Real-time simulation of impairments in the analog parts of the transmitter-receiver

We propose a method to simulate impairments caused by the nonideal analog parts of the transmitter-receiver. They include for example a high-power amplifier (HPA), mixers, and oscillators. The major advantage in our approach is that the model parameters are adjustable and the system works in real time in the digital domain. Conventional methods have either not been real time, or they have been implemented with analog circuits. The HPA model is implemented with the coordinate rotation digital computer (CORDIC) algorithm for rectangular to polar translations. A look-up table (LUT) is used for AM/AM and AM/PM distortion. To minimize the size of the LUT we have used cubic spline interpolation. For phase noise of the oscillators we propose a simple rotation mode CORDIC implementation that does not need any complex multiplication. Only one field-programmable gate array (FPGA) circuit is needed to implement the power amplifier and phase noise models.