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Intermediate frequency (IF) gain bandwidth (GBW) of terahertz (THz) mixers based on superconducting niobium nitride (NbN) hot electron bolometers (HEBs) has been improved. The IF GBW has been measured by 2 different methods and same values up to 7 GHz have been obtained.
JPL has developed an eight-element radar transceiver array operating at 340 GHz with a 9% bandwidth. The array elements were fabricated using an unconventional stack of micromachined silicon wafers to house the transceiver's submillimeter-wave diode frequency multipliers and mixers. Here we report on the performance assessment of the array elements and present radar images that showcase its potential...
Two backward wave oscillator (BWO) designs are proposed for a 346 GHz source for fusion plasma diagnostics applicable for the MAST and NSTX-U devices. Both designs feature a double grating machined from bulk copper, using nano-machining technology.
Millimeter-wave imaging diagnostics have been developed in the 50∼150 GHz region which provide 2D localized measurements of electron temperature and electron density fluctuations inside magnetic fusion plasma devices. New mixer and antenna geometries are being developed to extend these techniques to THz frequencies. Also under investigation are beam shaping techniques which offer the possibility of...
We report on the laboratory testing of KAPPa, a 16-pixel proof-of-concept array to enable the creation THz imaging spectrometer with −1000 pixels. Creating an array an order of magnitude larger than the existing state of the art of 64 pixels requires a simple and robust design as well as improvements to mixer selection, testing, and assembly. We present the characterization of the single pixel prototype,...
The performance of heterodyne receivers for frequencies beyond 1.4 THz will be reviewed. Emphasis will be on the development of the 4.7-THz frequency channel for the GREAT heterodyne spectrometer on SOFIA. This receiver is based on a phonon-cooled hot-electron bolometric mixer and a quantum-cascade laser as local oscillator.
We have phase locked a 4.7 THz Quantum Cascade Laser (QCL) to a stable microwave reference signal. The QCL is a 3rd order distributed feedback (DFB) laser with a low power consumption of 0.5 W and radiation power of about 0.25 mW. One of the key elements in our experimental setup is a superlattice diode operating as a harmonic mixer and providing the beat signal between the QCL and the 24th harmonic...
This letter presents the design and fabrication of a 340GHz sub-harmonic mixer (SHM), which mainly includes a pair of anti-parallel planar Schottky diodes fixed onto a quartz-based microstrip circuit chip. At room temperature, the mixer performances were measured in 313GHz-360GHz. Our recent results show that the signal side band (SSB) conversion losses were from 9.78 dB to 12.74dB, and the double...
A practical solution using a THz optical source as a Local Oscillator (LO) for radio astronomy above 2 THz requires that the source to be frequency or phase locked. Therefore, it is crucial to enable a high conversion efficiency heterodyne mixer to produce a stable LO source that can operate at room temperature. Harmonically pumped 1.9–3.2 THz Schottky diode based mixers have been designed to enable...
SuperCam is a 64-pixel heterodyne imaging array designed for use on ground-based submillimeter telescopes to observe the astrophysically important CO J=3–2 emission line at 345 GHz. Each pixel in the array has its own integrated superconductor-insulator-superconductor (SIS) mixer and low noise amplifier. In spring 2012, SuperCam was installed on the University of Arizona Submillimeter Telescope (SMT)...
This paper presents a tentative modelling of Superconductor-Insulator-Superconductor (SIS) junction used as frequency multiplier. The model is tested against the experimental data presented earlier and demonstrates good agreement between the measured data and simulation. Such a model will improve understanding of the SIS junction used as frequency multiplier and hopefully lead us to demonstration...
A compact, robust, and reliable broadband receiver has been developed for the ITER ECE diagnostic system. The system provides continuous diagnostic coverage of the 200–300 GHz band using all solid-state components and less than 10W total power dissipation.
Heterodyne receivers at millimeter and submillimeter wavelength are widely used for radiometric spectral line observations for atmospheric remote sensing or radio astronomy. The quantitative analysis of such observations requires an accurate knowledge of the mixers's sideband ratio. In addition, its potential sensitivity to spurious harmonics needs to be well understood. In this paper, we discuss...
A comparison between two mixer designs is presented in this paper. The electromagnetic performances of fourth-harmonic mixer are compared with the ones of a sub-harmonic mixer both working at an RF frequency of 440 GHz. The best results in terms of noise temperature and conversion loss values are obtained for the sub-harmonic mixer; however, a higher local oscillator frequency is required to pump...
We report on a 4.7 THz heterodyne receiver being developed to fly on the Stratospheric Terahertz Observatory (STO-2) balloon platform. The receiver is based on a single pixel hot electron bolometer (HEB) mixer pumped by a 4.7 THz 3rd order distributed feedback quantum cascade laser (QCL) as local oscillator and is designed for high resolution spectroscopy of the astronomically important neutral oxygen...
Schottky mixers have excellent sensitivity at room temperature and improve upon cooling, which make them a good candidate for long duration measurements where cryogens are difficult or impossible to use. The development and testing of a 1.46 THz Schottky diode receiver will be described, including measurements of the cryogenic performance of the local oscillator and the mixer. A receiver noise temperature...
A real-time wireless data link experiment at a carrier frequency of 120GHz is presented in this paper. Both the receiver and transmitter employ Schottky diode subharmonic mixers as direct frequency up- and down-converters without introducing amplifiers at the first stage of the receiver or at the last stage of the transmitter. The conversion loss of the subharmonic mixer is less than 10dB over 105∼135GHz...
We have developed a phase-locking system of a 3.1THz QCL (Quantum Cascade Laser) using a low noise hot electron bolometer mixer (HEBM) and a THz reference. The THz reference was generated by photomixing two optical modes of a frequency comb. The THz-QCL and HEBM devices are fabricated in our laboratory. A line width of the phase-locked QCL of narrower than 1Hz was achieved.
We present work on graphene devices and circuits for microwave and millimeter wave applications, including detectors, mixers and microwave amplifiers. Field effect transistors were fabricated from exfoliated graphene and graphene grown using chemical vapor deposition (CVD). Results from noise assessment in the microwave region, millimeter wave mixers and 0.6THz direct detectors are presented.
We report on our hot electron bolometer mixer development for the focal plane array extension upGREAT of the German Receiver for Astronomy at Terahertz frequencies (GREAT) operated on SOFIA. For (up)GREAT we have pushed the waveguide technology to 4.7 THz and present RF performance results. We describe the RF planar circuit design, the micro fabrication employing NbN microbridges on 2 μm thin Si membrane...
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