A low-power multi-rate cascade sigma delta modulator suitable for multi-mode wireless communication applications

A novel low-power multi-rate sigma delta modulator is proposed, which is capable to support a wide range of wireless communication standards. The modulator is based on the 2-2 cascade single-bit architecture for good stability and linearity. The multi-rate technique is adopted to decrease the sampling frequency of the 1^st stage integrators of the sigma delta modulator to reduce the power dissipation. A feedforward signal path is added to suppress the harmonic distortions and attain high linearity over a wide bandwidth. The effects of circuit nonidealities on the modulator performances are analyzed to extract the parameters of the basic blocks and verify the feasibility of the proposed architecture. A peak SNR of 85/81/65/63/54/48 dB is achieved for GSM/Bluetooth/GPS/WCDMA/WLAN/WiMAX mode. The simulation results demonstrate the efficiency and feasibility of the proposed modulator and indicate that the modulator is very suitable for the multi-mode wireless communication applications.