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Sub-Sampling Direct RF-to-Digital Converter With 1024-APSK Modulation for High Throughput
提出一种直接射频到数字转换器，支持1024-APSK调制，适用于极坐标接收器。
1.94 GB/s, 1024-APSK, 6 GHz, 3.8 mW, 1.1 V
直接射频到数字转换器极坐标接收器1024-APSK重构ADCTDC
▸创新点1：采用重构ADC检测信号幅度（方法创新）。通过可重构的模拟-数字转换器(ADC)动态适应不同调制波形（如QAM、PSK、APSK），显著提升幅度检测的灵活性和精度，支持1024-APSK等高阶调制，在6 GHz载频下实现1.94 GB/s数据率。
▸创新点2：使用TDC数字化相位（电路创新）。利用时间-数字转换器(TDC)直接量化射频信号的相位信息，替代传统混频器架构，降低系统复杂度与功耗（仅3.8 mW@1.1V），同时避免I/Q失衡问题。
▸创新点3：实现基带速率采样（系统创新）。提出亚采样技术，通过ADC采样位置调整单元和多相参考时钟发生器，在基带速率下完成射频直接采样，突破奈奎斯特限制，减少高频采样带来的功耗与噪声。
▸创新点4：支持高阶APSK调制（应用创新）。相比QAM，优化设计的1024-APSK调制方案降低了对相位噪声和线性度的要求，在相同频谱效率下提升系统鲁棒性，适用于高吞吐量通信场景。
Abstract
This article presents a direct RF-to-digital converter (RDC) for polar receivers, in which the amplitude information of the received signal is detected by a reconfigurable analog-to-digital converter (ADC) and its phase is digitized using a time-to-digital converter (TDC). The RDC prototype also includes a multi-phase reference generator and an ADC sampling position adjustment unit realizing the sub-sampling technique. Unlike conventional direct-RF sampling receivers, the proposed RDC samples the input RF signal at the baseband rate. The RDC is capable of digitizing a variety of modulation waveforms, such as quadrature amplitude modulation (QAM), phase shift keying (PSK), and amplitude phase shift keying (APSK). When comparing QAM to APSK, the later has advantages of relaxed system requirements on phase noise and linearity. The proposed direct RF-to-digital polar converter IC achieves a maximum data rate of 1.94 GB/s with a 1024-APSK modulation at a carrier frequency of 6 GHz, while consumes only 3.8 mW power under 1.1 V supply.