Efficient arctangent processor design for the frequency offset estimation of IEEE 802.11 wireless LAN system

This paper presents a hardware design of an arctangent processor for the OFDM-based wireless LAN system. The arctangent processor is required in most OFDM-based communication system to estimate the frequency offset. 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. We reduce the tangent look-up table size to one eighth of 2 pi rad using the imaginary and real component exchange method for memory size and operation speed. Consequently, the designed arctangent process for wireless LAN system takes seven clocks to evaluate an arctangent value and has the resolution of 2 pi/512 rad. The maximum absolute error of this arctangent hardware is 5.75e-3 rad (0.33 degrees) comparing to mathematical result.