Large signal network analyzer with trigger for baseband & RF system characterization with application to K-modeling & output baseband modulation linearization

Abstract

The modeling and balancing of IQ modulators and the development of linearization techniques for power amplifiers (PA) such as output baseband modulation (OBM) benefit from the availability of linear and nonlinear MIMO Volterra system parameters involving both baseband and RF signals. A triggered LSNA system is reported for this purpose. By synchronizing the LSNA measurements with the generation of the baseband modulation, RF signals with a stable envelope can be acquired. Applied to an IQ modulator the triggered LSNA facilitates the measurement of the correlation between the I and Q signals at baseband and RF, effectively yielding the modulator K-model. Inverting the K-model of the IQ modulator, an IQ balancing of about 43 dBc and 46 dBc for the lower and upper side-bands, respectively, was achieved using 14 bit signed DACs. Finally the triggered LSNA finds applications in the linearization of RF PAs with input (IBM) or output (OBM) baseband modulation by facilitating the extraction of the Y/sub md-/ and Y/sub md+/ Volterra nonlinear parameters.