Regenerative, Beyond-fmax, 3D-printed Terahertz Camera Transceiver (TeraCaT)

太赫兹信号具有独特的特性。与光信号不同的是，它们可以穿透许多介质表面。与微波信号不同，由于波长短，它们可以实现非常高分辨率的成像。为了在实际应用中充分利用太赫兹成像的潜在优势，需要具有多通道信号采集功能的紧凑、高效、连贯、高灵敏度的太赫兹相机。然而，它们的实现受到两个根本缺陷的限制。首先，在太赫兹频率下，传统外差收发器的增益较低，尤其是在接近或超过晶体管的fmax时。噪声大、功耗大、散热大、尺寸大。其次，现有的组装和太赫兹互连技术大多局限于芯片级或分块封装。这些方法不能扩展到大的多通道孔径，也不适合灵活的系统设计，并且对于传感器技术中典型的产量来说通常是不经济的。在不久的将来，这些挑战很可能无法通过基于传统方法的渐进式改进来解决。因此，TeraCaT的目标是建立一种替代的整体太赫兹系统设计方法。该方法采用了一种非常规的相干收发器架构，以及基于3D打印和介质波导的集成和制造技术。所提出的技术框架涵盖了从芯片集成、封装、馈电网络到大规模多通道天线阵列集成的各个方面。在TeraCaT中，将研究紧凑且极节能的超再生集成接收器电路，该电路具有高放大增益和高灵敏度，可实现高效的超fmax操作。这一雄心勃勃的目标是通过一种新颖的三次谐波下变频概念实现的，该概念分为两个步骤：1)使用脉冲本振结合利用正反馈的高超再生放大，将接收到的0.6太赫兹信号有效的低损耗基频混合到0.2太赫兹中频；2)无源下变频到基带。取代传统的芯片封装和互连技术，整个系统将建立在一个联合技术堆栈上。它由三维结构和介电元件组成，并与嵌入式集成电路一起进行分析、仿真、设计和3D打印。为了展示创新太赫兹系统设计方法的卓越实用性，TeraCaT将建立并演示一个功能齐全的太赫兹成像系统以及相关的定制组装、连接和集成技术。TeraCaT结合了FAU （M. Vossiek， C. Carlowitz）在雷达成像，系统设计，系统集成方面的互补和深刻证明的能力，以及德累斯顿工业大学（F. Ellinger， C. Carta）在高频集成电路方面的能力。

THz signals have unique properties. In contrast to optical signals, they can penetrate many dielectric surfaces. Unlike microwave signals, they allow for very high-resolution imaging, thanks to their small wavelength. To leverage the possible benefits of THz imaging in real-world applications, compact, efficient, and coherent, high sensitivity THz cameras with multi-channel signal acquisition are required. However, their realization is limited by two fundamental shortcomings. First, at THz-frequencies, conventional heterodyne transceivers suffer from low gain, especially when operating close to or beyond fmax of the transistors. Thus, the noise, power consumption, heat dissipation, and dimensions are large. Second, existing assembly and THz interconnection technologies are mostly limited to chip-scale or split-block packages. These approaches do not scale for large multichannel apertures and are not suited for flexible system design, and are often uneconomical for the production volumes that are typical in sensor technology. Those challenges will most likely not be solved in the near future with incremental improvements based on conventional approaches. Accordingly, it is the goal of TeraCaT to establish an alternative holistic THz system design methodology. The approach utilizes an unconventional coherent transceiver architecture and an integration and manufacturing technology that is based on 3D printing and dielectric waveguides. The proposed technology framework covers all aspects from chip integration, packaging, feed network, up to the integration of the massive multichannel antenna array. In TeraCaT, compact and extremely power-efficient super-regenerative integrated receiver circuits will be investigated, which enable efficient beyond-fmax operation with high amplification gain and high sensitivity. This ambitious goal is achieved with a novel 3rd-harmonic downconversion concept, structured in 2 steps: 1) Efficient low loss fundamental mixing step of the received 0.6 THz signals to a 0.2 THz IF using a pulsed local oscillator combined with a high super-regenerative amplification utilizing positive feedback; 2) Passive down-conversion to baseband. Instead of traditional chip-packaging and interconnect techniques, the complete system will be built upon a joint technology stack. It consists of 3-dimensional structures and dielectric components, which are analyzed, simulated, designed and 3D printed together with embedded integrated circuits.To show the outstanding practicability of the innovative THz system design approach TeraCaT will set up and demonstrate a fully-functional THz imaging system and the associated tailored assembly, connection, and integration technology. TeraCaT combines the complementary and profoundly proven competencies of FAU (M. Vossiek, C. Carlowitz) in radar imaging, system design, system integration, and of TU Dresden (F. Ellinger, C. Carta) regarding high frequency integrated circuits.