George Shaker

Inkjet Printing of Ultrawideband (UWB) Antennas on Paper-Based Substrates

For the first time, we demonstrate the feasibility of realizing ultrawideband antennas through ink-jetting of conductive inks on commercially available paper sheets. The characterization of the conductive ink as well as of the electrical properties of the paper substrate are reported for frequencies up to 10 GHz. This letter is one step further toward the development of low-cost, environment-friendly conformal printed antennas/electronics for ad hoc wireless sensor networks operating in rugged environments.

Inkjet Printed, Self Powered, Wireless Sensors for Environmental, Gas, and Authentication-Based Sensing

In this paper, inkjet-printed flexible sensors fabricated on paper substrates are introduced as a system-level solution for ultra-low-cost mass production of UHF Radio Frequency Identification (RFID) Tags and wireless sensor nodes in a “green” approach that could be easily extended to other microwave and wireless applications. The authors briefly touch up the state-of-the-art area of fully integrated wireless sensor modules on paper and show several active and power scavenging platforms to power on wireless sensors that could potentially set the foundation for the truly convergent wireless sensor ad hoc networks of the future.

Carbon-Nanotube Loaded Antenna-Based Ammonia Gas Sensor

Carbon nanotubes (CNTs) have been researched extensively for gas-sensing applications due to their unique electrical, chemical, and structural properties. Single-walled carbon nanotubes (SWNTs) have been predominantly used due to their superior electrical conductivity and higher sensitivity relative to multiwalled CNTs. This paper presents the design and characterization of a novel planar sensor fabricated on paper substrate to detect small concentrations of ammonia gas, using the shift in resonance frequency of a patch antenna as the discriminator. We have investigated three main design issues in depth. First, functionalization of the SWNTs with a polymer is studied in order to enhance the gas detection sensitivity. Second, a thin film of the functionalized SWNT is characterized to create a surface impedance model for the explanation and prediction of the resonance shift due to different gas concentrations. Finally, as a proof of concept, functionalized SWNTs are integrated into a patch antenna design and the return loss is measured in a closed-system environment to show high sensitivity for low concentrations of ammonia gas. The proposed antenna-based wireless gas sensor can be utilized in several applications, given its small form factor, light weight, and little to no power requirements.

Accelerated Antenna Design Methodology Exploiting Parameterized Cauchy Models

We propose an optimization methodology suitable for the design of various antenna structures. This methodology includes a rapidly-converging iterative scheme. In each iteration stage, the algorithm generates a parameterized Cauchy model using the available results from previous iterations. Optimization is then applied to this Cauchy model to obtain better design parameters that are also used in enhancing the accuracy of the model. This cycle continues until the speciflcations are met. In addition, this on-the-∞y technique produces an analytical model of the behavior of the antenna structure. Sensitivity and tolerance analysis can thus be e-ciently carried out without the need for further costly electromagnetic simulations.

Photonic-Crystal-Based Polarization Converter for Terahertz Integrated Circuit

In this paper, the fabrication and characterization of newly developed photonic crystal (PC) polarization-controlling devices on a silicon-on-insulator wafer for integrated terahertz applications are presented. The polarization converter is composed of periodic asymmetric loaded PC slab waveguide. Square- and circular-hole PC slab waveguides were studied using a 3-D finite-difference time-domain method. For a square-hole PC-based polarization rotator, polarization rotation efficiency higher than 90% was achieved within the normalized frequency band of a/ λ = 0.258-0.267 . In circular-hole PC polarization converter, the polarization conversion efficiency dropped to 70% for the aforementioned frequency band. Low polarization conversion efficiency of the circular-hole PC-based device is attributed to scattering loss at the top loaded layers. Thus, the square-hole PC structure is a better candidate for integrated terahertz polarization-controlling devices. Planar terahertz integrated circuit technology was developed to implement the proposed device. Characterization setup was designed using rigorous numerical methods to use the newly introduced Agilent Millimeter-wave PNA-X network analyzer (up to 500 GHz) as a source. Scattering parameter characterizations provide a good measure of polarization extinction ratio. For the devices designed for the central frequency of f = 200 GHz, it was observed that, within the frequency band of 198-208 GHz (α/λ = 0.26-0.272), the ratio of S21 to S11 was higher than 15 dB. The bandwidth is in good agreement with our preliminary design presented before.

Low-cost antennas for mm-Wave sensing applications using inkjet printing of silver nano-particles on liquid crystal polymers

For the first time, we demonstrate the possibility of realizing low-cost mm-Wave antennas using inkjet printing of silver nano-particles. It is widely spread that fabrication of mm-Wave antennas and microwave circuits using the typical (deposit/pattern/etch) scheme is a challenging and costly process, due to the strict limitations on permissible tolerances. Such fabrication technique becomes even more challenging when dealing with flexible substrate materials, such as liquid crystal polymers. On the other hand, inkjet printing of conductive inks managed to form an emerging fabrication technology that has gained lots of attention over the last few years. Such process allows the deposition of conductive particles directly at the desired location on a substrate of interest, without need for mask productions, alignments, or etching. This means the inkjet printing of conductive materials could present the future of environment-friendly low-cost rapid manufacturing of RF circuits and antennas.

Battery-free RFID-enabled wireless sensors

This paper introduces the realization of batter-free RFID-enable wireless sensors by integrating conformal RFID antennas with inkjet-printed carbon nanotubes (CNT) composites in a chipless RFID fashion for gas detection. The whole module is realized by inkjet printing on a low-cost paper-based substrate and the RFID tag is designed for the European UHF RFID band. The electrical conductivity of the CNT film changes in the presence of very small quantities of gases like ammonia, methanol, ethanol, acetone and nitrogen oxide (NOx), resulting in the variation of the backscattered power level which can be easily detected by the RFID reader to realize reliable wireless toxic gas sensing. The electrical performance characterization of the inkjet-printed CNT film is also reported in the UHF band.

Inkjet printing of dual band conformal antenna for use in wifi frequency bands

In this paper, a dual-band conformal antenna for use in Wifi frequency bands is designed and developed using conductive inkjet printing technique. Paper as a high frequency substrate is used for low cost reasons. Discussion about the benefits of using inkjet printing is also provided. Measured results are presented showing a good agreement with theoretical ones.

Integrated antenna with inkjet-printed compact artificial magnetic surface for UHF applications

A low-profile antenna on HIS/AMC/EBG surface was developed for UHF applications. The surface is inkjet-printed on paper which produces a low-cost, light-weight, and environment-friendly solution. More compact unit cells (and thus smaller overall size) and/or wider antenna bandwidth can be realized using alternative unit cells/antenna configurations as discussed in [5–6].

Highly Miniaturized Fractal Antennas

In this paper, the use of fractal elements in miniaturized antenna applications is discussed. Hilbert grounded wires are studied and a simple design routine is outlined. Using commercial software tools, the design of groundless fractals is shown to be simple and fast. We present grounded and groundless Hilbert and Meander antennas for 250 MHz, 400 MHz and 2 GHz applications. Application of Hubert antennas in GSM/PCS bands is also presented