GaN transistors on Si for switching and high-frequency applications
NASA Astrophysics Data System (ADS)
Ueda, Tetsuzo; Ishida, Masahiro; Tanaka, Tsuyoshi; Ueda, Daisuke
2014-10-01
In this paper, recent advances of GaN transistors on Si for switching and high-frequency applications are reviewed. Novel epitaxial structures including superlattice interlayers grown by metal organic chemical vapor deposition (MOCVD) relieve the strain and eliminate the cracks in the GaN over large-diameter Si substrates up to 8 in. As a new device structure for high-power switching application, Gate Injection Transistors (GITs) with a p-AlGaN gate over an AlGaN/GaN heterostructure successfully achieve normally-off operations maintaining high drain currents and low on-state resistances. Note that the GITs on Si are free from current collapse up to 600 V, by which the drain current would be markedly reduced after the application of high drain voltages. Highly efficient operations of an inverter and DC-DC converters are presented as promising applications of GITs for power switching. The high efficiencies in an inverter, a resonant LLC converter, and a point-of-load (POL) converter demonstrate the superior potential of the GaN transistors on Si. As for high-frequency transistors, AlGaN/GaN heterojuction field-effect transistors (HFETs) on Si designed specifically for microwave and millimeter-wave frequencies demonstrate a sufficiently high output power at these frequencies. Output powers of 203 W at 2.5 GHz and 10.7 W at 26.5 GHz are achieved by the fabricated GaN transistors. These devices for switching and high-frequency applications are very promising as future energy-efficient electronics because of their inherent low fabrication cost and superior device performance.
NASA Astrophysics Data System (ADS)
Stappel, M.; Steinborn, R.; Kolbe, D.; Walz, J.
2013-07-01
We present a high power single-frequency ytterbium fiber amplifier system with an output power of 30 W at 1091 nm. The amplifier system consists of two stages, a preamplifier stage in which amplified spontaneous emission is efficiently suppressed (>40 dB) and a high power amplifier with an efficiency of 52%. Two different approaches to frequency doubling are compared. We achieve 8.6 W at 545.5 nm by single-pass frequency doubling in a MgO-doped periodically poled stoichiometric LiTaO3 crystal and up to 19.3 W at 545.5 nm by frequency doubling with a lithium-triborate crystal in an external enhancement cavity.
Magnetic materials for mobile communication antennas substrate application
NASA Astrophysics Data System (ADS)
Chen, Hui; Liang, Difei; Li, Weijia; Pang, Chao
2017-11-01
In this work, 3Ba0.7Sr0.3O·2CoO·10.8Fe2O3 and Ba2Co2Fe12O22 had been fabricated successfully by conventional ceramic process. Crystallographic structure and electromagnetic properties of two kind of hexagonal ferrite with different sintering temperature were investigated. X-ray Diffraction (XRD), Agilent-N5230A Network Analyzer were used to measure ferrite samples. The mobile phone antenna performance was analysed by HFSS. The results revealed that the main phase of two ferrite samples generated at lower temperature due to additive. The optimized parameters of ferrite are sintering temperature at 1000°C. And to emulate antenna model by HFSS find that Z-type and Y-type ferrite substrate can contribute to antenna frequency shifting, radiation efficiency were affected a little.
NASA Astrophysics Data System (ADS)
Ibrahim, Omar A.; Elwi, Taha A.; Islam, Naz E.
2012-11-01
A miniaturized microstrip antenna is analyzed for implantable biomedical applications. The antenna is designed using two different commercial software packages, CST Microwave Studio and HFSS, to validate the results. The proposed design operates in the WMTS frequency band. The antenna performance is tested inside the human body, Hugo model. The antenna design is readjusted to get the desired resonant frequency. The resonant frequency, bandwidth, gain, and radiation pattern of the proposed antenna are provided in this paper. Furthermore, the effect of losses inside human body due to the fat layer is recognized.
Design, simulation and analysis a microstrip antenna using PU-EFB substrate
NASA Astrophysics Data System (ADS)
Mahmud, S. N. S.; Jusoh, M. A.; Jasim, S. E.; Zamani, A. H.; Abdullah, M. H.
2018-04-01
A low cost, light weight and easy to fabricate are the most important factor for future antennas. Microstrip patch antennas offer these advantages and suitable for communication and sensor application. This paper presents a design of simple microstrip patch antenna working on operating frequency of 2.4 GHz. The designed process has been carried out using MATLAB and HFSS software by entering 2.3 for the dielectric constant of PU-EFB. The results showed that high return loss, low bandwidth and good antenna radiation efficiency of which are -21.98 dB, 0.28 dB and 97.33%, respectively.
Real-time, high frequency QRS electrocardiograph with reduced amplitude zone detection
NASA Technical Reports Server (NTRS)
Schlegel, Todd T. (Inventor); DePalma, Jude L. (Inventor); Moradi, Saeed (Inventor)
2009-01-01
Real time cardiac electrical data are received from a patient, manipulated to determine various useful aspects of the ECG signal, and displayed in real time in a useful form on a computer screen or monitor. The monitor displays the high frequency data from the QRS complex in units of microvolts, juxtaposed with a display of conventional ECG data in units of millivolts or microvolts. The high frequency data are analyzed for their root mean square (RMS) voltage values and the discrete RMS values and related parameters are displayed in real time. The high frequency data from the QRS complex are analyzed with imbedded algorithms to determine the presence or absence of reduced amplitude zones, referred to herein as ''RAZs''. RAZs are displayed as ''go, no-go'' signals on the computer monitor. The RMS and related values of the high frequency components are displayed as time varying signals, and the presence or absence of RAZs may be similarly displayed over time.
High-frequency tone-pip-evoked otoacoustic emissions in chinchillas
NASA Astrophysics Data System (ADS)
Siegel, Jonathan H.; Charaziak, Karolina K.
2015-12-01
We measured otoacoustic emissions in anesthetized chinchillas evoked by short (1 ms) high-frequency (4 kHz) tone-pips (TEOAE) using either a compression or suppression method to separate the stimulus from the emission. Both methods revealed consistent features of the TEOAEs. The main spectral band of the emission generally corresponded to the spectrum of the stimulus, exhibiting a group delay similar to that of SFOAEs [9]. However, a second spectral band below 1.5 kHz, clearly separated from the low-frequency cut-off frequency of the stimulus spectrum, corresponded to an amplitude modulation of the waveform of the TEOAE. The group delay of this low-frequency band was similar to that of the main band near the probe frequency. The average level and group delay of the main band declined monotonically when revealed as the suppressor frequency was raised above the probe. The low-frequency band was more sensitive than the main band to shifts in compound action potential thresholds near the probe frequency induced by acute exposure to intense tones. Taken together, the experiments indicate that both the main and low-frequency bands of the TEOAE are generated primarily near the cochlear region maximally stimulated by the probe, but that significant contributions arise over a large region even more basal.
Research for the jamming mechanism of high-frequency laser to the laser seeker
NASA Astrophysics Data System (ADS)
Zheng, Xingyuan; Zhang, Haiyang; Wang, Yunping; Feng, Shuang; Zhao, Changming
2013-08-01
High-frequency laser will be able to enter the enemy laser signal processing systems without encoded identification and a copy. That makes it one of the research directions of new interference sources. In order to study the interference mechanism of high-frequency laser to laser guided weapons. According to the principle of high-frequency laser interference, a series of related theoretical models such as a semi-active laser seeker coded identification model, a time door model, multi-signal processing model and a interference signal modulation processing model are established. Then seeker interfere with effective 3σ criterion is proposed. Based on this, the study of the effect of multi-source interference and signal characteristics of the effect of high repetition frequency laser interference are key research. According to the simulation system testing, the results show that the multi-source interference and interference signal frequency modulation can effectively enhance the interference effect. While the interference effect of the interference signal amplitude modulation is not obvious. The research results will provide the evaluation of high-frequency laser interference effect and provide theoretical references for high-frequency laser interference system application.
Nanolaminated Permalloy Core for High-Flux, High-Frequency Ultracompact Power Conversion
DOE Office of Scientific and Technical Information (OSTI.GOV)
Kim, J; Kim, M; Galle, P
2013-09-01
Metallic magnetic materials have desirable magnetic properties, including high permeability, and high saturation flux density, when compared with their ferrite counterparts. However, eddy-current losses preclude their use in many switching converter applications, due to the challenge of simultaneously achieving sufficiently thin laminations such that eddy currents are suppressed (e.g., 500 nm-1 mu m for megahertz frequencies), while simultaneously achieving overall core thicknesses such that substantial power can be handled. A CMOS-compatible fabrication process based on robot-assisted sequential electrodeposition followed by selective chemical etching has been developed for the realization of a core of substantial overall thickness (tens to hundreds ofmore» micrometers) comprised of multiple, stacked permalloy (Ni80Fe20) nanolaminations. Tests of toroidal inductors with nanolaminated cores showed negligible eddy-current loss relative to total core loss even at a peak flux density of 0.5 T in the megahertz frequency range. To illustrate the use of these cores, a buck power converter topology is implemented with switching frequencies of 1-2 MHz. Power conversion efficiency greater than 85% with peak operating flux density of 0.3-0.5 T in the core and converter output power level exceeding 5 W was achieved.«less
NASA Astrophysics Data System (ADS)
Hardie, Marcus; Lisson, Shaun; Doyle, Richard; Cotching, William
2013-01-01
Preferential flow in agricultural soils has been demonstrated to result in agrochemical mobilisation to shallow ground water. Land managers and environmental regulators need simple cost effective techniques for identifying soil - land use combinations in which preferential flow occurs. Existing techniques for identifying preferential flow have a range of limitations including; often being destructive, non in situ, small sampling volumes, or are subject to artificial boundary conditions. This study demonstrated that high frequency soil moisture monitoring using a multi-sensory capacitance probe mounted within a vertically rammed access tube, was able to determine the occurrence, depth, and wetting front velocity of preferential flow events following rainfall. Occurrence of preferential flow was not related to either rainfall intensity or rainfall amount, rather preferential flow occurred when antecedent soil moisture content was below 226 mm soil moisture storage (0-70 cm). Results indicate that high temporal frequency soil moisture monitoring may be used to identify soil type - land use combinations in which the presence of preferential flow increases the risk of shallow groundwater contamination by rapid transport of agrochemicals through the soil profile. However use of high frequency based soil moisture monitoring to determine agrochemical mobilisation risk may be limited by, inability to determine the volume of preferential flow, difficulty observing macropore flow at high antecedent soil moisture content, and creation of artificial voids during installation of access tubes in stony soils.
High frequency plasma generator for ion thrusters
NASA Technical Reports Server (NTRS)
Goede, H.; Divergilio, W. F.; Fosnight, V. V.; Komatsu, G.
1984-01-01
The results of a program to experimentally develop two new types of plasma generators for 30 cm electrostatic argon ion thrusters are presented. The two plasma generating methods selected for this study were by radio frequency induction (RFI), operating at an input power frequency of 1 MHz, and by electron cyclotron heating (ECH) at an operating frequency of 5.0 GHz. Both of these generators utilize multiline cusp permanent magnet configurations for plasma confinement and beam profile optimization. The program goals were to develop a plasma generator possessing the characteristics of high electrical efficiency (low eV/ion) and simplicity of operation while maintaining the reliability and durability of the conventional hollow cathode plasma sources. The RFI plasma generator has achieved minimum discharge losses of 120 eV/ion while the ECH generator has obtained 145 eV/ion, assuming a 90% ion optical transparency of the electrostatic acceleration system. Details of experimental tests with a variety of magnet configurations are presented.
Microwave Imaging Sensor Using Compact Metamaterial UWB Antenna with a High Correlation Factor.
Islam, Md Moinul; Islam, Mohammad Tariqul; Faruque, Mohammad Rashed Iqbal; Samsuzzaman, Md; Misran, Norbahiah; Arshad, Haslina
2015-07-23
The design of a compact metamaterial ultra-wideband (UWB) antenna with a goal towards application in microwave imaging systems for detecting unwanted cells in human tissue, such as in cases of breast cancer, heart failure and brain stroke detection is proposed. This proposed UWB antenna is made of four metamaterial unit cells, where each cell is an integration of a modified split ring resonator (SRR), capacitive loaded strip (CLS) and wire, to attain a design layout that simultaneously exhibits both a negative magnetic permeability and a negative electrical permittivity. This design results in an astonishing negative refractive index that enables amplification of the radiated power of this reported antenna, and therefore, high antenna performance. A low-cost FR4 substrate material is used to design and print this reported antenna, and has the following characteristics: thickness of 1.6 mm, relative permeability of one, relative permittivity of 4.60 and loss tangent of 0.02. The overall antenna size is 19.36 mm × 27.72 mm × 1.6 mm where the electrical dimension is 0.20 λ × 0.28 λ × 0.016 λ at the 3.05 GHz lower frequency band. Voltage Standing Wave Ratio (VSWR) measurements have illustrated that this antenna exhibits an impedance bandwidth from 3.05 GHz to more than 15 GHz for VSWR < 2 with an average gain of 4.38 dBi throughout the operating frequency band. The simulations (both HFSS and computer simulation technology (CST)) and the measurements are in high agreement. A high correlation factor and the capability of detecting tumour simulants confirm that this reported UWB antenna can be used as an imaging sensor.
Microwave Imaging Sensor Using Compact Metamaterial UWB Antenna with a High Correlation Factor
Islam, Md. Moinul; Islam, Mohammad Tariqul; Faruque, Mohammad Rashed Iqbal; Samsuzzaman, Md.; Misran, Norbahiah; Arshad, Haslina
2015-01-01
The design of a compact metamaterial ultra-wideband (UWB) antenna with a goal towards application in microwave imaging systems for detecting unwanted cells in human tissue, such as in cases of breast cancer, heart failure and brain stroke detection is proposed. This proposed UWB antenna is made of four metamaterial unit cells, where each cell is an integration of a modified split ring resonator (SRR), capacitive loaded strip (CLS) and wire, to attain a design layout that simultaneously exhibits both a negative magnetic permeability and a negative electrical permittivity. This design results in an astonishing negative refractive index that enables amplification of the radiated power of this reported antenna, and therefore, high antenna performance. A low-cost FR4 substrate material is used to design and print this reported antenna, and has the following characteristics: thickness of 1.6 mm, relative permeability of one, relative permittivity of 4.60 and loss tangent of 0.02. The overall antenna size is 19.36 mm × 27.72 mm × 1.6 mm where the electrical dimension is 0.20 λ × 0.28 λ × 0.016 λ at the 3.05 GHz lower frequency band. Voltage Standing Wave Ratio (VSWR) measurements have illustrated that this antenna exhibits an impedance bandwidth from 3.05 GHz to more than 15 GHz for VSWR < 2 with an average gain of 4.38 dBi throughout the operating frequency band. The simulations (both HFSS and computer simulation technology (CST)) and the measurements are in high agreement. A high correlation factor and the capability of detecting tumour simulants confirm that this reported UWB antenna can be used as an imaging sensor. PMID:28793461
High-Frequency Mapping of the IPV6 Internet Using YARRP
2017-03-01
NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA APPLIED CYBER OPERATIONS CAPSTONE PROJECT REPORT HIGH -FREQUENCY MAPPING OF THE IPV6 INTERNET USING...03-30-2017 4. TITLE AND SUBTITLE HIGH -FREQUENCY MAPPING OF THE IPV6 INTERNET USING YARRP 5. FUNDING NUMBERS RCKHX 6. AUTHOR(S) Eric W. Gaston 7...the U.S. Government. IRB Protocol Number: N/A. 12a. DISTRIBUTION / AVAILABILITY STATEMENT Approved for public release. Distribution is unlimited. 12b
Planck 2013 results. VI. High Frequency Instrument data processing
NASA Astrophysics Data System (ADS)
Planck Collaboration; Ade, P. A. R.; Aghanim, N.; Armitage-Caplan, C.; Arnaud, M.; Ashdown, M.; Atrio-Barandela, F.; Aumont, J.; Baccigalupi, C.; Banday, A. J.; Barreiro, R. B.; Battaner, E.; Benabed, K.; Benoît, A.; Benoit-Lévy, A.; Bernard, J.-P.; Bersanelli, M.; Bielewicz, P.; Bobin, J.; Bock, J. J.; Bond, J. R.; Borrill, J.; Bouchet, F. R.; Boulanger, F.; Bowyer, J. W.; Bridges, M.; Bucher, M.; Burigana, C.; Cardoso, J.-F.; Catalano, A.; Chamballu, A.; Chary, R.-R.; Chen, X.; Chiang, H. C.; Chiang, L.-Y.; Christensen, P. R.; Church, S.; Clements, D. L.; Colombi, S.; Colombo, L. P. L.; Combet, C.; Couchot, F.; Coulais, A.; Crill, B. P.; Curto, A.; Cuttaia, F.; Danese, L.; Davies, R. D.; Davis, R. J.; de Bernardis, P.; de Rosa, A.; de Zotti, G.; Delabrouille, J.; Delouis, J.-M.; Désert, F.-X.; Dickinson, C.; Diego, J. M.; Dole, H.; Donzelli, S.; Doré, O.; Douspis, M.; Dunkley, J.; Dupac, X.; Efstathiou, G.; Enßlin, T. A.; Eriksen, H. K.; Finelli, F.; Forni, O.; Frailis, M.; Fraisse, A. A.; Franceschi, E.; Galeotta, S.; Ganga, K.; Giard, M.; Giardino, G.; Girard, D.; Giraud-Héraud, Y.; González-Nuevo, J.; Górski, K. M.; Gratton, S.; Gregorio, A.; Gruppuso, A.; Gudmundsson, J. E.; Hansen, F. K.; Hanson, D.; Harrison, D.; Helou, G.; Henrot-Versillé, S.; Herent, O.; Hernández-Monteagudo, C.; Herranz, D.; Hildebrandt, S. R.; Hivon, E.; Hobson, M.; Holmes, W. A.; Hornstrup, A.; Hou, Z.; Hovest, W.; Huffenberger, K. M.; Hurier, G.; Jaffe, A. H.; Jaffe, T. R.; Jones, W. C.; Juvela, M.; Keihänen, E.; Keskitalo, R.; Kisner, T. S.; Kneissl, R.; Knoche, J.; Knox, L.; Kunz, M.; Kurki-Suonio, H.; Lagache, G.; Lamarre, J.-M.; Lasenby, A.; Laureijs, R. J.; Lawrence, C. R.; Le Jeune, M.; Leonardi, R.; Leroy, C.; Lesgourgues, J.; Liguori, M.; Lilje, P. B.; Linden-Vørnle, M.; López-Caniego, M.; Lubin, P. M.; Macías-Pérez, J. F.; MacTavish, C. J.; Maffei, B.; Mandolesi, N.; Maris, M.; Marleau, F.; Marshall, D. J.; Martin, P. G.; Martínez-González, E.; Masi, S.; Massardi, M.; Matarrese, S.; Matthai, F.; Mazzotta, P.; McGehee, P.; Meinhold, P. R.; Melchiorri, A.; Melot, F.; Mendes, L.; Mennella, A.; Migliaccio, M.; Mitra, S.; Miville-Deschênes, M.-A.; Moneti, A.; Montier, L.; Morgante, G.; Mortlock, D.; Mottet, S.; Munshi, D.; Murphy, J. A.; Naselsky, P.; Nati, F.; Natoli, P.; Netterfield, C. B.; Nørgaard-Nielsen, H. U.; North, C.; Noviello, F.; Novikov, D.; Novikov, I.; Orieux, F.; Osborne, S.; Oxborrow, C. A.; Paci, F.; Pagano, L.; Pajot, F.; Paladini, R.; Paoletti, D.; Pasian, F.; Patanchon, G.; Perdereau, O.; Perotto, L.; Perrotta, F.; Piacentini, F.; Piat, M.; Pierpaoli, E.; Pietrobon, D.; Plaszczynski, S.; Pointecouteau, E.; Polenta, G.; Ponthieu, N.; Popa, L.; Poutanen, T.; Pratt, G. W.; Prézeau, G.; Prunet, S.; Puget, J.-L.; Rachen, J. P.; Racine, B.; Reach, W. T.; Rebolo, R.; Reinecke, M.; Remazeilles, M.; Renault, C.; Ricciardi, S.; Riller, T.; Ristorcelli, I.; Rocha, G.; Rosset, C.; Roudier, G.; Rowan-Robinson, M.; Rusholme, B.; Sanselme, L.; Santos, D.; Sauvé, A.; Savini, G.; Scott, D.; Shellard, E. P. S.; Spencer, L. D.; Starck, J.-L.; Stolyarov, V.; Stompor, R.; Sudiwala, R.; Sureau, F.; Sutton, D.; Suur-Uski, A.-S.; Sygnet, J.-F.; Tauber, J. A.; Tavagnacco, D.; Techene, S.; Terenzi, L.; Tomasi, M.; Tristram, M.; Tucci, M.; Umana, G.; Valenziano, L.; Valiviita, J.; Van Tent, B.; Vibert, L.; Vielva, P.; Villa, F.; Vittorio, N.; Wade, L. A.; Wandelt, B. D.; White, S. D. M.; Yvon, D.; Zacchei, A.; Zonca, A.
2014-11-01
Wedescribe the processing of the 531 billion raw data samples from the High Frequency Instrument (HFI), which we performed to produce six temperature maps from the first 473 days of Planck-HFI survey data. These maps provide an accurate rendition of the sky emission at 100, 143, 217, 353, 545, and 857GHz with an angular resolution ranging from 9.´7 to 4.´6. The detector noise per (effective) beam solid angle is respectively, 10, 6 , 12, and 39 μK in the four lowest HFI frequency channels (100-353GHz) and 13 and 14 kJy sr-1 in the 545 and 857 GHz channels. Relative to the 143 GHz channel, these two high frequency channels are calibrated to within 5% and the 353 GHz channel to the percent level. The 100 and 217 GHz channels, which together with the 143 GHz channel determine the high-multipole part of the CMB power spectrum (50 <ℓ < 2500), are calibrated relative to 143 GHz to better than 0.2%.
An integrated signal conditioner for high-frequency inductive position sensors
NASA Astrophysics Data System (ADS)
Rahal, Mohamad; Demosthenous, Andreas
2010-01-01
This paper describes the design, implementation and evaluation of a signal conditioner application-specific integrated circuit (ASIC) for high-frequency inductive non-contact position sensors. These sensors employ a radio frequency technology based on an antenna planar arrangement and a resonant target, have a high inherent resolution (0.1% of antenna length) and can measure target position over a wide distance range (<0.1 mm to >10 m). However, due to the relatively high-frequency excitation (1 MHz typically) and to the specific layouts of these sensors, there is unwanted capacitive coupling between the transmitter and receiver coils; this type of distortion reduces linearity and resolution. The ASIC, which is the first generation of its kind for this type of sensor, employs a differential mixer topology which suppresses the capacitive coupling offsets. The system architecture and circuit details are presented. The ASIC was fabricated in a 0.6 µm high-voltage CMOS technology occupying an area of 8 mm2. It dissipates about 30 mA from a 24 V power supply. The ASIC was tested with a high-frequency inductive position sensor (with an antenna length of 10.8 cm). The measured input-referred offset due to transmitter crosstalk is on average about 22 µV over a wide phase difference variation (-99° to +117°) between the transmitter and demodulating signals.
Interaural time sensitivity of high-frequency neurons in the inferior colliculus.
Yin, T C; Kuwada, S; Sujaku, Y
1984-11-01
Recent psychoacoustic experiments have shown that interaural time differences provide adequate cues for lateralizing high-frequency sounds, provided the stimuli are complex and not pure tones. We present here physiological evidence in support of these findings. Neurons of high best frequency in the cat inferior colliculus respond to interaural phase differences of amplitude modulated waveforms, and this response depends upon preservation of phase information of the modulating signal. Interaural phase differences were introduced in two ways: by interaural delays of the entire waveform and by binaural beats in which there was an interaural frequency difference in the modulating waveform. Results obtained with these two methods are similar. Our results show that high-frequency cells can respond to interaural time differences of amplitude modulated signals and that they do so by a sensitivity to interaural phase differences of the modulating waveform.
How High Frequency Trading Affects a Market Index
Kenett, Dror Y.; Ben-Jacob, Eshel; Stanley, H. Eugene; gur-Gershgoren, Gitit
2013-01-01
The relationship between a market index and its constituent stocks is complicated. While an index is a weighted average of its constituent stocks, when the investigated time scale is one day or longer the index has been found to have a stronger effect on the stocks than vice versa. We explore how this interaction changes in short time scales using high frequency data. Using a correlation-based analysis approach, we find that in short time scales stocks have a stronger influence on the index. These findings have implications for high frequency trading and suggest that the price of an index should be published on shorter time scales, as close as possible to those of the actual transaction time scale. PMID:23817553
A high-performance Hg(+) trapped ion frequency standard
NASA Technical Reports Server (NTRS)
Prestage, J. D.; Tjoelker, R. L.; Dick, G. J.; Maleki, L.
1992-01-01
A high-performance frequency standard based on (199)Hg(+) ions confined in a hybrid radio frequency (RF)/dc linear ion trap is demonstrated. This trap permits storage of large numbers of ions with reduced susceptibility to the second-order Doppler effect caused by the RF confining fields. A 160-mHz-wide atomic resonance line for the 40.5-GHz clock transition is used to steer the output of a 5-mHz crystal oscillator to obtain a stability of 2 x 10(exp -15) for 24,000-second averaging times. Measurements with a 37-mHz line width for the Hg(+) clock transition demonstrate that the inherent stability for this frequency standard is better than 1 x 10(exp -15) at 10,000-second averaging times.
Relationship between low and high frequencies in the \\delta Scuti star KIC 9764965
NASA Astrophysics Data System (ADS)
Rostopchina, A.; Breger, M.
2014-10-01
Two years of Kepler spacecraft data of the \\delta Sct/\\gamma Dor star KIC 9764965 revealed 67 statistically significant frequencies from 0.45 to 59.17 c d-1 (0.005 to 0.685 mHz). The 19 low frequencies do not show equidistant period spacing predicted for gravity modes of successive radial order. We note a favored frequency spacing of 2.053 c d-1 that appears in both the low-frequency (gravity mode) region and high-frequency (pressure mode) regions. The value of this frequency spacing also occurs as a dominant low frequency and in a high-frequency triplet. A peak at exactly twice the value of the 2.053 c d-1 mode is shown not to be a Fourier harmonic of the low-frequency peak due to a different amplitude variability. This behavior is also seen in other \\delta Sct stars. The test for resonant mode coupling between low and high frequencies could not be carried out due to the small amplitudes of the peaks, making it difficult to separate the parent and child modes.
