Muhammad Mubeen Masud

A Compact Dual-Band EMI Metasurface Shield With an Actively Tunable Polarized Lower Band

In this letter, a compact tunable metasurface for dual-band electromagnetic interference (EMI) shielding is being proposed. In particular, Jerusalem crosses intersecting diagonally are used to design and synthesize a prototype metasurface shield. It has been shown that a finite 4 × 3 array of the Jerusalem crosses can be used for EMI shielding in the 900 MHz and 1.8-GHz GSM bands. Then, to develop an active shield that is tunable, varactor diodes were attached to the dual-band metasurface. Measurements have shown that the lower band of the metasurface can be changed (tuned) with various control voltages. Finally, simulation, equivalent circuit computations, and measurements are shown to agree.

Analysis of the Noise Voltage Coupling (Crosstalk) Between Right-Handed and Composite Right/Left-Handed (CRLH) Transmission Lines on Printed Circuit Boards

One aspect of the electromagnetic compatibility (EMC) analysis of RF circuitry is the accurate modeling of the coupling between printed transmission lines. Correct modeling of this coupling is essential because unwanted noise voltages can be substantial and create adverse effects on sensitive components. Recently, the development of composite right-/left-handed transmission lines (CRLHTLs) has received considerable attention due to the unique propagation characteristics. Because of this increase in applications, CRLHTLs are being implemented in RF systems with other printed circuitry, such as microstrip transmission lines, in very close proximity. In many of these instances, the coupling may not be intentional. To study this interaction between CRLHTLs and other printed circuitry from an EMC point of view, this paper presents derived analytical expressions for computing the nearand far-end voltage coupling between right-handed (printed microstrip transmission lines) and CRLHTLs. More specifically, these expressions are used to determine the nearand far-end voltages weakly coupled to the CRLHTL when the conventional microstrip right-handed transmission line is driven with a source and terminated with a load. These expressions are then used to illustrate how the induced voltages on the CRLHTL can be reduced by the capacitance and inductance values that support left-handed propagation. This can be a useful alternative to conventional shielding. Furthermore, design guidelines and tradeoffs are presented on the layout of CRLHTL near other printed transmission lines. The expressions derived in this paper are validated with simulations and measurements.

A reconfigurable dual-band metasurface for EMI shielding of specific electromagnetic wave components

Metasurfaces are becoming more of an interest to the research community because of the unusual electromagnetic properties that can be achieved. This paper presents a reconfigurable metasurface for EMI shielding purposes. In particular, a dual-band Jersualem cross is developed and pin diodes are use to interconnect elements to control the specific polarization properties of the shield. It is shown that the response of the shield to specific field components can be controlled with simple control voltages. Simulations are validated with measurements throughout this work.

Radiation performance and Specific Absorption Rate (SAR) analysis of a compact dual band balanced antenna

This paper presents a compact dual-band dipole antenna with meander line radiating elements. The proposed antenna has a balanced structure with dimensions of 35×6×1.52 mm3, and mounted on a 36.2 × 100 mm2 floating ground plane. The balanced operation of the design is validated by incorporating a differential feed in the software simulation and a 180 ° hybrid junction is used for measurement with the network analyzer to verify the balanced concept of the prototype. Simulated and measured results of the S-parameters along with the de-tuning of the antenna in the presence of the human body shows good agreement. Moreover the proposed design is used as an exposure source to the simulated human head model. The human head is modeled as six layers in the Electromagnetic (EM) software HFSS to study the interaction between the proposed balanced antenna and the human head model. The Electric field (E-field) distribution in the six layers of the human head model is shown to estimate the penetration of the field when the antenna is placed at a distance of 7 mm from the proposed design. Also Local Specific Absorption Rates (SARs) and average SARs simulation results at 3.78 GHz and 4.29 GHz are shown. The SARs analysis showed that in all the six layers of the human head model, local SAR values are greater in fat and Cerebrospinal fluid (CSF) for both the frequencies while the average SAR values are not very high.

A note on the fundamental maximum gain limit of the projection method for conformal phased array antennas

New expressions for comparing the maximum gain of a phase-compensated conformal antenna have been analytically derived and validated to measurements. In particular, the newly derived analytical expressions were validated with a conformal phased-array antenna prototype attached to a wedgeand inverted-wedged shaped surface. Phase-compensation techniques based on the projection method were used to correct the radiation pattern. These expressions can be used by a designer to predict the maximum theoretical gain of a phase-compensated conformal antenna on a surface that changes shape with time.

A dual band balanced planar inverted F antenna (PIFA) for mobile applications

A new low profile dual-band balanced planar inverted F antenna with meandered lines resonating in the 1800 MHz and 2100 MHz bands is proposed. The antenna size is 50 × 12 × 10mm3 allowing it to be easily housed in mobile handsets. The return loss, radiation pattern, gain and current distribution of the proposed antenna is presented. Furthermore, agreement between simulations and measurements is shown for a balanced feed with zero phase difference. Then, the design with differential feeding is simulated for various feeding phase angles and the benefits of minimized current flow on the ground plane are highlighted.

Design of a Zeroth Order Resonator UHF RFID Passive Tag Antenna with Capacitive Loaded Coplanar Waveguide Structures

The use and development of Radio Frequency Identification (RFID) systems has undergone substantial growth in the past decade in many new areas. Some of these areas include wire‐ less sensor systems, metamaterials and compact antennas [1-8]. However, much of this new growth has required more performance from traditional passive RFID systems. In particu‐ lar, the need for more compact antennas with performances comparable to much larger res‐ onant antennas is one such condition. To fulfill the requirements of compact antennas, researchers have developed various novel RFID antenna designs [2-4], including metamate‐ rial-based RFID antenna designs [1,5-8] to improve the performance of RFID systems. Using composite right/left-handed (CRLH) transmission line (TL) based metamaterials to show the unique property of zeroth-order resonance (ZOR) [9,10] is one such method to reduce the overall size of an antenna. More specifically, a ZOR-TL can be used to make an electrically small antenna to appear electrically large; which leads to improved matching and radiation properties. This is done by producing a zero phase constant at a non-zero frequency (i.e. the wavelength of the travelling wave becomes infinite) on the TL. This is a unique property which makes the resonance condition independent from the physical dimensions of the an‐ tenna or TL [11-13] so it can be used to design miniature antennas for passive UHF RFID applications. The resonance of such antennas at any operating frequency only depend on its CRLH characteristics to acquire ZOR at that frequency and less to do with the physical di‐ mensions of corresponding antenna.

On the use of amplitude tapering for pattern correction of conformal (Curved) antennas

Using amplitude tapering to improve the radiation pattern of a conformal antenna on a surface that changes shape with time has been studied and is presented in this paper. In particular, a six element array was attached to a wedge-shape conformal surface with bend angles 10 degrees, 20 degrees, 30 degrees, 40 degrees, 45 degrees and 50 degrees and the amplitudes of each element were changed to improve the broadside radiation pattern. The amplitude coefficients of each element were computed using the array factor of a conformal antenna and a search algorithm.

UHF bowtie RFID antenna with resistive and inductive stubs

In this paper a passive UHF bowtie RFID antenna with resisitive and inductive stubs is discussed for the 868 MHz UHF RFID frequency band. The antenna was connected to a Philips SL3S1001FTT ASIC which has an impedance of 22 - j404 (Ω) at 868 MHz. The lengths of resistive and inductive stubs can be adjusted to change the resistance and reactance of the antenna. The measurements show good agreement with the simulations.