Philipp Hillger

A broadband three-stage pseudo-differential SiGe-interconnection bipolar transistor (HBT) power amplifier (PA) for high-speed communication at around 300 GHz is presented. The amplifier is fabricated in an experimental 130-nm SiGe BiCMOS technology with an $f_{t}/f_{\max }$ of 470/650 GHz. The use of asymmetric coupled line transformers is proposed to facilitate broadband impedance transformation with device reactance compensation at all amplifier interfaces. The amplifier achieves a maximum small-signal power gain of 23.0 dB and a $P_{\mathrm{ sat}}/{\mathrm{ OP}}_{\mathrm{ 1\,dB}}$ up to 9.7/6.7 dBm, respectively. It shows a 3-dB bandwidth of 63 GHz (239–302 GHz) in small-signal operation and 94 GHz (223–317 GHz) when saturated. The amplifier consumes about 360 mW at a 3-V supply voltage yielding a peak power-added efficiency (PAE) of 1.95% at 260 GHz.

This article presents a terahertz (THz) source system-on-a-chip (SoC) specifically designed for computational imaging with a single-pixel camera (SPC). The SoC consists of an 8x 8 array of independent, frequency-unlocked THz sources that together radiate maximum 10.3-dBm power at 0.42 THz. Each source pixel is composed of a fundamental Colpitts oscillator, followed by a common-collector doubler and an on-chip circular slot antenna. The THz power radiated from the array can be modulated in space by turning the pixels on or off individually with 100% modulation depth. The SoC integrates a dedicated memory space where 64 of such spatial patterns can be stored and triggered externally at up to 10-MHz modulation rate. The spatial modulation can be additionally multiplexed with separate programmable chopping rates for individual pixels. The combined modulation diversity provides a highly reconfigurable THz light projection for SPCs. Furthermore, each pixel also incorporates a built-in power-test (BIST) for an in situ radiation power monitoring and calibration. All of the aforementioned functions are programmable with an integrated application-specific integrated circuit (ASIC) through a standard SPI interface. This integration level readily allows low-cost aperture scaling by combining multiple chips at the board level. The SoC was applied in a compact, 8x 8 pixel, silicon-only THz SPC that captures transmission-mode images at 25 frames/s with 40-dB voltage dynamic range. With an appropriate receiver and baseband processing, the imaging speed of such SPCs can be extended to thousands of frames per second.

There is a need to reduce the cost and size of functional terahertz devices, in order to expedite this notoriously under-utilized frequency band toward practical applications. Electronic integrated circuits (ICs) are extremely useful to this end, as they provide a means to achieve miniaturization and mass-production, leveraging the foundries and techniques that have made digital electronics ubiquitous. Although integration of terahertz systems is expected to diminish performance and functionality, the increased number and availability of devices is likely to compensate for such disadvantages. In this work, we develop a terahertz-range spectroscope that combines a CMOS terahertz camera with custom-machined reflective optics. It is noted that the individual pixels of the camera employ incoherent detection, and hence a single pixel is not able to differentiate distinct frequencies. For this reason, the reflective optics are designed to split a terahertz beam into its constituent frequencies, and target each to a different position on the terahertz camera's focal plane array (FPA). The required frequency-scanning functionality is provided by a corrugated reflective optic that operates in a manner similar to a curved diffraction grating. The developed spectroscope is experimentally validated, and its functionality agrees closely with simulation. This work provides a pathway to a new generation of compact, low-cost, all-electronic terahertz spectrometers that employ mass-producible silicon ICs for all active components.

Presents information on the ISSCC 2019 Conference.

Traditional THz equipment faces major obstacles in providing the system cost and compactness necessary for widespread deployment of THz applications. Because of this, the field of THz integrated circuit (THz IC) design in CMOS and SiGe HBT technologies has surged in the last decade. An interplay of advances in silicon process technology, design technique, and microelectronic packaging promises to narrow the gap between the requirements and the reality of system cost and performance of THz components. Furthermore, the scalability, reconfigurability, and signal processing features of silicon technol- ogy have initiated research in complex THz ICs that expand the functionality of THz systems; this has enabled new applications, methods, and algorithms. This paper reviews the progress in THz IC research and investigates several realizations of THz imaging and sensing applications with silicon-based components regarding their motivation, system performance, and challenges. THz computed tomography, broadband multi-color imaging, high-resolution FMCW radar imaging, sub-wavelength resolution near-field imaging, and compressed sensing are presented.

Breast Cancer is one of the most frequently diagnosed cancer diseases worldwide, and the most common invasive tumour for women. As with all cancers, early detection plays a major role in reducing the mortality and morbidity rate. Currently, most breast cancers are detected due to clinical symptoms, or by screening mammography. The limitations of these techniques have resulted in research of alternative methods for imaging and detecting breast cancer. Apart from this, it is essential to define precise tumour margins during breast-conserving surgeries to reduce the re-excision rate. This study presents the advances in the development of a silicon-based THz sub-wavelength imager usable in life science applications, especially for tumour margin identification.

This paper presents a low-cost silicon-based terahertz computed tomography system for industrial volumetric imaging. The THz-CT scanner comprises a single radiator and detector at 490 GHz and a PTFE-lens based optical train that is fixed inside a portable cage system. It features a 2.5 mm resolution limited by the effective lens aperture and offers up to 62 dB SNR in chopped and 38 dB in a continuous-wave acquisition mode. To the authors best knowledge this work is the first demonstration of THz-CT that is entirely based on low-cost silicon components.