Wireless user terminal and system having signal clipping circuit for switched capacitor sigma delta analog to digital converters

摘要

A wireless user terminal ( 42 ) and system ( 40 ) implementing a mixed signal CODEC ( 100 ) including an improved sigma-delta ADC ( 18 ) which limits input signals into a switched capacitor configuration and avoids adding circuit overhead in the signal path is disclosed herein. This sigma-delta analog-to-digital converter ( 18 ), having an input signal and an output signal, includes a switch (sw₁), a clipping circuit ( 20 ), and a known sigma-delta ADC ( 34 ). It solves the clipping signal problem by limiting the signal right at the input of the sigma-delta ADC ( 34 ). The clipping circuit ( 20 ) couples to the switch (sw₁) and the sigma-delta ADC ( 34 ) for switching the voltage applied to the sigma-delta ADC between the input signal (v_in) and at least one threshold voltage (V_n and V_p).