Sayeed Z. Sajal

A microstrip patch antenna manufactured with flexible graphene-based conducting material

In this paper, a unique process for fabricating microstrip patch antennas with flexible graphene-based conductors is presented. In particular, this manufacturing process uses a commercially available micro-cutter to cut the outline of the patch antenna from the flexible graphene-based conductors, and then this piece is attached to a grounded FR4 substrate using adhesive to create a unique printed antenna. The design was modeled using a commercial simulator, and a prototype was fabricated and measured. Overall, it was shown that the S-parameter simulations agreed fairly well with measurements, and that this manufacturing process has the potential to develop more complicated designs, such as meander-line dipoles for example, that are difficult to cut-out manually.

On using graphene-based conductors as transmission lines for feed networks in printed antenna arrays

The use of graphene-based conductors (GBC) as a transmission line (TL) is presented as a conventional TL possessing right-handed (RH) nature and its coupling characteristics are investigated. In order to verify and demonstrate the wave propagation of a GBC TL, a 120 mm long 50 Ω TL was fabricated and tested. Performance of the single GBC TL was then compared to the conventional microstrip TL, analyzing the matching and wave propagation results. To investigate the unwanted coupling that may occur in a feed network, a similar GBC and a conventional microstrip TL, as well as two parallel GBC TLs on the same substrates were separately manufactured and tested to complete the study. It is shown that GBC TLs support the wave propagation in a fashion similar to the microstrip TL with an attenuation of less then 3.0 dB up to 7 GHz. Also the measurements of the near-end coupling showed that the two parallel GBC TLs have fairly good isolation in the frequency band of 4.5 KHz to 8.5 GHz, whereas the far-end coupling exhibits similar properties to that of the parallel microstrip TLs with same distance between them. The results demonstrated that GBC TLs could hence be a potential candidate for the feed network for planar antenna arrays.

A low cost flexible passive UHF RFID tag for sensing moisture based on antenna polarization

Cost optimization and performance are the continuous improvement areas in any technology. In this paper a flexible dipole antenna on a passive UHF RFID tag is designed on an inexpensive paper substrate which can sense the moisture based on the polarization of the antenna. An inexpensive paper substrate and copper (Cu) layer are used for the flexibility and the optimization of manufacturing cost. The dipole antenna is matched with the complex conjugate of the power harvesting circuit of the Higgs2 Integrated Circuit (13.88 -j143.6 at the frequency of 915 MHz). The key characteristic of this design is the sensitivity of the antenna polarization on the passive RFID tag to the moisture content in the paper substrate. In simulations, the antenna is circularly polarized when the substrate is dry (relative permittivity, ϵr= 2.38) and the antenna is linearly polarized when the substrate is wet (relative permittivity, ϵ r= 35.35). The read ranges of the fabricated dipole antenna (i.e., prototype RFID moisture sensor) are measured and the desired performance is achieved with overall tag dimensions of 0.144λo × 0.133λo where λo is the free space wavelength at 915 MHz.

An initial investigation on the use of carbon microfibers for conformal transmission lines

The use of carbon micro fiber tow (or bundle) for conformal transmission lines (TLs) is initially investigated in this work. Two different microfiber TLs have been synthesized and tested. A 28.2 mm long microfiber TL was manufactured to demonstrate the wave propagating properties. Once these characteristics were determined, a microstrip TL was prepared by attaching 1oz conducting copper tape to a conformal surface and a similar microfiber TL with the same length and on the same substrate was manufactured. This prototype was then used to compare the propagation characteristics of the microfiber TL to the traditional and well established microstrip TL. Overall, it has been shown that the microfiber TL can support wave propagation in a manner similar to a microstrip TL; however, the attenuation constant appears to be rather large for frequencies above 500 MHz.

A printed dipole reconfigured with magneto-static responsive structures that do not require a directly connected biasing circuit

An initial study of novel Magneto-static Responsive Structures (MRSs) and their application to the frequency reconfigurability of a printed dipole antenna is presented here. The embodiment of the MRSs consisted of a cylindrical cavity with a diameter of 0.9 mm drilled into a 20.0 mil thick 1.5 mm × 1.5 mm TMM4 substrate. The cavities were partially filled with silver coated magnetic particles and covered on the top and bottom with copper tape. The conducting magnetic particles responded to an externally applied magnetic field and formed columns in the direction of the magnetic field lines. The columns connected the top and bottom conducting planes, acting as a switch. It was demonstrated that the electrical length of an antenna could be changed and the resonant frequencies could be reconfigured from 1.5 GHz to 1.9 GHz by incorporating the MRSs into the dipole antenna and controlling the ON and OFF states of the MRS switch. Overall, it was shown that the simulated results agreed well with the measurements. It was also demonstrated that the proposed MRSs do not need directly connected biasing circuitry, making them particularly useful for complex antenna designs.

A conformal antenna on a passive UHF RFID tag using 97% carbon content graphene-based conductors and paper substrates

Passive UHF radio frequency identification (RFID) systems are being applied to many different industries and because of this, these systems are being required to operate in complex electromagnetic environments. This may require tags to operate on different surface types or time varying shapes. This paper presents a conformal antenna design that can be used on a passive UHF RFID tag with a paper substrate. More specifically, instead of copper conductors for the antenna, commercially available 97% carbon content graphene-based material is used to mitigate conductor failure; which has been observed in copper-based conformal antenna designs. Simulations and read-range measurements (2.1 meters) of a prototype UHF passive RFID tag with graphene-based conductors and dimensions similar to commercially available copper-based designs are shown.

Efficiency comparison of inductive and microwave power transfer for biomedical applications

In this paper two methods of wireless power transfer for implanted biomedical devices are compared: inductive coupling and radiative transmission. Simulation models for both methods were developed and comparison was made in terms of power transmission efficiency at different spacing between the transmitter and receiver. The simulation results show that inductive coupling is more efficient than radiative transmission for small distances, up to around 26 mm. For larger distances radiative transmission is more efficient.

Interactive sensitive data exposure detection through static analysis

Data security has become an increasingly important topic as information stored and transmitted in electronic form has become the preferred method. In order to protect this information, developers need to follow, at minimum, some basic guidelines to secure this data from malicious attackers. However, security often takes a backseat while developing software and is either not implemented at all or is patched into the software at the end. Both are undesirable as it leave the software vulnerable to sensitive data leaks and lowers the overall quality of the application. These issues can be introduced by developers of any skill level. Existing static or dynamic analysis tool does not provide the functionality of interaction with user, which we believe can be an extremely valuable feature. We present Secure Sensitive Data (SSD) Eclipse IDE plug-in that can help bridge the gap in sensitive data leaks by aiding software developers interactively by pointing out issues in real-time and enforcing certain standards to protect sensitive data. Our SSD plugin enforces five best practices and standards that should at minimum keep data encrypted and proper handling of sensitive data. By continuously involving and reminding the developers of the security implications, SSD helps to mitigate security flaws in future software applications.

On using biocomposite filaments to additively manufacture substrates for microstrip transmission lines

As the requirements for wireless systems become more complex, researchers and designers are turning to unique technologies for solutions. In support of this, a new design that uses biocomposite filaments to additively manufacture substrates for microstrip transmission lines is presented here. In particular, the measured complex permittivity of the material manufactured with three different biocomposite filaments; namely Buzzed, Entwined and Wound Up is determined. This information is then used to design prototype 50Ω microstrip transmission lines. Overall, simulations and measurements compare well and show that biocomposite filaments can be used to support propagation up to 3.0 GHz on the microstrip transmission lines.

A study of microstrip transmission lines on substrates created using additive manufacturing and flexible or semi-rigid filaments

Additive manufacturing is becoming more affordable and in recent years new techniques on implementing this emerging technology into microwave circuits are being developed. Therefore, understanding the propagation behavior of printed microstrip transmission lines implemented with these manufacturing techniques is needed. In this paper, the use of flexible and semi-rigid filaments to create substrates using additive manufacturing for printed microstrip transmission lines is presented. In particular, NinjaFlex, PLA and Armadillo filaments are used to manufacture 1.57 mm thick grounded substrates for 50Ω microstrip transmission lines. The dielectric properties (i.e., complex permittivity) of these newly manufactured substrates are determined by comparing the following three results: (1) measurements with a Keysight N1501A-101 high temperature dielectric probe; (2) measurements of a known transmission line problem and (3) full-wave simulations. The results in this paper show a good comparison between the three aforementioned techniques and that a 50Ω printed microstrip transmission line can be created on substrates manufactured using the NinjaFlex, PLA and Armadillo filaments up to 3.0 GHz.