Electrical and optical response of a very high frequency AlGaAs/GaAs heterojunction bipolar transistor

Abstract The very high frequency data exchange system (VDES) is promising in promoting electronic navigation (E-navigation) and improving navigation safety. The multiple access control (MAC) protocol is crucial to the transmission performance of VDES. The self-organising time division multiple access (SOTDMA) protocol, as the only access mode given by current recommendations, leads to a high rate of transmission collisions in the traditional automatic identification system (AIS), especially with heavy traffic loads. This paper proposes a novel feedback based time division multiple access (FBTDMA) protocol to address the problems caused by SOTDMA, such that collision of transmissions can be avoided in information transmission among vessels. Simulation results demonstrate that the proposed FBTDMA outperforms the traditional SOTDMA in terms of channel utilisation and throughput, and significantly reduces the transmission collision rate. The study is expected to provide insights into VDES standardisation and E-navigation modernisation.

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Measurement of Electrical Properties of Superconducting YBCO Thin Films in the VHF Range

Materials ◽

10.3390/ma14123360 ◽

2021 ◽

Vol 14 (12) ◽

pp. 3360

Author(s):

Yakir Dahan ◽

Eldad Holdengreber ◽

Elichai Glassner ◽

Oz Sorkin ◽

Shmuel E. Schacham ◽

...

Keyword(s):

Thin Films ◽

Theoretical Model ◽

Quality Factor ◽

High Frequency ◽

Unit Length ◽

Superconducting Thin Films ◽

Electrical Parameters ◽

Very High Frequency ◽

Production Constraints ◽

Very High

A new measurement technique of electrical parameters of superconducting thin films at the Very High Frequency (VHF) range is described, based on resonators with microstrip (MS) structures. The design of an optimal resonator was achieved, based on a thorough theoretical analysis, which is required for derivation of the exact configuration of the MS. A theoretical model is presented, from which an expression for the attenuation of a MS line can be derived. Accordingly, simulations were performed, and an optimal resonator for the VHF range was designed and implemented. Production constraints of YBa2Cu3O7 (YBCO) limited the diameter of the sapphire substrate to 3″. Therefore, a meander configuration was formed to fit the long λ/4 MS line on the wafer. By measuring the complex input reflection coefficients of a λ/4 resonator, we extracted the quality factor, which is mainly affected by the dielectric and conductor attenuations. The experimental results are well fitted by the theoretical model. The dielectric attenuation was calculated using the quasi-static analysis of the MS line. An identical copper resonator was produced and measured to compare the properties of the YBCO resonator in reference to the copper one. A quality factor of ~6·105 was calculated for the YBCO resonator, three orders of magnitude larger than that of the copper resonator. The attenuation per unit length of the YBCO layer was smaller by more than five orders of magnitude than that of the copper.

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Da eine oder mehrere betroffen …

Zeitschrift für Germanistische Linguistik ◽

10.1515/zgl-2020-0002 ◽

2020 ◽

Vol 48 (1) ◽

pp. 47-100

Author(s):

Melitta Gillmann

Keyword(s):

High Frequency ◽

Formal Language ◽

Subordinate Clause ◽

Matrix Clause ◽

Very High Frequency ◽

Corpus Study ◽

Causal Relations ◽

Legal Texts ◽

The Matrix ◽

Very High

AbstractBased on a corpus study conducted using the GerManC corpus (1650–1800), the paper sketches the functional and sociosymbolic development of subordinate clause constructions introduced by the subjunctor da ‘since’ in different text genres. In the second half of the 17th and the first half of the 18th century, the da clauses were characterized by semantic vagueness: Besides temporal, spatial and causal relations, the subjunctor established conditional, concessive, and adversative links between clauses. The corpus study reveals that different genres are crucial to the readings of da clauses. Spatial and temporal usages, for example, occur more often in sermons than in other genres. The conditional reading, in contrast, strongly tends to occur in legal texts, where it displays very high frequency. This could be the reason why da clauses carry indexical meaning in contemporary German and are associated with formal language. Over the course of the 18th century, the causal usages increase in all genres. Surprisingly, these causal da clauses tend to be placed in front of the matrix clause despite the overall tendency of causal clauses to follow the matrix clause.

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Upgrade possibilities for continuous wave rf electron guns based on room-temperature very high frequency technology

Physical Review Accelerators and Beams ◽

10.1103/physrevaccelbeams.20.113402 ◽

2017 ◽

Vol 20 (11) ◽

Cited By ~ 8

Author(s):

F. Sannibale ◽

D. Filippetto ◽

M. Johnson ◽

D. Li ◽

T. Luo ◽

...

Keyword(s):

High Frequency ◽

Room Temperature ◽

Continuous Wave ◽

Very High Frequency ◽

Electron Guns ◽

Very High

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Sintering, Microstructure, and Dielectric Properties of Copper Borates for High Frequency LTCC Applications

Materials ◽

10.3390/ma14144017 ◽

2021 ◽

Vol 14 (14) ◽

pp. 4017

Author(s):

Dorota Szwagierczak ◽

Beata Synkiewicz-Musialska ◽

Jan Kulawik ◽

Norbert Pałka

Keyword(s):

Dielectric Properties ◽

Dielectric Permittivity ◽

High Frequency ◽

Ceramic Materials ◽

Sintering Behavior ◽

Terahertz Time Domain Spectroscopy ◽

Very High Frequency ◽

X Ray ◽

Low Dielectric ◽

Very High

New ceramic materials based on two copper borates, CuB2O4 and Cu3B2O6, were prepared via solid state synthesis and sintering, and characterized as promising candidates for low dielectric permittivity substrates for very high frequency circuits. The sintering behavior, composition, microstructure, and dielectric properties of the ceramics were investigated using a heating microscope, X-ray diffractometry, scanning electron microscopy, energy dispersive spectroscopy, and terahertz time domain spectroscopy. The studies revealed a low dielectric permittivity of 5.1–6.7 and low dielectric loss in the frequency range 0.14–0.7 THz. The copper borate-based materials, owing to a low sintering temperature of 900–960 °C, are suitable for LTCC (low temperature cofired ceramics) applications.

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