Raafat R. Mansour

A wideband vibration-based energy harvester

We present a new architecture for wideband vibration-based micro-power generators (MPGs). It replaces a linear oscillator with a piecewise-linear oscillator as the energy harvesting element of the MPG. A prototype of an electromagnetic MPG designed accordingly is analyzed analytically, numerically and experimentally. We find that the new architecture increases the bandwidth of the MPG during a frequency up-sweep, while maintaining the same bandwidth in a down-sweep. Closed-form expressions for the response of the new MPG as well as the up-sweep bandwidth are presented and validated experimentally. Simulations show that under random-frequency excitations, the new MPG collects more energy than the traditional MPG.

Modeling of two-hot-arm horizontal thermal actuator

Electrothermal actuators have a very promising future in MEMS applications since they can generate large deflection and force with low actuating voltages and small device areas. In this study, a lumped model of a two-hot-arm horizontal thermal actuator is presented. In order to prove the accuracy of the lumped model, finite element analysis (FEA) and experimental results are provided. The two-hot-arm thermal actuator has been fabricated using the MUMPs process. Both the experimental and FEA results are in good agreement with the results of lumped modeling.

Design of superconductive multiplexers using single-mode and dual-mode filters

The objective of this short paper is twofold: 1) to present experimental and computer-simulated results for a number of single-mode and dual-mode high-temperature superconductor (HTS) filters; and 2) to present the measured performance of an integrated 3-channel circulator-coupled multiplexer employing dual-mode HTS thin film filters. The CAD algorithm used to design the HTS filters is also described. The results presented demonstrate the feasibility of building C-band compact-size superconductive multiplexers. >

Tunable Dielectric Resonator Bandpass Filter With Embedded MEMS Tuning Elements

This paper presents a novel approach for constructing a tunable dielectric resonator bandpass filter by using the microelectromechanical system (MEMS) technology. The tunability is achieved by unique MEMS tuning elements to perturb the electrical and magnetic fields surrounding the dielectric resonators. The use of such elements as a tuning mechanism results in a wide tuning range at a relatively low tuning voltage and fast tuning speed. A three-pole tunable dielectric resonator bandpass filter is designed, fabricated, and tested. The experimental filter has a center frequency of 15.6 GHz, a 1% relative bandwidth, and an unloaded Q of 1300. A tuning range of 400 MHz is obtained by using MEMS tuning elements with 2 mmtimes2 mm tuning disks. The measured results demonstrate the feasibility of the proposed concept

Filter technologies for wireless base stations

Phenomenal growth in the telecommunication industry in recent years has brought significant advances in filter technology as new communication systems emerged, demanding more stringent filter characteristics. In particular, the growth of the wireless communication industry has spurred tremendous activity in the area of microwave filter miniaturization and has been responsible for many advances made in this field. The filters that are currently being used in wireless base stations can be divided into two main categories: coaxial cavity resonator filters and dielectric resonator (DR) filters. While coaxial cavity filters have limited quality factor (Q) values, they offer the lowest cost design and are still being widely employed, particularly in wide bandwidth applications. With increased demands for high performance wireless systems, dielectric resonator filters are emerging as the baseline design for wireless base stations. Over the next five years, dielectric resonator filters are expected to have a significant share of the overall wireless base station filter market. High-temperature superconductor (HTS) filters are also expected to have a share of this market, particularly for systems, which have very stringent requirements for out-of-band interference. In this article, we begin by reviewing the main filter requirements, highlighting the technologies that are being currently employed. Emerging filter technologies that have the potential to replace the existing technologies are then described.

On the power handling capability of high temperature superconductive filters

This paper presents high power test results for high temperature superconductor (HTS) filters having six different configurations. The results demonstrate the possibility of realizing narrow band HTS filters that are capable of handling 30-50 W at 77 K. The paper also introduces a procedure for comparing the power handling capability of HTS filters with different RF characteristics. Issues related to thermal design of high power HTS filters are discussed in detail.

Multidimensional Cauchy method and adaptive sampling for an accurate microwave circuit modeling

This paper presents an effective generic approach for computer-aided design of microwave circuits. We extend the one-dimensional Cauchy method for frequency-response interpolation to a multidimensional Cauchy interpolation, with respect to both frequency and physical dimensions. This paper also demonstrates the feasibility of applying adaptive sampling to the multidimensional rational-function expansion. Three examples, including optimization and Monte Carlo analysis, have been given to verify the validity of the proposed approach.

Design considerations of superconductive input multiplexers for satellite applications

This paper describes the evolution and development of low power superconductive filters and multiplexers for satellite applications under the HTSSE-II program. Experimental results and tradeoffs are presented for thin film and dielectric loaded HTS multiplexer configurations, leading to the development and implementation of a fully integrated four-channel C-band HTS input multiplexer. Measured data shows performance comparable to conventional technology and promise of large reduction in mass and volume of such equipment. The multiplexer is scheduled to fly as part of the HTSSE-II package on the ARGOS satellite in 1996.

Computer-aided tuning of microwave filters using fuzzy logic

This paper introduces an algorithm based on fuzzy logic for tuning microwave filters. The approach is demonstrated by considering two filters: a four-pole Chebyshev filter and an eight-pole elliptic filter. Each filter is then detuned to perform two examples: one is slightly detuned and the other is highly detuned. In both cases, the approach has proven to be very efficient in identifying the filter elements that cause the detuning. The fuzzy rules are extracted from sampled data. The expert rules could also be added. The algorithm can be applied to any microwave circuit tuning problem.

A Design Procedure for Wideband Micropower Generators

We developed a design procedure for wideband electromagnetic micropower generators (WMPGs) based on piecewise-linear oscillators. We find that the dominant factors in the performance of this class of WMPGs are the stiffness ratio of the oscillator and the velocity of the moving structure at the point of impact with the stopper. We also find that designing these WMPGs requires additional steps beyond those required in the design of regular MPGs. The additional steps match the output power and bandwidth of the WMPG to the probability density function of environmental vibrations. While these steps add complexity to the design of WMPGs, they are shown to significantly increase harvested energy.