High-frequency measurements at cryogenic temperatures to 125 K of 0.3- mu m gate length GaAs-Al/sub 0.3/Ga/sub 0.7/As metal-insulator-semiconductor field-effect transistors (MISFETs) with a doped ...channel are discussed. Experimental results demonstrate significant improvement in performance including an increase in the maximum frequency of oscillation from 70 to 81 GHz and an increase in the unity current gain cutoff frequency from 46 to 57 GHz. Independently determined decreases in electron mobility and increases in electron velocity under similar conditions lead to the conclusion that carrier velocity and not mobility controls transport in these devices. These results show the high-speed potential of doped channel MISFETs at both room temperature and cryogenic temperatures.< >
A novel CMOS subharmonic mixing technique based on threshold voltage modulation with higher LO-to-RF isolation is presented in this paper. A 2.1GHz subharmonic mixer is designed using this technique ...in a 0.18µm standard digital CMOS process by applying the LO signals at the bulk terminal of PMOS transistors. The mixer has a measured conversion gain of 10.5dB, an IIP3 of −3.5dBm, and a noise figure of 17.7dB while consuming 2.5mW in each mixer core. This circuit architecture increases the second harmonic LO-to-RF isolation to above 67dB and hence can mitigate LO leakage issues in wireless receivers.
On the origin of compact radio sources Britzen, S.; Roland, J.; Laskar, J. ...
Astronomy and astrophysics (Berlin),
08/2001, Letnik:
374, Številka:
3
Journal Article
Recenzirano
Odprti dostop
VLBI monitoring of PKS 0420-014 at 3.6 cm performed during the period 1989.32-1992.48 reveals superluminal jet components in a strongly curved jet. We present a binary black hole model capable of ...simultaneously explaining the flux-density variations and the motions of jet components on helical trajectories in active galactic nuclei. From VLBI observations we derive the characteristics of the parsec-scale jet of PKS 0420-014. Moreover, we use the optical light curve of the quasar PKS 0420-014 over the time span 1989.67-1993.93 to determine the characteristics of the binary black hole system. We propose that galactic and extragalactic radio sources with jets are due to the existence of binary systems. Extragalactic binary systems are the results of mergers and provide a natural explanation why only a small fraction of quasars are radio sources and why extragalactic radio sources are associated with elliptical galaxies. These binary systems will be one of the primary targets for the Laser Interferometer Space Antenna (LISA).
A key issue for improving the performance of third generation light sources like the ESRF storage ring is the identification and correction of resonances that have a detrimental effect in the machine ...performance. Frequency analysis of experimental data, recorded on BPMs around the ring, is a powerful tool for studying the non-linear dynamics of an accelerator in operation. In a series of experiments, experimental frequency maps were produced using the 1000-turns measurement system. These maps revealed the resonance structure in the vicinity of the nominal working point which was limiting the dynamic aperture. Their comparison with maps produced by simulations was used as a guide for understanding the storage ring non-linear model. The possibility of using the quasi-periodic approximations of the experimental data for testing the efficiency of resonance correction schemes was finally investigated
A novel analog decision-feedback equalizer (ADFE) is presented to compensate for modal dispersion in multi-mode fibers. The unclocked continuous-time technique and circuit architecture aims to ...overcome the first feedback-loop latency challenge in conventional digital or mixed-signal DFEs. An ADFE employing a 4-tap forward filter and a 1-tap feedback filter is fabricated in a 0.18-μm CMOS process. The chip with pads occupies 1.04mm 2 and draws 240mA DC current from a 1.8V supply at a typical process corner. The circuit consumes significantly less area and power than a digital or mixed-signal approach and is used to equalize 300 meters of MMF at 10-Gb/sec.
Among the hundreds of known hot Jupiters (HJs), only five have been found to have companions on short-period orbits. Within this rare class of multiple planetary systems, the architecture of WASP-47 ...is unique, hosting an HJ (planet -b) with both an inner and an outer sub-Neptunian mass companion (-e and -d, respectively) as well as an additional non-transiting, long-period giant (-c). The small period ratio between planets -b and -d boosts the transit time variation (TTV) signal, making it possible to reliably measure the masses of these planets in synergy with the radial velocity (RV) technique. In this paper, we present new space- and ground-based photometric data of WASP-47b and WASP-47-d, including 11 unpublished light curves from the ESA mission CHEOPS. We analyzed the light curves in a homogeneous way together with all the publicly available data to carry out a global \(N\)-body dynamical modeling of the TTV and RV signals. We retrieved, among other parameters, a mass and density for planet -d of \(M_\mathrm{d}=15.5\pm 0.8\) \(M_\oplus\) and \(\rho_\mathrm{d}=1.69\pm 0.22\) g\,cm\(^{-3}\), which is in good agreement with the literature and consistent with a Neptune-like composition. For the inner planet (-e), we found a mass and density of \(M_\mathrm{e}=9.0\pm 0.5\) \(M_\oplus\) and \(\rho_\mathrm{e}=8.1\pm 0.5\) g\,cm\(^{-3}\), suggesting an Earth-like composition close to other ultra-hot planets at similar irradiation levels. Though this result is in agreement with previous RV+TTV studies, it is not in agreement with the most recent RV analysis (at 2.8\(\sigma\)), which yielded a lower density compatible with a pure silicate composition. This discrepancy highlights the still unresolved issue of suspected systematic offsets between RV and TTV measurements. In this paper, we also significantly improve the orbital ephemerides of all transiting planets, which will be crucial for any future follow-up.
To explain the unusual distribution of Kuiper Belt objects, several authors have advocated the existence of a super-Earth planet in the outer solar system. It has recently been proposed that a 10 ...M\(_{\oplus}\) object with an orbit of 700 AU semi major axis and 0.6 eccentricity can explain the observed distribution of Kuiper Belt objects around Sedna. Here we use the INPOP planetary ephemerides model as a sensor for testing for an additional body in the solar system. We test the possibility of adding the proposed planet without increasing the residuals of the planetary ephemerides, fitted over the whole INPOP planetary data sample. We demonstrate that the presence of such an object is not compatible with the most sensitive data set, the Cassini radio ranging data, if its true anomaly is in the intervals \(-130^\circ:-100^\circ\) or \(-65^\circ : 85^\circ\). Moreover, we find that the addition of this object can reduce the Cassini residuals, with a most probable position given by a true anomaly \(v = {117.8^\circ}^{ + 11^\circ}_{ - 10^\circ} \).
Two custom GaAs integrated circuits (ICs) have been developed for enabling vertical cavity surface emitting laser (VCSEL) arrays to be used for high throughput spatial division multiplexed (SDM) ...optical data links. A 16-channel driver IC was developed to drive the VCSEL array and an 8 x 8 monolithic photoreceiver, which spatially matches the VCSEL array, was developed for receive. Both of these circuits were fabricated in a standard commercial GaAs MESFET process with parasitic photodetectors used for the photoreceivers. Power dissipation and circuit size were primary design challenges for both circuits. The present 8 x 8 array size along with an estimated usable channel speed of 1 Gb/s allows for an aggregate throughput of 64 Gb/s.
Since the original work of Hansen and Tisserand in the XIXth century, there have been many variations in the analytical expansion of the three-body disturbing function in series of the semi-major ...axis ratio. With the increasing number of planetary systems of large eccentricity, these expansions are even more interesting as they allow us to obtain for the secular systems finite expressions that are valid for all eccentricities and inclinations. We revisited the derivation of the disturbing function in Legendre polynomial, with a special focus on the secular system. We provide here expressions of the disturbing function for the planar and spatial case at any order with respect to the ratio of the semi-major axes. Moreover, for orders in the ratio of semi-major axis up to ten in the planar case and five in the spatial case, we provide explicit expansions of the secular system, and simple algorithms with minimal computation to extend this to higher order, as well as the algorithms for the computation of non secular terms.
In this paper, we propose a new class of radio systems: a layer fusion radio (LFR) system that has potential to meet the emerging challenges of wireless communication and radar system. LFR includes ...three strategies: (i) Cross-layer system design, (ii) Cross-over functional block and iii) IP block sharing for multi-purposes.
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