60Co-γ射线辐射对AlGaN/GaN HEMT器件直流特性的影响

采用1.25Mev 60Co γ射线辐射源对钝化前后的AlGaN/GaN HEMT器件进行了1Mrad(Si)的总剂量辐射,实验发现：1Mrad总剂量辐射后未钝化器件的饱和漏电流和最大跨导分别下降了15%和9.1%,而且正向和反向栅电流明显增加,但是阈值电压几乎没有发生变化。相反的,同样的累积剂量下,钝化器件的饱和漏电流和最大跨导却基本没变。通过对钝化前后器件的不同辐射反应以及C-V测试的分析表明,栅-源和栅-漏间隔区辐射感生表面态负电荷的产生是低剂量下AlGaN/GaN HEMT器件电特性退化的主要原因,同时也说明钝化可以有效地抑制60Co γ辐射感生表面态电荷,它是一种有效的加固手段。     

A low cost integrated transceiver for mobile UHF passive RFID reader applications

2.5 mm2 including pads.     

一款便携式移动应用的低成本超高频无源射频识别读写器收发机芯片设计

A low cost integrated transceiver for mobile UHF passive RFID reader applications is implemented in a 0.18μm CMOS process. The transceiver contains an OOK modulator and a power amplifier in the transmitter chain, an IQ direct-down converter, variable-gain amplifiers, channel-select filters and a 10-bit ADC in the receiver chain. The measured output PldB power of the transmitter is 17.6 dBm and the measured receiver sensitivity is -70 dBm. The on-chip integer N synthesizer achieves a frequency resolution of 200 kHz with a phase noise of -104 dBc/Hz at 100 kHz frequency offset and -120.83 dBc/Hz at 1 MHz frequency offset. The transmitter, the receiver and the frequency synthesizer consume 201.34, 25.3 and 54 mW, respectively. The chip has a die area of 4 × 2.5 mm^2 including pads.     

X 波段氮化镓合成固态放大器

Based on a self-developed A1GaN/GaN HEMT with 2.5 mm gate width technology on a SiC substrate, an X-band GaN combined solid-state power amplifier module is fabricated. The module consists of an AIGaN/GaN HEMT, Wilkinson power couplers, DC-bias circuit and microstrip line. For each amplifier, we use a bipolar DC power source. Special RC networks at the input and output and a resistor between the DC power source and the gate of the transistor at the input are used for cancellation of self-oscillation and crosstalk of low-frequency of each amplifier. At the same time, branches of length 3λ/4 for Wilkinson power couplers are designed for the elimination of self-oscillation of the two amplifiers. Microstrip stub lines are used for input matching and output matching. Under Vds = 27 V, Vgs = -4.0 V, CW operating conditions at 8 GHz, the amplifier module exhibits a line gain of 5.6 dB with power added efficiency of 23.4%, and output power of 41.46 dBm （14 W）, and the power gain compression is 3 dB. Between 8 and 8.5 GHz, the variation of output power is less than 1.5 dB.     

Characterization of GaN grown on 4H-SiC and sapphire by Raman spectroscopy and high resolution XRD

and electron mobility in GaN grown on sapphire and 4H-SiC are analyzed.     

A fractional-N frequency synthesizer for WCDMA/Bluetooth/ZigBee applications

esented.     

Effects of Interfacial Dielectric Layers on the Electrical Performance of Top‐Gate In‐Ga‐Zn‐Oxide Thin‐Film Transistors

We investigate the effects of interfacial dielectric layers (IDLs) on the electrical properties of top‐gate In‐Ga‐Zn‐oxide (IGZO) thin film transistors (TFTs) fabricated at low temperatures below 200°C, using a target composition of In:Ga:Zn = 2:1:2 (atomic ratio). Using four types of TFT structures combined with such dielectric materials as Si₃N₄ and Al₂O₃, the electrical properties are analyzed. After post‐annealing at 200°C for 1 hour in an O₂ ambient, the sub‐threshold swing is improved in all TFT types, which indicates a reduction of the interfacial trap sites. During negative‐bias stress tests on TFTs with a Si3N4 IDL, the degradation sources are closely related to unstable bond states, such as Si‐based broken bonds and hydrogen‐based bonds. From constant‐current stress tests of Id = 3 µA, an IGZO‐TFT with heat‐treated Si₃N₄ IDL shows a good stability performance, which is attributed to the compensation effect of the original charge‐injection and electron‐trapping behavior.     

Design of the QoS framework for the IEEE 802.16 mesh networks

IEEE 802.16 (WiMax) technology is designed to support broadband speeds over wireless networks for the coming era of broadband wireless access (BWA). IEEE 802.16 is expected to provide transmission of high‐rate and high‐volume multimedia data streams for fixed and mobile applications. As an extension of point‐to‐multipoint (PMP) configuration, the IEEE 802.16 mesh mode provides a quicker and more flexible approach for network deployment. Multimedia networking requires quality‐of‐service (QoS) support, which demands elaborate mechanisms in addition to the four service types defined in the specification. By examining standard centralized and distributed scheduling/routing schemes in the mesh mode from QoS aspect, a BS‐controlled and delay‐sensitive scheduling/routing scheme is proposed in the paper. Associate mechanisms including admission control, flow setup and link state monitoring are also proposed. Integration of the proposed mechanisms is presented as a complete QoS framework. Simulation study has demonstrated that the average delay as well as the delay jitters per hop in the proposed scheme is smaller than that of the distributed scheme and much smaller than that of the centralized scheme. Furthermore, proposed mechanisms can also achieve higher throughput than the contrasts and generate much smaller signaling overhead, making the proposed framework a promising scheme for multimedia support in the IEEE 802.16 mesh network. Copyright © 2009 John Wiley & Sons, Ltd.     

Rational Design of Charge‐Neutral,Near‐Infrared‐Emitting Osmium(II) Complexes and OLED Fabrication

A new series of charge neutral Os(II) isoquinolyl triazolate complexes ( 1 – 4 ) with both trans and cis arrangement of phosphine donors are synthesized, and their structural, electrochemical and photophysical properties are established. In sharp contrast to the cis‐arranged complexes 2 – 4 , the trans derivative 1 , which shows a planar arrangement of chromophoric N‐substituted chelates, offers the most effective extended π‐delocalization and hence the lowest excited state energy gap. These complexes exhibit phosphorescence with peak wavelengths ranging from 692–805 nm in degassed CH₂Cl₂ at room temperature. Near‐infrared (NIR)‐emitting electroluminescent devices employing 6 wt % of 1 (or 4 ) doped in Alq₃ host material are successfully fabricated. The devices incorporating 1 as NIR phosphor exhibit fairly intense emission with a peak wavelength at 814 nm. Forward radiant emittance reaches as high as 65.02 µW cm^?2, and a peak EQE of ～1.5% with devices employing Alq₃, TPBi and/or TAZ as electron‐transporting/exciton‐blocking layers. Upon switching to phosphor 4 , the electroluminescence blue shifts to 718 nm, while the maximum EQE and radiance increase to 2.7% and 93.26 (μW cm^?2) respectively. Their performances are optimized upon using TAZ as the electron transporting and exciton‐blocking material. The OLEDs characterized represent the only NIR‐emitting devices fabricated using charge‐neutral and volatile Os(II) phosphors via thermal vacuum deposition.     

Ursolic acid,a naturally occurring triterpenoid,suppresses migration and invasion of human breast cancer cells by modulating c‐Jun N‐terminal kinase,Akt and mammalian target of rapamycin signaling

Metastasis is one of the most important factors related to breast cancer therapeutic efficacy. Ursolic acid, a naturally occurring triterpenoid, has various anticancer activities. In this study, we first observed that ursolic acid exerted a dose‐ and time‐dependent inhibitory effect on the migration and invasion of highly metastatic breast MDAMB231 cells at non‐cytotoxic concentrations. This effect was associated with reduced activities of metalloproteinase‐2 (MMP‐2) and u‐PA, which correlated with enhanced expression of tissue inhibitor of MMP‐2 and plasminogen activator inhibitor‐1, respectively. Ursolic acid suppressed the phosphorylation of Jun N‐terminal kinase, Akt and mammalian target of rapamycin, but had no effect on the phosphorylation of ERK and p38. Ursolic acid also strongly reduced the levels of NFκB p65, c‐Jun and c‐Fos proteins in the nucleus of MDAMB231 cells. A time‐dependent inhibition of the protein levels of Rho‐like GTPases, growth factor receptor‐bound protein 2, Ras and vascular endothelial growth factor in cytosol by ursolic acid treatment was also observed. In conclusion, we demonstrated that the anti‐invasive effects of ursolic acid on MDAMB231 cells might be through the inhibition of Jun N‐terminal kinase, Akt and mammalian target of rapamycin phosphorylation and a reduction of the level of NFκB protein in the nucleus, ultimately leading to downregulation of MMP‐2 and u‐PA expression. These results suggest that ursolic acid has potential as a chemopreventive agent for metastatic breast cancer.