A digitally calibrated CT quadrature bandpass ΣΔ ADC for Wimax/LTE

This paper presents a digitally calibrated continuous time quadrature SigmaDelta ADC for WiMAX/LTE narrow bands. The proposed architecture employs a 5^th order 2-bit quadrature bandpass SigmaDelta modulator. Dithering and Adaptive Line Enhancement techniques are combined to compensate for mismatch errors in the I/Q paths. The proposed calibration technique introduces no complexity in the ADC design and can be used online. The simulation results show an improvement of 16.75 dB in SINAD and 34.42 dB in Image Rejection, when a plusmn30% variation in the loop active RC filter coefficients is introduced in the behavioral model.