Ugur Olgun

Wireless power harvesting with planar rectennas for 2.45 GHz RFIDs

This paper presents a rectenna (rectifier + antenna) design to harvest electrical energy for powering RFIDs from ambient electromagnetic radiation at the 2.45 GHz ISM band (WiFi, Bluetooth, RFID, etc.). The rectenna structure is formed by a miniaturize 2nd iteration Koch fractal patch antenna and two stage Dickson charge pump voltage-doubler rectifier circuit. The proposed rectenna achieves a small size with relatively high realized gain (4 dBi) and good RF to DC conversion efficiency (up to 70%). As a result, the proposed rectenna harvests enough energy from a commercial RFID interrogator 3.1 meters away (4W EIRP at 2.45 GHz ISM band) to power up a 1.6 V LED, enough voltage to enable some RFID chips.

Efficient ambient WiFi energy harvesting technology and its applications

This paper is focused on powering wireless devices (including sensors) with high efficiency circuitry that can harvest ambient WiFi/Bluetooth energy and convert into direct current (dc). Herewith, we introduce a novel circuitry to generate a battery-like voltage from very low incoming RF energy (<;-20 dBm). The new RF energy harvesting front-end is demonstrated to have much better conversion efficiency than state-of-the-art commercial RF harvesting modules, notably for low power levels. Realization of this rectification circuitry is a game-changing technology in powering mobile devices. To verify our energy harvesting design, we carry out an experiment where our RF harvesting module provides enough power to drive a commercial temperature/humidity meter with an LCD display using nothing more than ambient WiFi signals in a typical office environment.

Low-profile planar rectenna for batteryless RFID sensors

Radio Frequency Identification (RFID) technology is highly desirable for sensing applications, where form-factor, unit price and lifetime are most important. However, current passive RFID technology is mostly limited to only identifying and inventorying items placed near the reader.

On the Capacity of Printed Planar Rectangular Patch Antenna Arrays in the MIMO Channel: Analysis and Measurements [Wireless Corner]

Printed arrays of rectangular patch antennas are analyzed in terms of their MIMO performance using a full-wave channel model. These antennas are designed and manufactured in various array configurations, and their MIMO performance is measured in an indoor environment. Good agreement is achieved between the measurements and simulations performed using the full-wave channel model. Effects on the MIMO capacity of the mutual coupling and the electrical properties of the printed patches, such as the relative permittivity and thickness of the dielectric material, are explored.

Low-profile vertically polarized printed antenna for body-worn applications

A low-profile printed vertically polarized antenna for on body applications is presented. This antenna is designed to operate within the new 40 MHz bandwidth allocated for medical body area network. A good isolation and purely vertical polarization are achieved with a λ/16 height printed antenna at 2.38 GHz. The antenna has 2.56 dBi gain and 98.3% efficiency when placed perpendicular to the 40mm × 30mm ground plane.

Improving the read range of RFID sensors

Active RFID sensors are increasingly replacing their wired counterparts. However, their need for batteries, high unit costs and vulnerability to harsh environmental conditions (i.e., vibration, shock, temperature) make the passive RFIDs a favored option, even if they are associated with shorter distance detections. In addition to their limited read range, current passive sensor tags are relatively large for tagging small objects, including many commercial products where bar codes are currently the norm. Also, reader systems associated with off-the-shelf passive RFID sensors are comparatively expensive. In this paper, we propose an alternative for both of these problems.

Wireless powering/harvesting for RFID sensors

Summary form only given. With the explosion of mobile phones and wireless internets, we are now living in a sea of radio waves. Unfortunately, most of the radio frequency (RF) energy just goes wasted unless its intercepted by its intended RF devices. We are also living in the world of sensors which play important roles in safeguarding our modern technologies and infrastructures. Most sensors require electrical power for either sensing operations or for sending sensed data to data collection and processing devices. Such power is commonly provided from batteries that need to be recharged or replaced periodically, which undesirably increases operation cost and decreases sensors life cycle. There are many applications where embedded sensors would be very useful but have not been taken advantage of due to the inability to service the batteries. Therefore, it makes sense to harvest the ubiquitous RF energy for sensors or to wirelessly deliver power to sensors. In the case of wireless power delivery, a narrow RF beamwidth is used for maximal and targeted power delivery. The input power to the rectifier can be much higher than previous ambient RF energy case, and therefore the efficiency needs to be optimized for such condition. This efficiency optimization involves input impedance matching network, output load optimization, and most importantly, choosing the right rectifying diode. We will discuss about the diode selection guidelines and present some rectifier circuit design examples for input power in a few Watts range.