From Performance to Manufacturing Implementation and Yield: A Receiver Comparison for GSM/GPRS Applications

The current generation of wireless transceivers, for applications ranging from personal area networks to mobile handsets, incorporates two predominant receiver architectures that can offer significantly different benefits depending upon the system requirements. Utilizing either a direct conversion or a digital low-IF architecture, the latest GSM transceivers cleverly eliminate the second analog downconversion stage. These architectures remove the expensive and bulky intermediate frequency (IF) components necessary in the conventional superheterodyne approach, which has long been revered for its performance. Phone buyers relentlessly pressure handset manufacturers to reduce size and cost, and increase features. This forces handset manufacturers to place a premium on printed circuit board (PCB) space, the bill of materials (BOM), and handset differentiation as seen in Table 1. For these reasons, digital low-IF and direct conversion radios have increased the choices beyond the superheterodyne as the sole architecture for mobile handsets. But how do these two receiver architectures compare? A brief analysis will provide cellular handset designers the information needed to evaluate the implications of each architecture as it applies not only to achieving full type approval (FTA), but also the impact they have on performance, footprint size, power consumption, software overhead, manufacturability and yield.