Efficient RF Front-End Non-Linear Multi Antenna Coupling Cancellation Techniques

One of the recent trends in mobile communication industry is the use of multiple antennas in transmitter and at the receiver in order to gain diversity and achieve high bit rates. At the same time, as the mobile terminals are getting smaller, the number of electronic elements squeezed inside of them increases. Inside this hostile environment the coupling, which can considerably alter the overall system performance, is bound to emerge. To combat the multi antenna RF front-end coupling a DSP software module, positioned between the output of AD converter and any further digital signal processing is proposed. The coupling is modelled with polynomials limited to third order nonlinear behaviour. The inverse nonlinear coupling function of the 9^th degree is solved using simulated annealing (SA) approximation method. The proposed coupling cancellation algorithm is analyzed under different system conditions with different processing power requirements. A trade off between the guaranteed precision and speed is made, and the simplified algorithm version, showing good coupling cancellation characteristics, is presented.