Majid Manteghi

A parallel electromagnetic genetic-algorithm optimization (EGO) application for patch antenna design

In this paper, we describe an electromagnetic genetic algorithm (GA) optimization (EGO) application developed for the cluster supercomputing platform. A representative patch antenna design example for commercial wireless applications is detailed, which illustrates the versatility and applicability of the method. We show that EGO allows us to combine the accuracy of full-wave EM analysis with the robustness of GA optimization and the speed of a parallel computing algorithm. A representative patch antenna design case study is presented. We illustrate the use of EGO to design a dual-band antenna element for wireless communication (1.9 and 2.4 GHz) applications. The resulting antenna exhibits acceptable dual-band operation (i.e., better than -10 dB return loss with 5.3 and 7% operating bandwidths at 1.9 and 2.4 GHz) while maintaining a cross-pol maximum field level at least 11 dB below the co-pol maximum.

Multiport characteristics of a wide-band cavity backed annular patch antenna for multipolarization operations

This paper focuses on the multiport characterization of antennas. In particular, special attention is given to the cavity backed annular patch antenna (CABAPA) for multipolarization operations. We will show that the reflection coefficient is not the best representative parameter to determine the frequency response of the multiport antenna and its radiation performance. Therefore, we seek a new generalized parameter that conveys the frequency response of multiport antennas. The total active reflection coefficient (TARC) is introduced as the square root of the sum of all incident powers at the ports minus radiated power, divided by the sum of all incident powers at the ports. The TARC is a function of frequency and is a real number between zero and one. With this definition we can characterize the multiport antennas frequency bandwidth and radiation performance. A method for calculating the TARC is detailed for different port excitations directly from the scattering matrix of the antenna and independent of the feeding network. First, the CABAPA is analyzed by the method of moments. Next, the corresponding scattering matrix is employed to calculate the TARC for different polarizations. The calculated results, when compared to the measured results, show good agreement. The measured -10 dB TARC bandwidth of the CABAPA is 30% compared with 68% as measured using only the s/sub 11/.

Embedded Singularity Chipless RFID Tags

Every structure scatters an impulse plane wave in a unique fashion. The structural information of an object can be extracted by analyzing the late-time scattered field as the impulse-response of the structure. The late-time scattered field, which represents the source-free response of the structure, contains a summation of damped sinusoids. The frequency and damping factor of these damped sinusoids are uniquely associated with the structural information, and can be used to identify an unknown object. We propose to create uniquely identifiable scattered fields from an object by incorporating “notches” in the structure giving rise to specific damped sinusoids in the source-free scattered field of the structure. In this manner, data can be embedded into the structure of an object which is detectable using electromagnetic waves, allowing a metallic object to serve as a chipless radio-frequency identification tag (RFID). Data is encoded as complex natural resonant frequencies (referred to as poles) in the structure and is retrieved from the scattered field. Data retrieval is based on Singularity Expansion Method (SEM) analysis using target identification techniques. Each complex-frequency pole provides two-dimensional data (real and imaginary) which can be extracted from the late-time impulse response of the structure using a numerical technique such as the Matrix Pencil Method. We have designed and prototyped a 6-bit (3-pole) tag. The tag is analyzed using simulations and measurements. The tag is successfully read remotely via its scattered fields. The measured data are compared with simulation, and are in close agreement.

Complex-Natural-Resonance-Based Design of Chipless RFID Tag for High-Density Data

Each scatterer responds to the incident wave in a unique manner. The backscattered signal from the scatterer is affected by two distinct phenomena: early-time response which emanates from the scattering centers of the scatterer and late-time response which is the summation of the complex natural resonances (CNRs) with some weighting residues. Based on the singularity expansion method (SEM), CNRs are aspect-independent parameters which include some structural information of the scattering target. Based on this fact, the data can be embedded on the RFID tag as CNRs associated to the structural parameters. In this paper, a low-profile chipless RFID tag as a suitable device for high-density data is introduced. By incorporating several slots on the chipless RFID tag, the data can be encoded as CNRs on the structure. The designed RFID tag operates in the frequency band of 3.1-10.6 GHz. The data are decoded in the reader by applying short-time matrix pencil method (STMPM) to the transient backscattered response of the tag. In addition, the turn-on times, damping factors, and resonant frequencies of the poles are distinguished. After studying the effects of various parameters of the tag, a 24-bit tag is designed on the area of 24 × 24 mm2, simulated and measured. The measurement is performed in the frequency domain and, after applying inverse fast Fourier transform (IFFT), STMPM is employed to extract the signature of the tag. The tag is successfully read remotely via its scattered fields.

Short-Time Matrix Pencil Method for Chipless RFID Detection Applications

In this paper, the concept of short-time matrix pencil method (STMPM) is introduced and experimentally demonstrated as an efficient approach to extract a set of embedded poles in a chipless RFID. Here, by incorporating a few notches on the elliptical dipole antenna as a chipless RFID, the data is encoded as complex natural resonant frequencies of the structure. In this new detection approach, a sliding time window is introduced and the matrix pencil method (MPM) is applied to extract embedded poles and residues from the sliding time-window at each snapshot of time. The resulting complex poles and residues have a time index which allows us to process them as a set of time-frequency data. This time-frequency analysis enables us to discriminate late-time from early-time. Furthermore, averaging complex poles over the time increases the accuracy of the technique in a noisy environment. The measured data agrees well with our simulations and support the STMPM effectiveness in comparison to the MPM.

Pole residue techniques for chipless RFID detection

By isolating individual notches we were able to show that a distinct modification to a scattering body can predictably create a pole in the scattered field. The pole can be and interpreted as encoded data and used in the retrieval process.

A novel lightweight dual-frequency dual-polarized sixteen-element stacked patch microstrip array antenna for soil-moisture and sea-surface-salinity missions

The main motivation for this paper is to discuss the development of a novel compact and light-weight dual-frequency, dual linearly polarized, high-efficiency, stacked-patch microstrip-array antenna for use in standalone aircraft-based remote sensing applications. Results from simulation, fabrication, and testing of a sixteen-element stacked-patch array antenna, optimized for an L-band frequency of operation, are presented. The design center frequencies were 1.26 GHz and 1.413 GHz with 10 MHz and 25 MHz bandwidths in each band, respectively. Due to the large number of design parameters and demanding design requirements of beam-efficiency, sidelobe levels, and polarization characteristics, particle-swarm optimization (PSO) and finite-difference time-domain (FDTD) simulations were used for synthesis and analysis. Cancellation techniques, based on symmetry, were applied to the antenna ports, with a custom-built feed network to reduce cross polarization. Simulations and measurement results from a spherical near-field test facility confirmed excellent performance of the array configuration, with a beam efficiency of greater than 90%, isolation better than -35 dB, and cross polarization in the main beam of the array better than -40 dB. From the sixteen-element array simulations and experimental verifications, one of the objectives of the present study is to suggest the possibility of using customized dual-frequency, dual-polarized arrays as potential feeds for reflectors to replace the traditionally used conical horns for future soil-moisture and sea-salinity missions

A novel UWB feeding mechanism for the TEM horn antenna, reflector IRA, and the Vivaldi antenna

This work proposes a method for feeding a balanced IRA with an unbalanced transmission line. This method is based on the current distribution on the surface of the antenna. The method of moments (MoM) simulations show that for the IRAs, there are some areas with low current density in comparison to the current density of the feeding points, almost over the entire frequency range. The coaxial cable is attached to the antennas body all the way from the feeding point to an area of low current density, and extends out of the antenna structure at that point. This tremendously reduces the current density on the body of the coaxial cable. As a result, the current balance between two parts of the antenna is not disturbed. This method is applied to the TEM horn antenna, the reflector IRA, and the Vivaldi antenna. The TEM horn antenna was simulated using the HEMI software, and was fed by an unbalanced coaxial cable, both directly at the feeding point and using this method. This method was also applied to the reflector impulse-radiating antenna. Also, the Vivaldi antenna was fed both by considering the low-current density area and direct feeding. The E-plane far-field pattern of the new feeding method had good agreement with the result generated by the HEMI software for the balanced-fed antenna.

A Switch-Band Antenna for Software-Defined Radio Applications

A novel method is introduced which enables the use of a tunable narrowband antenna within a wide frequency range. The resulting antenna is able to operate in multifrequency bands simultaneously. In addition, the number of frequency bands and their center frequencies can be changed dynamically. A time domain simulation is provided using a simple circuit model for two simultaneous frequency bands. A tunable antenna is designed and tested for two simultaneous frequency bands as well.

Novel Compact Tri-Band Two-Element and Four-Element MIMO Antenna Designs

This paper presents a novel miniaturized tri-band antenna which can be used as a single element or as an element of a compact array in MIMO applications. Specifically, the tri-band MIMO antenna has been constructed and used, in arrays of two and four, in a laptop PCMCIA wireless LAN card. The size of the four element MIMO antenna array is 50 mm times 13 mm times 8 mm which translates to 0.4 lambda times 0.1 lambda times 0.07 lambda at 2.45 GHz. The antenna has a return loss lower than -10 dB in the 2.4 to 2.5 GHz, 5.15 to 5.35 GHz, and 5.7 to 5.85 GHz bands. The total active reflection coefficient (TARC) has been calculated for various combinations of excitations of the two-element and four-element MIMO systems. The antenna was simulated using the Ansoft HFSS. MIMO antenna prototypes have been constructed and measured to demonstrate their functionalities