WIRELESS USER TERMINAL AND SYSTEM HAVING SIGNAL CLIPPING CIRCUIT FOR SWITCHED CAPACITOR SIGMA-DELTA ANALOG-TO- DIGITAL CONVERTER

摘要

PROBLEM TO BE SOLVED: To provide an improved sigma-delta analog/digital converter that can substantially reduce problems of overshoot and settling, often caused in a user terminal additionally. SOLUTION: This invention discloses a wireless user terminal (42) and a system (40) implementing a mixed signal CODEC (100) (codifier/decodier), including an improved sigma-delta analog/digital converter (18), which limits input signals into a switched capacitor configuration and avoids adding circuits overhead in the signal path. The sigma-delta analog/digital converter (18), having an input signal and an output signal, includes a switch (SW1), a clipping circuit (20), and a known sigma-delta analog/digital converter (34). It solves the clipping signal problem, by limiting the signal right at the input of the sigma-delta analog/digital converter (34). The clipping circuit (20) couples to the switch (SW1) and the sigma-delta analog/digital converter (34) for switching the voltage applied to the sigma-delta analog/digital converter (34) between the input signal (υin ) and at least one threshold voltage (VN and VP).