A 10-b Fourth-Order Quadrature Bandpass Continuous-Time Sigma Delta Modulator With 33-MHz Bandwidth for a Dual-Channel GNSS Receiver

作者：Zhang, Junfeng; Xu, Yang; Zhang, Zehong; Sun, Yichuang; Wang, Zhihua; Chi, Baoyong^*

来源：IEEE Transactions on Microwave Theory and Techniques, 2017, 65(4): 1303-1314.

DOI：10.1109/TMTT.2017.2662378

• Continuous time (CT)
• power-efficient amplifier
• quadrature bandpass (QBP)
• return-to-zero (RZ) excess loop delay (ELD) compensation
• sigma-delta (Sigma Delta) modulator
• wideband

A fourth-order quadrature bandpass continuoustime sigma-delta modulator for a dual-channel global navigation satellite system (GNSS) receiver is presented. With a bandwidth (BW) of 33 MHz, the modulator is able to digitalize the downconverted GNSS signals in two adjacent signal bands simultaneously, realizing dual-channel GNSS reception with one receiver channel instead of two independent receiver channels. To maintain the loop-stability of the high-order architecture, any extra loop phase shifting should be minimized. In the system architecture, a feedback and feedforward hybrid architecture is used to implement the fourth-order loop-filter, and a return-tozero (RZ) feedback after the discrete-time differential operation is introduced into the input of the final integrator to realize the excess loop delay compensation, saving a spare summing amplifier. In the circuit implementation, power-efficient amplifiers with high-frequency active feedforward and antipole-splitting techniques are employed in the active RC integrators, and self-calibrated comparators are used to implement the low-power 3-b quantizers. These power saving techniques help achieve superior figure of merit for the presented modulator. With a sampling rate of 460 MHz, current-steering digital-analog converters are chosen to guarantee high conversion speed. Implemented in only 180-nm CMOS, the modulator achieves 62.1-dB peak signal to noise and distortion ratio, 64-dB dynamic range, and 59.3-dB image rejection ratio, with a BW of 33 MHz, and consumes 54.4 mW from a 1.8 V power supply.

• 出版日期2017-4
• 单位清华大学