23 March, 2017, 11:00