The RF transceivers architectures are to integrate the concept of Sotware Radio. But, in the case of mobile terminal, hard constraints are imposed by the factor of mobility. Low power and very complex circuits are claimed by the telecommunication industry. Classical architectures are no more sufficient to challenge this goal. New systems are thus proposed, and the concept of Software Defined Radio (SDR) is a step on the roadmap toward Software Radio (SR). This paper presents a state of the art of SDR circuits and explores the application of a Analog Signal Processor SR chip.