Field test of HTS receivers on CDMA demonstration cluster in China

Wei, Bin; Guo, Xubo; Piao, Yunlong; Jin, S.; Zhang, Xiaoping; Gao, Liangmin; Peng, Hao; Yin, Z. S.; Cao, Bisong

doi:10.1007/s11434-009-0052-3

Cited by 21 publications

(11 citation statements)

References 7 publications

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“…In recent years, superconducting devices, such as superconducting Josephson junctions [1], filters [2][3][4][5], single photon detector [6] and hot electron bolometer (HEB) mixer [7] have attracted a great deal of interest in China. Important aspects to qubit applications are Josephson junctions and Superconducting Quantum Interference Device (SQUID) [8][9][10][11][12].…”

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confidence: 99%

Character and fabrication of Al/Al2O3/Al tunnel junctions for qubit application

Shen

Zhu

et al. 2012

Chin. Sci. Bull.

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The superconductive Josephson junction is the key device for superconducting quantum computation. We have fabricated Al/ Al 2 O 3 /Al tunnel junctions using a double angle evaporation method based on a suspended shadow mask. The Al 2 O 3 junction barrier has been formed by introducing pure oxygen into the chamber during the fabrication process. We have adjusted exposure conditions by changing either the oxygen pressure or the oxidizing time during the formation of tunnel barriers to control the critical current density J c and the junction specific resistance R c . [8][9][10][11][12]. Quantum computation entails a new computation system that exceeds its classical counterpart. It is anticipated there will be an exponential speed up in solving problems which are difficult for classical computers, such as prime factorization. This prospect has fuelled much research into various experimental realizations of a quantum computer. Superconducting quantum computation is a viable and scalable approach to achieving a quantum computation scheme. Because of their solid state nature, their macroscopic phase coherence and their similarity to conventional semiconductor circuits, Josephson junction circuits are a promising technology within superconducting quantum computation schemes [13][14][15][16]. A typical flux qubit [16][17][18][19] consists of an isolated superconductive junction and a SQUID. In a SQUID the tunnel junctions are arranged in parallel to form a superconducting loop. The superconductive Josephson junction is the key device for superconducting quantum computation. The most commonly used materials for Josephson junction qubits are Aluminum (Al) and Niobium (Nb), because of the purity of their superconducting state as well as their relatively low transition temperatures (T c = 1.2 K and 9.3 K, respectively) [20]. We have chosen to work with aluminum for several reasons. Firstly, high quality aluminum oxide has been shown to be less detrimental to Josephson junction qubits than other materials [21], with longer coherence times seen in aluminum-based devices [22]. Also, the fabrication of Al is flexible because of the fact that its melting point (660°C) is significantly lower than that of other popular superconducting materials, such as Nb (2477°C). For qubit applications, we have explored the electronic properties of the Al/Al 2 O 3 /Al tunnel junction, including the critical current density J c and the junction specific resistance R c , which depend on the oxygen pressure and the oxidation

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confidence: 99%

Character and fabrication of Al/Al2O3/Al tunnel junctions for qubit application

Shen

Zhu

et al. 2012

Chin. Sci. Bull.

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“…Finally, we give a use case of RF for autonomous CRM, where the optimal RF is achieved to guarantee the resource-imbalanced requests of different service traffic flows. With the rapid growth in mobile communications, deployment and maintenance of future networks are becoming more and more complicated, time-consuming, and expensive [1][2][3]. In most existing networks, parameters are mutually adjusted to achieve a high level of network performance.…”

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confidence: 99%

“…With the rapid growth in mobile communications, deployment and maintenance of future networks are becoming more and more complicated, time-consuming, and expensive [1][2][3]. In most existing networks, parameters are mutually adjusted to achieve a high level of network performance.…”

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confidence: 99%

Resource flow: Autonomous cognitive resource management framework for future networks

Yang

Sheng

et al. 2012

Chin. Sci. Bull.

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From an end-to-end performance perspective, a multi-agent-based cognitive resource management (MA-CRM) framework is proposed in this article. More importantly, we introduce a novel concept of resource flow (RF) as integrated CRM in a multi-dimensional environment scenario. We concentrate on the autonomous CRM framework in cognitive radio (CR) networks. Specifically, we first summarize the necessity of the novel concept for implementing intelligent and autonomous resource management considering both the requirements of various types of resource and the unified framework of the CRM scheme. Then, we introduce the concept of RF, including the technical aspects, purpose, classification, and description. Finally, we give a use case of RF for autonomous CRM, where the optimal RF is achieved to guarantee the resource-imbalanced requests of different service traffic flows. With the rapid growth in mobile communications, deployment and maintenance of future networks are becoming more and more complicated, time-consuming, and expensive [1][2][3]. In most existing networks, parameters are mutually adjusted to achieve a high level of network performance. In Long Term Evolution (LTE), the concept of a self-organizing network is introduced, where system parameter tuning is done astronomically based on network measurements [4]. Meanwhile, cognitive terminals in future convergence networks of multi-heterogeneous radio access networks will be faced with a flexible environment including radio, networks, and user context. Therefore, more efficient cognitive resource management (CRM) strategies and algorithms have to be integrated in future mobile networks to further reduce capital expenditure (CAPEX) and operational expenditure (OPEX) [5][6][7][8][9]. In addition, the deployment and optimization of mobile networks are significantly complicated and challenging engineering tasks requiring a comprehensive systematic CRM and allocation approach, which determines the overall performance of the current communication systems and better guarantees the varying quality of service (QoS) of the different traffic flows [1,7,9]. Under the condition of high convergence of heterogeneous networks, how to achieve effective utilization of multidomain resources is a great challenge and filled with strategic meaning. Highly efficient use of resources not only means more revenue for the operators, but also bridges the gap between resource scarcity and resource under-utilization. To break the resource gridlock [10], CRM has been followed with great interest. For instance, multi-agent system-based cognitive resource management architecture is proposed in [11], while a multi-agent learning optimal power control policy and channel selection without negotiation in CR systems are investigated respectively in [11] and [12]. In [13], layer-less dynamic networks enabling the characterization of fundamental performance regions without a presupposition of protocol stack layering are considered. This study is typically distinguished from previous results of cross-...

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“…Superconducting materials have been widely used in the development of kinds of devices, such as filters [1][2][3][4], single photon detector [5] and hot electron bolometer (HEB) mixer [6]. Among these, an important aspect is the development of high-performance narrowband microwave filters.…”

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confidence: 99%

A high-performance narrowband high temperature superconducting filter

et al. 2010

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Recent development of a high-performance narrowband high-temperature superconducting (HTS) filter is presented. A 10-pole quasi-elliptic function response filter with two pairs of transmission zeros (for high selectivity), which has a center frequency of 2.185 GHz and a 3 dB bandwidth of 10 MHz (a fractional bandwidth of 0.45%), is introduced. The filter was fabricated on a 40 mm×16 mm×0.5 mm MgO wafer with double-sided YBCO films. The measured results show that the filter has 0.15 dB insertion loss at the center of the passband and a return loss better than −22.5 dB at a temperature of 67 K. Band edge steepness reaches over 28.3 dB/MHz at both the low and high frequency edges. The out-of-band rejection is over 78 dB at 8 MHz away from the center frequency and close to 100 dB in a wideband range. high-performance, narrowband, HTS, filterCitation: Cui B, Zhang X Q, Sun L, et al. A high-performance narrowband high temperature superconducting filter. Recently, superconducting devices have been developed steadily in China. Superconducting materials have been widely used in the development of kinds of devices, such as filters [1-4], single photon detector [5] and hot electron bolometer (HEB) mixer [6]. Among these, an important aspect is the development of high-performance narrowband microwave filters. Generally speaking, the insertion loss of a filter is inversely proportional to its fractional bandwidth (FBW), and thus it is difficult to realize narrowband filters (for example FBW<0.5%) using normal metals. The hightemperature superconducting (HTS) films have a thousand times smaller microwave surface resistance than normal metal films. Therefore they are suitable for use in fabricating such narrowband filters and many works on narrowband HTS filters have been reported since early 1990s [7][8][9][10][11][12].In most cases, to realize high selectivity, HTS filters are constructed by numbers of resonators which are arranged within a testing house. The compact size of HTS filters will introduce some unwanted parasitic couplings between nonadjacent resonators, which makes it hard to realize a high out-of-band rejection. Besides, it is not easy to achieve better return loss (such as, better than −20 dB) due to the complexity of tuning at low temperature and in vacuum. There are, to our knowledge, only a couple of reports in the literature of HTS filters with high-performance specification of return loss (< −20 dB) and/or out-of-band rejection (> 95 dB) [13][14][15].In this work, we present a 10-pole high-performance narrowband HTS filter with a cascaded quadruplet coupling structure. The filter has an excellent return loss (−22.5 dB in the passband) and a high out-of-band rejection (close to 100 dB in a wideband range). A double-folded resonator structure [16], which has been developed in our laboratory for a filter with a center frequency of 8 GHz, is used in our design to realize the high out-of-band rejection level. A novel asymmetrical cross coupling structure is introduced to implement the filter with two pairs of t...

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Field test of HTS receivers on CDMA demonstration cluster in China

Cited by 21 publications

References 7 publications

Character and fabrication of Al/Al2O3/Al tunnel junctions for qubit application

Character and fabrication of Al/Al2O3/Al tunnel junctions for qubit application

Resource flow: Autonomous cognitive resource management framework for future networks

A high-performance narrowband high temperature superconducting filter

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