研究目的
To characterize the memory effects in a nonlinear concurrent dual-band transmitter by extending the conventional two-tone test for power amplifiers to concurrent dual-band transmitters.
研究成果
The proposed method effectively characterizes memory effects in concurrent dual-band amplifiers, showing that third-order IM products have dominant memory effects compared to CM products. The method can be used prior to the implementation of DPD algorithms for the linearization of nonlinear multiband transmitters, optimizing parametric memory polynomial models in terms of nonlinear order and memory depth.
研究不足
The method requires careful consideration of the baseband and RF coherency between two test signals in the error analysis. The performance of the measurement setup was limited to a -71-dB adjacent channel power ratio. The effects of a noisy RF source and linear/nonlinear distortions of the input signals were not fully compensated.
1：Experimental Design and Method Selection:
The method involves exciting the transmitter with two two-tone signals in each input channel, sweeping both the power and frequency of both signals. The Volterra kernels are excited along paths similar to those of a conventional two-tone test.
2：Sample Selection and Data Sources:
Two different amplifiers were used as DUTs: a wideband PA (model ZVE8G+ amplifier of Mini-Circuits Inc.) and a Freescale Doherty PA (transistor model MRF8S21120HS-Doherty of Freescale Inc.).
3：List of Experimental Equipment and Materials:
The test signals were generated using MATLAB and uploaded to two R&S SMBV100a vector signal generators (VSGs). The generated RF signals were combined using an HP 87302C power combiner and fed to the DUT. The output RF signal was downconverted to an IF signal using a wideband downconverter and digitized by an SP-devices-ADQ-214 ADC.
4：Experimental Procedures and Operational Workflow:
The two-tone signals were swept in frequency and power, and the upper and lower third-order IM and CM products were measured. The asymmetry between the upper and lower IM and CM products was analyzed to characterize memory effects.
5：Data Analysis Methods:
The linear least square estimation (LSE) method was used to estimate the parameters of IM and CM products from the measured data.
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