3,232 research outputs found
Compensation technique for nonlinear distortion in RF circuits for multi-standard wireless systems
Recent technological advances in the RF and wireless industry has led to the design requirement of more sophisticated devices which can meet stringent specifications of bandwidth, data rate and throughput. These devices are required to be extremely sensitive and hence any external interference from other systems can severely affect the device and the output.
This thesis introduces the existing problem in nonlinear components in a multi-standard wireless system due to interfering signals and suggests potential solution to the problem. Advances in RF and wireless systems with emerging new communication standards have made reconfigurablility and tunability a very viable option. RF transceivers are optimised for multi-standard operation, where one band of frequency can act as an interfering signal to the other band. Due to the presence of nonlinear circuits in the transceiver chains such as power amplifiers, reconfigurable and tunable filters and modulators, these interfering signals produce nonlinear distortion products which can deform the output signal considerably. Hence it becomes necessary to block these interfering signals using special components.
The main objective of this thesis is to analyse and experimentally verify the nonlinear distortions in various RF circuits such as reconfigurable and tunable filters and devise ways to minimize the overall nonlinear distortion in the presence of other interfering signals. Reconfigurbality and tunablity in filters can be achieved using components such as varactor diodes, PIN diodes and optical switches. Nonlinear distortions in such components are measured using different signals and results noted.
The compensation method developed to minimize nonlinear distortions in RF circuits caused due to interfering signals is explored thoroughly in this thesis. Compensation method used involves the design of novel microstrip bandstop filters which can block the interfering signals and hence give a clean output spectrum at the final stage. Recent years have seen the emergence of electronic band gap technology which has “band gap” properties meaning that a bandstop response is seen within particular range of frequency. This concept was utilised in the design of several novel bandstop filters using defected microstrip structure. Novel tunable bandstop filters has been introduced in order to block the unwanted signal. Fixed single-band and dual-band filters using DMS were fabricated with excellent achieved results. These filters were further extended to tunable structures. A dual-band tunable filter with miniaturized size was developed and designed.
The designed filters were further used in the compensation technique where different scenarios showing the effect of interfering signals in wireless transceiver were described. Mathematical analysis proved the validation of the use of a bandstop filter as an inter-stage component. Distortion improvements of around 10dB have been experimentally verified using a power amplifier as device under test. Further experimental verification was carried out with a transmitter which included reconfigurable RF filters and power amplifier where an improvement of 15dB was achieved
Mother or Motherland: Can a Government Have an Impact on Educational Attainment of the Population? Preliminary Evidence from India
In this paper, using data from the 61st round of the (Indian) National Sample Survey, we examine the relative impacts of personal-household and state-level characteristics (including government policy) on the likelihood of transition from one educational level to the next. Our analysis suggests that the most important factors driving these transition likelihoods are personal and household characteristics like gender and education of household heads. However, state-level characteristics and government policies have a significant impact on these transition likelihoods as well, especially for transitions from the lowest levels of education to somewhat higher levels. The odds of making the transition to higher education, especially tertiary education, are systematically lower for women than for men, for individuals in rural areas than those in urban areas, and for Muslims than for Hindus. An important conclusion of our analysis is that there is significant scope for government policy to address educational gaps between various demographic and other groups in the country.educational attainment, likelihood of transition, government policy
Yield Enhancement of Digital Microfluidics-Based Biochips Using Space Redundancy and Local Reconfiguration
As microfluidics-based biochips become more complex, manufacturing yield will
have significant influence on production volume and product cost. We propose an
interstitial redundancy approach to enhance the yield of biochips that are
based on droplet-based microfluidics. In this design method, spare cells are
placed in the interstitial sites within the microfluidic array, and they
replace neighboring faulty cells via local reconfiguration. The proposed design
method is evaluated using a set of concurrent real-life bioassays.Comment: Submitted on behalf of EDAA (http://www.edaa.com/
A Double Outburst from IGR J00291+5934: Implications for Accretion Disk Instability Theory
The accretion-powered millisecond pulsar IGR J00291+5934 underwent two ~10 d
long outbursts during 2008, separated by 30 d in quiescence. Such a short
quiescent period between outbursts has never been seen before from a neutron
star X-ray transient. X-ray pulsations at the 599 Hz spin frequency are
detected throughout both outbursts. For the first time, we derive a pulse phase
model that connects two outbursts, providing a long baseline for spin frequency
measurement. Comparison with the frequency measured during the 2004 outburst of
this source gives a spin-down during quiescence of -4(1)x10^-15 Hz/s,
approximately an order of magnitude larger than the long-term spin-down
observed in the 401 Hz accretion-powered pulsar SAX J1808.4-3658. If this
spin-down is due to magnetic dipole radiation, it requires a 2x10^8 G field
strength, and its high spin-down luminosity may be detectable with the Fermi
Large Area Telescope. Alternatively, this large spin-down could be produced by
gravitational wave emission from a fractional mass quadrupole moment of Q/I =
1x10^{-9}. The rapid succession of the outbursts also provides a unique test of
models for accretion in low-mass X-ray binaries. Disk instability models
generally predict that an outburst will leave the accretion disk too depleted
to fuel a second outburst after such a brief quiescence. We suggest a
modification in which the outburst is shut off by the onset of a propeller
effect before the disk is depleted. This model can explain the short quiescence
and the unusually slow rise of the light curve of the second 2008 outburst.Comment: 17 pages, 8 figures; accepted by Ap
Local, nonlocal quantumness and information theoretic measures
It has been suggested that there may exist quantum correlations that go
beyond entanglement. The existence of such correlations can be revealed by
quantum discord, but not by the conventional measure of entanglement. We argue
that a state displays quantumness that can be of local and nonlocal origin. The
physical quantity such as the quantum discord probes not only the nonlocal
quantumness but also the local quantumness, such as the "local superposition".
This can be a reason why such measures are non-zero when there is no
entanglement. We consider a generalized version of the Werner state to
demonstrate the interplay of local quantumness, nonlocal quantumness, and
classical mixedness of a state.Comment: 7 pages, 8 figures. Title changed. Accepted for publication in IJQ
Complementarity of Quantum Correlations in Cloning and Deleting of Quantum State
We quantify the amount of correlation generated between two different output
modes in the process of im- perfect cloning and deletion processes. We use
three different measures of correlations and study their role in determining
the fidelity of the cloning and deletion. We obtain a bound on the total
correlation generated in the successive process of cloning and deleting
operations. This displays a new kind of complementary relationship between the
quantum correlation required in generating a copy of a quantum state and the
amount of correlation required in bringing it back to the original state by
deleting and vice versa. Our result shows that better we clone (delete) a
state, more difficult it will be to bring the state back to its original form
by the process of deleting (cloning).Comment: 10 pages, 3 figures, Accepted in Physical Review
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