ADC modeling from a system perspective and design of RF-sampling radio receivers

Abstract: The analog-to-digital converter (ADC) is the key component in many modem electronic systems. Examples are wire-line communication systems such as digital subscriber line modems, wireless communication systems such as radio receivers, and sensor systems such as military radar. To perform complete system simulations on these complex systems, high-level models are necessary. However, despite the fact that the ADC performance has a great impact on the system performance, most current design environments only include very simple ADC models. To investigate the relevance of accurate ADC models, a high-level MATLAB model of a successive-approximation ADC including realistic errors is developed. This model is integrated into two application models: an asymmetric digital subscriber line modem and an frequency-modulated continuous wave radar receiver. System simulations are performed and compared to the case when a simple ADC model is used.The advances in wireless communication have led to a demand for portable multi-standard radio transceivers, which should be small, low-power, and low-cost. The aim for the future is to use software-defined radio, where one set of hardware is reconfigured by software and can thus handle several standards. One component in a possible software radio, a flexible RF-sampling front-end, is proposed and experimentally demonstrated. It includes an RF-sampling quadrature downconverter, tunable band-pass finite impulse response filters with decimation, and a multi-phase clock-generation circuit capable of very accurate phase shifts. Accurate phase shift between I and Q channels and low jitter are key issues in sampling radio-receiver design and circuitry as well as measurement methods to support this are developed.