Sub-THz sampling AD converters using resonant tunneling diodes

该项目的目的是利用谐振隧道逻辑门MOBILES（单稳态双稳态过渡逻辑元件）建立高性能模数转换（ADC）技术。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）。研究的详细情况如下。首先，我们提出了一种新的共振隧道逻辑门，SMOBILE （Symmetric MOBILE）。SMOBILE可以在双时钟速率下工作。此外，它的工作几乎不受输出电流的影响。这些特点使SMOBILE有望实现超高速操作。在InP衬底上制作的电路中，用互补的50 GHz时钟演示了100gb /s的操作。SMOBILE是高性能模数转换器的量化器。MOBILE的输出信号为rz模式（归零）。这阻碍了将MOBILE电路集成到传统电路中。在此，我们提出了NRZ-MOBILE (Non Return to Zero MOBILE)，它的输出与传统电路兼容。在确定了NRZ-MOBILE的基本工作原理后，我们研究了NRZ-MOBILE在调频Delta Sigma adc关键部件FMDSM（调频Delta Sigma调制器）中的应用。即使我们考虑到hemt的阈值电压波动，使用NRZ-MOBILE的FMDSM也证明了良好的SNDR（信噪比和失真比）。此外，我们证实了使用nrz - mobile可以改善并行FMDSM的SNDR。提高压控振荡器（VCO）的线性度是FMDSM的难点之一。我们提出了互补压控振荡器的方法来解决这个问题，其中两个压控振荡器由互补输入信号驱动。结果表明，该方案能有效地降低二次谐波峰值，并能获得良好的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.