A novel envelope-domain approach for in-band intermodulation distortions characterization

To characterize the in-band intermodulation (IM) distortions of the microwave amplifiers, a novel prediction method based on the dynamic X-parameters theory is proposed in this paper. The proposed method describes the relationships between the input two-tone signal and the IMs products. Compared to the traditional approaches, it can accurately predict both the amplitudes and the consistent phase information of the output signals at all desired frequencies, which is an important supplement and extension to the theory of behavioral modeling. Benefit from the wideband detection of the pulse profile measurement, the in-band IMs products are sampled and down converted with the RF signal simultaneously in the NVNA. Therefore, it provides a possibility to distinguish each of the frequency spectrum products. Finally, the output spectrums of the RF pre-amplifier ZFL_11AD have been analyzed and verified based on the theoretical and practical measurements.