Zeitschriftenartikel zum Thema „Coaxial shunt“

Transducers of current to voltage, such as current shunts are widely used in control systems for the mechanical engineering. The shunt is required to determine the value of its resistance on DC and AC currents to determine the transfer ratio error in the wide frequency band in process of verification or calibration. Well-known methods for resistance measuring (by Thompson' double bridge; magnetic comparator, compensation technique, etc.) require a commerce resistance and difficult to implement for shunts with resistance less than 0.1 Ohms. The paper describes a procedure for measuring the complex impedance of transfer ratio of current shunts in the frequency band using the lock-in amplifier with the differential input. The experimental results of the proposed procedure for coaxial shunt with nominal resistance at DC 750 uOhm and 160 uOhm are described.

Subject and Purpose. Two types of new dual-frequency microwave antennas with coaxial and two-wire shunts are considered with a view to improve calculation methods of radio engineering and design parameters of the antennas of the kind. Methods and Methodology. The mathematical methods of equivalent long line and the method of integral equation and optimization of objective functions are used, involving set-point and current values of the voltage standing-wave ratios at the antenna input connectors in the two operating frequency bands. Results. The research and development results have been presented for two variants of dual-frequency (dual-band) vibrator antennas according to whether the shunts are placed inside metal radiating tubes or outside the central conductive rod of the antenna. The shunts are in coaxial and two-wire versions. As applied to the first antenna variant, the method of shunt length optimization upon a minimization of the objective functions yields desired values of antenna electrical parameters (voltage standing-wave ratio, radiation patterns, etc.). For the second antenna variant with both coaxial and two-wire external shunts and provided that the design and operation principle of these antennas are similar, conditions under which the double-frequency mode is possible have been determined for the first time. Conclusion. The proposed method of design and development of tubular dual-frequency vibrator antennas with coaxial shunts has been used to yield a two-frequency circular (elliptical) polarization turnstile antenna as part of sea buoys in the project "Ocean" of the National Space Agency of Ukraine and other spaceborne dual-frequency antennas. The new dual-frequency microstrip antenna discussed in this paper saves us significant drawbacks peculiar to the known dual-frequency antennas and can be used aboard spacecraft and other mobile objects due to its small size.

This paper proposes a current sensor for wide bandgap (WBG) devices. The current of a power semiconductor device is mainly measured using a Rogowski coil, an active current transformer, and a coaxial shunt resistor. The Rogowski coil and active current transformer are not suitable for the current measurement of surface mount WBG devices due to their operating principle. The coaxial shunt resistor causes parasitic inductance. Since WBG devices are more sensitive to parasitic inductance than silicon devices, parasitic inductance may affect circuit operation. To overcome these problems, this paper proposes a printed circuit board (PCB)-embedded spiral pattern pick-up coil current measurement for WBG devices. The proposed pick-up coil has high mutual inductance compared to the conventional pick-up coil, so the measurement sensitivity is high. In addition, there is no need for additional processing outside the PCB. Experimental results using a double pulse tester circuit are provided to verify the performance of the proposed current sensor.

This paper presents a novel ultra-low-loss high-pass filter with 3 dB cutoff frequency of 890 MHz for astronomical receiver radio frequency interference mitigation application. The filter consists of three series capacitors, four shunt inductors, and microstrip circuit board. Specially, 4 shunt inductors are actualized by fabricating air-core short-circuit coaxial cable inductors in the filter box body, and the quality factor of these cable inductors is up to 762.2 and 1046, respectively, at 1.4 GHz. In the expected passband of 1.1–1.9 GHz, S parameters measurement show that insertion loss is lower than 0.16 dB and two-port return loss is larger than 20 dB; noise measurement show that filter noise temperature is lower than 8 at 300 K ambient temperature. Noise sources of this filter are analyzed by simulation and measurement.

The broadband transfer power wattmeter with the correction of the own consumption error for measuring the active power against the background of large reactive components in the radio frequency range is considered in article. The objects of research are electromagnetic elements (chokes / transfor­mers), operating at high frequencies and have strongly distorted forms of signals. When measuring at high frequencies, the channels of the wattmeter become very sensitive to phase errors. It is necessary to minimize links that cause phase shifts. In this connection, it is important to correctly construct the input units of the wattmeter and to make such a transformation, which will provide operations with signal rms valueswithout links phase shifts. The proposed scheme allows this to be achieved, and required gain is carried out without taking into account the phase shift of the signals. In the basic scheme of the wattmeter(fig. 1), the input device is executed from the main shunt and parallel to the auxiliary distributed shunt connected to it, which is connected to the main resistance of the voltage divider, in which the value of all resistances of the input device is determined by conditions of invariance to the squares of the voltage and load current , and the partially distributed auxiliary shunt is calculated with additional weighting factors to provide the conditions for invariance of the squared of voltage and current and eliminate the error from its own revives. Features of the construction of the input link of the wattmeter of transfer power with additional measurement of shunt voltage are given in the article(fig.2). Active power with taking into account the influence of the shunt reactive component calculation formulas (7)-(14)is presented. The basic error of the wattmeter is the error of the low-ohm shunt. It is expedient to use coaxial or triaxial shunts to extend the frequency range. Transfer power wattmeter input link, which contains additional measurement of shunt voltage simulations was performed in the article(fig.3and table 1). The advantages of such wattmeter are: possibility to expand the frequency range by taking into account shunt resistance reactive component influence on the measurement final result , which can be achieved not only by hardware (shunt inductance reduction), but also the introduction of the calculated correction after measuring the values of the shunt active and reactive component; the values of the input device elements can be optimized by the criterion of maximum broadband, since the error from own consumption is taken into account; in the scheme one low-level shunt is used, which reduces the cost of the wattmeter; additive errors of the voltage conversion channel are minimized.

The plasma produced by a high-current capacitive discharge through a graphite fiber bundle is compressed by a magnetic field coaxial with the plasma. The magnetic field is generated by the plasma current in a large coil surrounding the plasma. The field induces an azimuthal (theta) current in the plasma. This current couples with the external magnetic field and produces a radial Lorentz force which reduces the rate of plasma expansion. A diode shunt in the capacitive discharge circuit is used for the generation of a unidirectional discharge current. This arrangement eliminates zero-crossings of the discharge current and thus increases the effectiveness of the magnetic field in controlling the radiative properties of the plasma. Design features of the discharge circuit are presented, as well as a comparison of the plasma properties with oscillatory and unidirectional discharge current waveforms.

This study aims to observe the efficacy of a new recovery technology of cerebrospinal fluid flow obstacle for the treatment of subarachnoid haemorrhage with intracranial aneurysms, and review the overview of this new technology and new surgical instruments.MethodsFifth patients with subarachnoid haemorrhage caused by intracranial aneurysms, whose the HUNT-HESS were grade 2∼4. According to the operation methods of a coaxial catheter in vascular intervention, author envisaged that insert some specialized utensils into subarachnoid cavity to carry out thrombolysis, intelligence mechanical shunt of cerebrospinal fluid through lumbar puncture under the DSA watching to achieve an aim of resuming cerebrospinal fluid (CSF) and rebuilding CSF circulation.ResultsSeven consciousness disorder patients awaked in 8 to 26 hours after treatment by this technique, 15 patients were cured, no patient died and no any complication. Our observation suggests that the new technology restoring cerebrospinal fluid circulation on the treatment of subarachnoid haemorrhage with intracranial aneurysm is efficacy, worthy of further clinical observation.

Ion-selective microelectrodes (ISMs) have been used extensively in neurophysiological studies. ISMs selective for H+ and Ca2+ are notable for their sensitivity and selectivity, but suffer from a slow response time, and susceptibility to noise because of the high electrical resistance of the respective ion exchange cocktails. These drawbacks can be overcome by using a “coaxial” or “concentric” inner micropipette to shunt the bulk of the ion exchanger resistance. This approach was used decades ago to record extracellular [Ca2+] transients in cat cortex, but has not been subsequently used. Here, we describe a method for the rapid fabrication of concentric pH- and Ca2+-selective microelectrodes useful for extracellular studies in brain slices or other work in vitro. Construction was simplified compared with previous implementations, by using commercially available, thin-walled borosilicate glass, drawing an outer barrel with a rapid taper (similar to a patch pipette), and by use of a quick and reliable silanization procedure. Using a piezoelectric stepper to effect a rapid solution change, the response time constants of the concentric pH and Ca2+-electrodes were 14.9 ± 1.3 and 5.3 ± 0.90 ms, respectively. Use of these concentric ISMs is demonstrated in rat hippocampal slices. Activity-dependent, extracellular pH, and [Ca2+] transients are shown to arise two- to threefold faster, and attain amplitudes two- to fourfold greater, when recorded by concentric versus conventional ISMs. The advantage of concentric ISMs for studies of ion transport and ion diffusion is discussed.

AbstractA new type of two-dimensional (2D) composite right/left-handed transmission lines (CRLH TL) which is composed of four one-dimensional (1D) CRLH TL is proposed in this letter. Each 1D CRLH TL consists of three metallic vias added for shunt inductance and an etched patch slot for series capacitance. Based on this structure, an antenna operating on zeroth-order resonance (ZOR) and first-order resonance (FOR) is designed and fabricated. By taking advantage of coaxially center feed and symmetric structure, a well omnidirectional radiation in XoY plane both in ZOR and FOR and a homogeneously suppressed cross-polarization is obtained. Also, the antenna has a gain value of 2.06 dB in ZOR

The convergence of suburban homes and digital media and communications technologies is set to undergo a major shift as next-generation broadband infrastructures are installed. Embodied in the Australian Government’s National Broadband Network (NBN) and the delivery of fibre-optic cable to the front door of every suburban home, is an anticipated future of digital living that will transform the landscape and experience of suburban life. Drawing from our research, and from industry, policy and media documents, we map some scenarios of the NBN rollout in its early stages to show that this imaginary of seamless broadband in the suburbs and the transformation of digital homes it anticipates is challenged by local cultural and material geographies, which we describe as a politics of spectrum. The universal implementation of policy across Australia faces a considerable challenge in dealing with Australia’s physical environment. Geography has always had a major impact on communications technologies and services in Australia, and a major impetus of building a national broadband network has been to overcome the “tyranny of distance” experienced by people in many remote, regional and suburban areas. In 2009 the minister for Broadband, Communications and the Digital Economy (DBCDE), Stephen Conroy, announced that with the Government’s NBN policy “every person and business in Australia, no-matter where they are located, will have access to affordable, fast broadband at their fingertips” (Conroy). This ambition to digitally connect and include imagines the NBN as the solution to the current patchwork of connectivity and Internet speeds experienced across the country (ACCAN). Overcoming geographic difference and providing fast, universal and equitable digital access is to be realised through an open access broadband network built by the newly established NBN Co. Limited, jointly owned by the Government and the private sector at a cost estimated at $43 billion over eight years. In the main this network will depend upon fibre-optics reaching over 90% of the population, and achieving download speeds of up to 100 Mbit/s. The remaining population, mostly living in rural and remote areas, will receive wireless and satellite connections providing speeds of 12 Mbit/s (Conroy). Differential implementation in relation to comparisons of urban and remote populations is thus already embedded in the policy, yet distance is not the only characteristic of Australia’s material geographies that will shape the physical implementation of the NBN and create a varied spectrum of the experience of broadband. Instead, in this article we examine the uneven experience of broadband we may see occurring within suburban regions; places in which enhanced and collective participation in the digital economy relies upon the provision of faster transmission speeds and the delivery of fibre “the last mile” to each and every premise. The crucial platform for delivering broadband to the ’burbs is the digital home. The notion of the connected or smart or digital home has been around in different guises for a number of decades (e.g. Edwards et al.), and received wide press coverage in the 1990s (e.g. Howard). It has since been concretised in the wake of the NBN as telecommunications companies struggle to envision a viable “next step” in broadband consumption. Novel to the NBN imaginary of the digital home is a shift from thinking about the digital home in terms of consumer electronics and interoperable or automatic devices, based on shared standards or home networking, to addressing the home as a platform embedded within the economy. The digital home is imagined as an integral part of a network of digital living with seamless transitions between home, office, supermarket, school, and hospital. In the imaginary of the NBN, the digital home becomes a vital connection in the growing digital economy. Communications Patchwork, NBN Roll-Out and Infrastructure Despite this imagined future of seamless connectivity and universal integration of suburban life with the digital economy, there has been an uneven take-up of fibre connections. We argue that this suggests that the particularities of place and the materialities of geography are relevant for understanding the differential uptake of the NBN across the test sites. Furthermore, we maintain that these issues provide a useful model for understanding the ongoing process and challenges that the rollout of the NBN will face in providing even access to the imagined future of the digital home to all Australians. As of June 2011 an average of 70 per cent of homes in the five first release NBN sites have agreed to have the fibre cables installed (Grubb). However, there is a dramatic variation between these sites: in Armidale, NSW, and Willunga, SA, the percentage of properties consenting to fibre connections on their house is between 80-90 per cent; whereas in Brunswick, Victoria, and Midway Point, Tasmania, the take-up rate is closer to 50 per cent (Grubb). We suggest that these variations are created by a differential geography of connectivity that will continue to grow in significance as the NBN is rolled out to more locations around Australia. These can be seen to emerge as a consequence of localised conditions relating to, for example, installation policy, a focus on cost, and installation logistics. Another significant factor, unable to be addressed within the scope of this paper, is the integration of the NBN with each household’s domestic network of hardware devices, internal connections, software, and of course skill and interest. Installation Policy The opt-in policy of the NBN Co requires that owners of properties agree to become connected—as opposed to being automatically connected unless they opt-out. This makes getting connected a far simpler task for owner-occupiers over renters, because the latter group were required to triangulate with their landlords in order to get connected. This was considered to be a factor that impacted on the relatively low uptake of the NBN in Brunswick and Midway Point, and is reflected in media reports (Grubb) and our research: There was a bit of a problem with Midway Point, because I think it is about fifty percent of the houses here are rentals, and you needed signatures from the owners for the box to be put onto the building (anon. “Broadband in the Home” project). …a lot of people rent here, so unless their landlord filled it in they wouldn’t know (anon. “Broadband in the Home” project). The issue is exacerbated by the concentration of rental properties in particular suburbs and complicated rental arrangements mediated through agents, which prevent effective communication between the occupiers and owners of a property. In order to increase take-up in Tasmania, former State Premier, David Bartlett, successfully introduced legislation to the Tasmanian state legislature in late 2010 to make the NBN opt-out rather than opt-in. This reversed the onus of responsibility and meant that in Tasmania all houses and businesses would be automatically connected unless otherwise requested, and in order to effect this simple policy change, the government had to change trespass laws. However, other state legislatures are hesitant to follow the opt-out model (Grubb). Differentials in owner-occupied and rental properties within urban centres, combined with opt-in policies, are likely to see a continuation of the connectivity patchwork that that has thus far characterised Australian communications experience. A Focus on Cost Despite a great deal of public debate about the NBN, there is relatively little discussion of its proposed benefits. The fibre-to-the-home structure of the NBN is also subject to fierce partisan political debate between Australia’s major political parties, particularly around the form and cost of its implementation. As a consequence of this preoccupation with cost, many Australian consumers cannot see a “value proposition” in connecting, and are not convinced of the benefits of the NBN (Brown). The NBN is often reduced to an increased minimum download rate, and to increased ISP fees associated with high speeds, rather than a broader discussion of how the infrastructure can impact on commerce, education, entertainment, healthcare, and work (Barr). Moreover, this lack of balance in the discussion of costs and benefits extends in some instances to outright misunderstandings about the difference between infrastructure and service provision: …my neighbour across the road did not understand what that letter meant, and she would have to have been one of dozens if not hundreds in the exactly the same situation, who thought they were signing up for a broadband plan rather than just access to the infrastructure (anon. “Broadband in the Home” project) Lastly, the advent of the NBN in the first release areas does not override the costs of existing contracts for broadband delivered over the current copper network. Australians are often required to sign long-term contracts that prevent them from switching immediately to the new HSB infrastructure. Installation Logistics Local variations in fibre installation were evident prior to the rollout of the NBN, when the increased provision of HSB was already being used as a marketing device for greenfield (newly developed) estates in suburban Australia. In the wake of the NBN rollouts, some housing developers have begun to lay “NBN-ready” optic fibre in greenfield estates. While this is a positive development for those who a purchasing a newly-developed property, those that invest in brownfield “re-developments,” may have to pay over twice the amount for the installation of the NBN (Neales). These varying local conditions of installation are reflected in the contractual arrangements for installing the fibre, the installers’ policies for installation, and the processes of installation (Darling): They’re gonna have to do 4000 houses a day … and it was a solid six months to get about 800 houses hooked up here. So, logistically I just can’t see it happening. (anon. “Broadband in the Home” project) Finally, for those who do not take-up the free initial installation offer, for whatever reason, there will be costs to have contractors return and connect the fibre (Grubb; Neales). Spectrum Politics, Fibre in the Neighbourhood The promise that the NBN will provide fast, universal and equitable digital access realised through a fibre-optic network is challenged by the experience of first release sites such as Midway Point. As evident above, and due to a number of factors, there is a likelihood in supposedly NBN-connected places of varied connectivity in which service will range from dial-up to DSL and ADSL to fibre and wireless, all within a single location. The varied connectivity in the early NBN rollout stages suggests that the patchwork of Internet connections commonly experienced in Australian suburbs will continue rather than disappear. This varied patchwork can be understood as a politics of spectrum. Rod Tucker (13-14) emphasises that the crucial element of spectrum is its bandwidth, or information carrying capacity. In light of this the politics of spectrum reframes the key issue of access to participation in the digital economy to examine stakes of the varying quality of connection (particularly download speeds), through the available medium (wireless, copper, coaxial cable, optical fibre), connection (modem, antenna, gateway) and service type (DSL, WiFi, Satellite, FTTP). This technical emphasis follows in the wake of debates about digital inclusion (e.g., Warschauer) to re-introduce the importance of connection quality—embedded in older “digital divide” discourse—into approaches that look beyond technical infrastructure to the social conditions of their use. This is a shift that takes account of the various and intertwined socio-technical factors influencing the quality of access and use. This spectrum politics also has important implications for the Universal Service Obligation (USO). Telstra (the former Telecom) continues to have the responsibility to provide every premise in Australia with a standard telephone service, that is at least a single copper line—or equivalent service—connection. However, the creation of the NBN Co. relieves Telstra of this obligation in the areas which have coverage from the fibre network. This agreement means that Telstra will gradually shut down its ageing copper network, following the pattern of the NBN rollout and transfer customers to the newly developed broadband fibre network (Hepworth and Wilson). Consequently, every individual phone service in those areas will be required to move onto the NBN to maintain the USO. This means that premises not connected to the NBN because the owners of the property opted out—by default or by choice—are faced with an uncertain future vis-à-vis the meaning and provision of the USO because they will not have access to either copper or fibre networks. At this extreme of spectrum politics, the current policy setting may result in households that have no possibility of a broadband connection. This potential problem can be resolved by a retro-rollout, in which NBN fibre connection is installed at some point in the future to every premises regardless of whether they originally agreed or not. Currently, however, the cost of a retrospective connection is expected to be borne by the consumer: “those who decline to allow NBN Co on to their property will need to pay up to $300 to connect to the NBN at a later date” (Grubb) Smaller, often brownfield development estates also face particular difficulties in the current long-term switch of responsibilities from Telstra to the NBN Co. This is because Telstra is reluctant to install new copper networks knowing that they will soon become obsolete. Instead, “in housing estates of fewer than 100 houses, Telstra is often providing residents with wireless phones that are unable to connect to the Internet” (Thompson). Thus a limbo is created, where new residents will not have access to either copper or fibre fixed line connections. Rather, they will have to use whatever wireless Internet is available in the area. Particularly concerning is that the period of the rollout is projected to last for eight years. As a result: “Thousands of Australians—many of them in regional areas—can expect years of worse, rather than better, Internet services as the National Broadband Network rolls out across the country” (Thompson). And, given different take-up rates and costs of retro-fitting, this situation could continue for many people and for many years after the initial rollout is completed. Implications of Spectrum Politics for the Digital Home What does this uncertain and patchwork future of connectivity imply for digital living and the next-generation broadband suburb? In contrast to the imagined post-NBN geography of the seamless digital home, local material and cultural factors will still create varied levels of service. This predicament challenges the ideals of organisations such as the Digital Living Network, an industry body comprised of corporate members, “based on principles of open standards and home networking interoperability [which] will unleash a rich digital media environment of interconnected devices that enable us all to experience our favorite content and services wherever and whenever we want” (Vohringer). Such a vision of convergence takes a domestic approach to the “Internet of things” by imagining a user-friendly network of personal computing, consumer electronics, mobile technologies, utilities, and other domestic technologies. The NBN anticipates a digital home that is integrated into the digital economy as a node of production and consumption. But this future is challenged by the patchwork of connectivity. Bruno Latour famously remarked that even the most extensive and powerful networks are local at every point. Although he was speaking of actor-networks, not broadband networks, analysis of the Australian experience of high-speed broadband would do well to look beyond its national characteristics to include its local characteristics, and the constellations between them. It is at the local level, importantly, at the level of the household and suburb, that the NBN will be experienced in daily life. As we have argued here, we have reason to expect that this experience will be as disparate as the network is distributed, and we have reason to believe that local cultural and material factors such as installation policies, discussions around costs and benefits, the household’s own internal digital infrastructure, and installation logistics at the level of the house and the neighbourhood, will continue to shape a patchworked geography of media and communications experiences for digital homes. References Australian Communications Consumer Action Network (ACCAN). 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