1,103 research outputs found
Putting away childish things: incidents of recovery in Tolkien and Haddon
The article discusses the philosophy of author J.R.R. Tolkien. Borrowing concepts from Gerard Manley Hopkins and John Duns Scotus, Tolkien developed the concept of recovery, in which a person is able to interact with the world as though they have never done so before. Using Mark Haddon's novel "The Curious Incident of the Dog in the Night-Time" the article details how recovery can lead people to seeing things differently rather than just glancing at them and accepting it for what it is. The author also uses examples from Tolkien's "Lord of the Rings" series to prove his point
A wideband high-linearity RF receiver front-end in CMOS
This paper presents a wideband high-linearity RF receiver-front-end, implemented in standard 0.18 /spl mu/m CMOS technology. The design employs a noise-canceling LNA in combination with two passive mixers, followed by lowpass-filtering and amplification at IF. The achieved bandwidth is >2 GHz, with a noise figure of 6.5 dB, +1 dBm IIP/sub 3/, +34.5 dBm IIP/sub 2/ and <50 kHz 1/f-noise corner frequency
Variable Bandwidth Analog Channel Filters for Software Defined Radio
An important aspect of Software Defined Radio is the ability to define the bandwidth of the filter that selects the desired channel. This paper first explains the importance of channel filtering. Then the advantage of analog channel filtering with a variable bandwidth in a Software Defined Radio is demonstrated. This is done by comparing the requirements of the analog-to-digital converter with and without an analog filter with a variable bandwidth. Then, a technique for channel filtering is described, in which two passive filters are combined to obtain a variable bandwidth. Passive filters have the advantage of high linearity, low noise and inherent energy efficiency. Some limitations of the concept are discussed. Finally, conclusions are drawn and our ideas for further research are presented
An Analogue Front-End Test-Bed for Software Defined Radio
A Software Defined Radio (SDR) is a radio receiver and/or transmitter, whose characteristics can to a large extent be defined by software. Thus, an SDR can receive and/or transmit a wide variety of signals, supporting many different standards. In our research, we currently focus on a demonstrator that is able to receive both Bluetooth and HiperLAN/2. This helps us to identify problems associated with SDR, and will provide a test-bed for possible solutions to these problems. The two standards differ significantly in characteristics like frequency band, signal bandwidth and modulation type. Combining two different standards in one receiver appears to pose new design challenges. For example, in the wide frequency range that we want to receive, many strong signals\ud
may exist. This leads to severe linearity requirements for wideband receivers. This paper describes some receiver architectures. One\ud
design has been selected. This receiver has been built, and some measurement results are included
High-Q variable bandwidth passive filters for Software Defined Radio
An important aspect of Software Defined Radio is the ability to define the bandwidth of the filter that selects the desired channel. This paper describes a technique for channel filtering, in which two passive filters are combined to obtain a variable bandwidth. Passive filters have the advantage of high linearity, low noise and inherent energy efficiency. After an explanation of the concept, the requirements on the subsequent analog-todigital conversion are compared with those in a system where (part of) the channel selection is performed digitally. Some drawbacks of the concept are discussed. Finally, conclusions are drawn and our ideas for further research are presented
An Analogue Front-End Architecture for Software Defined Radio
A Software Defined Radio (SDR) is a radio receiver and/or transmitter, whose characteristics can to a large extent be defined by software. Thus, an SDR can receive and/or transmit a wide variety of signals, supporting many different standards. In our research, we currently focus on a demonstrator that is able to receive both Bluetooth and HiperLAN/2. This helps us to identify problems associated with SDR, and will provide a test-bed for possible solutions to these problems. The two standards differ significantly in characteristics like frequency band, signal bandwidth and modulation type. Combining two different standards in one receiver appears to pose new design challenges. For example, in the wide frequency range that we want to receive, many strong signals\ud
may exist. This leads to severe linearity requirements for wideband receivers. This paper describes some receiver architectures. One\ud
design has been selected. This receiver has been built, and some measurement results are included
A Wideband Inductorless CMOS Front-End for Software Defined
The number of wireless communication links is witnessing tremendous growth and new standards are being introduced at high pace. These standards heavily rely on digital signal processing, making CMOS the first technology of choice. However, RF CMOS circuit development is costly and time consuming due to mask costs and design iterations. This pleads for a Software Defined Radio approach, in which one piece of flexible radio hardware is re-used for different applications and standards, downloadable and under software control. To the best of our knowledge, little work has been done in this field based on CMOS technology. Recently, a bipolar downconverter front-end has been proposed [1]. In CMOS, only wideband low-noise amplifiers have been proposed, and some CMOS tuner ICs for satellite reception (which have less stringent noise requirements because they are preceded by an outdoor low-noise converter). This paper presents a wideband RF downconverter frontend in 0.18 um CMOS (also published in [2]), designed in the context of a research project exploring the feasibility of software defined radio, using a combined Bluetooth/WLAN receiver as a vehicle. Usually, RF receivers are optimised for low power consumption. In contrast, we have taken the approach to optimise for flexibility. The paper discusses the main system and circuit design choices, and assesses the achievable performance via measurements on a front-end implemented in 0.18um CMOS. The flexible design achieves a 0.2-2.2 GHz -3 dB bandwidth, a gain of 25 dB with 6 dB noise figure and +1 dBm IIP3
Jitter requirements of the sampling clock in software radio receivers
The effective number of bits of an analog-to-digital converter (ADC) is not only limited by the quantization step inaccuracy but also by sampling time uncertainty. According to a commonly used model, the error caused by timing jitter, integrated over the whole bandwidth, should not be bigger than the quantization noise, for a full swing input signals at the maximum input frequency. This results in unfeasible phase noise requirements for the sampling clock in software radio receivers with direct RF sampling. However, for a radio receiver not the total integrated error is relevant, but only the error signal in the channel bandwidth. This paper explores the clock jitter requirements for a software radio application, using a more realistic model and taking into account the power spectrum of both the input signal and the spectrum of the sampling clock jitter. Using this model, we show that the clock jitter requirements are very similar to reciprocal mixing requirements of superheterodyne receivers
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Criticality Safety Envelope for Receipt, Handling, and Storage of Transuranic Waste
Current criticality safety limits for Solid Waste Management Facility (SWMF) Transuranic (TRU) Waste Storage Pads are based on analysis of systems where mass is the only independent parameter and all other parameters are assumed at their most reactive values (Ref. 1). These limits result in administrative controls (i.e., limit stacking of containers, coordination of drums for culvert storage based on individual drum fissile inventories, and mass limits for accumulation of polyethylene boxes in culverts) which can only be met by redundant SWMF administrative controls. These analyses did not credit the nature of the waste generator process that would provide bounding limits on the other parameters (i.e. less than optimal moderation and configurations within packages (containers)). They also did not indicate the margin of safety associated with operating to these mass limits. However, by crediting the waste generator processes (and maintaining such process assumptions via controls in the criteria for waste acceptance) sufficient margin of safety can be demonstrated to justify continued SWMF TRU pad operation with fewer administrative controls than specified in the Double Contingency analysis (DCA) (Ref. 1)
Behaviour of shot peening combined with WC-Co HVOF coating under complex fretting wear and fretting fatigue loading conditions
This study investigated the fretting and fretting fatigue performance of tungsten carbide–cobalt (WC–Co) HVOF spray coating systems. Fretting wear and fretting fatigue tests of specimens with shot peening and WC–Co coatings on 30NiCrMo substrates were conducted. The WC-Co coating presents very good wear resistance and decreases by more than 9 times the energy wear coefficient (α) under fretting conditions. The tested coating reduces crack nucleation under both fretting and fretting fatigue studied situations. Finally the crack arrest conditions are evaluated by the combined fretting and fretting fatigue investigation. It is shown and explained how and why this combined surface treatment (shot peening and WC–Co) presents a very good compromise against wear and cracking fretting damage
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