A comparison of analog front end architectures for digital receivers

Radio receivers that perform analog to digital conversion closer to the antenna and do most of the signal processing in the digital domain are known as digital receivers. Digital receivers are desirable because they can be more easily re-configured for multi-standard operation, they can facilitate performance improvements by using digital filters for signal processing, and they can potentially realize savings in chip area, power consumption and cost. The definition of a digital receiver is general and there are several types of receiver architectures that fall into this category. Digital receiver architectures which have been proposed include direct RF Nyquist sampling, RF bandpass sampling or sub-sampling, direct IF Nyquist sampling, and IF bandpass sampling or sub-sampling. This paper compares these digital receiver architectures in various categories including susceptibility to aperture jitter and aperture distortion, noise figure degradation due to aliasing, ease of anti-aliasing filter implementation, ease of ADC implementation, linearity, power consumption, chip area, and re-configurability. System and circuit level simulations using a commercial RF simulator are performed to quantitatively compare the different digital receiver architectures in some of the aforementioned categories. The feasibility of using the proposed digital receiver architectures for various standards is then examined and a survey of published digital receiver architectures is presented