A reconfigurable double sampling sigma delta modulator for 4G mobile terminals

A reconfigurable cascade sigma delta modulator for multi-mode zero-IF receivers is presented on the system level. A feed-forward path is introduced in the modulator to diminish the harmonic distortion and achieve a high resolution. In comparison with other feed-forward structures presented before, the circuit complexity is decreased, and the chip area and power dissipation are saved in the proposed modulator. The double sampling integrator is employed to increase the over-sampling ratio. The coefficient scaling is deduced. The non-idealities of the operational amplifiers, comparators and capacitor mismatch are analyzed and modeled in Matlab/ Simulink. The parameter requirements for the basic circuit cells are obtained. The simulation results indicate that a peak SNDR of 85/81/67/65/58/52 dB is achieved for GSM /Bluetooth /GPS /WCDMA /WLAN /WiMAX mode. The efficiency and feasibility of the proposed modulator are validated by the behavioral simulations. The performances of the modulator meet the requirements of the considered application.