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Browsing Environment Institute publications by Author "Abbott, D."
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Item Metadata only A 1 GHz differential 2nd-order lowpass sigma delta modulator in CMOS for wireless receivers(SPIE, 2004) Zhu, Y.; Al-Sarawi, S.; Liebelt, M.; Microelectronics, MEMS, and Nanotechnology (2003 : Perth, Australia); Abbott, D.; Eshraghian, K.; Musca, C.; Pavlidis, D.; Weste, N.This paper presents the design of a 1 GHz continuous-time second order Lowpass Sigma Delta Modulator (LPSDM). The design is intended to meet the future requirements of wideband wireless receivers. The continuous-time Noise Transfer Function (NTF) for the modulator is realized using two Gm-C integrators with negative transconductance feedback and three linearized Gm elements. A three-stage delayed comparator is employed for designing the one bit quantizer, therefore a delayed NTF had to be synthesized. The presented target design is 0.18µm CMOS process. The designed chip uses both 3.3V and 1.8V MOSFETs and consumes 80mW including the clock driver and the output buffer. The performance of the modulator based on post layout simulation is 11 bits for a 5 MHz bandwidth and 8.6 bits for an 11MHz bandwidth.Item Metadata only Amplification and modelling of bioaffinity detection with terahertz spectroscopy(SPIE, 2002) Mickan, S.; Menikh, A.; Munch, J.; Abbott, D.; Zhang, X.; International Symposium on Smart Materials, Nano- and Micro-Smart Systems (2002 : Melbourne, Australia); Nicolau, D.V.; Lee, A.P.A new bioaffinity sensor based on pulsed terahertz (THz) spectroscopy is able to sensitively detect the presence of ultra-thin bound biomolecular layers. The protein avidin and lipid biotin are noted for their very high binding affinity, and the ease for which they can be attached to residues with importance in many biosensing applications. We demonstrate the sensitivity of the pulsed THz spectrometer to thin avidin layers and to avidin amplified with micron-sized agarose beads. The experimental results can be simply modelled by considering transmission of the THz radiation at the thin film interfaces. We detect less than 10.3 ng/cm2 avidin, giving the THz system a detection capability of sub-thin solid films better than ellipsometry and reflectometry techniques.Item Metadata only Analysis of system trade-offs for terahertz imaging(Elsevier Sci Ltd, 2000) Mickan, S.; Abbott, D.; Munch, J.; Zhang, X.; Van Doorn, T.In this paper we analyse the trade-offs for a terahertz imaging system and discuss implementation of a terahertz micro antenna array for imaging. We also describe applications of terahertz imaging and improvements in the signal processing. © 2000 Elsevier Science Ltd. All rights reserved.Item Metadata only Chemical sensing in the submillimeter wave regime(THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 2001) Mickan, S.; Zhang, X.; Munch, J.; Abbott, D.; Smart Structures and Devices (2000 : Melbourne, VIC); Sood, D.K.; Lawes, R.A.; Varadan, V.V.T-ray systems offer an exciting range of capabilities for chemical and biological diagnostics using the emerging technology of terahertz pulse imaging. We report results from the first Australian T-ray program and discuss how MOEMS techniques can be applied to decrease the system size. A small portable T-Ray system will cost less and is needed, for example, in endoscopic applications.Item Metadata only Cylindrical and conical electrostatic wobble micromotors(THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING, 2001) Sarros, A.; Chew, E.; Crase, S.; Tay, B.; Soong, W.; Smart Electronics and MEMS II (2000 : Melbourne, Australia); Abbott, D.; Varadan, V.; Boehringer, K.This paper describes the analysis, design, construction and testing of two electrostatic wobble micromotors; a conventional cylindrical design and a new conical design. Both designs have stators with eight segments. The cylindrical micromotor rotor is about 4mm in diameter and 20mm long while the conical rotor has a maximum diameter of about 10mm and is 12mm long. The advantage of the new conical design is that it eliminates the need for a pivot and hence substantially reduces the size of the motor. A detailed theoretical analysis of the designs is shown and compared with experimental results. The micromotors are operated under open-loop control and the rotation of the rotor was tested at an applied voltage of up to 500V.Item Metadata only Double modulated differential THz-TDS for thin film dielectric characterization(Elsevier Sci Ltd, 2002) Mickan, S.; Lee, K.S.; Lu, T.M.; Munch, J.; Abbott, D.; Zhang, X.Terahertz differential time-domain spectroscopy (DTDS) is a new technique that uses pulsed terahertz radiation to characterize the optical properties of thin dielectric films. Characterizing thin films in the GHz to THz range is critical for the development of new technologies in integrated circuitry, photonic systems and micro-electro-mechanical systems. There are potential applications for gene and protein chips. This paper shows how DTDS can be combined with double modulation in the pump-probe system to improve sensitivity by an order of magnitude. An iterative algorithm is presented to estimate the optical properties of a given thin film. The technique is experimentally verified using 1-μm-thick samples of silicon dioxide on silicon.Item Metadata only Increased sensitivity in T-ray liquid spectroscopy using rapid sample modulation(SPIE, 2004) Mickan, S.; Munch, J.; Zhang, X.; Abbott, D.; Terahertz and Gigahertz Electronics and Photonics III (2004 : San Jose, California); Hwu, R.J.Pulsed THz (T-ray) spectroscopy is sensitive, non-invasive tool for studying materials from physics to biology, but transmission measurements of liquid samples, especially water, have been limited by noise. This paper shows that the accuracy of T-ray material parameter measurements of liquid samples can be greatly increased, especially for highly-absorbing liquids, by using a rapid modulation of the liquid in the T-ray beam path, coupled with a novel implementation of mean and amplitude detection to T-ray spectroscopy. The experiments are supported by calculations quantifying the sources of uncertainty. Liquid transmission T-ray studies are valuable for understanding solvation dynamics of salts, exploring long-range structure in mixtures and probing biomolecules in suspension.Item Metadata only Investigation of small motors operating under the Huber effect(THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 2001) Lauterbach, A.; Soong, W.; Abbott, D.; Smart Electronics and MEMS II (2000 : Melbourne, Australia); Abbott, D.; Varadan, V.K.; Boehringer, K.F.The Huber effect is an interesting and potential useful means for creating extremely small and simple motors. It is based on the observation that torque is produced when current is passed through a rotating ball bearing. This paper reviews the alternative explanations for its operation and describes the design, construction and characterization of two prototype ball-bearing motors based on high precision miniature ball bearings. A key limitation of earlier work has been difficulties in repeatability due to rapid wear of the motor. This was overcome by using a data acquisition system to record the dynamic acceleration characteristics and hence predict acceleration torque versus speed characteristics.Item Metadata only Label-free bioaffinity detection using terahertz technology(IOP Publishing Ltd, 2002) Mickan, S.; Menikh, A.; Liu, H.; Mannella, C.; MacColl, R.; Abbott, D.; Munch, J.; Zhang, X.We report the first use of differential terahertz time-domain spectroscopy for bioaffinity sensing. Binding is observed by measuring the transmission of a thin layer of biotin bound to the sensor protein avidin. We demonstrate the THz wave transmission of a sub-micron-thick film and sensitivity to 0.1 µg cm−2 of biotin. These results point the way for a host of biosensor applications using T-rays, or pulsed far-infrared (FIR) radiation.Item Metadata only Low noise laser-based T-ray spectroscopy of liquids using double-modulated differential time-domain spectroscopy(IOP Publishing Ltd, 2004) Mickan, S.; Shvartsman, R.; Munch, J.; Zhang, X.; Abbott, D.Liquid transmission studies at terahertz frequencies (0.1–10 THz) are valuable for understanding solvation dynamics of salts, exploring long-range structure in mixtures and probing biomolecules in suspension. T-ray (or THz) time-domain spectroscopy, based on terahertz pulse generation from ultrafast lasers, is a sensitive technique for measuring material parameters in this frequency range. This paper proposes and demonstrates a novel technique for increasing the sensitivity and repeatability of liquid studies with T-ray time-domain spectroscopy (TDS), reducing relative parameter measurement errors below 0.0001. The proposed technique combines dual-thickness liquid measurement with rapid modulation (double-modulated differential TDS) to reduce the effect of both thickness-measurement errors and T-ray noise errors below 0.0001. The possible reduction in error is calculated and a liquid differential TDS (DTDS) prototype is demonstrated, incorporating amplitude and mean detection for near-simultaneous measurement of two T-ray waveforms.Item Metadata only Noise reduction in terahertz thin film measurements using a double modulated differential technique(World Scientific Publishing Co. Pty. Ltd., 2002) Mickan, S.; Abbott, D.; Munch, J.; Zhang, X.Differential terahertz (THz) time-domain spectroscopy (TDS) is a technique for decreasing noise levels in THz thin film characterization experiments. Characterizing thin films in the GHz to THz range is critical for the development of fast integrated circuits and photonic systems, and is potentially applicable to biosensors and proteomics. This paper shows how the differential technique, combined with double modulation, enables the study of thin films with noise reduction over normal TDS that improves at the film gets thinner. Double modulated differential THz-TDS has enabled the characterization of films with less than 1-μm thickness.Item Metadata only Optimal Design of an Offset Strip Fin Heat Sink Using Harmony Search(Engineers Australia, 2010) Mehdizadeh, A.; Miremadi, M.; Al-Sarawi, S.; Arjomandi, M.; Mehdizadeh, S.; Dally, B.; Abbott, D.; CHEMECA (38th : 2010 : Adelaide, Australia)A method for optimizing design configuration of an offset strip fin heat sink is proposed with a comparative study of the results. Optimization was conducted through common entropy generation rate minimization using the newly developed Harmony Search. For comparison and proof of viability of the proposed method, results of both Harmony Search and Genetic Algorithm are given. These results demonstrate the merit of Harmony Search optimization in such complex engineering problems.Item Metadata only Pulsed THz protein spectroscopy in organic solvents(Optical Society of America, 2002) Mickan, S.; Dordick, J.; Munch, J.; Abbott, D.; Zhang, X.; Conference on Lasers and Electro-Optics (23rd : 2002 : Long Beach, California); Whitaker, J.F.Measurements of the refractive index and extinction coefficient of organic solvents were presented. The material parameters for the samples were estimated using an iterative technique. The results for iso-octane, toluene and cyclo hexane showed that the protein refractive index was profoundly affected by even small amounts of water present in the solvents.Item Metadata only Review tradeoffs for quenched avalanche photodiode sensors for imaging turbid media(Elsevier Sci Ltd, 2000) Perkins, M.; Hill, S.; Mickan, S.; Abbott, D.; Munch, J.; Van Doorn, T.We evaluate the efficiency of a new optoelectronic quenched avalanche photodiode sensor (QAPD), with the potential of enabling high-resolution imaging through turbid media with femtosecond-lasers. Our target application is for imaging cancer in the human breast. We aim to improve the contrast ratio of the unscattered, image bearing photons by reducing or removing the large background of multiply scattered photons that result in poor spatial resolution. The approach that we are taking is to use temporal discrimination: ultra-short (less than a picosecond) laser pulses and time gated detection can select only those photons which travel almost straight through the tissue. The feasibility of resolving a 1 mm structure in 50 mm turbid tissue sample, using our system, will be discussed-there are no results reported to date that approach this performance. We aim to enhance the detection of short pulses through time resolved single photon counting technique. In this technique, the earliest arriving photon of the transmitted pulse is detected with a QAPD. When combined with an efficient electronic quenching circuit, the QAPD is insensitive to the later arriving diffuse photons. High accuracy and efficient measurement of the arrival time of the first photons is achieved by time to amplitude conversion electronics with a temporal resolution of 3 ps. This paper contains a discussion of the laser source, detection circuit, including QAPD, high-speed comparator, critical biasing and intensity counter. © 2000 Elsevier Science Ltd. All rights reserved.Item Metadata only Taguchi based performance analysis of an offset strip fin heat sink(Engineers Australia, 2010) Miremadi, M.; Mehdizadeh, A.; Arjomandi, M.; Al-Sarawi, S.; Kahrom, M.; Dally, B.; Abbott, D.; CHEMECA (38th : 2010 : Adelaide, Australia)Item Metadata only Terahertz spectroscopy of bound water in nano suspensions(SPIE, 2002) Mickan, S.; Dordick, J.; Munch, J.; Abbott, D.; Zhang, X.; International Symposium on Smart Materials, Nano- and Micro-Smart Systems (2002 : Melbourne, Australia); Nicolau, D.V.; Lee, A.P.The study of enzymatic protein molecules using terahertz time-domain spectroscopy (THz-TDS) has the potential to reveal molecular activity in real time without the use of labelling. Molecular hydration, or bound water, is a critical parameter in enzyme activity and THz-TDS measurements. For the first time we experimentally measure the terahertz-frequency response of nano-sized particles of protein and their level of molecular hydration. These measurements are valuable in understanding the terahertz response of biological systems and in studying the interaction between bound water and proteins.Item Metadata only The limit of spectral resolution in THz time-domain spectroscopy(SPIE, 2004) Mickan, S.; Xu, J.; Munch, J.; Zhang, X.; Abbott, D.; Microelectronics, MEMS, and Nanotechnology (2003 : Perth, Australia); Faraone, L.; Varadan, V.K.This paper describes a study conducted into the limit on spectral resolution due to the dynamic range of a T-ray spectrometer. The pulsed nature of terahertz time-domain spectroscopy (THz-TDS) sets a fundamental limit on its spectral resolution. The spectral resolution of THz-TDS can be improved by increasing the duration of the temporal measurement, but is limited by the dynamic range of the system in the time-domain. This paper presents calculations and experimental results relating the temporal dynamic range of a THz-TDS system to its spectral resolution. We discuss three typical pulsed terahertz sources in terms of their dynamic range and hence achievable spectral resolution.Item Metadata only Thin film characterization using terahertz differential time-domain spectroscopy and double modulation(THE SOCIETY OF PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 2001) Mickan, S.; Lee, K.S.; Lu, T.M.; Barnat, E.; Munch, J.; Abbott, D.; Zhang, X.; Electronics and Structures for MEMS II (2nd : 2001 : Adelaide, Australia); Bergmann, N.W.Characterizing the optical and dielectric properties of thin films in the GHz to THz range is critical for the development of new technologies in integrated circuitry, photonics systems and micro-opto-electro-mechanical systems (MOEMS). Terahertz differential time-domain spectroscopy (DTDS) is a new technique that uses pulsed terahertz (THz) radiation to detect phase changes of less than 0.6 femtoseconds (fs) and absorption changes corresponding to several molecular monolayers. This paper shows how DTDS can be combined with double modulation in the pump-probe system to improve sensitivity by an order of magnitude. The technique is experimentally verified using 1 µm thick samples of silicon dioxide on silicon.Item Metadata only Toward characterization of Huber's ball-bearing motor(SPIE, 2005) Choo, J.; Soong, W.; Abbott, D.; SPIE International Symposium on Smart Structures, Devices, and Systems II (2004 : Sydney, Australia); Al Sarawi, S.A motor that can be powered up by either a DC or AC supply and rotates in either direction, based on the so-called Huber effect, is investigated. For the first time, this paper examines the motor characteristics under both DC and AC conditions, for quantitative comparisons. Earlier work has not examined, in detail, the effect of an AC supply on the Huber motor operation. Previous work on the Huber or ball-bearing motor suffered from alignment problems and herewe describe a new methodology to address this. The new construction is also a step toward a micromotor realization. The motor, with its reduced dimensions, also has the advantage of reduced operating current. Since 1959, the principle of operation of this motor has remained an unsolved mystery and various theories exist in the literature. We show various empirical findings that shed some light on the hotly contested debate. The discovery of carbon on the bearings, under AC supply conditions, reported here creates a new open question. Motor acceleration versus torque characteristics areobtained, using a data acquisition system to facilitate dynamic real-time recording.Item Metadata only Variable centre frequency bandpass sigma-delta modulator(SPIE, 2002) Zhu, Y.; Al-Sarawi, S.; Liebelt, M.; International Symposium on Smart Materials, Nano- and Micro-Smart Systems (2002 : Melbourne, Australia); Harvey, E.; Abbott, D.; Varadan, V.In wideband surveillance and digital radio systems, there is a need to sweep the centre fequency of the data converter to detect a broadcast i nthe band of interest. Hence there is a need to design data converters with variable centre frequencies. Sigma-Delta modulators with programmable center frequency are chosen for this purpose. In this paper new resonators for a variable centre frequency bandpass Sigma-Delta modulator are presented. The new resonators have a centre frequency that extends from very low frequency up to half the sampling frequency. Simulation results of a fourth order discrete-time bandpass modulator employing the new resonator are presented using MATLAB and SPICE.