Abstract-CMOS fully integrated terahertz thermal detector using metamaterial absorber and proportional-to-absolute temperature sensor Xu Wang

 

Xu Wang

https://www.spiedigitallibrary.org/journals/optical-engineering/volume-59/issue-9/097106/CMOS-fully-integrated-terahertz-thermal-detector-using-metamaterial-absorber-and/10.1117/1.OE.59.9.097106.short?SSO=1

Terahertz (THz) detectors have drawn much attention and have been widely applied in imaging, spectroscopy, and sensing fields. An uncooled monolithic resonant THz thermal detector implemented in a standard 55-nm CMOS process is presented. The integration of a frequency selective metamaterial (MM) absorber coupled with an optimized proportional-to-absolute temperature (PTAT) sensor leads to an approach toward uncooled, compact, low-cost, easy-integration, and mass-production THz detectors. The theoretical analysis, design considerations, and characteristic measurements are demonstrated in detail. The proposed thermal detector is designed to resonate at 2.58 THz for the accessible THz source and the natural atmospheric window. The MM absorber achieves near-perfect absorptivity of 98.6%, and the optimized PTAT sensor obtains a high-temperature sensitivity of 10.11  mV  /    °  C. The calculated responsivity is 49.81  V  /  W at 2.58 THz with a calculated noise-equivalent power (NEP) of 0.78  μW  /  Hz^0.5 at a modulation frequency of 3 Hz. Relatively better experimental results are obtained at 2.58 THz with a maximum responsivity of 48.3  V  /  W and a minimum NEP of 1.06  μW  /  Hz^0.5.

© 2020 Society of Photo-Optical Instrumentation Engineers (SPIE) 0091-3286/2020/$28.00 © 2020 SPIE

CMOS terahertz startup gets EC equity backing

TiHive in Grenoble has raised €8.6m ($10m) for its CMOS terahertz chip, including equity funding from an fund run by the European Commission
By Nick Flaherty
https://www.eenewseurope.com/news/cmos-terahertz-startup-gets-ec-equity-backing

French industrial IoT startup TiHive has raised a total of €8.6m ($10m) to scale up production of its CMOS-based terahertz imaging sensor chip.

The backing comes as a grant and equity from the EIC Accelerator program, a European Innovation Council scheme within the framework of Horizon 2020.

“The really cool thing is the EC has funded academic organisation or SMEs via grants but now have seen they go beyond that, so €2.3m is a grant and €6.3m is in equity as a partners and we will be attracting other investors,” said Hani Sherry, CEO and co-founder of TiHive in Grenoble, France.

“They won’t be a majority shareholder, it’s like a Series A and will own a part of the company, so it is actually a pretty big round but we are phasing it,” he said. “This development is capital intensive so we need cash and Europe would like to boost strategic technologies in Europe and they have identified us as the leader in the technology. They would like to behave like VCs with a return on investment and the idea is to continue investing.” An ‘EU representative’ will sit on the board.

The chip is built in 65nm and the company says it has multiple foundry partnerships, including a partnership with ST. The terahertz sensor is combined with AI processing to simplify detection of contaminants and errors on a production line.

“We have tried multiple nodes, including 28FD-SOI, and we have mastered the different technologies. 65nm is a sweet spot for us, it has fantastic performance and a good cost at large scale and it has the libraries available,” said Sherry. “We operate from a few hundred GHz to 1THz and we have demonstrated chips at 2 and 3THz but for the applications we have found the unexplored applications range from 300 to 600GHz, that’s a major area.”

“We have succeeded in generating and detecting terahertz in CMOS and we

do the processing. We have built camera systems, to a CMOS chip with optics, then AI embedded on the camera,” he said. Each camera has 1000 pixels with 12bit resolution operating at 1000 frame/s.

“This can democratise terahertz sensing in a similar fashion to smartphones with cameras that can be integrated almost anywhere and can be produced at large scale. In a couple of years we want to provide tens of thousands of cameras,” he said.

“We want to develop that one standard die camera with a standard API to develop applications of your choice. We will unlock one application that requires many cameras as the beachhead market. When that camera is standardised it will be a matter of software,” he said. “But we are not yet there. Today everything is on a single chip with off the shelf processing. When we detect THz, its a complex mechanism, and we need to process this before it goes to the processor at high speed. WeE have developed that chip with the camera and embedded systems.

The first application is in hygiene and personal care, measuring the dosage of absorbent polymer that goes into nappies/diapers. This is half the cost of the product, and overdosing costs the industry one to two billion euros a year on factory lines that produce 1200 items a minute. Hundreds of TiHive cameras can be added to existing lines to monitor the amount of polymer delivered.

“TiHive’s plug and play solution consists of integrated circuit-based technology and artificial intelligence algorithms. It includes a transmitter and receiver, which, when positioned either side of an object, reveal physical characteristics or quality indicators that have previously been impossible to measure,” said Clement Jany, CTO of TiHive.

“That will reduce costs by €2bn and reduce waste of the non-bio-degradable materials,” said Sherry. “With the same camera we are detecting other factors such as contaminants.”

TiHive estimates a €10 billion opportunity in potential material savings and quality improvements for manufacturers of personal care products. Sherry also points to 6G cellular communications operating in the 200 to 300GHz range as a key opportunity.

www.tihive.com

Silicon technology boost with graphene and 2-D materials

Artistic illustration of silicon technology combined with 2D materials. Credit: ICFO / F. Vialla

https://phys.org/news/2019-09-silicon-technology-boost-graphene-d.html

Silicon semiconductor technology has done marvels for the advancement of our society, which has benefited tremendously from its versatile use and amazing capabilities. The development of electronics, automation, computers, digital cameras and recent smartphones based on this material and its underpinning technology has skyrocketed, downscaling the physical size of devices and wires to the nanometre regime.

Although this technology has been developing since the late 1960s, the miniaturization of circuits seems to have reached a possible end point, since transistors can only be shrunk down to a certain size and no further. Thus, there is a pressing need to complement Si CMOS technology with new materials, and to fulfill the future computing requirements as well as the needs for diversification of applications.

Now, graphene and related two-dimensional (2-D) materials offer prospects for unprecedented advances in device performance at the atomic limit. Their amazing potential has proven to be a possible solution to overcome the limitations of silicon technology, where the combination of 2-D materials with silicon chips promises to surpass current technological limitations.

In a new review article in Nature, a team of international researchers including ICFO researchers Dr. Stijn Goossens and ICREA Prof at ICFO Frank Koppens, and industrial leaders from IMEC and TSMC have come together to provide an in-depth and thorough review on the opportunities, progress and challenges of integrating atomically thin materials with Si-based technology. They provide insights on how and why 2-D materials (2DMs) may overcome current challenges posed by the existing technology and how they can enhance both device component function and performance, to boost the features of future technologies, in the areas of computational and non-computational applications.

For non-computational applications, they review the possible integration of these materials for future cameras, low power optical data communications and gas and bio-sensors. In particular, image sensors and photodetectors, are areas where graphene and 2DMs could enable a new vision in the infrared and terahertz range in addition to the visible range of the spectrum. These can serve, for example, in autonomous vehicles, security at airports and augmented reality.

For computational systems, and in particular in the field of transistors, they show how challenges such as doping, contact resistance and dielectrics/encapsulation can be diminished when integrating 2DMs with Si technology. 2DMs could also radically improve memory and data storage devices with novel switching mechanisms for meta;-insulator-metal structures, avoid sneak currents in memory arrays, or even push performance gains of copper wired based circuitry by adhering graphene to the ultrathin copper barrier materials and thus reduce resistance, scattering and self-heating.

The review provides insight to all stakeholders about the challenges and impact of solving the 2-D material integration with CMOS technology. It provides a roadmap of 2-D integration and CMOS technology, pinpointing the stage at which all challenges regarding growth, transfer, interface, doping, contacting, and design are currently standing today and what possible processes are expected to be resolved to achieve such goals of moving from a research laboratory environment to a pilot line for production of the first devices that combine both technologies.

The first 2-D material-CMOS roadmap, as presented in this review, gives an exciting glimpse in the future, with the first pilot production to be expected just a few years from now.

Abstract-Design of Terahertz CMOS Integrated Circuits for High-Speed Wireless Communication

Minoru Fujishima, Shuhei Amakawa,

https://digital-library.theiet.org/content/books/cs/pbcs035e

Communications technology at a frequency range into Terahertz (THz) levels has attracted attention because it promises near-fibre-optic-speed wireless links for the 5G and post-5G world. Transmitter and receiver integrated circuits based on CMOS, which has the ability to realize such circuits with low power consumption at a low cost, are expected to become increasingly widespread, with much research into the underlying electronics currently underway. This book describes recent research on terahertz CMOS design for high-speed wireless communication. The topics covered include fundamental technologies for terahertz CMOS design, amplifier design, physical design approaches, transceiver design, and future prospects. This concise source of key information, written by leading experts in the field, is intended for researchers and professional circuit designers working in RFIC and CMOS design for telecommunications.

Abstract-Physical design techniques for RF CMOS

Minoru Fujishima, Shuhei Amakawa

https://digital-library.theiet.org/content/books/10.1049/pbcs035e_ch3

Even in the case of a terahertz circuit design, circuit simulators are still used in circuit design. However, design environments and techniques are not as well established as for radio-frequency (RF) complementary metal-oxide-semiconductor (CMOS) circuits. Thus, various preparations are required before using the circuit simulator to design ultrahigh-frequency circuits operating at millimeter wave (mmw) or terahertz. Although this preparation occasionally occupies a lot of time of work, it is no exaggeration to say that the success or failure of circuit design is determined by the quality of this preparation. This section reviews recent progress made by the authors in terahertz CMOS design including device characterization and modeling techniques

Tuning terahertz transmission

A mounted device including the new tunable metasurface developed by Ding, Teng and co-workers. (right) When terahertz radiation hits the surface of interlinked p-type and n-type semiconducting silicon fingers, the amount of radiation reflected and transmitted can be controlled precisely using an applied voltage. Credit: A*STAR Institute of Materials Research and Engineering

https://phys.org/news/2019-04-tuning-terahertz-transmission.html

The ability to manipulate light on a subwavelength-scale could lead to a revolution in photonic devices such as antennas, solar panels, and even cloaking devices. Nanotechnology advances have made this possible through the development of metasurfaces, materials covered in features smaller than the wavelength of the light.

Now, a team led by A*STAR researchers has produced a highly promising metasurface that can be precisely controlled using a conventional electrical circuit so that it reflects and transmits different amounts of radiation. It can even reach the condition of 'perfect antireflection' where it reflects no radiation at all. Specifically, the surface works with broadband terahertz radiation, which is found at the far end of the infrared spectrum and has many potential uses, particularly in security or medical fields.

"Terahertz radiation can penetrate a wide variety of non-conducting materials, but is blocked by liquid water or metals," explains Lu Ding, who led the work with Jinghua Teng at the A*STAR Institute of Materials Research and Engineering (IMRE). "This means that terahertz beams can be used for material characterization, layer inspection, and producing high-resolution images of the interior of solid objects. It is non-ionizing radiation, and safer than X-rays."

Previous metasurfaces have been designed to manipulate the reflection of terahertz radiation. However, their application has been limited, as Ding explains: "Conventional terahertz antireflection surfaces are passive and often employ an ultrathin metal coating that, once fabricated, becomes fixed and you can't actively tune its performance."

"An electrically tunable metasurface would produce more versatile devices and render more flexibility in system design," adds Teng. "It is the breakthrough the community is looking for."

Ding and Teng, along with coworkers at the A*STAR Institute of Microelectronics (IME), Nanyang Technological University, National University of Singapore and Jilin University in China, fabricated their new metasurface on a silicon wafer, using a process entirely compatible with the complementary metal–oxide semiconductor (CMOS) technologies that underpin most electronics.

The exposed metasurface contains stripes of semiconducting silicon, doped with other elements. These stripes are alternately n-type, in which the moving charge carriers are electrons, and p-type, in which the carriers are positively-charged 'holes' in the electron structure. When the voltage supplied to the p-n junctions is changed, the reflection and transmission of the radiation also change.

The team realized that the reflection coefficient increased in response to a temperature rise caused by the applied voltage. Meanwhile, the transmission showed a more complex response depending on the voltage polarity, which affected the type of charge carrier that became dominant. Using terahertz time-domain spectroscopy, the team showed that certain voltage conditions caused the echo pulse from the metasurface to vanish, representing complete antireflection.

As well as providing this unprecedented control over reflection and transmission, the metasurface has the benefit of being almost entirely flat at an atomic level. This makes it ideal for building up smooth layers in more complex devices.

"Another big advantage is for our research looking into how 2-D materials interact with 2-D metamaterials or metasurfaces, a topic in our project in A*STAR's 2-D Semiconductors Pharos Program," says Teng. "The atomically smooth surface makes the transfer and formation of 2-D-Si heterostructures much easier than the patterned surfaces of nano-sized pillars or disks seen on conventional metasurfaces."

"We could further exploit this type of metasurface by independently biasing the p-n junctions or designing modular functions, meaning that we would have pre-programmable metamaterials," says Ding. Teng adds that the same platform could be used for studying promising 2-D materials like molybdenum disulfide, which exhibits impressive electronic and optical properties for use in new flexible circuits.

CMOS Integrated Circuit Technology Offers High-Speed Terahertz Transceiver

https://www.adsenseinternetmarketing.com/80/cmos-integrated-circuit-technology-offers-high-speed-terahertz-transceiver

• by Pareesh Phulkar

Researchers from Hiroshima University developed a high-speed transceiver that can receive or send data at a speed of 80 gigabits per second    

A team of researchers from Hiroshima University, National Institute of Information and Communications Technology, and Panasonic Corporation developed a high-speed terahertz (THz) transceiver. The device can send or receive digital data at 80 gigabits per second (Gbit/s). The technology will be presented at the International Solid-State Circuits Conference (ISSCC) 2019 to be held from February 17 to February 21 in San Francisco, California, U.S. The team used a silicon metal oxide semiconductor (CMOS) integrated circuit technology to develop the transceiver

THz band offers a new and vast frequency and can be used for ultrahigh-speed wireless communication services. The single-chip transceiver can receive or transfer data at a speed of 80 Gbit/s with the help of channel 66 defined by the Institute of Electrical and Electronics Engineers™ (IEEE) Standard. According to the standard, lower THz frequency range between 252 gigahertz (GHz) and 325 GHz is considered as a high-speed wireless communication channel.

In 2017, the team developed a band transmitter chip with a strength of 300-GHz and a receiver chip with 32 Gbit/s capability. The chip can achieve a speed of 105 Gbit/s. The current approach deals with the combination of a transmitter and a receiver into a single transceiver chip. Power combining as a technique can be used in transmitters to boost performance. However, the approach cannot be applied to receivers, which reduces the performance speed of the overall system unless an equally fast receiver is available.

The ability to achieve CMOS receiver performance close to 100 Gbit/s is a breakthrough in technological singularity. Research and innovation in computational power, communication speed, and capacity within and between computers is important. Such high-speed CMOS integrated circuit technology can be used in data transfer during space missions and can help to offer real-time data services over long distances, which can again prove vital in healthcare services.  

Terahertz wireless makes big strides in paving the way to technological singularity

Medical AI and doctors at earth stations could remotely conduct a zero-gravity operation aboard a space plane connected via terahertz wireless links.(CREDIT ©HIROSHIMA UNIVERSITY, NICT, PANASONIC, AND 123RF.COM)

https://www.eurekalert.org/pub_releases/2019-02/hu-twm021419.php

Hiroshima, Japan, February 19, 2019--Hiroshima University, National Institute of Information and Communications Technology, and Panasonic Corporation announced the successful development of a terahertz (THz) transceiver that can transmit or receive digital data at 80 gigabits per second (Gbit/s). The transceiver was implemented using silicon CMOS integrated circuit technology, which would have a great advantage for volume production. Details of the technology will be presented at the International Solid-State Circuits Conference (ISSCC) 2019 to be held from February 17 to February 21 in San Francisco, California [1].

The THz band is a new and vast frequency resource expected to be used for future ultrahigh-speed wireless communications. IEEE Standard 802.15.3d, published in October 2017, defines the use of the lower THz frequency range between 252 gigahertz (GHz) and 325 GHz (the "300-GHz band") as high-speed wireless communication channels. The research group has developed a single-chip transceiver that achieves a communication speed of 80 Gbit/s using the channel 66 defined by the Standard. The research group developed a 300-GHz-band transmitter chip capable of 105 Gbit/s [2] and a receiver chip capable of 32 Gbit/s [3] in the past few years. The group has now integrated a transmitter and a receiver into a single transceiver chip. 

"We presented a CMOS transmitter that could do 105 Gbit/s in 2017, but the performance of receivers we developed, or anybody else did for that matter, were way behind [3] for a reason. We can use a technique called 'power combining' in transmitters for performance boosting, but the same technique cannot be applied to receivers. An ultrafast transmitter is useless unless an equally fast receiver is available. We have finally managed to bring the CMOS receiver performance close to 100 Gbit/s," said Prof. Minoru Fujishima, Graduate School of Advanced Sciences of Matter, Hiroshima University.

"People talk a lot about technological singularity these days. The main point of interest seems to be whether artificial superintelligence will appear. But a more meaningful question to ask myself as an engineer is how we can keep the ever-accelerating technological advancement going. That's a prerequisite. Advances in not only computational power but also in communication speed and capacity within and between computers are vitally important. You wouldn't want to have a zero-grav operation on board a space plane without real-time connection with earth stations staffed by medical super-AI and doctors. After all, singularity is a self-fulfilling prophecy. It's not something some genius out there will make happen all of a sudden. It will be a distant outcome of what we develop today and tomorrow," said Prof. Fujishima.

"Of course, there still is a long way to go, but I hope we are steadily paving the way to such a day. And don't you worry you might use up your ten-gigabyte monthly quota within hours, because your monthly quota then will be in terabytes," he added.

Abstract-High-Transmittance 2π Electrically Tunable Terahertz Phase Shifter with CMOS-Compatible Driving Voltage Enabled by Liquid Crystals

Chan-Shan Yang  Chun Kuo, Po-Han Chen, Wei-Ta Wu, Ru-Pin Pan, Peichen Yu, Ci-Ling Pan,

Figure 1. (a) Schematic diagrams of three different configurations of indium–tin–oxide-nanowhiskers (ITO-NWhs)-based phase shifters, type A, B, and C, respectively. The cross-sectional images of (b) the substrate of ITO NWhs, (c) ITO NWhs coated with polyimide, and (d) ITO NWhs treated with the rubbing process.

https://www.mdpi.com/2076-3417/9/2/271/htm

We have investigated tunable terahertz (THz) phase shifters that are based on a sandwiched liquid crystal (LC) cell with indium–tin–oxide (ITO) nanowhiskers (NWhs) as transparent electrodes. More than 360° of phase shift at 1.0 THz was achieved at a driving voltage as low as ~2.6 V (rms). This is approximately 40 times smaller than that reported in previous works using an electrically tuned LC device. Significance of the NWhs in reducing the required voltage is demonstrated. Overall transmittance of the device is as high as 30%, which is accountable by absorption losses of ITO NWhs, quartz substrate and LC. Experimental results are in good agreement with a theoretical formulism while taking into account super-thick LC cells (~1 mm) and pretilt angles. We also propose and demonstrate a novel THz technique for measuring pretilt angles of liquid crystals.

Abstract-Invited Article: Ultra-broadband terahertz coherent detection via a silicon nitride-based deep sub-wavelength metallic slit

APL Photonics

A. Tomasino, R. Piccoli, Y. Jestin, S. Delprat1, M. Chaker,   M. Peccianti,   M. Clerici4, A. Busacca, L. Razzari,  R. Morandotti,

FIG. 1.3D sketch of the deep sub-λ slit (G) device embedded in a thin layer (T) of SiN, deposited on a quartz substrate. L and W are the length and the width of the metal pads, respectively.

https://aip.scitation.org/doi/abs/10.1063/1.5052628

We present a novel class of CMOS-compatible devices aimed to perform the solid-state-biased coherent detection of ultrashort terahertz pulses, i.e., featuring a gap-free bandwidth at least two decades-wide. Such a structure relies on a 1-µm-wide slit aperture located between two parallel aluminum pads, embedded in a 1-µm-thick layer of silicon nitride, and deposited on a quartz substrate. We show that this device can detect ultra-broadband terahertz pulses by employing unprecedented low optical probe energies of only a few tens of nanojoules. This is due to the more than one order of magnitude higher nonlinear coefficient of silicon nitride with respect to silica, the nonlinear material employed in the previous generations. In addition, due to the reduced distance between the aluminum pads, very high static electric fields can be generated within the slit by applying extremely low external bias voltages (in the order of few tens of volts), which strongly enhance the dynamic range of the detected THz waveforms. These results pave the way to the integration of solid-state ultra-broadband detection in compact and miniaturized terahertz systems fed by high repetition-rate laser oscillators and low-noise, low-voltage generators.

Chinese, U.S. scientists develop tiny, efficient modulator, revolutionize industry

http://www.xinhuanet.com/english/2018-09/24/c_137490235.htm

WASHINGTON, Sept. 24 (Xinhua) -- An international team led by Chinese scientists have built a smaller, more efficient on-chip modulator that is set to revolutionize the communication industry.

The lithium niobate modulator is only 1-2 cm long and its surface area is less than 1 percent of traditional ones, according to a study published Monday in the journal Nature.

Electro-optic modulators are critical components in modern communications, converting high-speed electronic signals in computational devices such as computers to optical signals before transmitting them through optical fibers.

However, the existing and commonly used lithium niobate modulators require a high drive voltage of 3-5V, significantly higher than 1V, a voltage provided by a typical CMOS (complementary metal-oxide-semiconductor) circuitry. Therefore, an electrical amplifier makes the whole device bulky, expensive and energy-consuming.

Scientists from the City University of Hong Kong, Harvard University and Nokia Bell Labs used nano fabrication approaches to build a lithium niobate modulator that can be operated at ultra-high electro-optic bandwidths with a voltage compatible with CMOS.

Its data bandwidth triples from 35 GHz to 100 GHz, but with less energy consumption and ultra-low optical losses.

The tiny modulator can transmit data at rates up to 210 Gbit per second, with about 10 times lower optical losses than existing modulators.

The new invention will pave the way for future high-speed, low power and cost-effective communication networks as well as quantum photonic computation.

"In the future, we will be able to put the CMOS right next to the modulator, so they can be more integrated, with less power consumption. The electrical amplifier will no longer be needed," said Wang Cheng, assistant professor in the Department of Electronic Engineering at City University of Hong Kong and co-first author of the paper.

Wang is looking into its application for the coming 5G communication together with the research team at China's State Key Laboratory of Terahertz and Millimeter Waves at the City University of Hong Kong.

"Millimeter wave will be used to transmit data in free space, but to and from and within base stations, for example, it can be done in optics, which will be less expensive and less lossy," said Wang.

Abstract-A CMOS Fully Integrated 860-GHz Terahertz Sensor

Zhao-yang Liu,  Li-yuan Liu,  Jie Yang,  Nan-jian Wu

https://ieeexplore.ieee.org/document/7926419/

This paper proposes a CMOS fully integrated 860-GHz terahertz (THz) sensor. The sensor integrates a single-NMOS THz detector, a low-noise chopper instrumentation amplifier and a high-resolution ΔΣ-ADC. The detector consists of a novel on-chip grounded patch antenna and a source-feeding NMOS field-effect transistor (FET) of the minimum size. A microstrip transmission line is designed to improve the power transfer efficiency between the antenna and the NMOS transistor. A notch filter is proposed to improve detector performance. To enable the theoretical analysis of the operation of the THz detector and the formulation of design guidelines, we propose a THz-FET device model in which a source-coupled FET for THz detection is modeled as a dc voltage source with a resistor. The model indicates that an FET with the minimum physical dimensions for a given CMOS process can produce the maximum output signal. The sensor is implemented in a 180-nm standard CMOS process. The detector achieves a voltage responsivity of 3.3 kV/W and an NEP of 106 pW/Hz 1/2 at 860 GHz. The sensor noise and the readout circuit noise are 10.81 and 2.03 μVrms, respectively. The sensor obtains clear raster-scanning transmission images under continuous THz illumination.

Abstract-A Terahertz CMOS V-Shaped Patch Antenna with Defected Ground Structure

Hyeongjin Kim, Wonseok Choe, Jinho Jeong,

http://www.mdpi.com/1424-8220/18/8/2432

In this paper, a V-shaped patch antenna with defected ground structure is proposed at terahertz to overcome the limited performance of a standard complementary metal-oxide semiconductor (CMOS) patch antenna consisting of several metal layers and very thin interdielectric layers. The proposed V-shaped patch with slots allows the increased radiation resistance and broadband performance. In addition, the patch resonating at different frequency from the V-shaped patch is stacked on the top to broaden the impedance-matching bandwidth. More importantly, the slots are formed in the ground plane, which is called the defected ground structure, to further increase the radiation resistance and thus improve the bandwidth and efficiency. It is verified from electromagnetic simulations that the leakage waves from the defected ground can enhance the antenna directivity and gain by coherently interfering with the topside radiation. The proposed on-chip antenna is fabricated using a standard 65 nm CMOS process. The on-wafer measurement shows very wide bandwidth in input reflection coefficient (<−10 dB), greater than 28.7% from 240 to >320 GHz. The measured peak gain was as high as 5.48 dBi at 295 GHz. To the best of the authors’ knowledge, these results belong to the best performance among the terahertz CMOS on-chip antennas without using additional components or processes such as dielectric resonators, lens, or substrate thinning.

Abstract-A Low-Noise Direct Incremental A/D Converter for FET-Based THz Imaging Detectors

Moustafa Khatib,  Matteo Perenzoni

http://www.mdpi.com/1424-8220/18/6/1867

This paper presents the design, implementation and characterization results of a pixel-level readout chain integrated with a FET-based terahertz (THz) detector for imaging applications. The readout chain is fabricated in a standard 150-nm CMOS technology and contains a cascade of a preamplification and noise reduction stage based on a parametric chopper amplifier and a direct analog-to-digital conversion by means of an incremental ΣΔ$$ converter, performing a lock-in operation with modulated sources. The FET detector is integrated with an on-chip antenna operating in the frequency range of 325–375 GHz and compliant with all process design rules. The cascade of the FET THz detector and readout chain is evaluated in terms of responsivity and Noise Equivalent Power (NEP) measurements. The measured readout input-referred noise of 1.6 μ$$Vrms$$ allows preserving the FET detector sensitivity by achieving a minimum NEP of 376 pW/Hz−−−√$$ in the optimum bias condition, while directly providing a digital output. The integrated readout chain features 65-dB peak-SNR and 80-μ$$W power consumption from a 1.8-V supply. The area of the antenna-coupled FET detector and the readout chain fits a pixel pitch of 455 μ$$m, which is suitable for pixel array implementation. The proposed THz pixel has been successfully applied for imaging of concealed objects in a paper envelope under continuous-wave illumination.

Abstract-Molecular Detection for Unconcentrated Gas With ppm Sensitivity Using 220-to-320-GHz Dual-Frequency-Comb Spectrometer in CMOS

Cheng Wang, Bradford Perkins, Zihan Wang, Ruonan Han,

https://ieeexplore.ieee.org/document/8331906/

Millimeter-wave/terahertz rotational spectroscopy of polar gaseous molecules provides a powerful tool for complicated gas mixture analysis. In this paper, a 220-to-320-GHz dual-frequency-comb spectrometer in 65-nm bulk CMOS is presented, along with a systematic analysis on fundamental issues of rotational spectrometer, including the impacts of various noise mechanisms, gas cell, molecular properties, detection sensitivity, etc. Our comb spectrometer, based on a high-parallelism architecture, probes gas sample with 20 comb lines simultaneously. It does not only improve the scanning speed by 20×, but also reduces the overall energy consumption to 90 mJ/point with 1 Hz bandwidth (or 0.5 s integration time). With its channelized 100-GHz scanning range and sub-kHz specificity, wide range of molecules can be detected. In the measurements, state-of-the-art total radiated power of 5.2 mW and single sideband noise figure of 14.6–19.5 dB are achieved, which further boost the scanning speed and sensitivity. Finally, spectroscopic measurements for carbonyl sulfide (OCS) and acetonitrile (CH3CN) are presented. With a path length of 70 cm and 1 Hz bandwidth, the measured minimum detectable absorption coefficient reaches αgas,min=7.2×10−7 cm−1. For OCS that enables a minimum detectable concentration of 11 ppm. The predicted sensitivity for some other molecules reaches ppm level (e.g., 3 ppm for hydrogen cyanide), or 10 ppt level if gas preconcentration with a typical gain of 105 is used.