Majid Khodier

Linear array geometry synthesis with minimum sidelobe level and null control using particle swarm optimization

This paper describes the synthesis method of linear array geometry with minimum sidelobe level and null control using the particle swarm optimization (PSO) algorithm. The PSO algorithm is a newly discovered, high-performance evolutionary algorithm capable of solving general N-dimensional, linear and nonlinear optimization problems. Compared to other evolutionary methods such as genetic algorithms and simulated annealing, the PSO algorithm is much easier to understand and implement and requires the least of mathematical preprocessing. The array geometry synthesis is first formulated as an optimization problem with the goal of sidelobe level (SLL) suppression and/or null placement in certain directions, and then solved by the PSO algorithm for the optimum element locations. Three design examples are presented that illustrate the use of the PSO algorithm, and the optimization goal in each example is easily achieved. The results of the PSO algorithm are validated by comparing with results obtained using the quadratic programming method (QPM).

LINEAR AND CIRCULAR ARRAY OPTIMIZATION: A STUDY USING PARTICLE SWARM INTELLIGENCE

Linear and circular arrays are optimized using the particle swarm optimization (PSO) method. Also, arrays of isotropic and cylindrical dipole elements are considered. The parameters of isotropic arrays are elements excitation amplitude, excitation phase and locations, while for dipole array the optimized parameters are elements excitation amplitude, excitation phase, location, and length. PSO is a high-performance stochastic evolutionary algorithm used to solve N-dimensional problems. The method of PSO is used to determine a set of parameters of antenna elements that provide the goal radiation pattern. The efiectiveness of PSO for the design of antenna arrays is shown by means of numerical results. Comparison with other methods is made whenever possible. The results reveal that design of antenna arrays using the PSO method provides considerable enhancements compared with the uniform array and the synthesis obtained from other optimization techniques.

A technique to further increase the bandwidth of stacked microstrip antennas

A new stacked microstrip antenna structure that enhances the bandwidth without changing the resonance frequency is proposed and studied in this paper. The effect of the various antenna parameters on the bandwidth is investigated. The resulting antenna using the proposed structure has an ultra-wide bandwidth of 35%, compared to 21.8% for the conventional stacked antenna structure. The proposed structure has a little effect on the antenna radiation characteristics. The analysis of the proposed structure is carried out using the FDTD method.

Planar Array Synthesis with Minimum Sidelobe Level and Null Control Using Particle Swarm Optimization

This paper describes a synthesis method of planar array geometry with minimum sidelobe level and null control using the particle swarm optimization (PSO) algorithm. The array geometry synthesis is first formulated as an optimization problem with the goal of sidelobe level (SLL) reduction and/or null placement in certain directions, and then solved by the PSO algorithm for optimized elements locations. The steps in the problem formulation are presented along with a design example that illustrates the performance of the PSO algorithm.

A Bowtie Antenna Coupled Tunable Photon-Assisted Tunneling Double Quantum Well (DQW) THz Detector

Abstract : The integration of a bowtie antenna with a double electron layer tunneling transistor (DELTT) device for the purposes of THz detection is investigated in this paper. The concept of THz detection, based on photon-assisted tunneling (PAT) between the two electron layers in a double quantum well (DQW) heterostructure, will be explained. The detector is expected to have narrowband, electrically tunable, fast response, and the possibility to operate at relatively high temperatures. Since the active area of the detector is very small, which is necessary to achieve fast response, it is not efficient in collecting THz radiation. Therefore, a broadband bowtie antenna is integrated with the detector to efficiently collect the THz radiation. Characteristics of different bowtie antenna geometries at THz frequencies were studied. An equivalent circuit model of the THz detector was developed, for the first time, to estimate the impedance characteristics at THz frequencies. Such a model is crucial for achieving impedance matching between the DELTT and the antenna to increase the overall coupling efficiency.

Transient response of optoelectronic integrated bistable device

In this paper, the transient response of an optical bistable device with optically controlled set and reset functions is analyzed. The device is made from a vertical integration of two heterojunction phototransistors (HPTs) and a laser diode (LD). One of the HPTs (HPT-A) is integrated just above the active layer of the LD and is utilized in the set operation, while the other HPT (HPT-B) is used to achieve the reset operation. The effect of the various device parameters on the set and reset operations is outlined. Finally, expressions for the rise time during the setting, and fall time during the resetting conditions are derived.

Design of Multi-Band Transmission Line Transformer using Particle Swarm Optimization

The design of N-section matching transformer operating at N arbitrary frequencies using the particle swarm optimization (PSO) method is demonstrated. Although analytical methods based on standard transmission line theory can be used in such designs, however, the analysis becomes cumbersome if N exceeds three, and numerical methods should be used to solve the resulting nonlinear equations. The design using the PSO, however, is much easier, and gives the same results as the analytical methods. Different examples are presented and compared with published literature

Radiation characteristics of an infinite line source surrounded by concentric shells of metamaterials

This paper presents an analytical study on the effect of concentric circular shells of metamaterials on the radiation properties of an infinite line source. The results show that with proper design, it is possible to increase the gain of the line source when surrounded by cylindrical shells of metamaterials, relative to the case where the line source is surrounded by free space.

Optically driven CPW fed slot antennas and arrays for wireless communications

This paper presents a comparison of three different types of CPW fed slot antennas integrated with a photodetector. The antennas are driven by optical power converted into microwave power using the photodetector which is directly attached to the antennas without the use of any amplifying devices. The operating frequency of these antennas is around 18.5 GHz. This paper presents the approach for matching a photodetector to a single element or to an array of elements. Measured data and simulations for various antenna/photodetector configurations are compared and discussed.

Equivalent circuit model for a THz detector based on the double-electron layer tunneling transistor (DELTT)

An equivalent circuit model for the double-electron layer tunneling transistor (DELTT) integrated with an antenna is presented in this paper. This device is used basically for THz detection, and the antenna is used to efficiently couple THz radiation into the device for processing. Developing an equivalent circuit model is extremely helpful in matching the antenna to the device.