| 1. |
- Acciari, V. A., et al.
(författare)
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Radio Imaging of the Very-High-Energy gamma-Ray Emission Region in the Central Engine of a Radio Galaxy
- 2009
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 325:5939, s. 444-448
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Tidskriftsartikel (refereegranskat)abstract
- The accretion of matter onto a massive black hole is believed to feed the relativistic plasma jets found in many active galactic nuclei (AGN). Although some AGN accelerate particles to energies exceeding 10(12) electron volts and are bright sources of very-high-energy (VHE) gamma-ray emission, it is not yet known where the VHE emission originates. Here we report on radio and VHE observations of the radio galaxy Messier 87, revealing a period of extremely strong VHE gamma-ray flares accompanied by a strong increase of the radio flux from its nucleus. These results imply that charged particles are accelerated to very high energies in the immediate vicinity of the black hole.
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| 4. |
- Wu, W. C., et al.
(författare)
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Design, Fabrication, and Characterization of Novel Vertical Coaxial Transitions for Flip-Chip Interconnects
- 2009
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Ingår i: IEEE Transactions on Advanced Packaging. - 1521-3323. ; 32:2, s. 362-371
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a novel transition design using vertical "coaxial transition" for coplanar waveguide (CPW-to-CPW) flip-chip interconnect is proposed and presented for the first time. The signal continuity is greatly improved since the coaxial-type transition provides more return current paths compared to the conventional transition in the flip-chip structure. The proposed coaxial transition structure shows a real coaxial property from the 3-D electromagnetic wave simulation results. The design rules for the coaxial transition are presented in detail with the key parameters of the coaxial transition structure discussed. For demonstration, the back-to-back flip-chip interconnect structures with the vertical coaxial transitions have been successfully fabricated and characterized. The demonstrated interconnect structure using the coaxial transition exhibits the return loss below 25 dB and the insertion loss within 0.4 dB from dc to 40 GHz. Furthermore, the measurement and simulation results show good agreement. The novel coaxial transition demonstrates excellent interconnect performance for flip-chip interconnects and shows great potential for flip-chip packaging applications at millimeter waves.
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| 5. |
- Hsiao, C.L., et al.
(författare)
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High-phase-purity zinc-blende InN on r -plane sapphire substrate with controlled nitridation pretreatment
- 2008
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 92:11
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Tidskriftsartikel (refereegranskat)abstract
- High-phase-purity zinc-blende (zb) InN thin film has been grown by plasma-assisted molecular-beam epitaxy on r -plane sapphire substrate pretreated with nitridation. X-ray diffraction analysis shows that the phase of the InN films changes from wurtzite (w) InN to a mixture of w-InN and zb-InN, to zb-InN with increasing nitridation time. High-resolution transmission electron microscopy reveals an ultrathin crystallized interlayer produced by substrate nitridation, which plays an important role in controlling the InN phase. Photoluminescence emission of zb-InN measured at 20 K shows a peak at a very low energy, 0.636 eV, and an absorption edge at ∼0.62 eV is observed at 2 K, which is the lowest bandgap reported to date among the III-nitride semiconductors. © 2008 American Institute of Physics.
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| 7. |
- Wu, W.C., et al.
(författare)
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60 GHz broadband 0=1-level RF-via interconnect for RF-MEMS packaging
- 2007
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Ingår i: Electronics Letters. ; 43:22, Oct. 25
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Tidskriftsartikel (refereegranskat)abstract
- The RF-via interconnect structure from the 0- to the 1-level packagefor coplanar RF-MEMS devices packaging is evaluated. The 0=1-levelinterconnect structure was designed and optimised using the electromagneticsimulation tool. The structure was then successfully fabricatedand characterised up to 67 GHz. The measured and simulatedresults show good agreement, demonstrating DC-to-60 GHz broadbandinterconnect performance through the two levels package
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| 8. |
- Wu, W.-C., et al.
(författare)
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60 GHz Broadband MS-to-CPW Hot-Via Flip Chip Interconnects
- 2007
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Ingår i: Microwave and Wireless Components Letters, IEEE. ; 17:11, Nov. 2007, s. 784-786
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Tidskriftsartikel (refereegranskat)abstract
- In this letter, the microstrip-to-coplanar waveguide(MS-to-CPW) hot-via flip chip interconnect has been experimentallydemonstrated to have broadband performance from dc to67 GHz. The interconnect structures with the hot-via transitions were first designed and optimized by using the electromagnetic simulation tool. Three types of designs were investigated in this letter. The interconnect structures were then fabricated and radio frequency (RF) tested up to 67 GHz. The optimized interconnectstructure with the compensation design demonstrated excellent RFcharacteristics with the insertion loss less than 0.5 dB and the returnloss below 18 dB over a very broad bandwidth from dc to67 GHz. This is to our
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| 9. |
- Wu, W. C., et al.
(författare)
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Coaxial transitions for CPW-to-CPW flip chip interconnects
- 2007
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Ingår i: Electronics Letters. ; 43:17, Aug. 16, s. 929-930
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Tidskriftsartikel (refereegranskat)abstract
- A novel coaxial transition for CPW-to-CPW flip chip interconnect ispresented and experimentally demonstrated. To realise the coaxialtransition on the CPW circuit, benzocyclobutene was used as theinterlayer dielectric between the vertical coaxial transition and theCPW circuit. The coaxial interconnect structure was successfullyfabricated and RF characterised to 67 GHz. The structure showedexcellent interconnect performance from DC up to 55 GHz with lowreturn loss below 20 dB and low insertion loss less
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