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Block diagram of the 2-band TX/RX system with the two frequency ranges: a) 222-256 GHz, and b) 250-270 GHz.
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This paper presents transmitter and receiver components for a gas spectroscopy system. The components are fabricated in IHP’s
0.13 �m SiGe BiCMOS technology. Two fractional-N phase-locked loops are used to generate dedicated frequency ramps for the
transmitter and receiver and frequency shift keying for the transmitter. The signal-to-noise ratio (S...
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Citations
... For those lines, the minimal concentration would be at the level of 100 ppb −110 ppm. The levels of concentration sensitivities are better (for H2S) or comparable (for some other substances) with the sensitivity (relative to concentration) in [10,13]. ...
Nowadays, physicochemical methods of analysis are used in medical diagnostics. One can identify metabolites characteristic of a particular disease. The compilation of a metabolic profile will facilitate the diagnosis of diseases, evaluate their stage and etiology, and predict treatment. The goal of the study is to analyze the metabolite composition of the ear-nose-throat (ENT) tissues by high-resolution THz spectroscopy based on nonstationary effects and compare metabolites formed during the thermal decomposition of relatively healthy mucosa, polyps, and cysts. Studies were performed with the spectrometers operating from 118 to 178 GHz. The chemical compounds were identified using online catalogs. In all samples, there are such substances as methanol, propanediol, acetaldehyde, acetonitrile, butyronitrile, methyl mercaptan, azole, ethylene sulfide, carbon sulfide, and sulfur dioxide. In the spectrum of relatively healthy mucosa, the number of absorption lines of these substances is much less than in the spectrum of the polyps and cysts, which indicates their lower concentration. In the products of the polyps and cysts, acetone, hydroxyacetone, dihydroxyacetone, propionitrile, acrylonitrile, aminopropionitrile, hydroxyacetonitrile, aminoacetonitrile, methylbutironitrile, propanal, glycolaldehyde, lactaldehyde, and malone dialdehyde appear. The products of cysts’ thermal decomposition also contain acetic and acrylic acids. High-resolution THz spectroscopy has been shown to be promising for detecting disease metabolites in ENT tissues.
... To further increase the operating frequency range, it is possible to integrate multiple TX or RX chains with a recentered frequency of operation on a single die. This has been demonstrated in [134] and resulted in an overall operational frequency range of 222-270 GHz. Today's integrated circuit technology allows for the realization of circuits for even higher spectral analysis. ...
This invited paper reviews the progress of silicon-based integrated analyzers for biomedical applications over the last two decades. Focus is set on various integrated circuit realizations in the millimeter-wave range from 30 GHz and at the terahertz frequencies of above 300 GHz. This article discusses high-frequency architectures and concrete implementations of both narrowband as well as broadband integrated readout circuits, including their use in miniaturized sensor solutions. A variety of circuits ranging from low-power sensing oscillators to highly integrated broadband vector network analyzers (VNAs), and example realizations of millimeter-wave cardiovascular sensors and implants to THz microfluidic labs-on-chip and exhaled human breath analyzers are recapitulated. This article closes with an outlook on emerging fields of research for future advancement of such biomedical sensors toward reliable and specific systems.
... The design of the TX-and RX-circuits is described in detail in [19]- [24]. A 2-band TX-chip and a 2-band RX-chip were reported, which were implemented by combining two TX-and two RX-circuits with their own on-chip antennas on corresponding single chips to realize an effective bandwidth of 222-270 GHz for a gas spectroscopy system [25]. LBE (Localized Backside Etching) technology, which is available at IHP, was used to realize on-chip antennas with high efficiency. ...
... Our previous paper, [26] describes the implementation of a single bowtie-antenna with silicon lens for a 2-band TX and RX, increasing their performance parameters considerably compared to the former 2-band TX and RX with two separate LBE on-chip antennas, [25]. ...
This paper presents a transmitter (TX) and a receiver (RX) with a cross-polarized bowtie-antenna on a silicon lens for gas spectroscopy at 222–270 GHz and the doubled frequency at 444–540 GHz. TX and RX are fabricated in 0.13 μm SiGe BiCMOS technology. Both use two integrated local oscillators for frequency subbands 222–256 GHz and 250–270 GHz, which allow operating in one branch of the TX and RX at 222–270 GHz and in a second branch of the TX and RX at 444–540 GHz by frequency doubling. The directivity of the cross-polarized bowtie-antenna of the TX and RX is optimized for these two frequency bands with an estimated value of 24.4 dBi at 260 GHz, and 29.5 dBi at 520 GHz. Absorption spectroscopy of gaseous methanol is used as a measure for the performance of the TX and RX in the lower and upper frequency bands.
... Hence, THz absorption spectroscopy and gas sensing can be valuable in many scientific, industrial and environmental applications [1][2][3][4][5]. Moreover, recent advances in microelectronic THz sources and detectors has increased the viability of portable, miniature spectrometers capable of sensing a wide variety of gas molecules which are active in the THz region [6][7][8][9][10][11][12][13][14][15][16]. Similar to other spectroscopic techniques, rotational spectra in the THz frequency region require signal/data processing for spectral interpretation, gas species identification, and quantitative gas sensing. ...
... Figure 12. VOC-Net classification of experimental spectra (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). The corresponding softmax scores for each classification are given with each spectra. ...
Conventional black box machine learning (ML) algorithms for gas-phase species identification from THz frequency region absorption spectra have been reported in the literature. While the robust classification performance of such ML models is promising, the black box nature of these ML tools limits their interpretability and acceptance in application. Here, a one-dimensional convolutional neural network (CNN), VOC-Net, is developed and demonstrated for the classification of absorption spectra for volatile organic compounds (VOCs) in the THz frequency range, specifically from 220 to 330 GHz where prior experimental data is available. VOC-Net is trained and validated against simulated spectra, and also demonstrated and tested against experimental spectra. The performance of VOC-Net is examined by the consideration of confusion matrices and receiver-operator-characteristic (ROC) curves. The model is shown to be 99+% accurate for the classification of simulated spectra and 97% accurate for the classification of noisy experimental spectra. The model’s internal logic is examined using the Gradient-weighted Class Activation Mapping (Grad-CAM) method, which provides a visual and interpretable explanation of the model’s decision making process with respect to the important distinguishing spectral features.
... The lack of a "toolbox" of compact and economically viable THz devices, such as powerful sources and sensitive detectors, have impeded advances in this field. All-electronic, CMOS-based Transmission -Receiver systems (TRx) have increased their operation frequencies up to the THz range [6,7]. Such TRx systems are highly integrated circuits that will enable compact and economic devices for THz detection [8]. ...
Localized Surface Plasmon Resonances (LSPR) based on highly doped semiconductors microstructures, such as antennas, can be engineered to exhibit resonant features at THz frequencies. In this work, we demonstrate plasmonic antennas with increased quality factor LSPRs from Fano coupling to dark modes. We also discuss the advances in the biofunctionalization of n-doped Ge antennas for specific protein immobilization and cell interfacing. Finally, albumin biolayers with a thickness of a few hundred nanometers are used to demonstrate the performance of the fano-coupled n-Ge antennas as sensors. A resonant change of over 10% in transmission, due to the presence of the biolayer, can be detected within a bandwidth of only 20 GHz.
... The advantages of THz-wave absorption spectroscopy, together with recent and rapid progress in microelectronics-based THz-wave sources and detectors [6,[10][11][12], make possible the development of low-power and miniaturized systems for industrial and environmental remote gas sensing of polar molecules, including the four nitrogen-containing compounds investigated here, nitrous oxide, acetonitrile, nitric acid, and nitromethane. ...
Gas sensing for four nitrogen-containing compounds (nitrous oxide, acetonitrile, nitric acid, and nitromethane) is explored and demonstrated using rotational absorption spectroscopy carried out with a compact terahertz-wave microelectronics-based spectrometer operating in the 220-330 GHz frequency range. The four gases investigated are important in industrial processes, as well as in chemical, combustion, environmental, and agricultural contexts. Absorption measurements were made at room temperature (297 K) and moderate pressures (33.3-2133 Pa or 0.25-16 Torr) for the characterization of spectra that are comprised of distinct fingerprint features that include isolated single transitions and bands of pressure-broadened transitions, emanating from both ground vibrational states, as well as low-lying vibrationally-excited states. The measurements demonstrate that terahertz-wave quantitative gas sensing using all-electronic miniaturized systems is possible for nitrogen-containing compounds with detection limits of the order 10¹²-10¹³ molecules cm⁻³ per meter pathlength and for dilute gases in air at 1 atm at concentrations of 5-1000 ppm per meter pathlength.
... The single-band TX/RX system was extended to a 2-band system to cover the range 225 -273 GHz with two antennas [29]. A 2-band TX-chip and a 2-band RX-chip were reported, which were implemented by combining two TX-and two RXcircuits with their own on-chip antennas on corresponding single chips to realize an effective bandwidth of 222 -270 GHz for our gas spectroscopy system [30]. LBE (Localized Backside Etching) technology, which is available at IHP, was used to realize on-chip antennas with high efficiency by removing the lossy silicon under the radiator. ...
... It was further shown that a RX with a mixer as first element has improved the performance of the spectroscopy system due to the higher linearity of the RX compared to a former RX in case of a 4xTX-array with high output power. We observed a lower signal-noise ratio (SNR) for gas spectroscopy by about a half when using a single TX with lower output power instead of the 4xTX-array, see [30]. This paper describes the implementation of a single bowtieantenna with silicon lens for a 2-band TX and RX to increase their performance parameters considerably compared to the previous 2-band TX and RX with two separate LBE on-chip antennas. ...
... Fig. 3 shows the schematic of the frequency doubler connected to the two-stage power amplifier. The frequency doubler has already been used in our previous TX-and RX-chips [30]. To avoid mixing of the two LOsignals, only one LO is operating at a time, while the other one is switched off from its supply voltage electronically, and vice versa. ...
This paper presents a transmitter (TX) and a receiver (RX) with bowtie-antenna and silicon lens for gas spectroscopy at 222-270 GHz, which are fabricated in IHP’s 0.13 μm SiGe BiCMOS technology. The TX and RX use two integrated local oscillators for 222 – 256 GHz and 250 – 270 GHz, which are switched for dual-band operation. Due to its directivity of about 27 dBi, the single integrated bowtie-antenna with silicon lens enables an EIRP of about 25 dBm for the TX, and therefore a considerably higher EIRP for the 2-band TX compared to previously reported systems. The double sideband noise temperature of the RX is 20,000 K (18.5 dB noise figure) as measured by the Y-factor method. Absorption spectroscopy of gaseous methanol is used as a measure for the performance of the gas spectroscopy system with TX- and RX-modules.
... By building a purpose-designed system that comprised an electronic sensor operating between 210-270 GHz and a gas cell capable of collecting and concentrating gas samples, Neese et al [169] were able to detect and identify mixtures of 14 gases (acetonitrile, methyl fluoride, acrylonitrile, sulfur dioxide, methyl iodide, methyl bromide, trifluoromethane, acrolein, propionitrile, 1,1 difluoroethene, vinyl fluoride, oxetane, vinyl bromide, 1,2 dichloroethane) at ppt levels, meeting the requirements of the Clean Air Act (http://www.epa.gov) ( Figure 23). Similar custom-built gas sensing electronic systems were described in [170,171]. Another custom-built sensing system and the gas cell were used to monitor food spoilage by detecting hydrogen sulphide at around 611.4 GHz, achieving a sensitivity of 0.5 ppm [172]. In contrast, a system employing a vector network analyser (VNA) at 238-252 GHz was used to detect acetaldehyde, methanol, deuterated methanol, acetone, isopropyl alcohol, acetonitrile, and ethanol, and their mixtures [173]. ...
This paper is a survey of existing and upcoming industrial applications of terahertz technologies, comprising sections on polymers, paint and coatings, pharmaceuticals, electronics, petrochemicals, gas sensing, and paper and wood industries. Finally, an estimate of the market size and growth rates is given, as obtained from a comparison of market reports.
... MmW/THz gas spectrometers have been realized with different technologies and high sensitivity has been demonstrated [26][27][28][29][30][31][32][33]. Ethanol, methanol, and acetone have been unambiguously detected in human breath down to ppt levels [34][35][36]. ...
... The RX has a 33 GHz IF bandwidth, a single sideband noise figure of 12 dB and a typical system conversion gain of +2 dB. A discussion of the sensitivity of a similar spectrometer can be found in [30]. The emitted TX frequency and the local oscillator frequency of the RX are controlled by two synthesizers operating between 9 and 14 GHz whose output frequencies are multiplied by a factor of 24. ...
Breath gas analysis is a promising tool for medical research and diagnosis. A particularly powerful technological approach is millimeter-wave/terahertz (mmW/THz) spectroscopy, because it is a very sensitive and highly selective technique. In addition, it offers the potential for compact and affordable sensing systems for wide use. In this work, we demonstrate the capability of a mmW/THz spectrometer for breath analysis. Samples from three volunteers and a sample from ambient air were analyzed with respect to 31 different molecular species. High-resolution absorption spectra were measured by scanning two absorption lines from each species. Out of the 31, a total of 21 species were detected. The results demonstrate the potential of mmW/THz spectroscopy for breath analysis.
