Speedy Derivative-Corrective Mass Spring Algorithm For Adaptive Impedance Matching Networks

Adaptive impedance matching algorithms are used to preserve the link quality of mobile phones, under fluctuating user conditions. It is highly desirable to reduce the search time for minimising the risk of data loss during the impedance tuning process. Presented is a novel technique to reduce the search time by more than an order of magnitude by exploiting the relationships among the mass spring's coefficient values derived from the matching network parameters, thereby significantly reducing the convergence time of the algorithm

Practical Design Strategy for Two-phase Step up DC-DC Fibonacci Switched-Capacitor Converter

The Fibonacci Switched-Capacitor (SC) converter demonstrates the highest performance by using minimum number of capacitors. However, as the Fibonacci SC requires a wide range of voltage rating of the devices, its implementation is difficult. This paper presents two gate driving techniques for designing and implementing two-phase Fibonacci SC converter for both low and high step-up conversion ratios. The proposed gate driving techniques only require few auxiliary transistors to provide the required boosted voltages for turning the charge transfer switches in the converter on and off. As a result, the proposed gate driving techniques reduce the design complexity and increase the reliability of the Fibonacci SC converter. Practical 8X and 5X Fibonacci SC converters are simulated and constructed based on the proposed techniques. The high conversion efficiencies achieved prove the effectiveness of the proposed techniques

An Evaluation of 2-phase Charge Pump Topologies with Charge Transfer Switches for Green Mobile Technology

The development of charge pumps has been motivated by the power supply requirements of portable electronic devices. Charge pumps are inductorless DC-DC converters that are small size and high integration. The quality of the charge pump greatly depends on the effectiveness of switches to turn on and off at the designated clock phases. However, to date, no analysis has been carried out on the overall performance of charge pumps based on switch components in practice. This work demonstrates the characteristics of transistors as charge transfer switches and their effects on the performance of a charge pump. Three most common charge pump topologies are evaluated in terms of voltage drop due to on-resistance and charge loss per switch. Simulations are performed in 0.35μm Austriamicrosystems (AMS) technology for Dickson, Voltage Doubler and Makowski charge pump topologies in steady and dynamic states. In addition, the effect of switch parameters for different charge pump topologies are compared and analysed. We demonstrate that the Makowski charge pump is the topology for future green mobile technology

Parylene based low actuation MEMS phase shifters for reconfigurable antenna applications

Wireless networks face ever-changing demands on their spectrum and infrastructure resources such as, increased communication bands, capacity-intensive data applications, and the steady growth of worldwide wireless subscribers. This rapid increase in the use of wireless communication and the dependence on a reliable connectivity leads manufacturers to seek systems which are ever smaller, low power, provide long range, and high bandwidth, whilst giving higher reliable technologies. In modern communication systems MEMS is now finding its way, replacing older more high power and non-linear systems. One of the important components of RF MEMS technology is the implementation of MEMS phase shifters for phased array applications that require better performance than arrays of conventional phase shifters. An important example is where RF MEMS devices can be applied to vary the characteristics of an antenna, such as beam steering or tuning in a multiband antenna. The core of this thesis is the development and fabrication of a novel Parylene based MEMS phase shifter. This is the first novel application of Parylene as the strength member of the MEMS bridge. The implementation provided MEMS devices with lower actuation voltage of < 25 V. The fabricated phases shifters provide higher RF performance such as 65 dBm, and return loss of < -15 dB. The reliability of the fabricated devices were tested beyond 2 billion switching cycles. This is higher than competing MEMS capacitive devices with a maximum lifetime of 500 million cycles. The fabricated device provides a maximum phase shift of 16.82° at 2.5 GHz, whilst the nominal value of phase shift was 5.4° at 2.5 GHz within the stable region of operation. The fabricated device provides comparable results with respect to reference DMTL designs. The research carried out in this thesis has lead to a number of international publications and four granted patents. The generic nature of this technology can open new opportunities in the conception and application of new MEMS devices in communication and sensing applications. The ability to deliver miniature, low power and high efficiency MEMS capacitive devices, will revolutionise the next generation of tuneable RF components suitable for mobile and handheld devices of the future

Triangular Lattices for Mutual Coupling Reduction in Patch Antenna Arrays

One of the issues in antenna arrays is the mutual coupling that occurs when two radiating elements are placed together. Mutual coupling can significantly degrade the performance of an antenna array. In this paper, we propose a triangular lattice configuration as a technique to reduce the mutual coupling in patch antenna arrays. A 4-element circular patch array with a triangular lattice is simulated and compared against a 4-element circular patch array with a square lattice in terms of their mutual coupling and radiation pattern. Comparisons are also made with other mutual coupling reduction techniques for closely packed antennas such as ground structure with slits, ground structures with removed substrates and ground structures with metal wall. The triangular lattice concept is then extended to the 9-element circular patch array. The 4-elements circular patch array with the triangular lattice and square lattice operating at 2.6GHz are then fabricated on FR4 printed circuit board

Uniform Circular Arrays for Phased Array Antenna

This paper compares the performances of a number of uniform circular array (UCA) configurations for phased array antennas. A UCA geometry is targeted due to its symmetrical configuration which enables the phased array antenna to scan azimuthally with minimal changes in its beam width and sidelobe levels. Each UCA configuration consists of 19 isotropic elements. Particle Swarm Optimization (PSO) is used to calculate the complex weights of the antenna array elements in order to adapt the antenna to the changing environments. Comparisons are made in the context of adaptive beamforming properties and Signal to Interference Ratio (SIR). The results obtained suggest that a planar uniform hexagonal array PUHA (1:6:12) is suitable for high resolution applications as its sidelobe levels are the lowest compared to the other geometries

Antenna Array with Wide Angle Scanning Properties

This paper presents a 3-faceted linear array with wide angle scanning property targeting portable devices. With this property, the antenna gain is maintained even when the main beam is steered away from zenith. The arrangement consists of a linear array of eight circular patches conformed to a 3-faceted structure. The radiation pattern and mutual coupling of the proposed structure are compared with three other structures; linear array on a flat surface, linear array on a curved surface and linear array on a 2-faceted surface. Each of the array structures is simulated with the CST Design Suite. Simulation results show that the main beam of the proposed 3-faceted array can be steered to a wide range of ±70° from the zenith, but with a trade off in wider beam width and increased side lobe levels. The circular patch array on a 3-faceted surface is fabricated on a FR4 (1.6 mm) substrate. The coupling coefficients are measured and compared to the simulated results