Ultrahigh-speed bandpass delta-sigma modulators using resonant-tunneling devices

利用谐振隧道二极管（rtd）和高电子迁移率晶体管（hemt），设计了多ghz连续时间多位δ - σ调制器。首先设计了量化器和Gm-C滤波器等基本电路模块。该2位量化器由四个传统的单端量化器组成，以获得准微分操作模式。滤波器采用全差分HEMT运算放大器。然后通过组合这些电路模块构建低通和带通δ - σ调制器。采用基于inp的RTD/HEMT技术进行了晶体管级电路仿真。在时钟频率f_c为13 GHz的情况下，成功设计了一个分辨率为9位、输入带宽为100 mhz的低通调制器。对于带通调制器，在BW=30 MHz和f_c=4 GHz时获得了7位分辨率。由于设计方法已经明确，包括电路仿真中使用的RTD器件模型，因此未来可以通过优化电路参数进一步提高性能。我们的研究清楚地表明，基于RTD/ hemt的多ghz δ - σ调制器具有很高的潜力。

By using resonant-tunneling diodes (RTDs) and high-electron-mobility transistors (HEMTs), multi-GHz continuous-time multi-bit delta-sigma modulators have been designed. Fundamental circuit blocks, such as quantizers and Gm-C filters, were designed first. The present 2-bit quantizer consisted of four conventional single-ended ones to obtain a quasi-differential operation mode. The filters employed fully differential HEMT operational amplifiers. The lowpass and bandpass delta-sigma modulators were then constructed by combining these circuit blocks. Transistor-level circuit simulation was carried out by assuming InP-based RTD/HEMT technology. A lowpass modulator was successfully designed with a 9-bit resolution and a100-MHz input bandwidth BW at a clock frequency f_c of 13 GHz. Regarding a bandpass modulator, a 7-bit resolution was obtained for BW=30 MHz and f_c=4 GHz. Since the design method have been clarified including an RTD device model used in the circuit simulation, further improvement in performance is possible by optimizing circuit parameters in the future. Our study clearly demonstrated a high potential of RTD/HEMT-based multi-GHz delta-sigma modulators.