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

Frequency response of atmospheric pressure gas breakdown in micro/nanogaps

In this paper, we study gas breakdown in micro/nanogaps at atmospheric pressure from low RF to high millimeter band. For gaps larger than about 10 lm, the breakdown voltage agrees with macroscale vacuum experiments, exhibiting a sharp decrease at a critical frequency, due to transition between the boundary- and diffusion-controlled regimes, and a gradual increase at very high frequencies as a result of inefficient energy transfer by field. For sub-micron gaps, a much lower breakdown is obtained almost independent of frequency because of the dominance of field emissio

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

Pre-breakdown evaluation of gas discharge mechanisms in microgaps

The individual contributions of various gas discharge mechanisms to total pre-breakdown current in microgaps are quantified numerically. The variation of contributions of field emission and secondary electron emission with increasing electric field shows contrasting behavior even for a given gap size. The total current near breakdown decreases rapidly with gap size indicating that microscale discharges operate in a high-current, low-voltage regime. This study provides the first such analysis of breakdown mechanisms and aids in the formulation of physics-based theories for microscale breakdown. (C) 2013 AIP Publishing LL

Microwave Gas Breakdown in Tunable Evanescent-Mode Cavity Resonators

Microwave gas breakdown in strongly-coupled evanescent-mode cavity resonators in atmospheric pressure and room temperature is investigated both numerically and experimentally. This high-Q resonator is widely tunable by changing the gap between its loading post and top wall. In this letter, we study the effect of different gap spacings on breakdown characteristics of this resonator. Good agreement is observed between measured breakdown powers and ones by plasma simulations for resonators with gaps of 14.8-51.2 mu m, working in the 6-8.25 GHz frequency range with input breakdown power in the range of 45-48 dBm