Design of Highly Efficient Broadband Class-E Power Amplifier Using Synthesized Low-Pass Matching Networks

A new methodology for designing and implementing high-efficiency broadband Class-E power amplifiers (PAs) using high-order low-pass filter-prototype is proposed in this paper. A GaN transistor is used in this work, which is carefully modeled and characterized to prescribe the optimal output impedance for the broadband Class-E operation. A sixth-order low-pass filter-matching network is designed and implemented for the output matching, which provides optimized fundamental and harmonic impedances within an octave bandwidth (L-band). Simulation and experimental results show that an optimal Class-E PA is realized from 1.2 to 2 GHz (50%) with a measured efficiency of 80%-89%, which is the highest reported today for such a bandwidth. An overall PA bandwidth of 0.9-2.2 GHz (84%) is measured with 10-20-W output power, 10-13-dB gain, and 63%-89% efficiency throughout the band. Furthermore, the Class-E PA is characterized through measurements using constant-envelop global system for mobile communications signals, indicating a favorable adjacent channel power ratio from -40 to -50 dBc within the entire bandwidth

High frequency tuning mechanism using nanoplasma

The ever growing demand for reconfigurable electronic devices at mobile form factors makes RF tunable devices and circuits increasingly important. Conventional tuning mechanisms typically rely on controlling material properties or dimensions. These are often achieved by using electrical, mechanical, or thermal approach. On the other hand, the tuning principle of this study is based on changing the electron number density and consequently the permittivity and conductivity of a plasma region which are functions of the applied electric field strength. Consequently, it is possible to form a controllable RF medium by just changing the applied DC voltage without involving mechanical motion as is the case in tunable MEMS devices. As an illustrative example, a dual-capacitively-loaded cavity resonator is considered in this study. Tunable RF filters are critical parts in modern wireless communication systems for selecting the desired frequency bands. Because of the limited bandwidth, widely tunable filters with narrow instantaneous bandwidths and high quality factors (Q) are in high demand these days. Such filters have been successfully implemented by using high-Q resonators. Capacitively-loaded or evanescent-mode (EVA) cavity resonators have been used widely for this end, which have much smaller size and the ability to tune with a moderate reduction of their Q. An EVA resonator is formed by placing a loading post in the center of a simple cavity. In this way, most of the electric field is concentrated in the gap between the post-top surface and the top wall which actually forms the quasi-static capacitance of the resonator. Instead of changing the gap size by displacing the top wall that is often accomplished by MEMS tuners, the resonant frequency can also be tuned over a large frequency range by creating a nano-plasma layer. In this study, the initial static resonator is designed to have two resonant frequencies to continuously cover a wide range. It is shown that for a sample designed resonator with initial resonant frequencies of 39 GHz and 55 GHz, the frequency tuning range will be from 27.2 GHz to 55 GHz which means more than one octave of tuning. Another advantage of this technique is that it is possible to have either dual frequency operation or a single band by appropriately selecting the two initial resonances

An ANT-based Sensor Measurement Data Gathering System

Large-scale industries involved with a great amount of sensor measurements in their work are facing many challenges in data collection. Sensors are not on the same network; therefore each measurement has to be managed separately. Gathering all the measurement data to one terminal could be difficult. Once a measurement is obtained, it takes significant amount of time to process the data.The approaches our group takes here is to build a giant ANT wireless network that holds all the sensors’ measurements. To be more specific, every sensor has an ANT chip set up on its side. Each ANT chip is as a single node. And on PC terminal, there is also a ANT chip which is collecting data from all the nodes. Microsoft Visual C++ and Keil uVision are used to program the program on PC and the program on ANT chip, respectively. Sending a “start measurement operation code” from ANT USB stick on PC terminal to the embedded ANT board starts the measurement. During the development, acknowledged data transfer type was found to be most effective, out of three data transfer types: broadcast, burst, acknowledged. This generalized solution can be easily applied to all kinds of sensor application

Design A Continuously Tunable Microwave Filter With A Generalized Constant and Frequency Mapping Technique

As the demand for agile and accurate communication increases, the fundamental of communication must be improved to support the needs. Current communication operates on an agreement, that each network company pays government to get licensed a range of frequency on the spectrum, and no others are legally allowed to use. This allows a limited number of users to operates at the same time. As the number of users increase, the spectrum become congested and user experience problem like dropping call. This problem can be solved, if users can be shifted between different licensed frequencies, depending on the capacity of the current spectrum. In this paper, a design method of continuously reconfigurable low-pass filter (LPF) is proposed, to allow shifting between different frequencies. The circuit proposed is the classic ladder type circuit in generalized unit element (GUE) form. The circuit is analyzed using techniques like even/odd-mode analysis, and synthesized using constant and frequency mapping technique. Simulation results on advanced design system (ADS) showed a band pass filter, which can be tuned from 0.5Ghz to 1.0Ghz having a bandwidth of 0.1Ghz. The filter can also be tuned to an ultra-wideband filter with bandwidth from 0.5Ghz to 1.6Ghz, and anything in between. The results have proved the validity and reliability of the design method

Damage-growth-induced evolution of contact resistance of a RF MEMS switch

This study presented the evolution of the contact resistance induced by the growth of the contact damage between the switch contact tip and the drain surface in the lifetime of an ohmic RF MEMS switch. Omron 2SMES-01 commercial switch was selected for the experiment. All switches were operated under the hot-switching condition with a steeply rising actuation voltage. The voltage across the switch (switching voltage) was maintained as 20x of manufacturer’s specified value. Per million-cycle interval, the switching voltage, current, and contact resistance were recorded. The measurements showed three different situations of the contact resistance evolution: (i) the contact resistance monotonically decreases initially to a minimum and then monotonically increases; (ii) the resistance initially decreases to a local minimum, then increases to a local maximum, subsequently decreases to another local minimum, and finally increases; (iii) the resistance decreases initially and then increases until the switch fails in contact; the switch functions again after an intermitted response, and subsequently the resistance decreases again and then increases. A nonadhesive contact model is developed to explain these three situations. The modeling results show that the hot-switching condition changes properties of the contact materials, i.e., the elastic modulus and the yield strength, around the contact region and then causes some plastic deformation around the tip summit. The contact penetration and the contact area increase gradually due to the growth of the plastic deformation. Thus, the contact resistance which is reciprocally proportional to the contact area decreases in the initial stages of all cases. After unloading the tip per contact cycle, a residual depth is produced between the tip and the drain. The growth of the plastic deformation increases the residual depth. When the contact penetration reaches the value corresponding to the maximum contact area, the fixed electrostatic force cannot make the tip a deeper penetration due to a quite large residual depth. Consequently, the reduced contact penetration decreases the contact area. Therefore, the contact resistance dependent on the contact area rises gradually in the second stage as the first case. If the tip displacement caused by the electrostatic force is close to the tip–drain gap within a residual depth, a local minimum contact area will be produced to cause a local maximum contact resistance in the switch lifetime as the second case. A temporary failure in contact occurs when the tip displacement is smaller than the tip–drain gap within a residual depth. The slowing growth of the residual depth allows the tip–drain contact again as the third case

A High-Efficiency Low Power Rectifier for Wireless Power Transfer

With the number of implantable devices that utilize electronics increasing, there is an increasing need to find alternative ways of powering them. Currently, surgery is required to replace a battery for these devices; however, with advancements in Wireless Power Transfer (WPT) methods, the need for further surgeries will become negated. This paper explores the ability of WPT as an alternative powering method by investigating rectifier Power Conversion Efficiency (PCE). The rectifier converts high frequency waves to Direct Current (DC) energy that can provide usable power to devices requiring electrical power. It is targeted for low power applications centered around a 233 MHz fundamental frequency, and the rectification circuit was designed and simulated in Advanced Design Systems (ADS) following the shunt diode circuit topology. The rectifier has a measured peak efficiency of 59.4% at -3 dBm and displays efficiencies above 40% from -22 dBm up until diode breakdown around 0 dBm. This device will provide a constant DC power source for use in powering devices wirelessly at low power

Technology and Information Fusion Needs to Address the Food, Energy, Water Systems (FEWS) Nexus Challenges

In response to the Food, Energy, Water Systems (FEWS) Nexus Challenge grant awarded by NSF, the team of investigators led by David Ebert, along with Christian Butzke, Melba Crawford, Phillip Owens, and Dimitrios Peroulis conducted a two-day workshop in Napa, California on November 5th and 6th, 2015. The workshop addressed the emerging issues in the food/energy/water systems throughout the diverse geography of the United States and over various crops and environmental conditions to better understand and model and ultimately devise a solution for the challenges to the FEWS nexus. One of the intended outcomes of the workshop was to generate a report that will chart the research challenges and opportunities for solving these challenges and have an impact on scientific fields including, sensing technology, hydrology, soil science, climate, data fusion, analysis, visualization, and data driven decision 2 making, as well as agricultural production, local and regional economies, sustainability and planning. The information contained in this post-workshop report serves as that foundation.In response to the Food, Energy, Water Systems (FEWS) Nexus Challenge grant awarded by NSF, the team of investigators led by David Ebert, along with Christian Butzke, Melba Crawford, Phillip Owens, and Dimitrios Peroulis conducted a two-day workshop in Napa, California on November 5th and 6th, 2015. The workshop addressed the emerging issues in the food/energy/water systems throughout the diverse geography of the United States and over various crops and environmental conditions to better understand and model and ultimately devise a solution for the challenges to the FEWS nexus. One of the intended outcomes of the workshop was to generate a report that will chart the research challenges and opportunities for solving these challenges and have an impact on scientific fields including, sensing technology, hydrology, soil science, climate, data fusion, analysis, visualization, and data driven decision 2 making, as well as agricultural production, local and regional economies, sustainability and planning. The information contained in this post-workshop report serves as that foundation

Wireless power transfer to a small, remote control boat

Over the past few decades, researchers have explored and implemented methods of wireless power transmission to operate devices that traditionally have been powered using plug-in power supplies and batteries. It is with this objective in mind that we built a boat, which is powered wirelessly from a field of harvestable energy. This project sought to develop a wirelessly powered remote control boat to be a proof of concept for the idea of wireless power transfer. Our criteria for success is that the boat should receive sufficient power to run anywhere in a 2.5 meter squared area. Having defined the field in which power will be required by our boat, we will fill this field with microwave RF energy. Finally, using a rectifying antenna, or rectenna, the energy will be harvested and delivered to the boat’s motors. We first developed three different topologies for our motor boat. For each boat, we made the minimization of power consumption a priority, while still maintaining speed and control. Operating between 100 and 200 milliwatts, each of the three topologies has a unique advantages and disadvantages with respect to its power consumption, speed, and controllability, and each has the ability to be powered wirelessly. From here, we plan to combine the rectenna with the boat, and deliver the power to our system. We will then characterize the radiation pattern of our power-receiving monopole antenna, and quantify the efficiencies of our various rectifier topologies