9.6 A 6th-Order Quadrature CTDSM using Double-OTA and Quadrature NSSAR with 171.3dB FoMs in 14nm

In order to mitigate 1/f noise and DC offset with less area overhead, the low-intermediate-frequency (low-IF) architecture is widely chosen for energy efficient wireless communication systems, such as Bluetooth Low Energy (BLE) and IoT. The low-IF architecture typically requires filters for anti-aliasing and image rejection to suppress aliasing from the adjacent channels. The use of the continuous-time delta-sigma modulator (CTDSM) ADC makes the low-IF receivers more efficient with its inherent anti-aliasing property. In addition, by shifting the noise transfer function (NTF) we can optimize the order and sampling speed of the CTDSM ADC to minimize the in-band quantization noise [1]. We present a sixth-order CTDSM that maximizes power efficiency by implementing the integrator using a single-amplifier quadrature biquad (SAQB) filter and low-IF shifted NTF-based quadrature-noise shaping SAR (QNSSAR) using dynamic amplifier (Fig. 9.6.1). Our quadrature DSM operates at an 80MHz sampling rate with 4MHz input bandwidth, and achieves 74.7dB SNDR with 0.88mW, resulting in a 171.3dB Schreier FoM.