Arctangent Processor Design for the Frequency Offset Estimation of IEEE 802.16D Wirelessman-OFDM System

This paper presents a hardware design of an arctangent processor for the IEEE 802.16d WirelessMAN-OFDM system. The arctangent processor is required in most OFDM-based communication system to estimate the frequency offset. We proposed an arctangent processor which can perform arctangent evaluation with efficiency of hardware size considering the operating speed. The proposed arctangent processor does not require the division value of imaginary/real for the input argument, and uses these two values, respectively, to look up the tangent ROM table which has only the arctangent values for octant phase, i.e. zero to ¿/4 rad. The contribution of this design is the suggestion about the trade-off between the accuracy and complexity for arctangent evaluation considering the requirement allowed in WirelessMAN-OFDM standard. Consequently, the designed arctangent process for WirelessMAN-OFDM system takes six clocks to evaluate an arctangent value and has the resolution of 2¿/256 rad. The maximum absolute error of this arctangent hardware is 1.225e-2 rad (0.7°) comparing to mathematical result.