Jennifer Rayno

Synthesis of Broadband True-3D Metamaterial Artificial Magnetic Conductor Ground Planes Using Genetic Programming

The development and use of genetic programming (GP) software to synthesize true-3D artificial magnetic conductor (AMC) ground planes is presented, with the focus on achieving a lower frequency response (particularly in the high VHF to low UHF bands), low-profile, broadband designs without the use of absorbing or magnetic materials. Metallic 3D patterns are embedded in one or more substrate layers with a PEC bottom, and the patterning in the unit cell is allowed to extend into neighboring unit cells, thus achieving a lower frequency response with much smaller unit cell size and thickness. Four designs synthesized using the developed GP software are presented with achieved bandwidths ranging from 32.7% to 71.1% when using the ±90° reflection phase criterion. Further, it is shown that through the use of a parametric study, the center frequency (0 ° reflection phase) of one of the designs can be reduced from 381.3 MHz to 87.8 MHz, which is a 77% reduction. The edge of the square unit cell size for this miniaturized design is λ0/51 and the thickness is λ0/61 at 83.9 MHz.

Synthesis of broadband 3D AMC ground planes using genetic programming

The development and use of genetic programming (GP) software to synthesize true-3D artificial magnetic conductor (AMC) ground planes is presented, with the focus on achieving a lower frequency response (particularly in the high VHF to low UHF bands), low-profile, broadband designs without the use of absorbing or magnetic materials. Metallic 3D patterns are embedded in one or more substrate layers with a PEC bottom, and the patterning in the unit cell is allowed to extend into neighboring unit cells, thus achieving a lower frequency response with much smaller unit cell size and thickness. Two designs synthesized using the developed GP software are presented with achieved bandwidths of 71.1% and 51.6% when using the ±90° reflection phase criterion.

3D metamaterial broadband ground plane designed using genetic programming for the long slot array antenna

Previously developed MATLAB code for designing planar (2D) metamaterial broadband ground planes is extended to design volumetric (3D) metamaterial structures. A 3D ground plane designed to operate as an artificial magnetic conductor (AMC) in the 225-450 MHz frequency range is presented. Its performance when used as the ground plane of the planar long slot array (PLSA) antenna and cylindrical long slot array (CLSA) antenna is evaluated and compared to the previously used absorbing ferrite ground plane, resulting in enhanced gain performance due to in phase reflection and minimal absorption.

Dual-Polarization Cylindrical Long-Slot Array (CLSA) Antenna Integrated With Compact Broadband Baluns and Slot Impedance Transformers

In this letter, a realistic method for feeding the dual-polarized cylindrical long-slot array (CLSA) antenna is presented. A compact lumped-element balun with 2.5:1 bandwidth is designed, fabricated, measured, and used for feeding the dipole-mode, while a compact microstrip coupled-line impedance transformer is used for feeding the slot mode of the antenna. Simulation results of these feeds are compared to experimental measurements, and the overall performance of the dual-polarized CLSA antenna with these feeds is also simulated. Simulation results agree with measured data, and it is shown that this antenna has the capability of achieving four polarization modes [vertical, horizontal, left-handed circular polarization (LHCP), right-handed circular polarization (RHCP)]. The gain over 225-450 MHz ranges from -1.42 to -3.15 dBi for the dipole mode, -0.44 to -2.24 dBi for the slot mode, -1.76 to -2.70 dBic for the LHCP mode, and -1.80 to -2.68 dBic for the RHCP mode.

Hybrid genetic programming with accelerating optimizer for 3D metamaterial design

In this paper, the hybridization of previously developed genetic programming (GP) software with a low-level optimizer, which uses genetic algorithm (GA), is presented. Key variables are selected for low-level optimization of each GP topology. Two low frequency design examples are included, with each covering at least 225-450 MHz. The first design (from the 142nd generation of the original GP software) has 73.4% bandwidth (±90° reflection phase) while being 17.0% thinner than a previously presented design covering this band, whereas the second design (from the 6th generation of the hybrid software) has 68.9% bandwidth and is 25.3% thinner.

Hybrid Genetic Programming With Accelerating Genetic Algorithm Optimizer for 3-D Metamaterial Design

The computational efficiency of existing genetic programming (GP) software is improved through the addition of parallelization and hybridization with a low-level optimizer. The low-level optimizer is implemented using genetic algorithm, and two different versions of the developed hybrid GP program are presented. Timing and efficiency performance are discussed, which includes a method of making the original optimizer more than eight times faster. Efficiency results indicate that through the use of the optimizer, with sufficient variables included, significantly fewer (about ¼ to ½) GP generations are required to achieve working metamaterial designs. Two low-frequency broadband (225-450 MHz) ground plane design examples, which are 25.3% thinner than a previously published design covering the same frequency band, are included.

Dual-polarization cylindrical long slot array (CLSA) antenna integrated with compact broadband baluns and slot impedance transformers

In this paper a realistic method for feeding the dipole mode of the dual-polarized CLSA antenna is presented. A compact lumped-element impedance transforming balun is designed, fabricated, and tested with a broadband dipole. The broadband balun is then simulated to verify its performance in the dual-polarized CLSA antenna along with the slot impedance transformers. This antenna has the capability of achieving 4 polarization modes (vertical, horizontal, LHCP, RHCP).

Novel 3D loops and coils utilizing fourier series for low frequency AMC ground planes

Previously developed hybrid genetic programming with low-level optimizer software is used along with two novel building block designs (3D loop and coil utilizing Fourier series) to design low frequency artificial magnetic conductor (AMC) ground planes using only design specifications. The methodology used to create these building block designs in the existing GP software is described, and an AMC design example covering 225-450 MHz is given. The design has 72.9% bandwidth and a thickness of λ0/15.

Hybrid genetic programming with modified conjugate direction search for 3D metamaterial design

Hybridization of Genetic Programming and global low-level optimizer, namely Genetic Algorithm was previously developed. With the aim of improving computational efficiency, conjugate direction search method is modified and proposed as a new low-level optimizer for upper level Genetic Programming. In order to demonstrate computational efficiency, Genetic Programming and two low-level optimizers are employed to design broadband, low frequency ground plane (225 MHz-450 MHz). When applying optimizers on a single processor, preliminary results show that optimized unit cell found by new low level optimizer has a better reflection magnitude (at least 0.8 over the frequency range) than the one found by Genetic Algorithm (as low as 0.25 over the frequency band). Details of proposed method will be presented and discussed in the paper.

Development of untral wide bandwidth (UWB) cylindrical long slot array (CLSA) antenna integrated with novel microstrip feeders

A low cost, light weight, ultra wideband width, and omni-directional cylindrical long slot array (CLSA) antenna integrated with a practical feeding structure was developed and prototyped. This antenna was designed to operate from 225 MHz to 450 MHz. The novel feeding structures were directly fabricated on the conducting strips of the CLSA and connected to typical 50 ohm coaxial cable. Performances of this antenna were evaluated by measurements. Measurement results showed that the developed antenna provided omnidirectional pattern and mostly reasonable impedance matching together when RF absorber foam was used as a backing material in the ground plane.