Determination method for complex valued LTI transfer functions causing memory effect of power amplifier

Abstract

This paper proposes a method to measure complex valued transfer functions of linear time-invariant (LTI) circuits by assuming a memory polynomial model for a power amplifier (PA). To preserve phase information, the method uses cross-correlation of the device under test (DUT) with another PA without memory effect. This paper has clarified possibility that all coefficients in the memory polynomials are directly determined by the impulse responses of the measured transfer functions. An iterative algorithm is described to obtain accurate estimates for the LTI transfer functions using the measured cross-correlation. Virtual data of the cross-correlations are generated for the assumed model of the PA. Validity of the method including the algorithm is examined by computer simulations where the input signal is assumed to be an orthogonal frequency-division multiplexing (OFDM) signal consisting of 200 subcarriers. It has been verified that the LTI transfer functions converge to the assumed ones within five iterations in the case of the blind start.