An Accurate ADC Model in Radar System Simulation
Kalle Folkesson, Christer M. Svensson · 2003
Modem system design methods are based on early system simulation using behavioral models. Since the ADC often is the critical component it is especially important that it is mode led correctly. Most current design environments use very simple ADC models such as ideal sampling and quantization to give a certain effective number of bits (ENOB). The ENOB is typically found by a single-tone test where the input is an amplitude-limited sine wave. Real applications may have inputs very different from this simple test signal and the ADC can then have a completely different performance. Detailed knowledge of the behavior in a system allows the ADC design margin to be minimized thus saving cost and power consumption.ln the work included in this thesis an accurate model of a successive-approximation ADC is developed. It is aimed for integration into existing system simulators and can thus not be too complex or the simulation time will be unreasonably long. Measurements are performed to validate the model andcomparisons between simulated and measured data are done in both time and frequency domains. This is used to test some error hypotheses in order to find the performance limiting errors of the successive-approximation architecture.Further, the need for accurate ADC models in system simulation is investigated. A complex model is of no use if the same information can be obtained with a simple one. To do this, the ADC model is integrated in two different systems: an ADSL modem and a radar receiver. System simulations are performed and the results are compared to the case when a simple ADC model is used. In both cases the accurate ADC model showed to be useful. System performance varied quite much for ADCs with the same specified performance in terms of ENOB depending on which error mechanism was active.