Sub-THz sampling AD converters using resonant tunneling diodes

本项目的目的是建立高性能的模数转换(ADC)技术，使用共振隧道逻辑门移位器(单稳态双稳态转换逻辑元件)。我们研究了一种新型的Delta Sigma ADC，它使用调频中间信号(FM Delta Sigma ADC)。这些研究的详细情况如下1.首先，我们提出了一种新的共振隧穿逻辑门SMobile(对称移动)。SMobile可以以双时钟频率运行。此外，它的运行几乎不受输出电流的影响。这些特点使SMobile在超高速运行中大有希望。在InP衬底上制作的电路中，采用互补的50 GHz时钟，实现了100Gb/S的工作。SMobile有望成为高性能模数转换器的量化器。手机的输出信号处于RZ模式(归零)。这阻碍了移动电路与传统电路的集成。本文提出了NRZ-MOBILE(Non Return To Zero Mobile)，其输出与传统电路兼容。在确定了NRZ-MOBILE的基本工作原理后，研究了它在FM Delta Sigma模数转换器的关键部件FMDSM(FM Delta Sigma调制器)中的应用。即使我们考虑HEMT的阈值电压波动，使用NRZ-MOBILE的FMDSM也表现出良好的SNDR(信噪比和失真比)。此外，我们还证实了基于NRZ-MOBILES的并行FMDSM的SNDR改善。提高压控振荡器(VCO)线性度是FMDSM最难解决的问题之一。为了解决这一问题，我们提出了互补压控振荡器的方法，其中两个压控振荡器由互补的输入信号驱动。结果表明，该方案能有效降低二次谐波峰值，获得较好的SFDR。

The purpose of this project is to establish high performance Analog to Digital Conversion (ADC) technology using resonant tunneling logic gate MOBILES (Monostable Bistable Transition Logic Elements). We investigated a novel type of Delta Sigma ADC, which uses frequency modulated intermediate signals (FM Delta Sigma ADC). The details of the studies are shown below.1. First, we proposed a novel resonant tunneling logic gate, SMOBILE (Symmetric MOBILE). The SMOBILE can operate at double-clock rate. Furthermore, its operation is scarcely affected by the output current. These features make the SMOBILE promising for ultrahigh speed operations. 100 Gb/s operation is demonstrated with complementary 50 GHz clocks for circuits fabricated on InP substrates. The SMOBILE is promising for quantizers for high-performance analog-digital converters.2. The output signal of the MOBILE is in a RZ-mode (Return to Zero). This obstructs integration of the MOBILE circuits into conventional circuits. Here we proposed NRZ-MOBILE (Non Return to Zero MOBILE), the output of which is compatible to the conventional circuits. After confirming the basic operation of the NRZ-MOBILE, we investigated its application to the FMDSM (FM Delta Sigma Modulator), which is a key component of the FM Delta Sigma ADCs. Even if we take the threshold voltage fluctuation of the HEMTs into account, good SNDR (Signal to Noise and Distortion ratio) was demonstrated for FMDSM using the NRZ-MOBILE. Moreover, we confirmed SNDR improvement for parallel FMDSM using NRZ-MOBILEs.3. One of the most difficult problems of the FMDSM is to improve linearity of the voltage controlled oscillator (VCO). We proposed complementary VCO approach to solve this problem, where two VCOs are driven by the complementary input signals. It is demonstrated the 2nd harmonic peak can be decreased and the good SFDR can be obtained by this scheme.