Frequency Multiplier Chain Research Articles

A 0.46–0.52-THz fully-differential quasi-monostatic FMCW radar transceiver in 90-nm SiGe BiCMOS

A 0.46–0.52-THz fully-differential quasi-monostatic frequency-modulated continuous-wave (FMCW) radar transceiver was designed in a 90-nm SiGe bipolar CMOS technology with fT/fmax\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ extit{f}_{ \ extit{T}}/{f}_{\ ext{max}}$$\\end{document} of 300/480 GHz. The transceiver chip has an area of 2.84 mm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ ext{mm}^{2}$$\\end{document}. A multiply-by-24 frequency multiplier chain is used to generate a 0.48-THz signal from a 20-GHz input signal. Two 0.48-THz push–push doublers are driven in quadrature for a differential output signal with a measured effective isotropic radiated power of up to -\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$-$$\\end{document}8.8 dBm at the transmitter at 0.47 THz. A differential subharmonic receiver mixer with a stacked quad topology achieves a measured system conversion gain of 7 dB and a measured single-sideband noise figure of 25.2 dB at 0.471 THz. FMCW radar measurements are performed using an on-board frequency source of a credit card-sized demonstrator at a bandwidth of 60 GHz.

A 223–276-GHz Cascadable FMCW Transceiver in 130-nm SiGe BiCMOS for Scalable MIMO Radar Arrays

This article reports a 223–276-GHz monostatic frequency-modulated continuous-wave (FMCW) radar transceiver (TRX) chip. The TRX is suitable for building massive multiple-input multiple-output (MIMO) radar arrays in the daisy-chain topology because of its cascadable feature based on the injection-locking feedthrough technique. The TRX is based on 18 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> frequency multiplication chain that can be fed by either an external signal generator (SG) or its internal voltage-controlled oscillator (VCO). The modulation bandwidth (BW) is about 53 GHz when the internal VCO is activated, resulting in a range resolution of better than 3 mm. The peak output power is 3.1 dBm at 240 GHz with a 3-dB BW of 41 GHz. Its receiver (RX) channel is based on the in-phase/quadrature architecture enabling complex signal sampling. The minimum single-sideband (SSB) noise figure (NF) is 18.7 dB at 255 GHz, and the average value is 20.7 dB. The TRX chip includes an on-chip antenna coupled with a silicon lens, offering a peak effective isotropic radiated power (EIRP) of 27 dBm at 240 GHz. The TRX consumes a dc current of 234 and 270.1 mA from a single supply voltage of 3.3 V for external and internal VCO operations, respectively. The chip occupies a total area of 2.7 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (2.16 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 1.26 mm).

Optical injection locking of a THz quantum-cascade VECSEL with an electronic source.

Optical injection locking of a metasurface quantum-cascade (QC) vertical-external-cavity surface-emitting laser (VECSEL) is demonstrated at 2.5 THz using a Schottky diode frequency multiplier chain as the injection source. The spectral properties of the source are transferred to the laser output with a locked linewidth of ∼1 Hz, as measured by a separate subharmonic diode mixer, and a locking bandwidth of ∼300 MHz is achieved. The large locking range is enabled by the microwatt power levels available from modern diode multipliers. The interplay between the injected signal and feedback from external reflections is studied and demonstrated to increase or decrease the locking bandwidth relative to the classic locking range depending on the phase of the feedback.

A 205–273-GHz Frequency Multiplier Chain (×6) With 9-dBm Output Power and 1.92% DC-to-RF Efficiency in 0.13-µm SiGe BiCMOS

This article presents a 205–273-GHz wideband frequency multiplier chain (FMC) in a 0.13- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $</tex-math> </inline-formula> m SiGe BiCMOS technology with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{\mathrm{T}}\text{/}f_{\mathrm{max}}$</tex-math> </inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$=$</tex-math> </inline-formula> 300/500 GHz. The proposed FMC consists of a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$</tex-math> </inline-formula> -band input transformer (TF) balun, an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$F$</tex-math> </inline-formula> -band frequency tripler, an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$F$</tex-math> </inline-formula> -band power amplifier (PA), and a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$G$</tex-math> </inline-formula> -/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$J$</tex-math> </inline-formula> -band frequency doubler, which results in a sixth multiplier. To obtain high output power and high efficiency, a two-way power combining push–push doubler with second harmonic resonators is introduced. The high quality factor ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$</tex-math> </inline-formula> -factor) cross-fingers capacitor is employed in the wideband output matching network to reduce the insertion loss (IL). A wideband PA is utilized to drive the following doubler. The frequency tripler with an adaptive bias circuit is proposed to exhibit high output power while relatively flat conversion gain (CG), with which the output power of the tripler can be easily controlled. An analysis of the input TF balun is introduced for improving the common mode rejection, which results in high even harmonic suppression of the tripler. The proposed FMC exhibits 9-dBm saturated output power ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\mathrm{sat}})$</tex-math> </inline-formula> , with a 3-dB bandwidth of 68 GHz. The dc-to-RF efficiency of 1.92% is achieved with more than 10-dB CG at 252 GHz. The FMC consumes less than 0.5 W and occupies a small chip area. To the best of our knowledge, the proposed FMC exhibits the highest <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\mathrm{sat}}$</tex-math> </inline-formula> and dc-to-RF efficiency in silicon-based implementations beyond 200 GHz.

An E-Band Transformer-Based ×8 Frequency Multiplier With Enhanced Harmonic Rejection

We present an efficient method of enhancing the harmonic rejection ratio (HRR) of a millimeter-wave frequency multiplier (FM) by utilizing optimal capacitive loads with minimal area overheads. To verify the proposed method, we demonstrate an eight-times FM ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times 8$ </tex-math></inline-formula> FM) with an HRR of 35–50 dBc over a wideband of 20.8 GHz from 70.4 to 91.2 GHz in the 65-nm CMOS technology. The designed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times 8$ </tex-math></inline-formula> FM comprises three stages of push–push doublers (PPDs), and each PPD is followed by a driving amplifier (DA) to suppress undesirable spurs and provide optimal power levels. The transformer (TF)-based baluns in each PPD are rebalanced using two separate capacitive loads connected to the output terminals of the TF. The proposed technique achieves more than 10 dB of improvement in the HRR for the entire FM chain with a significant bandwidth enhancement in simulation. The fabricated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times 8$ </tex-math></inline-formula> FM achieves a peak output power of 6.3 dBm at 78.16 GHz with a dc current of 164 mA from a 1.2-V supply voltage. The chip area is 0.95 mm2, including the pads, whereas the core layout area is only 0.35 mm2.

A 260-GHz Four-Way Phase Compensated CMOS Frequency Multiplier Chain

A novel × 6 frequency multiplier chain with a center frequency of 260 GHz is developed in 40 nm CMOS and measured through this work. The multiplication is accomplished through an × 3 frequency multiplier followed by a doubler successive stage. A four-way signal combiner is employed to enhance the output power, whereas phase shifters are dedicated for compensating the possible phase deviations between the different combined ways, and consequently maintain the combining efficiency. For further output power boosting, the output matching network of 260-GHz frequency doubler is optimized, and a stacked amplifier with 11.5 dBm is employed as a driving amplifier. The multiplier has been fabricated and a peak output power of 3.0 dBm is measured at 260 GHz with a 3-dB bandwidth of 17 GHz.

System-on-chip approach microwave imaging reflectometer on DIII-D tokamak.

System-on-chip millimeter wave integrated circuit technology is used on the two-dimensional millimeter-wave imaging reflectometer (MIR) upgrade for density fluctuation imaging on the DIII-D tokamak fusion plasma. Customized CMOS chips have been successfully developed for the transmitter module and receiver module array, covering the 55-75GHz working band. The transmitter module has the capability of simultaneously launching eight tunable probe frequencies (>0 dBm output power each). The receiver enclosure contains 12 receiver modules in two vertical lines. The quasi-optical local oscillator coupling of previous MIR systems has been replaced with an internal active frequency multiplier chain for improved local oscillator power delivery and flexible installation in a narrow space together with improved shielding against electromagnetic interference. The 55-75GHz low noise amplifier, used between the receiver antenna and the first-stage mixer, significantly improves module sensitivity and suppresses electronics noise. The receiver module has a 20 dB gain improvement compared with the mini-lens approach and better than -75 dBm sensitivity, and its electronics noise temperature has been reduced from 55000K down to 11200K. The V-band MIR system is developed for co-located multi-field investigation of MHD-scale fluctuations in the pedestal region with W-band electron cyclotron emission imaging on DIII-D tokamak.

A quantitative analysis method based on collision broadening for trace gas using terahertz heterodyne spectrometer

Quantitative analysis of trace gases is an important research field in analytical chemistry. The terahertz electronic spectrometer is one of the most powerful tools for detecting trace gas. Here, a terahertz spectrometer based on frequency multiplier chain and heterodyne detection was presented. The rotational spectra of acetonitrile (CH3CN) gas were measured in the 290–370 GHz frequency band with 100 kHz spectral resolution. The spectrometer demonstrated excellent spectral specificity and the extrapolated limit of detection for CH3CN gas of 1.4 ppm. Furthermore, a novel quantification method of trace gas was proposed based on broadening mechanisms. The CH3CN self- and nitrogen (N2)- collisional broadening coefficients were obtained experimentally for verifying the method. The CH3CN concentration of the validation group was calculated, and the relative error was 0.1%. The error analysis of the different number of measurements of the method was carried out. The method could provide a new perspective for trace gas quantitative analysis.

Material and thickness selection of dielectrics for high transmittance terahertz window and metasurface

Dielectric materials, commonly used in conventional terahertz devices, are applied in all-dielectric metasurfaces for many functional applications in recent years. Various measurement systems, including time-domain spectrometer (TDS), vector network analyzer (VNA) and Fourier transform infrared (FTIR) spectrometer, have been used to analyze the dielectric properties of common materials in terahertz region. However, only the influence of thickness or Fabry-Perot (FP) term on transmittance under a specified incident angle was considered. In this paper, the influences of refractive index, absorption coefficient and thickness on the extrema and fluctuation period of transmittance spectra are systematically analyzed for the first time. Moreover, the transmittance spectra of four plates, which are two different thicknesses of each TPX and HDPE material, were measured by 3 THz systems. These three systems are frequency multiplication chain (FMC), VNA and TDS which are corresponding to direct and coherent detection methods by electronic, and optical coherent detection method. For each plate, the transmittance spectra measured by three systems have been compared, which can obtain the average error of each system. These measurement results are in good agreement with the theoretical calculation values. The electronic coherent detection technique shows half of the test error compared with the other two techniques. The criteria for dielectrics selection proposed in this paper can provide some guidance for the selection of suitable material and thickness of high transmittance windows and the substrate of dielectric metasurfaces.

A 440–540-GHz Transmitter in 130-nm SiGe BiCMOS

This letter presents a four-way combined frequency multiplier chain (FMC), which converts a single-ended 110-135-GHz input signal to a differential 440-540-GHz output signal. The four-way combined FMC uses four identical FMCs, which consist of two amplification and two frequency doubling stages. These blocks are designed with optimized parameters to be used as the transmitter of a gas spectroscopy system at 440-540 GHz. The four-way combined FMC has 0.5 dBm measured maximum output power at 450 GHz and -4.5 dBm at 500 GHz.

240-GHz Reflectometer-Based Dielectric Sensor With Integrated Transducers in a 130-nm SiGe BiCMOS Technology

This article presents a reflectometer-based on-chip dielectric sensor with integrated transducers at 240 GHz. The chip simplifies the measurement of a vector network analyzer (VNA) to sense the incident and reflected waves by using two heterodyne mixer-based receivers with a dielectric sensing element. Radio frequency (RF) and local oscillator (LO) submillimeter waves are generated by two frequency multiplier chains, respectively. Two back-to-back identical differential side-coupled directive couplers are proposed to separate the incident and reflected signals and couple them to mixers. Both transmission line and coplanar stripline transducers are proposed and integrated with reflectometer to investigate the sensitivity of dielectric sensors. The latter leads to a larger power variation of the reflectometer by providing more sufficient operating bands for the magnitude and phase slope of $S_{11}$ . The readout of the transducers upon exposure to liquids is performed by the measurement of their reflected signals using two external excitation sources. The experimental dielectric sensing is demonstrated by using binary methanol–ethanol mixture placed on the proposed on-chip dielectric sensor in the assembled printed circuit board. It enables a maximum 8 dB of the power difference between the incident and reflected channels on the measurement of liquid solvents. Both chips occupy an area of 4.03 mm2 and consume 560 mW. Along with a wide operational frequency range from 200 to 240 GHz, this simplified one-port-VNA-based on-chip device makes it feasible for the use of handle product and suitable for the submillimeter-wave dielectric spectroscopy applications.

Reinvestigation of the rotation-tunneling spectrum of the CH2OH radical

Context. The hydroxymethyl radical (CH2OH) is one of two structural isomers, together with the methoxy radical (CH3O), that can be produced by abstraction of a hydrogen atom from methanol (CH3OH). In the interstellar medium (ISM), both CH2OH and CH3O are suspected to be intermediate species in many chemical reactions, including those of formation and destruction of methanol. The determination of the CH3O/CH2OH ratio in the ISM would bring important information concerning the formation processes of these species in the gas and solid phases. Interestingly, only CH3O has been detected in the ISM so far, despite the recent first laboratory measurement of the CH2OH rotation-tunneling spectrum. This lack of detection is possibly due to the non-observation in the laboratory of the most intense rotation-tunneling transitions at low temperatures. Aims. To support further searches for the hydroxymethyl radical in space, we present a thorough spectroscopic study of its rotation-tunneling spectrum, with a particular focus on transitions involving the lowest quantum numbers of the species. Methods. We recorded the rotation-tunneling spectrum of CH2OH at room temperature in the millimeter-wave domain using a frequency multiplication chain spectrometer. A fluorine-induced H-abstraction method from methanol was used to produce the radical. Results. About 180 transitions were observed, including those involving the lowest N and Ka quantum numbers, which are predicted to be intense under cold astrophysical conditions. These transitions were fitted together with available millimeter-wave lines from the literature. A systematic observation of all components of the rotational transitions yields a large improvement of the spectroscopic parameters allowing confident searches of the hydroxymethyl radical in cold to warm environments of the ISM.

Large Amplitude Torsions in Nitrotoluene Isomers Studied by Rotational Spectroscopy and Quantum Chemistry Calculations.

Rotational spectra of ortho-nitrotoluene (2-NT) and para-nitrotoluene (4-NT) have been recorded at low and room temperatures using a supersonic jet Fourier Transform microwave (MW) spectrometer and a millimeter-wave frequency multiplier chain, respectively. Supported by quantum chemistry calculations, the spectral analysis of pure rotation lines in the vibrational ground state has allowed to characterise the rotational energy, the hyperfine structure due to the 14 N nucleus and the internal rotation splittings arising from the methyl group. For 2-NT, an anisotropic internal rotation of coupled -CH3 and -NO2 torsional motions was identified by quantum chemistry calculations and discussed from the results of the MW analysis. The study of the internal rotation splittings in the spectra of three NT isomers allowed to characterise the internal rotation potentials of the methyl group and to compare them with other mono-substituted toluene derivatives in order to study the isomeric influence on the internal rotation barrier.

220–360-GHz Broadband Frequency Multiplier Chains (x8) in 130-nm BiCMOS Technology

This article presents two broadband frequency multiplier chains (FMCs) fabricated with a standard 130-nm SiGe BiCMOS process. In both solutions, a broadband push-push frequency doubler (x2) operating at 220-360 GHz was employed. In order to properly drive such a doubler, with sufficient input power and bandwidth, two different power amplifiers (PAs) have been adopted: the former is based on a cascode configuration and the latter is based on a stacked topology. In addition, a D-band frequency quadrupler (x4) has been integrated before the PAs and doubler, to complete the design of frequency eighth tupler (x8) chains. The first FMC with the cascode PA achieves peak output power of 2.3 dBm, with maximum conversion gain (G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> ) and bandwidth of 15 dB and 127 GHz, respectively. The second FMC with the stacked PA delivers a saturated output power of 2.5 dBm, with a maximum G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</sub> and a bandwidth of 12 dB and 72 GHz, respectively. The two FMCs consume maximum dc power of 0.537 and 0.542 W. The complete design procedure of the FMCs is presented in this article. To the best of our knowledge, the reported bandwidth is state-of-the-art and widest among SiGe based FMCs.

A +3.0-dBm 115–129-GHz CMOS Power-Efficient Injection-Locked Frequency Tripler Chain

A CMOS power-efficient injection-locked (IL) frequency multiplier chain is presented in this letter. An input IL oscillator buffer, frequency tripler, and IL oscillator buffer were cascaded and designed under an optimum <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$V_{\mathrm {DD}}$ </tex-math></inline-formula> to achieve a high-power efficiency. The switched transformer presented both efficient power transfer and frequency tuning. The proposed tripler chain achieved a peak power efficiency of 3.70%, with a 3.0-dBm peak output power at 121 GHz in a 40-nm GP CMOS process. A 115–129-GHz 3-dB output bandwidth was measured under an input power of 0 dBm. The fundamental and second harmonic suppressions were greater than 30.8 and 20 dB, respectively, across the 3-dB output bandwidth. The total dc power dissipation was 53.2 mW under a supply of 0.7 V.

240-GHz Four-Channel Power-Tuning Heterodyne Sensing Readout System With Reflection and Transmission Measurements in a 130-nm SiGe BiCMOS Technology

This article presents a fully differential power-tuning heterodyne on-chip sensing readout system at 240 GHz. The chip enables the measurement of not only the transmission parameter but also the reflection parameter to sense the permittivity of different materials by using four heterodyne mixer-based receiving channels connected to a dielectric sensing element. To facilitate the operation and characterization, three frequency multiplier chains are included to generate the required two identical radio frequency (RF) and one local oscillator (LO) subterahertz signals. RF frequency multiplier chain is configured to enable a tunable power level of the RF signal by using a variable attenuator. A chip prototype using 130-nm silicon–germanium (SiGe) BiCMOS is implemented with a size of 11 mm2 and dc power consumption of 2.7 W. The measured 10-dB bandwidth of 20.8% is achieved in a frequency range from 207 to 257 GHz with 14-dB measured power-tuning range. The transmission and reflection parameters’ measurements for copper and gummi show a differentiated value in terms of magnitude and phase, which demonstrates the sensing function of the proposed readout system.

Conformational landscape and inertial defect of methoxyphenol isomers studied by mm-wave spectroscopy and quantum chemistry calculations.

Because methoxyphenols (MP) are emitted in significant quantities during biomass fires and contribute to the secondary organic aerosols formation which impacts the climate, their gas phase monitoring in the atmosphere is crucial and requires accurate rovibrational cross sections determined with a good knowledge of their ground state (GS) and vibrationally excited state (ES) molecular parameters. Therefore, the rotational spectra of the two isomers, 2-MP (guaïacol) and 4-MP (mequinol), have been measured in absorption and in emission at room temperature using a frequency multiplication chain and a mm-wave Fourier transform chirped-pulse spectrometer, respectively. Guided by quantum chemistry calculations, the conformational landscape has been characterised and the observation of only one rotamer in the spectra of 2-MP and 4-MP has been explained. For 2-MP, the most stable conformation is justified by an intramolecular O-H⋯OCH3 hydrogen-bond which has been characterised by a topology analysis of the electron density. In a global fit including more than 30 000 line assignments, rotational and quartic centrifugal constants of the GS and the three lowest energy ES have been determined allowing to reproduce the millimeter-wave spectra at the experimental accuracy. The same work has been performed on the cis-rotamer of 4-MP highlighting some perturbations marring the fit quality for two vibrationally ES. Finally, the isomeric dependence of the negative inertial defect ΔI agrees with that of the lowest energy out of plane mode ν45, and the variation of ΔI with the degree of vibrational excitation allows a fine estimation of v45 = 1 vibrational wavenumber.

Integrated 240-GHz Dielectric Sensor With dc Readout Circuit in a 130-nm SiGe BiCMOS Technology

This paper presents a high-integration miniaturized dielectric spectroscopy system for sensing the change of permittivity at 240 GHz in the SiGe BiCMOS technology. The sensor features a transducer with a resonator to perform bandpass frequency response, whose complex value of $S_{21}$ is varied with the permittivity of the sample under test. This variation can be detected and recorded as the change of amplitude and phase of the 240-GHz in-phase and quadrature direct conversion mixer. An external 30-GHz source is employed with cascade frequency multiplier chain to deliver a signal through the system with a wide tuning range of 215–245 GHz. An additional probe is employed to carry the sample and implement chip measurements on the probe station. The sensing function of this system is performed with the leaded wire as a metallic sample to be placed on the top of the transducer. Based on the measured dc output voltage changes, the calculated magnitude and phase of IQ signal in the 215–245-GHz range are used to estimate the complex permittivity change of MUTs. This dielectric spectroscopy system is also suitable for sensing the complexy permittivity change at higher frequencies in the future terahertz Lab-on-Chip measurements.

High-resolution THz gain measurements in optically pumped ammonia.

This study is aimed at the evaluation of THz gain properties in an optically pumped NH3 gas. NH3 molecules undergo rotational-vibrational excitation by mid-infrared (MIR) optical pumping provided by a MIR quantum cascade laser (QCL) which enables precise tuning to the NH3 infrared transition around 10.3 μm. Pure inversion transitions, (J = 3, K = 3) at 1.073 THz and (J = 4, K = 4) at 1.083 THz were selected. The THz measurements were performed using a THz frequency multiplier chain. The results show line profiles with and without optical pumping at different NH3 pressures, and with different MIR tuning. The highest gain at room temperature under the best conditions obtained during single pass on the (3,3) line was 10.1 dB×m-1 at 26 μbar with a pumping power of 40 mW. The (4,4) line showed lower gain of 6.4 dB×m-1 at 34 μbar with a pumping power of 62 mW. To our knowledge these THz gains are the highest measured in a continuous-wave MIR pumped gas.

A 216–256 GHz fully differential frequency multiplier-by-8 chain with 0 dBm output power

AbstractThis work presents a fully differential wideband and low power 240 GHz multiplier-by-8 chain, manufactured in IHP's 130 nm SiGe:C BiCMOS technology with fT/fmax = 300/500 GHz. A single ended 30 GHz input signal is multiplied by 8 using Gilbert cell-based quadrupler and doubler, and then amplified with a wideband differential 3-stage cascode amplifier. To achieve wide bandwidth and optimize for power consumption, the power budget has been designed in order to operate the frequency multipliers and the output amplifier in saturation. With this architecture the presented circuit achieves a 3 dB bandwidth of 40 GHz, meaning a relative 3 dB bandwidth of 17%, and a peak saturated output power of 0 dBm. Harmonic rejections better than 25 dB were measured for the 5th, 6th, and 7th harmonics. It dissipates 255 mW from 3 V supply which results in drain efficiency of 0.4%, while occupying 1.2 mm2. With these characteristics the presented circuit suits very well as a frequency multiplier chain for driving balanced mixers in 240 GHz transceivers for radar, communication, and sensing applications.