Analysis Of ADC Errors For Digital Sampling Aperture Synthesis Radiometer

With the increase of the number of antennas, the number of signal processing devices in analog aperture synthesis radiometer (ASR) will grow exponentially, which will cause the system to become much more complex. In order to solve this problem, researchers began the study on digital sampling ASR and transformed the equipments'complexity to calculating complexity.Analog-to-Digital converter (ADC) is the key part of the digital ASR. There are lots of errors in ADC because of its non-ideality. These errors will affect the sensitivity and the imaging performance of the digital ASR. So it's a quite meaningful and valuable topic to analyze the impacts of ADC errors on the performances of the digital ASR.Firstly, we represent the state-of-art of the digital ASR and describe the models of ADC errors. After that, we focus on analyzing the visibility function with the existence of ideal quantization noise and derive the relationship among the sensitivity, quantization bits and ADC range. The impact of quantization bits on system complexity is also studied. The research shows that 4-bit is a good compromise between the sensitivity and the system complexity.In the end, some researches on how the nonlinearity errors affect the performances of the digital ASR have been carried out. The impacts of the DNL errors on sensitivity are studied firstly, the research shows that quantization below 4-bit is greatly affected by DNL and above 4-bit is less affected. Then the sampling errors'impacts on the system imaging performance are analyzed, the simulation results show that the sampling error over 1/36 of the sampling period will bring some bias in system imaging result; more than 1/12 will cause scene brightness temperature distribution distorted.