Bounds Estimation for Trade Openness and Government Expenditure Nexus of ASEAN-4 Countries

Southeast Asia countries are encountering several challenges as they are moving towards the globalization and trade liberalization era. Due to that, government intervention is essential in ensuring that the economy is resilience against the severe implications of trade openness. Therefore, this study aims to examine the relationship between trade openness and government expenditure of ASEAN-4 countries using the Autoregressive Distributed Lag [ARDL] bounds testing approach that covers a sample period of annually data from 1974-2006. Empirical results indicate that there is an existence of a significant positive long-run linkage between trade openness and government expenditure of all the ASEAN-4 countries under study. This means that government intervention in an open economy is crucial as to cushion the risks associated with trade liberalization.ARDL, ASEAN-4, openness, government expenditure

A 30mV input battery-less power management system

This paper presents a fully-integrated on chip battery-less power management system through energy harvesting circuit developed in a 130nm CMOS process. A 30mV input voltage from a TEG is able to be boosted by the proposed Complementary Metal-Oxide-Semiconductor (CMOS) voltage booster and a dynamic closed loop power management to a regulated 1.2V. Waste body heat is harvested through Thermoelectric energy harvesting to power up low power devices such as Wireless Body Area Network. A significant finding where 1 Degree Celsius thermal difference produces a minimum 30mV is able to be boosted to 1.2V. Discontinuous Conduction Mode (DCM) digital control oscillator is the key component for the gate control of the proposed voltage booster. Radio Frequency (RF) rectifier is utilized to act as a start-up mechanism for voltage booster and power up the low voltage closed loop power management circuit. The digitally control oscillator and comparator are able to operate at low voltage 600mV which are powered up by a RF rectifier, and thus to kick-start the voltage booster

128 mA CMOS LDO with 108 db PSRR at 2.4 MHz frequency

A low dropout (LDO) voltage regulator with high power supply rejection ratio (PSRR) and low temperature coefficient (TC) is presented in this paper. Large 1µF off-chip load capacitor is used to achieve the high PSRR. However, this decreases the gain and pushes the LDO’s output pole to lower frequency causing the circuit to become unstable. The proposed LDO uses rail-to-rail folded cascode amplifier to compensate the gain and stability problems. 2nd order curvature characteristic is used in bandgap voltage reference circuit that is applied at the input of the amplifier to minimize the TC. The characteristic is achieved by implementing MOSFET transistors operate in weak and strong inversions. The LDO is designed using 0.18µm CMOS technology and achieves a constant 1.8V output voltage for input voltages from 3.2V to 5V and load current up to a 128mA at temperature between -40°C to 125°C. The proposed LDO is targeted for RF application which has stringent requirement on noise rejection over a broad range of frequency

3.3V DC Output At-16dBm Sensitivity And 77% PCE Rectifier For RF Energy Harvesting

This paper presents a high voltage conversion at high sensitivity RF energy harvesting system for IoT applications. The harvesting system comprises bulk-to-source (BTMOS) differential-drive based rectifier to produce a high efficiency RF energy harvesting system. Low-pass upward impedance matching network is applied at the rectifier input to increase the sensitivity and output voltage. Dual-oxide-thickness transistors are used in the rectifier circuit to maintain the power efficiency at each stage of the rectifier. The system is designed using 0.18μm Silterra RF in deep n-well process technology and achieves 4.07V output at -16dBm sensitivity without the need of complex auxiliary control circuit and DC-DC charge-pump circuit. The system is targeted for urban environment

Impedance matching and DC-DC converter designs for tunable radio frequency based mobile telecommunication systems

Tunability and adaptability for radio frequency (RF) front-ends are highly desirable because they not only enhance functionality and performance but also reduce the circuit size and cost. This thesis presents a number of novel design strategies in DC-DC converters, impedance networks and adaptive algorithms for tunable and adaptable RF based mobile telecommunication systems. Specifically, the studies are divided into three major directions: (a) high voltage switch controller based DC-DC converters for RF switch actuation; (b) impedance network designs for impedance transformation of RF switches; and (c) adaptive algorithms for determining the required impedance states at the RF switches. In the first stage, two-phase step-up switched-capacitor (SC) DC-DC converters are explored. The SC converter has a simple control method and a reduced physical volume. The research investigations started with the linear and the non-linear voltage gain topologies. The non-linear voltage gain topology provides a higher voltage gain in a smaller number of stages compared to the linear voltage gain topology. Amongst the non-linear voltage gain topologies, a Fibonacci SC converter has been identified as having lower losses and a higher conversion ratio compared to other topologies. However, the implementation of a high voltage (HV) gain Fibonacci SC converter is complex due to the requirement of widely different gate voltages for the transistors in the Fibonacci converter. Gate driving strategies have been proposed that only require a few auxiliary transistors in order to provide the required boosted voltages for switching the transistors on and off. This technique reduces the design complexity and increases the reliability of the HV Fibonacci SC converter. For the linear voltage gain topology, a high performance complementary-metaloxide- semiconductor (CMOS) based SC DC-DC converter has been proposed in this work. The HV SC DC-DC converter has been designed in low voltage (LV) transistors technology in order to achieve higher voltage gain. Adaptive biasing circuits have been proposed to eliminate the leakage current, hence avoiding latch-up which normally occurs with low voltage transistors when they are used in a high voltage design. Thus, the SC DC-DC converter achieves more than 25% higher boosted voltage compared to converters that use HV transistors. The proposed design provides a 40% power reduction through the charge recycling circuit that reduces the effect of non-ideality in integrated HV capacitors. Moreover, the SC DC-DC converter achieves a 45% smaller area than the conventional converter through optimising the design parameters. In the second stage, the impedance network designs for transforming the impedance of RF switches to the maximum achievable impedance tuning region are investigated. The maximum achievable tuning region is bounded by the fundamental properties of the selected impedance network topology and by the tunable values of the RF switches that are variable over a limited range. A novel design technique has been proposed in order to achieve the maximum impedance tuning region, through identifying the optimum electrical distance between the RF switches at the impedance network. By varying the electrical distance between the RF switches, high impedance tuning regions are achieved across multi frequency standards. This technique reduces the cost and the insertion loss of an impedance network as the required number of RF switches is reduced. The prototype demonstrates high impedance coverages at LTE (700MHz), GSM (900MHz) and GPS (1575MHz). Integration of a tunable impedance network with an antenna for frequency-agility at the RF front-end has also been discussed in this work. The integrated system enlarges the bandwidth of a patch antenna by four times the original bandwidth and also improves the antenna return loss. The prototype achieves frequency-agility from 700MHz to 3GHz. This work demonstrates that a single transceiver with multi frequency standards can be realised by using a tunable impedance network. In the final stage, improvement to an adaptive algorithm for determining the impedance states at the RF switches has been proposed. The work has resulted in one more novel design techniques which reduce the search time in the algorithm, thus minimising the risk of data loss during the impedance tuning process. The approach reduces the search time by more than an order of magnitude by exploiting the relationships among the mass spring’s coefficient values derived from the impedance network parameters, thereby significantly reducing the convergence time of the algorithm. The algorithm with the proposed technique converges in less than half of the computational time compared to the conventional approach, hence significantly improving the search time of the algorithm. The design strategies proposed in this work contribute towards the realisation of tunable and adaptable RF based mobile telecommunication systems

Modelling the effects of textile preform architecture on permeability

Liquid Composite Moulding (LCM) processes are identified as one of the most potentially advantageous manufacturing routes. The challenge currently is to increase their reliability and expand their applicability. To that end, it was perceived that there was a lack of an advanced integrated simulation tool for the manufacture of three-dimensional, multi-layer textile composites. The tools for the analyses of fabric forming and subsequent flow during LCM processes were simple and immature, with the latter suitable to describe flow in thin structures only. Another noted deficiency was that the simulations provided a single answer to any given problem. Industrial experience has shown that during mould filling, due to the nature of statistical variation in the material properties, the filling patterns and arising cycle times are rarely the same between a given set of identical mouldings. This thesis focuses on permeability prediction of textile reinforcements for LCM processes. The issue of textile variability was also explored through the use of the permeability models' predictive capability. Two novel and efficient numerical approaches were developed to predict textile permeability based on the fabric architecture. The objective was to reduce the complexity of the flow domain and hence provide a faster method to fully characterise the permeability of a textile. Within a wider context, these models were implemented within an integrated modelling framework encompassing draping, compaction and impregnation, based on the TexGen textile schema. TexGen is a generic geometric textile modeller that can be used to create a wide range of textile models. Several validation studies were performed using a range of reinforcements including woven and non-crimp fabrics. A stochastic analysis technique was developed to account for the effect of material variability on permeability. The study based on this technique provided important insights into permeability variations. It was shown that the permeability distribution is a strong function of the textile architecture. The permeability models developed from this work can be used to account for the effects of fabric shear/compaction and statistical variations on permeability. These predicted permeability data can complement experimental data in order to enhance flow simulations at the component scale

Design consideration in low dropout voltage regulator for batteryless power management unit

Harvesting energy from ambient Radio Frequency (RF) source is a great deal toward batteryless Internet of Thing (IoT) System on Chip (SoC) application as green technology has become a future interest. However, the harvested energy is unregulated thus it is highly susceptible to noise and cannot be used efficiently. Therefore, a dedicated low noise and high Power Supply Ripple Rejection (PSRR) of Low Dropout (LDO) voltage regulator are needed in the later stages of system development to supply the desired load voltage. Detailed analysis of the noise and PSRR of an LDO is not sufficient. This work presents a design of LDO to generate a regulated output voltage of 1.8V from 3.3V input supply targeted for 120mA load application. The performance of LDO is evaluated and analyzed. The PSRR and noise in LDO have been investigated by applying a low-pass filter. The proposed design achieves the design specification through the simulation results by obtaining 90.85dB of open-loop gain, 76.39º of phase margin and 63.46dB of PSRR respectively. The post-layout simulation shows degradation of gain and maximum load current due to parasitic issue. The measurement of maximum load regulation is dropped to 96mA compared 140mA from post-layout. The proposed LDO is designed using 180nm Silterra CMOS process technology

Modelling the effects of textile preform architecture on permeability

Liquid Composite Moulding (LCM) processes are identified as one of the most potentially advantageous manufacturing routes. The challenge currently is to increase their reliability and expand their applicability. To that end, it was perceived that there was a lack of an advanced integrated simulation tool for the manufacture of three-dimensional, multi-layer textile composites. The tools for the analyses of fabric forming and subsequent flow during LCM processes were simple and immature, with the latter suitable to describe flow in thin structures only. Another noted deficiency was that the simulations provided a single answer to any given problem. Industrial experience has shown that during mould filling, due to the nature of statistical variation in the material properties, the filling patterns and arising cycle times are rarely the same between a given set of identical mouldings. This thesis focuses on permeability prediction of textile reinforcements for LCM processes. The issue of textile variability was also explored through the use of the permeability models' predictive capability. Two novel and efficient numerical approaches were developed to predict textile permeability based on the fabric architecture. The objective was to reduce the complexity of the flow domain and hence provide a faster method to fully characterise the permeability of a textile. Within a wider context, these models were implemented within an integrated modelling framework encompassing draping, compaction and impregnation, based on the TexGen textile schema. TexGen is a generic geometric textile modeller that can be used to create a wide range of textile models. Several validation studies were performed using a range of reinforcements including woven and non-crimp fabrics. A stochastic analysis technique was developed to account for the effect of material variability on permeability. The study based on this technique provided important insights into permeability variations. It was shown that the permeability distribution is a strong function of the textile architecture. The permeability models developed from this work can be used to account for the effects of fabric shear/compaction and statistical variations on permeability. These predicted permeability data can complement experimental data in order to enhance flow simulations at the component scale