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1.
Chip design of a 5.8-GHz fractional-N frequency synthesizer with a tunable Gm—C loop filter
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This paper proposes a novel Gm-C loop filter instead of a conventional passive loop filter used in a phase-locked loop.The innovative advantage of the proposed architecture is tunable loop filter bandwidth and hence the process variations of passive elements of resistance R and capacitance C can be overcome and the chip area is greatly reduced.Furthermore,the MASH 1-1-1 sigma-delta(Σ▽) modulator is adopted for performing the fractional division number and hence improves the phase noise as well.Measured results show that the locked phase noise is 114.1 dBc/Hz with lower G m-C bandwidth and 111.7 dBm/C with higher G m-C bandwidth at 1 MHz offset from carrier of 5.68 GHz.Including pads and built-in Gm-C filter,the chip area of the proposed frequency synthesizer is 1.06 mm 2.The output power is 8.69 dBm at 5.68 GHz and consumes 56 mW with an off-chip buffer from 1.8-V supply voltage. 相似文献
2.
Timo J. Tolmunen Antti V. R?is?nen 《International Journal of Infrared and Millimeter Waves》1989,10(4):475-504
In this research the efficiency of a millimeter-wave Schottky-varactor quadrupler was studied. Theoretical simulations were carried out by using a nonlinear analysis program to find the optimum embedding impedances for a given diode. Emphasis was placed on the study of optimum idlers at the 2nd and 3rd harmonics, which are essential for a high quadrupling efficiency. For experimental verification a quadrupler for 140–155 GHz output frequency range with fixed idler terminations was constructed. This quadrupler was tested with different output configurations. A 10% tunable bandwidth was obtained with output power in the range of 1.5–2.7 mW whenP
in
=40 mW. The highest efficiency measured was 11.3% at 148 GHz with 10 mW input power. 相似文献
3.
对基于半导体光放大器(SOA)环形腔结构的一阶无限冲击响应(IIR)微波光子学滤波器的品质因数(Q值)进行了实验和理论研究. 通过在有源环内置入窄带光滤波器,并调节有源环的输入光功率、SOA抽运电流、实验得到的最高Q值接近200. 理论分析表明为了得到较高的Q值,应尽可能提高信噪比和信号光的环路增益. 在考虑了 SOA中放大的自发辐射(ASE)噪声的基础上,计算了输入光功率、SOA抽运电流、环内光滤波器的带宽对Q值的影响. 数值计算的结果与实验现象基
关键词:
微波光子学滤波器
Q值')" href="#">Q值
半导体光放大器
放大的自发辐射 相似文献
4.
Baoxin Gao Ke Gong Yingxin Sun Guanhui Iang 《International Journal of Infrared and Millimeter Waves》1999,20(4):611-616
This paper discusses design and implementation of a millimeterwave monolithic integrated balanced mixer, the measured performance compared with the predicted one is also reported. By designing this MMIC mixer, various mathematical methods are used, in which the Method of Conversion Matrix has been extended by the author to meet the requirement of inter-modulation analysis. The mixer is realized in a 2×3mm
2
GaAs chip, working in Ka band with bandwidth of 5GHz with a noise figure less than 10 dB. 相似文献
5.
A. I. Harris J. Stutzki U. U. Graf R. Genzel 《International Journal of Infrared and Millimeter Waves》1989,10(11):1371-1376
We accurately measured the noise temperature and conversion loss of a cryogenically cooled Schottky diode operating near 800 GHz, using the UCB/MPE Submillimeter Receiver at the James Clerk Maxwell Telescope. The receiver temperature was in the range of the best we now routinely measure, 3150 K (DSB). Without correcting for optical loss or IF mismatch, the raw measurements set upper limits ofT
M=2850 K andL
M=9.1 dB (DSB), constant over at least a 1 GHz IF band centered at 6.4 GHz with an LO frequency of 803 GHz. Correction for estimated optical coupling and mismatch effects yieldsT
M=1600 K andL
M=5.5 dB (DSB) for the mixer diode itself. These values indicate that our receiver noise temperature is dominated by the corner cube antenna's optical efficiency and by mixer noise, but not by conversion loss or IF mismatch. The small fractional IF bandwidth, measured mixer IF band flatness from 2 to 8 GHz, and similarly good receiver temperatures at other IF frequencies imply that these values are representative over a range of frequencies near 800 GHz. 相似文献
6.
Starting from the space-time Wigner distribution function and taking the Gaussian Schell-model pulsed beam as a typical example, the M2 factor of partially coherent ultrashort pulsed beams is studied. It is shown that the M2 factor increases with increasing bandwidth and decreases with increasing spatial correlation. Furthermore, for chirped pulse, the M2 factor increases as the chirp parameter increases. 相似文献
7.
M. W. Evans 《Foundations of Physics Letters》1995,8(4):359-364
It has been argued theoretically that the recently proposed vacuum fieldB
(3)
is not accompanied by a real electric fieldE
(3)
. Experimental evidence for this interence is available in the data reported by Deschampset al. [10], using microwave magnetization of an electron plasma set up in helium gas. Faraday induction due toB
(3)
does not occur in the inert gas and is not observed experimentally in the absence of free electrons. WheneverB
(3)
interacts with free electrons, however, Faraday induction occurs through a pulse of induced magnetization (i.e., induced orbital electronic angular momentum). 相似文献
8.
Stimulated supercontinuum-radiation generation of carbon disulfide by all-trans-β-carotene fluorescence enhancement effect in liquid core optical fibre
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We demonstrate stimulated supercontinuum-radiation of carbon disulfide (CS2) influenced by biological molecules all-trans-β -carotene in liquid core optical fibre (LCOF). By virtue of the broad fluorescence characteristics and large third-order optical nonlinearities of all-{trans}-β-carotene,the high-order Stokes lines of stimulated Raman scattering (SRS) and the multi-order Stokes lines of stimulated Brillouin scattering (SBS) excitated by SRS are observed at low input-laser energies. The results indicate that the fluorescence not only enhances the SRS, but also the SBS. These Stokes lines generate the SRS--SBS supercontinuum radiation (RBSR). A flat-amplitude bandwidth of 110 nm from 515nm to 625nm is observed when a frequency-doubled Nd:YAG laser at 532nm with an energy of 0.86mJ is used. This result is expected to be useful for the multi-wavelength fibre laser. 相似文献
9.
A broad band polarization-independent reflector working in the telecommunication C+L band is proposed using the guided mode resonance effect of a periodic surface relief element deposited by a layer of silicon medium. It is shown that this structure can provide high reflection (R>99.5%) and wide angular bandwidth (θ≈20°, R>98%) for both TE and TM polarizations over a wide spectrum band 1.5 μm~1.6 μm. Furthermore, it is found by rigorous coupled wave analysis that the polarization-independent reflector proposed here is tolerant of a deviation of grating thickness, which makes it very easy to fabricate in experiments. 相似文献
10.
O. Prakash H.-H. Lim B.-J. Kim K. Pandiyan M. Cha B. K. Rhee 《Applied physics. B, Lasers and optics》2008,92(4):535-541
Collinear broadband optical parametric generation (OPG) using periodically poled lithium niobate (PPLN) crystals were designed
and experimentally demonstrated with the quasi-phase matching (QPM) periods of 21.5, 24.0, and 27.0 μm. The broad gain bandwidth was accomplished by choosing a specific set of the period and the pump wavelength that allows
the group velocities of the signal and the idler to match close to the degeneracy point. OPG gain bandwidth and also the spectral
region could be controlled by proper design of QPM period and pump wavelength. The total OPG gain bandwidth of 600, 900, and
1200 nm was observed for the PPLN devices with QPM periods of 21.5, 24.0, and 27.0 μm, respectively. We have also observed multiple color visible generation whenever the OPG spectrum was significantly broad.
From the visible peaks of the three PPLN samples, it is found that broad gain bandwidth is crucial in the temperature-insensitive
collinear simultaneous RGB generation from a single crystal. 相似文献
11.
Karen B. Paul 《Central European Journal of Physics》2005,3(1):115-126
A monocrystal ofFe
3
O
4 is characterized by resistance, magnetoresistance and magnetic measurements in a temperature range from 4.2 K to 350 K and
magnetic field-cycling from −9 T to 9 T. The resistance measurements revealed a metal-insulator Verwey transition (VT) atT
v
=123.76 K with activation energy E=92.5 meV at T >T
v
and temperature-substitute for the activation energy below the VT,T
0=E/k
B
≈3800 K within 70 K–110K. The magnetotransport results independently verified the VT at 123.70 K, with discontinuous change
in the magnetic moment ΔM≈0.21 ΔM≈0.21μ
B
and resistance hysteresis, dependent on the magnetic field in a narrow temperature range of 0.4° around theT
v
. The magnetic characterization established self consistentlyT
v
as ≈123.67 K, the jump in the magnetization at the VT≈0.25μ
B
and confirmed, that the magnetocrystalline anisotropy is the main microscopic mechanism responsible for the magnetization
of the monocrystal (88%) with additional natural and imposed defects contributing as 12%. 相似文献
12.
Compact and broadband circularly polarized ring antenna with wide beam-width for multiple global navigation satellite systems
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A compact and broadband circularly polarized (CP) annular ring antenna with wide beam-width is proposed for multiple global navigation satellite systems (GNSS) in the L1 band. The annular ring is excited by two modified L-probes with quadrature phase difference. It has a 36.3% 10-dB return loss bandwidth and a 13% 3-dB axial ratio bandwidth, because of the orthogonal L-probes with 90° phase difference. The measured peak gain of the antenna is 3.9 dBic. It can detect the satellites at lower elevation as its half power beam-width (HPBW) is 113° in both the x-z and y-z planes, achieving a cross-polarization level of larger than 25 dB. Noticeably, the antenna achieves 89% size reduction compared with the conventional half wavelength patch antennas. It can be used in hand-held navigation devices of multiple GNSS such as COMPASS, Galileo, GPS and GLONASS. 相似文献
13.
The problem of transition prediction for hypersonic boundary layers over a sharp cone has been studied in this work. The Mach
number of the oncoming flow is 6, the cone half-angle is 5°, and the angle of attack is 1°. The conventional e
N
method is used, but the transition location so obtained is obviously incorrect. The reason is that in the conventional method,
only the amplifying waves are taken into account, while in fact, for different meridians the decay processes of the disturbances
before they begin to grow are different. Based on our own previous work, new interpretation and essential improvement for
the e
N
method are proposed. Not only the amplification process but also the decay process is considered. The location, where by
linear stability theory, the amplitude of disturbance wave is amplified from its initial small value to 1%, is considered
to be the transition location. The new result for transition prediction thus obtained is found to be fairly satisfactory.
It is also indicated that for the calculation of base flow, boundary layer equations can be used for a small angle of attack.
Its computational cost is much smaller than those for DNS.
Supported by the National Natural Science Foundation of China (Grant Nos. 10632050 and 90716007), the Special Foundation for
the Authors of National Excellent Doctoral Dissertations (Grant No. 200328), and the Foundation of Liu-Hui Center of Applied
Mathematics of Nankai University and Tianjin University 相似文献
14.
Pseudoelasticity caused by pseudotwinning in short-range ordered In-Pb alloys (6, 8 and 11.6 at. % Pb) is studied in the temperature
range 0.48–180 K. The mechanical hysteresis parameters, namely, the thermodynamic stress τ
T
which provides the reversibility of plastic deformation and the frictional stress τ
f
which characterizes the resistance offered by crystal lattice and its defects to twin boundaries motion are estimated. It
is found that athermal processes determine the reversible deformation: the mechanical parameters τ
T
and τ
f
do not depend on temperature and strain rate. The stress τ
T
increases and the stress τ
f
decreases with increasing Pb content. One of the main conditions of the exhibition of superelasticity is the fulfillment
of the inequality τ
T
>τ
f
. 相似文献
15.
A specific state variable in a class of 3D continuous fractional-order chaotic systems is presented.All state variables of fractional-order chaotic systems of this class can be obtained via a specific state variable and its (q-order and 2q-order) time derivatives.This idea is demonstrated by using several well-known fractional-order chaotic systems.Finally,a synchronization scheme is investigated for this fractional-order chaotic system via a specific state variable and its (q-order and 2q-order) time derivatives.Some examples are used to illustrate the effectiveness of the proposed synchronization method. 相似文献
16.
Metsaev和Tseytlin(MT)给出的AdS5S5背景中Green-Schwarz(GS) IIB超弦的Polyakov作用量可以写成等价的Nambu-Goto形式.对于这种形式,给出了新的与靶空间的流有关的投影算子,并用其构造了使作用量不变的局域κ-变换.κ-对称性的这种新方案是由Schwarz对于GS模型提出的.由于MT模型与GS模型有所不同,文中所构造的局域κ-变换有一些新的特点,且适用于其他类似于MT模型的系统.文中分别以AdS5S1背景中IIB弦及Polyakov新提出的模型为例,构造了κ-对称性的靶空间形式.
关键词:
Green-Schwarz超弦
κ-对称性')" href="#">κ-对称性
AdS5S5')" href="#">AdS5S5
AdS5S1')" href="#">AdS5S1 相似文献
17.
Y. Z. Cheng Y. Nie R. Z. Gong 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(2):62
In this paper, we numerically demonstrate a broadband 3D isotropic negative index
metamaterial (NIM) at microwave frequency ranges, which is composed of double periodic
array metallic fishnet structure (FS) etched on the six sides of a cubic dielectric
substrate. The electric and magnetic L-C resonance
circuit models are constructed to demonstrate the broadband resonance properties of the
proposed 3D metamaterial. The finite integration technology (FIT) simulation and standard
S parameters retrieval methods are used to calculate and analyze the
negative characteristics, isotropy and polarization of the 3D model. The numerical results
show that the negative index bandwidth is about 7 GHz and relative bandwidth can be up
nearly to 63%, the negative-index pass band is independent of the polarization of incident
waves and is almost the same for different oblique incident angles. Thus, the proposed
metamaterial is good candidate as a broad-band 3D isotropic NIMs. 相似文献
18.
Tumpa Bhattacharjee Somen Chanda Sarmishtha Bhattacharyya Swapan Kumar Basu R.K. Bhowmik S. Muralithar R.P. Singh N.S. Pattabiraman S.S. Ghugre U. Datta Pramanik S. Bhattacharya 《Nuclear Physics A》2005,750(2-4):199-217
The high spin states in the N=79 odd–odd 136La nucleus have been investigated by in-beam γ-spectroscopic techniques following the 130Te(11B, 5n)136La reaction at E=52 MeV using an array, consisting of eight Compton-suppressed clover germanium detectors. Thirty nine new γ rays have been assigned to 136La on the basis of γ ray singles and γγ-coincidence data. The level scheme of 136La has been extended above the known 115 ms isomer upto an excitation energy of 4.6 MeV and spin 18. Thirty one new levels have been proposed and spin-parity assignments for most of the newly proposed levels have been made on the basis of the deduced asymmetry ratios and polarisation information for the de-exciting transitions. The observed positive parity yrast band has been compared with the theoretical calculation, done within the framework of particle rotor coupling model (PRM) where the two odd quasi-particles are coupled to an axially symmetric core. The level structure has been discussed in the light of the known systematics of the neighbouring N=79 isotonic nuclei. 相似文献
19.
Ge1-xSnx是一种新型IV族合金材料, 在光子学和微电子学器件研制中具有重要应用前景. 本文使用低温分子束外延(MBE)法, 在Ge(001)衬底上生长高质量的Ge1-xSnx合金, 组分x分别为1.5%, 2.4%, 2.8%, 5.3%和14%, 采用高分辨X射线衍射(HR-XRD)、卢瑟福背散射谱(RBS) 和透射电子显微镜(TEM)等方法表征Ge1-xSnx合金的材料质量. 对于低Sn组分(x≤ 5.3%)的样品, Ge1-xSnx合金的晶体质量非常好, RBS的沟道/随机产额比(χmin)只有5.0%, HR-XRD曲线中Ge1-xSnx衍射峰的半高全宽(FWHM)仅100' 左右. 对于x=14%的样品, Ge1-xSnx合金的晶体质量相对差一些, FWHM=264.6'.
关键词:
锗锡合金
锗
分子束外延 相似文献
20.
Choon Ki Ahn 《中国物理 B》2010,19(10):100201-100201
This paper proposes an L2 -L∞ learning law as a new learning method for dynamic neural networks with external disturbance. Based on linear matrix inequality (LMI) formulation, the L2-L∞ learning law is presented to not only guarantee asymptotical stability of dynamic neural networks but also reduce the effect of external disturbance to an L2-L∞ induced norm constraint. It is shown that the design of the L2-L∞ learning law for such neural networks can be achieved by solving LMIs, which can be easily facilitated by using some standard numerical packages. A numerical example is presented to demonstrate the validity of the proposed learning law. 相似文献