Pub Date : 2004-11-30DOI: 10.1109/HFPSC.2004.1360337
A. Milne, P. Curtis, M. Missous, W. S. Truscott, E. Linfield, C. Worrall
Summary form only given. The results of measurements on photon-assisted tunnelling in triple-barrier quantum well structures are reported. The series of AlGaAs/GaAs structures have been extensively characterised and have quantum well confinement energies of 40 to 90 meV. The energy width of the quantum well states is appropriately 1.2 meV. A Cavendish Laboratory quantum cascade laser (2.9 THz, >50 mW) excites transitions between quantum wells when the first well is thermally populated and the correct separation of the quantum well states has been achieved by the applied bias. The electromagnetic field is coupled into the structures by metallic diffraction gratings with periods between 15 and 29 /spl mu/m. The photo-induced currents have been measured as a function of bias and temperature. The estimated detectivities are compared with those for other Terahertz detectors. The potential for improvement in detectivity by optimizing the coupling of the electromagnetic field into the structures is discussed.
只提供摘要形式。报道了三势垒量子阱结构中光子辅助隧穿的测量结果。AlGaAs/GaAs结构系列已被广泛表征，其量子阱约束能为40至90 meV。量子阱态的能量宽度为1.2 meV。卡文迪什实验室的量子级联激光器(2.9太赫兹，>50兆瓦)在第一个量子阱被热填充时激发量子阱之间的跃迁，并且通过施加偏置实现了量子阱态的正确分离。电磁场通过周期在15 ~ 29 μ l /m之间的金属衍射光栅耦合到结构中。测量了光感应电流作为偏置和温度的函数。估计的探测率与其他太赫兹探测器的探测率进行了比较。讨论了通过优化电磁场与结构的耦合来提高探测能力的可能性。
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Pub Date : 2004-11-30DOI: 10.1109/HFPSC.2004.1360348
I. Leonte, M. Hunt, G. Sehra, M. Cole, J. Gardner
A system based on shear horizontal surface acoustic wave (SH-SAW) devices operating in the 433 MHz and 869 MHz industrial, scientific and medical (ISM) bands is proposed for wireless identification and characterisation of bioliquids. The theory of operation is briefly explained and details of the passive microsensors design and fabrication are presented. A small device antenna is analyzed and the interrogation unit implementation is discussed. A new low cost solution for measuring inter-pulse time delays with nanosecond resolution is also proposed.
{"title":"SAW bioliquids sensor with RF interrogation","authors":"I. Leonte, M. Hunt, G. Sehra, M. Cole, J. Gardner","doi":"10.1109/HFPSC.2004.1360348","DOIUrl":"https://doi.org/10.1109/HFPSC.2004.1360348","url":null,"abstract":"A system based on shear horizontal surface acoustic wave (SH-SAW) devices operating in the 433 MHz and 869 MHz industrial, scientific and medical (ISM) bands is proposed for wireless identification and characterisation of bioliquids. The theory of operation is briefly explained and details of the passive microsensors design and fabrication are presented. A small device antenna is analyzed and the interrogation unit implementation is discussed. A new low cost solution for measuring inter-pulse time delays with nanosecond resolution is also proposed.","PeriodicalId":405718,"journal":{"name":"High Frequency Postgraduate Student Colloquium, 2004","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127724486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2004-11-30DOI: 10.1109/HFPSC.2004.1360387
Hing Weng Seng, R. Sloan, K. Williams
Microwave limiters are used to prevent burnout and permanent damage in power sensitive components such as receivers and mixers. State-of-the-art limiters are implemented employing PIN diodes, in which limiting is provided by varying the RF resistance of the diode. The PIN diode is a cheap and easy-to-use devices but its bandwidth and power rating is limited. Furthermore, PIN diodes cannot readily be fabricated. in MMIC technology. Here, an investigation is presented on the feasibility of employing heterojunction devices in limiters. This paper presents a T-switch attenuator formed by HEMTs simulated at X-band.
{"title":"Implementing RF signal limiter with heterojunction devices","authors":"Hing Weng Seng, R. Sloan, K. Williams","doi":"10.1109/HFPSC.2004.1360387","DOIUrl":"https://doi.org/10.1109/HFPSC.2004.1360387","url":null,"abstract":"Microwave limiters are used to prevent burnout and permanent damage in power sensitive components such as receivers and mixers. State-of-the-art limiters are implemented employing PIN diodes, in which limiting is provided by varying the RF resistance of the diode. The PIN diode is a cheap and easy-to-use devices but its bandwidth and power rating is limited. Furthermore, PIN diodes cannot readily be fabricated. in MMIC technology. Here, an investigation is presented on the feasibility of employing heterojunction devices in limiters. This paper presents a T-switch attenuator formed by HEMTs simulated at X-band.","PeriodicalId":405718,"journal":{"name":"High Frequency Postgraduate Student Colloquium, 2004","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128556803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2004-11-30DOI: 10.1109/HFPSC.2004.1360388
H. Chua, M. Mantle, A. Haigh, F. Thompson, A. Gibson, L. Gladden
In this paper, we used the magnetic resonance imaging (MRI) technique to image moisture and lipid oil distribution in a single wheat grain kernel. Spatial information on both oil and water distribution of 10% and 20% moisture content grain kernels is presented. 2D cut-plane images indicate that the lipid oil is mainly concentrated in the germ region and the outer epidermis layer, whereas, the moisture content (MC) is evenly distributed through the cross sectional area of the wheat grain. The results also show that for lower moisture contents, the MR images are dominated by the lipid signals opposed to the water, which is attributed to the differences in T/sub 2/ relaxation behaviour.
{"title":"Non-invasive measurement of lipid and water in single wheat grains using magnetic resonance imaging","authors":"H. Chua, M. Mantle, A. Haigh, F. Thompson, A. Gibson, L. Gladden","doi":"10.1109/HFPSC.2004.1360388","DOIUrl":"https://doi.org/10.1109/HFPSC.2004.1360388","url":null,"abstract":"In this paper, we used the magnetic resonance imaging (MRI) technique to image moisture and lipid oil distribution in a single wheat grain kernel. Spatial information on both oil and water distribution of 10% and 20% moisture content grain kernels is presented. 2D cut-plane images indicate that the lipid oil is mainly concentrated in the germ region and the outer epidermis layer, whereas, the moisture content (MC) is evenly distributed through the cross sectional area of the wheat grain. The results also show that for lower moisture contents, the MR images are dominated by the lipid signals opposed to the water, which is attributed to the differences in T/sub 2/ relaxation behaviour.","PeriodicalId":405718,"journal":{"name":"High Frequency Postgraduate Student Colloquium, 2004","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-11-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115315278","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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