Patent ID: 8116363

Claim:
A method, comprising the steps of: (a) supplying a plurality of test signals to a transmitter arrangement of a wireless local area network (WLAN), each test signal including data modulated onto a sub-carrier of an Orthogonal Frequency Division Multiplexed (OFDM) signal and having a test signal amplitude and phase, each sub-carrier having a predetermined position within a bandwidth of the OFDM signal, the plurality of test signals comprising at least a first test signal and a second test signal, and wherein the position of the sub-carrier for the first test signal and the position of the sub-carrier for the second test signal are symmetrically arranged about the mid-point of the bandwidth of the OFDM signal, and wherein the first and second test signals each comprise a known training sequence of data which cause finite shifts at each point of an ideal signal constellation of the test signal; (b) measuring an amplitude and phase of the test signals once they have passed through the transmitter arrangement; (c) allocating each of the measured amplitude and phase values to one of a finite plurality of data groups, wherein the allocation to a data group of the measured amplitude and phase values corresponding to the first test signal is based on the first test signal amplitude and phase and the second test signal amplitude and phase; (d) determining the spread in the said measured values, within each of the data groups; and (e) calculating an Error Vector Magnitude (EVM), resulting only from non-systematic effects within the transmitter arrangement, based upon the determined spread of the measured values within the data groups.