CMOS RF Transceiver considerations for Dynamic Spectrum Access

Cognitive Radio (CR), and in particular dynamic spectrum access (DSA), promises a much more efficient use of the spectrum by opportunistically using available frequencies. This asks for specific functionality, like spectrum sensing and frequency-agile transmission and reception. We will show that this functionality poses challenging hardware requirements, which go far beyond what is currently possible with an analogue-to-digital converter (ADC) and digital-to-analogue converter (DAC). Instead, a transceiver (transmitter+receiver) with filtering and frequency conversion is required. By starting from a mathematical abstraction for the description of transceivers and an overview on transceiver implementation, we will show that the flexibility required by CR calls for changes in the architecture, putting severe constraints on linearity and spurious emission performance. We will discuss several existing and proposed solutions to alleviate the design of CR transceivers and spectrum sensing functionality, with a special emphasis on CMOS as it is low-cost and enables the integration of both analogue and digital on one integrated circuit (IC). *****