Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE credits
Nyquist Shannon theory states that sampling rate of ADC should be at least twice of signal bandwidth in order to avoid aliasing. According to this theory, extracting an accurate behavior model of power amplifier by digitizing its output signal is a difficult task for current general ADC in the market, due to the trade off among the sampling rate, resolution and reasonable cost. Because of nonlinear effect that a power amplifier presents, the signal bandwidth further spread in spectrum at output side, which results in shortage of sampling rate of ADC to sample such broadband signal. To solve this problem, a special designed system named ZGST is considered in this work.
This works mainly considers characterizing ZGST measurement system which consists of a wide bandwidth down convertor and a high speed ADC. For down convertor, calibrations are carried on radio frequency, local oscillator and intermediate frequency. Thus a three port calibration is applied by using a vector network analyzer. Meanwhile, its dynamic performance is evaluated by measuring SFDR. For ADC, the amplitude response is characterized by using a signal analyzer.
This thesis work also describes a smart sampling strategy which reduces the requirement on sampling rate for repetitive signal. This strategy is able to compact a broadband digital signal into a relative small Nyquist region without overlapping. Thus, in spite of analog digital convertor does not meet the Nyquit sampling constraint, it still can sample a wide bandwidth signal.
Finally, a broadband output signal of a power amplifier is collected by ZGST measurement system, and it is reconstructed by removing the conversion loss in both amplitude and phase which is caused by system.
2011. , 73 p.