Comparison of two methods for I/Q imbalance compensation applied in RF power amplifiers

In this paper, the design and implementation of two methods for I/Q imbalance compensation is presented, based on a low cost phase measurement approach. The design methodology for an I/Q imbalance correction system is presented based on a DSP-FPGA board. The first method employs some trigonometric properties. The second employs Volterra series to model the non-linear behavior of the I/Q imbalance. The system performance is verified using a complex signal with phase and amplitude imbalance. The implemented systems have the advantage of having low implementation cost and a high design flexibility, which allows for future revisions or enhancement. The Stratix III FPGA board from Altera is employed for the practical implementation and results verification of the system. A comparison between methods is introduced for correcting (I or Q) branches respectively to guarantee amplitude and phase balancing condition in the modulator output. Experimental results are implemented employing an FPGA by using DSP-Builder to bit true VHDL hardware description of proposed model. This work can be considered as a low cost alternative for I/Q imbalance correction given that it does not require additional measurement equipment nor uses complex algorithms.