An MMIC Low-Noise Amplifier Design Technique Varonen, Mikko; Reeves, Rodrigo; Kangaslahti, Pekka ...
IEEE transactions on microwave theory and techniques,
03/2016, Letnik:
64, Številka:
3
Journal Article
Recenzirano
In this paper we discuss the design of low-noise amplifiers (LNAs) for both cryogenic and room-temperature operation in general and take the stability and linearity of the amplifiers into special ...consideration. Oscillations that can occur within a multi-finger transistor are studied and verified with simulations and measurements. To overcome the stability problem related to the multi-finger transistor design approach a parallel two-finger unit transistor monolithic microwave integrated circuit LNA design technique, which enables the design of wideband and high-linearity LNAs with very stable, predictable, and repeatable operation, is proposed. The feasibility of the proposed design technique is proved by demonstrating a three-stage LNA packaged in a WR10 waveguide housing and fabricated using a 35-nm InP HEMT technology that achieves more than a 20-dB gain from 75 to 116 GHz and 26-33-K noise temperature from 85 to 116 GHz when cryogenically cooled to 27 K.
The Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) is a dual-frequency ice-penetrating radar (9 and 60 MHz) onboard the Europa Clipper mission. REASON is designed to probe ...Europa from exosphere to subsurface ocean, contributing the third dimension to observations of this enigmatic world. The hypotheses REASON will test are that (1) the ice shell of Europa hosts liquid water, (2) the ice shell overlies an ocean and is subject to tidal flexing, and (3) the exosphere, near-surface, ice shell, and ocean participate in material exchange essential to the habitability of this moon. REASON will investigate processes governing this material exchange by characterizing the distribution of putative non-ice material (e.g., brines, salts) in the subsurface, searching for an ice–ocean interface, characterizing the ice shell’s global structure, and constraining the amplitude of Europa’s radial tidal deformations. REASON will accomplish these science objectives using a combination of radar measurement techniques including
altimetry
,
reflectometry
,
sounding
,
interferometry
,
plasma characterization
, and
ranging
. Building on a rich heritage from Earth, the moon, and Mars, REASON will be the first ice-penetrating radar to explore the outer solar system. Because these radars are untested for the icy worlds in the outer solar system, a novel approach to measurement quality assessment was developed to represent uncertainties in key properties of Europa that affect REASON performance and ensure robustness across a range of plausible parameters suggested for the icy moon. REASON will shed light on a never-before-seen dimension of Europa and – in concert with other instruments on Europa Clipper – help to investigate whether Europa is a habitable world.
We have developed a programmable, fast switching, accurate, and miniaturized calibration load for use in millimeter and submillimeter low-noise amplifier characterization, and Earth/planetary science ...radiometers. The proposed solution uses a thermally conductive waveguide vane attenuator with low thermal mass, integrated heater, and silicon thermometer. In the present design, we utilize a 125-<inline-formula><tex-math notation="LaTeX">\mu</tex-math> </inline-formula>m-thick z-cut crystal quartz vane due to its low dielectric constant (relative to silicon), high cryogenic thermal conductivity, chemical robustness, and small thermal contraction. To provide adequate attenuation, the bottom side of the quartz fabrication wafer has an nm thick resistive Ti metal layer deposited. On the top of the quartz wafer, a pattern of Au is deposited to allow adhesion of the heater resistor, thermometer, and internal heat strap. The z-cut quartz vane is mounted on three low thermally conductive Torlon posts, centered on the maximum E-field, and positioned across the waveguide. With this approach the quartz vane, protruding all the way into the waveguide, approximates a blackbody with a physical temperature T . The design uniqueness lies in the choice of cryogenically suitable materials coupled with detailed thermal analyses and proper miniaturization. When operated in a proportional<inline-formula><tex-math notation="LaTeX">-</tex-math></inline-formula>integral <inline-formula><tex-math notation="LaTeX">-</tex-math></inline-formula>derivative loop, these properties combine to facilitate a programmable calibration load with a switching speed of <inline-formula><tex-math notation="LaTeX"> \lesssim</tex-math></inline-formula>10 s. It will be shown that the W-band design operates overmoded to <inline-formula><tex-math notation="LaTeX">\sim</tex-math></inline-formula>230 GHz and that the concept is in principle scalable to terahertz frequencies.
Future radio astronomy arrays will benefit greatly from an ultra wideband feed that provides high efficiency and exhibit low noise behavior. A comparison based on G/T sys sensitivity is presented for ...three sinuous based feeds. The analysis can be easily extended to a wider range of feeds and used for a side by side comparison. Results from Table 1 show that the three cases have comparable performance at room temperature with the ground plane based version with the highest sensitivity. The T spill contribution is considered the same for both ambient and cryogenic tem peratures, as it is not feasible to cool the absorber used for suppression of the back lobe. As a result, the ground plane version shows significantly higher sensitivity at cryogenic temperature. Based on this analysis we plan to build a cryogenic version of the ground plane based antenna in the near future.
Next generation of instruments for radio astronomy will benefit greatly from reflector antenna feeds that demonstrate very wide instantaneous bandwidth and exhibit low noise behavior. Our study ...focuses on design and measurement of an ultra-wideband inverted conical sinuous antenna and its integration with a low noise pseudo differential amplifier. The self-complementary, frequency independent nature of the planar sinuous geometry results in a nearly constant beam pattern and fixed phase center over more than a 10:1 operating frequency range. In order to eliminate the back-lobe response over such a wide frequency range, we have projected the sinuous pattern onto a cone, and a ground plane is placed directly behind the cone's apex. This inverted, conical geometry assures wide bandwidth operation by locating each sinuous resonator a quarter wavelength above the ground plane. The presence of a ground plane near a self complementary antenna destroys the self complementary nature of the composite structure resulting in frequency dependent impedance variations. We demonstrate, using simulations and measurements, how the return loss can be improved by modifying the sinuous geometry. A physically smaller, laboratory version of the 0.3 to 3 GHz antenna that is truncated to operate from 1 to 3 GHz was fabricated to verify proper LNA-feed integration through careful modeling and measurements. Over this range, a return loss of better than 9 dB is measured while simulations indicate a nearly constant beam pattern. A full decade bandwidth, low noise amplifier was specially designed for noise match to the higher terminal impedance encountered by this antenna yielding an improved sensitivity over what is possible with conventional 50 Ω amplifiers. A measured system noise temperature of less than 100 K is reported. Based on these results, we will increase the bandwidth of the system to 10:1 by simply attaching additional resonators to the sinuous arms.
The increase in antibacterial drug resistance is threatening global health conditions. Recently, antibacterial photodynamic therapy (aPDT) has emerged as an effective antibacterial treatment with ...high cure gain. In this work, three Zn(II) complexes viz., Zn(en)(acac)Cl (1), Zn(bpy)(acac)Cl (2), Zn(en)(cur)Cl (3), where en=ethylenediamine (1 and 3), bpy=2,2'-bipyridine (2), acac=acetylacetonate (1 and 2), cur=curcumin monoanionic (3) were developed as aPDT agents. Complexes 1-3 were synthesized and fully characterized using NMR, HRMS, FTIR, UV-Vis. and fluorescence spectroscopy. The HOMO-LUMO energy gap (Eg), and adiabatic splittings (Δ
and Δ
) obtained from DFT calculation indicated the photosensivity of the complexes. These complexes have not shown any potent antibacterial activity under dark conditions but the antibacterial activity of these complexes was significantly enhanced upon light exposure (MIC value up to 0.025 μg/mL) due to their light-mediated
O
generation abilities. The molecular docking study suggested that complexes 1-3 interact efficiently with DNA gyrase B (PDB ID: 4uro). Importantly, 1-3 did not show any toxicity toward normal HEK-293 cells. Overall, in this work, we have demonstrated the promising potential of Zn(II) complexes as effective antibacterial agents under the influence of visible light.
We present deep CCS and HC7N observations of the L1495-B218 filaments in the Taurus molecular cloud obtained using the K-band focal plane array on the 100 m Green Bank Telescope. We observed the ...L1495-B218 filaments in CCS JN = 21-10 and HC7N J = 21−20 with a spectral resolution of 0.038 km s−1 and an angular resolution of 31″. We observed strong CCS emission in both evolved and young regions and weak emission in two evolved regions. HC7N emission is observed only in L1495A-N and L1521D. We find that CCS and HC7N intensity peaks do not coincide with NH3 or dust continuum intensity peaks. We also find that the fractional abundance of CCS does not show a clear correlation with the dynamical evolutionary stage of dense cores. Our findings and chemical modeling indicate that the fractional abundances of CCS and HC7N are sensitive to the initial gas-phase C/O ratio, and they are good tracers of young condensed gas only when the initial C/O is close to solar value. Kinematic analysis using multiple lines, including NH3, HC7N, CCS, CO, HCN, and HCO+, suggests that there may be three different star formation modes in the L1495-B218 filaments. At the hub of the filaments, L1495A/B7N has formed a stellar cluster with large-scale inward flows (fast mode), whereas L1521D, a core embedded in a filament, is slowly contracting because of its self-gravity (slow mode). There is also one isolated core that appears to be marginally stable and may undergo quasi-static evolution (isolated mode).
Abstract
We present deep CCS and HC
7
N observations of the L1495-B218 filaments in the Taurus molecular cloud obtained using the
K
-band focal plane array on the 100 m Green Bank Telescope. We ...observed the L1495-B218 filaments in CCS
J
N
= 2
1
–1
0
and HC
7
N
J
= 21−20 with a spectral resolution of 0.038 km s
−1
and an angular resolution of 31″. We observed strong CCS emission in both evolved and young regions and weak emission in two evolved regions. HC
7
N emission is observed only in L1495A-N and L1521D. We find that CCS and HC
7
N intensity peaks do not coincide with NH
3
or dust continuum intensity peaks. We also find that the fractional abundance of CCS does not show a clear correlation with the dynamical evolutionary stage of dense cores. Our findings and chemical modeling indicate that the fractional abundances of CCS and HC
7
N are sensitive to the initial gas-phase C/O ratio, and they are good tracers of young condensed gas only when the initial C/O is close to solar value. Kinematic analysis using multiple lines, including NH
3
, HC
7
N, CCS, CO, HCN, and HCO
+
, suggests that there may be three different star formation modes in the L1495-B218 filaments. At the hub of the filaments, L1495A/B7N has formed a stellar cluster with large-scale inward flows (fast mode), whereas L1521D, a core embedded in a filament, is slowly contracting because of its self-gravity (slow mode). There is also one isolated core that appears to be marginally stable and may undergo quasi-static evolution (isolated mode).
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