Collaborative Research: Terahertz PLL-Based Phased Array for Wideband Radar/Sensing Systems in Silicon

毫米波和太赫兹(300 GHz-3 THz)系统在健康、安全和工业中具有独特而重要的应用。遥感和主动/被动成像是这些应用中的一种，它们正在不断快速地向毫米波和太赫兹(THz)频率发展，以实现更高的分辨率。这些系统用于高分辨率雷达、3D成像、安全检查和隐蔽武器检测。然而，今天，太赫兹(THz)系统是使用昂贵而笨重的设备实现的。该项目引入了一种新的方法来实现紧凑型芯片上的太赫兹系统，并克服了这些高频系统面临的许多挑战。虽然所提出的电路和系统对下一代太赫兹系统的集成和小型化有重大影响，但这个项目的影响超出了几个新的电路拓扑的设计和实现。拟议的方法是变革性的，并为设计师打开了新的大门。此外，随着片上太赫兹系统的出现，独特的太赫兹应用将迅速发展，从而为高科技市场和研究机构带来新的机遇。在雷达应用中，横向距离分辨率和距离分辨率分别随着带宽和工作频率的增加而提高。然而，在太赫兹频率下宽带产生和辐射射频功率是具有挑战性的，特别是因为这些频率接近最先进的硅技术平台的截止频率。稳定和准确的辐射频率对于大多数传感/雷达应用是必不可少的，例如调频雷达。由于压控振荡器(VCO)的低输出功率和硅中分频器的锁定范围较小，THz频率下锁相环(PLL)的宽带频率锁定变得极其困难。此外，还需要相控阵来提高辐射功率和定位天线波束。在传统相控阵系统中，本地振荡器(LO)或射频(RF)信号路径中存在有损移相器，以及将锁定信号与相控阵系统集成的复杂性，使得设计者无法在芯片上实现THz相控阵系统。本文提出了一种新颖的基于锁相环的相控阵结构，它利用耦合锁相环阵列中的控制电压来校准和改变辐射信号的相位，并控制阵列波束。这可以在不使用显式移相器的情况下实现。这种结构的核心是锁相机构，它采用了一种新的方法来设计压控振荡器(VCO)和后续的分频器，本质上有助于增加输出功率和调谐范围，并降低相位噪声。

The mm-wave and terahertz (300 GHz - 3 THz) systems are known to have unique and significant applications in health, security and industry. Remote sensing and active/passive imaging are among these applications and are continually evolving at a rapid pace toward mm-wave and terahertz (THz) frequencies in order to achieve higher resolution. These systems are used for high-resolution radar, 3D imaging, security screening, and detection of concealed weapons. Today, however, terahertz (THz) systems are realized using expensive and bulky devices. This project introduces a novel methodology to implement a compact and on-chip THz system and to overcome many challenges facing these high frequency systems. While the proposed circuits and systems have significant effect on integrating and miniaturizing next generation THz systems, the impact of this project is beyond the design and implementation of few novel circuit topologies. The proposed methodologies are transformative and open new doors to designers. Furthermore, with on-chip THz systems the unique THz applications will rapidly flourish, resulting in new opportunities in the high-tech marketplace and research institutions.In radar applications the cross-range and range resolutions improve as the bandwidth and the operation frequency increase, respectively. However, wide-band generation and radiation of the RF power at THz frequencies is challenging, especially because, these frequencies are close to the cut-off frequencies of most advanced silicon technology platforms. Stable and accurate radiated frequency is a necessity for most sensing/radar applications such as frequency-modulated radars. Wide-band frequency locking in a phase-locked loop (PLL) at THz frequencies becomes extremely challenging mainly because of low output power of voltage controlled oscillators (VCO) and low locking range of frequency dividers in silicon. Moreover, phased arrays are needed to boost the radiated power and to localize the antenna beam. Having lossy phase shifters in the Local Oscillator(LO) or Radio-frequency(RF) signal paths in conventional phased array systems and the complications of integrating a locked signal with a phased array system have prevented designers to implement THz phased array systems on chip. Here,a novel PLL-based phased array architecture is proposed, which uses control voltages in the coupled PLL array to both calibrate and vary the phase of the radiated signal and steer the array beam. This can be achieved without the use of explicit phase shifters. At the heart of this architecture is a phase-locking mechanism, which adopts a new approach in designing the Voltage-Controlled Oscillator(VCO) and the following frequency divider that essentially helps increase the output power and tuning range and lower the phase noise.