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DC Bias Dependent Dynamic Properties of Injection Lasers (Part B)Goodwin, John C. January 1977 (has links)
One of two project reports. Part A can be found at: http://hdl.handle.net/11375/17866 / <p> It was observed that the spontaneous carrier lifetimes of GaAlAs injection lasers, as measured by the time delay method, exhibit a strong dependence on the DC bias current flowing through the laser. As the DC bias current is increased, the measured lifetimes decrease, passing through a minimum at bias currents less than 0.1 mA, and then rise again to an intermediate value at high bias currents. It was also found that the impedance of these lasers to fast current pulses drops sharply at the same DC bias currents as the minimum measured lifetime mentioned above. Evidence is presented to suggest that both of these effects are due to an electrical resonance between the stray drive circuit inductance and the DC bias dependent capacitance of the laser's junction under forward bias. </p> <p> In addition, two methods of determining the spontaneous carrier lifetime by other than the time delay method are described. One method involves measurement of the vector impedance of lasers to sinusoidal drive currents at frequencies less than 100 MHz, as a function of DC bias. The second method is based upon the frequency dependence of the phase shift between a sinusoidal drive current and the resulting spontaneous light. </p> / Thesis / Master of Engineering (ME)
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Low voltage autonomous buck-boost regulator for wide input energy harvestingAhmed, Khondker Zakir 08 June 2015 (has links)
While high power buck-boost regulators have been extensively researched and
developed in the academia and industry, low power counterparts have only recently gained
momentum due to the advent of different battery powered and remote electronics. The
application life-time of such applications, e.g., remote surveillance electronics can be
extended tremendously by enabling energy autonomy. While battery powered electronics
last long but they must be replenished once the battery is depleted either by replacing the
battery or by retrieving the electronics and then recharging. Instead, energy harvesting from
available ambient sources on the spot will enable these electronics continuous operation
unboundedly, probably even beyond the lifetime of the electronics. Interestingly enough,
recent advancements in micro-scale energy transducers compliment these demand [1-13].
Micro-transducers producing energy from different ambient sources have been reported.
These transducers produce enough energy to support a wide range of operations of the
remote electronics concurrently. These transducers along with an additional storage
elements greatly increase the energy autonomy as well as guaranteed operation since
harvested energy can then be stored for future use when harvestable energy is temporarily
unavailable.
Recently several buck-boost regulators with low power and low input operating
voltage have been reported both from academia and industry [14-24]. Some of this work
focuses on increasing efficiency in the mid-load range (10mA-100mA), while some other
focuses on lowering input range. However, so far no one has reported a buck-boost
regulator operating with sub-200nW bias power while harvesting energy from sub-500mV input range. This work focuses on the development of a low voltage low bias current buckboost regulator to attain these goals.
In this work, complete design of a PFM mode buck-boost regulator has been
discussed in details. Basic topology of the regulator and working principle of the
implemented architecture along with the advantages of the specific topology over that of
the others have been discussed in short to provide an uninterrupted flow of idea. Later,
Transistor level design of the basic building blocks of the buck-boost regulator is discussed
in details with different design features and how those are attained through transistor level
implementation are discussed. Subsequently, the physical layout design technique and
considerations are discussed to inform the reader about the importance of the layout process
and to avoid pitfalls of design failure due to layout quality issues.
Measurement results are presented with the fabricated IC. Different
characterization profile of the IC have been discussed with measured data and capture
oscilloscope waveforms. Load regulation, line regulation, efficiency, start-up from low
voltage, regulation with line and load transient events are measured, presented and
discussed. Different characteristics of the prototype are compared with prior arts and are
presented in a comparison table. Die micrograph is also presented along with the different
issue of the IC testing
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A Non-Contact Sensor Interface for High-Temperature, MEMS Capacitive SensorsNarayanaswamy, Anand Subramanian January 2010 (has links)
No description available.
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Circuit techniques for the design of power-efficient radio receiversGhosh, Diptendu 02 August 2011 (has links)
The demand for low power wireless transceiver implementations has
been fueled by multiple applications in the recent decades, including cellular
systems, wireless local area networks, personal area networks, biotelemetry and sensor networks. Dynamic range, which is set by linearity and sensitivity performance, is a critical design metric in many of these systems. Both linearity and sensitivity requirements continue to become progressively challenging in
many systems due to greater spectrum usage and the need for high data rates respectively. The objective of this research is to investigate power-efficient
circuit techniques for reducing the power requirement in receiver front-ends without compromising the dynamic range performance.
In the first part of the dissertation, a low power receiver down-converter topology for enhancing dynamic range performance is presented. Current
mode down-converters with passive mixer cores have been shown to provide excellent dynamic range performance. However, in contrast to a current commutating
Gilbert cell, these down-converters require separate bias current paths for the RF transconductor and the baseband transimpedance amplifier.
The proposed topology reduces the power requirement of conventional
current mode passive down-converter by sharing the bias current between the transconductance and transimpedance stages. This is achieved without compromising
the available voltage headroom for either stage, which is a limitation
of bias-sharing based on the use of stacked stages. The dynamic range of the basic bias-current-shared topology is further enhanced through suppression of
low frequency noise and IM3 products. Two variants of the down-converter, employing a broadband common-gate and a narrowband common-source input stage, are implemented in a 0.18-μm CMOS technology. The dynamic range performance of the architecture is analyzed. Finally, a prototype of a
full direct-conversion receiver implementation with quadrature outputs and integrated LO synthesis is demonstrated.
A power-efficient oscillator design for phase noise minimization is presented
in the second part of this dissertation. This design is targeted towards multi-radio platforms where several communication links operate simultaneously over multiple frequency bands. Blockers from concurrently operating radios present a major design challenge. The blockers not only make the frontend linearity requirement more stringent but also degrade receiver sensitivity through reciprocal mixing with the phase noise sidebands of LO. Phase noise
minimization is thus critical for ensuring high sensitivity in frequency bands where large blockers are present and not sufficiently attenuated by pre-select filters.
A capacitive power combining technique in oscillators is introduced to improve phase noise performance. By combining this approach with current reuse,
the phase noise is reduced at lower power, compared to conventional LC oscillators. This leads to improved power efficiency. Moreover, the technique
mitigates modeling uncertainty arising from phase noise reduction through simultaneous impedance and current scaling. The mode selection in this oscillator,
which employs multiple coupled resonators, is analyzed and the impact of coupling on far-out phase noise performance is discussed.
Multi-mode oscillation can potentially arise in other oscillator topologies too, e.g., in multiphase oscillators. Mode selection in a widely used
transistor-coupled quadrature oscillator is analyzed in detail in the final part of the dissertation. The analysis shows how cross-compression among multiple competing modes can lead to suppression of non-dominant modes in the steady state. / text
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