Patent ID: 8238458

Claim:
A method for evaluating a transmitter by estimating IQ impairments in an orthogonal frequency division multiplexed (OFDM) signal generated by the transmitter, the method comprising: receiving the OFDM signal from a transmitter, wherein the OFDM signal represents a stream of symbols each comprising a plurality of subcarriers, wherein at least a subset of the plurality of subcarriers are pilot subcarriers; grouping the pilot subcarriers into a plurality of groups of pilot subcarriers based on a plurality of different conditions, wherein pilot subcarriers which each relate to a respective mirror subcarrier in a way that satisfies a condition of the plurality of different conditions are grouped together; calculating an estimate of complex IQ imbalance parameters, wherein calculating the estimate of the complex IQ imbalance parameters comprises solving a plurality of equations for the complex IQ imbalance parameters, wherein the plurality of equations comprise a plurality of different relations between groups of pilot subcarriers and the complex IQ imbalance parameters, wherein the plurality of different relations are based on the plurality of different conditions; calculating an estimate of gain imbalance and quadrature skew of the OFDM signal based on the complex IQ imbalance parameters, wherein calculating the estimate of gain imbalance and quadrature skew comprises solving equations relating the complex IQ imbalance parameters to gain imbalance and quadrature skew of the OFDM signal; wherein the estimate of gain imbalance and quadrature skew of the OFDM signal is used to evaluate the transmitter.