Joshua C. Myers

Affordable 3D printed microwave antennas

In this paper, a variety of 3D printed microwave antennas are presented including wide band, narrow band, multiband and reconfigurable designs. In particular, single layer patch, folded E-patch, a bilateral Vivaldi, Spartan logo and Lego-like assembled antennas are demonstrated. 3D printing provides significant flexibility in the design of antennas that combine the assembly of both dielectric and metal layers to achieve desired performance characteristics such as resonant frequency and radiation pattern. Also, small Lego-like blocks can be printed that allows in the design and assembly of novel antennas structures using a combination of dielectric and metal coated blocks.

Affordable terahertz components using 3D printing

This paper presents the design and characterization of 3D printed photonic crystal filter (quasi optic component) and dielectric ridge waveguide (integrated component). Commercially available 3D printer was used to print polymer based components. Design and characterization of these devices is carried out over a frequency range of 0.15 - 0.5 THz. The photonic crystal filter shows a stop band from 0.25 - 0.35 THz. Also a very narrow defect mode (notch filter) was introduced by altering the structure of photonic crystal. The dielectric ridge waveguide shows broadband THz propagation characteristics. The transmission loss was determined to be largely dominated by the loss characteristics of the polymer material used.

Design study of electronically steerable half-width microstrip leaky wave antennas

A half-width microstrip leaky-wave antenna (HMLWA) having electronic beam steering capabilities is presented. Electronic beam scanning is demonstrated in X-, Ku- and Ka-bands through detailed design analysis and measurements. Two physical design approaches are studied; one requiring multi-layer processing and another requiring only a single layer metallization. In this paper, only the single layer design was implemented. Varactor diodes are edge coupled to the antenna element to achieve beam scanning as a function of the applied voltage at a fixed frequency. Beam scanning of 45-degrees for an 8 GHz design and 30-degrees for a 16 GHz antenna design are demonstrated. Details of design, fabrication and measurements are presented.

A Multilayered Metamaterial-Inspired Miniaturized Dynamically Tunable Antenna

A multilayered metamaterial-inspired antenna with a pixel grid loading structure is introduced. The antenna consists of two patterned metal layers separated by a thin dielectric film. The first layer contains a folded monopole antenna surrounded by a metal pixel-based loading structure, whereas the second layer consists of a photoconductive pixel grid utilized to tune the antenna. Appropriate pixel configurations to produce a desired performance are implemented in simulation using a binary genetic algorithm (GA) and a MATLAB-HFSS (high-frequency simulation software) interface. HFSS simulations show that the antenna can be tuned over a wide frequency range by appropriate choice of pixel states on the second layer, using a variety of conductivities. As a proof of concept, the pixel grid on the second layer is initially made of a metal conductor. Multiple antenna configurations corresponding to a wide frequency range are constructed using a multilayer fabrication method. The measured reflection coefficients and radiation patterns are shown to be in good agreement with HFSS simulations, successfully demonstrating the ability to tune the antenna using the pixel grid on the second layer.

Planar surface plasmonic structures for terahertz circuits and sensors

This paper presents planar metal patterned structures that support surface plasmon polaritons (SPPs) like propagation mode. Four unit cells, each having a solid ground plane, were designed that support SPPs. To optimize return loss, these structures were first simulated as infinitely periodic in two dimensions. These were then further optimized by designing waveguide structures. Using multi-band unit cell designs, THz circuits (transmission line and power splitter) were fabricated and tested. A new approach to probe these planar plasmonic devices is presented using wide band THz dielectric probes. Measured results of THz circuits match closely with simulation results. It is also shown through simulations that these structures can be used in the design of THz chemical and biological sensors.

Integration of piezoelectric energy harvesting and antenna elements on a common substrate

A patch antenna integrated onto a piezoelectric polyvinylidene fluoride (PVDF) substrate is introduced. The patch antenna is designed for operation at 12.5 GHz and the PVDF material is sputtered with copper to host the antenna and ground plane. The measured reflection coefficient and antenna radiation patterns are shown to be in good agreement with HFSS simulations. In addition, energy harvesting properties of the material are investigated through an excitation of the fundamental cantilever mode of the substrate. Trade offs between optimal antenna and substrate configurations are also considered to maximize power output while maintaining minimal system impact. Results show that the structure is capable of simultaneously acting as both an energy harvesting device and antenna.

Design of thin-film quasi-optical terahertz components using evolutionary algorithms

In this paper, the design of THz thin-film components using single and multi-objective evolutionary algorithms is introduced. Each structure is optimized through a HFSS-MATLAB interface with infinitely periodic boundary conditions and plane wave incidence. First, terahertz band-stop filters are investigated based on a dual-cross structure. The filters are optimized for rejection, bandwidth, and multi-resonant properties. A bandwidth of approximately 45 GHz with -25 dB of rejection at 300 GHz is observed, as well as multi-resonant filters at 250 and 300 GHz. The miniaturization of a THz bolometer is also investigated using a single-objective genetic algorithm in order to improve its noise equivalent power. From the optimization, a unit cell approximately λ0=25 in size at 100 GHz is found, which is significantly smaller than the typical size constraints of traditional periodic structures.

Investigation of modulation-capable silicon waveguides for efficient on-wafer terahertz interconnects

In this paper, silicon-based waveguides are investigated for on-wafer THz interconnect applications. A silicon based dielectric ribbon and ridge waveguide are both shown through HFSS modeling and simulation to have very low-loss transmission characteristics as low as .3dB/mm in the THz frequency spectrum. In addition, the modulation properties of both waveguides are investigated through a Drude model analysis as well as EM simulation. Several silicon ridge waveguide samples are fabricated using a simple silicon wet-etching technique. These waveguides are shown to efficiently transmit THz radiation, especially when the ridge is narrow. The low-loss nature of these waveguides shows the potential of silicon-based interconnects with built-in modulation capabilities for THz integrated circuit applications.

A multi-layered metamaterial inspired dynamically tunable antenna

A multi-layered metamaterial inspired antenna with a pixel grid loading structure is introduced. The antenna consists of two layers separated by a thin dielectric substrate. The first layer contains a folded monopole antenna surrounded by a metal pixel based loading structure, while the second layer is envisioned to consist of a photoconductive pixel grid utilized to tune the antenna. The state of each pixel is controlled by a binary genetic algorithm, which is implemented with a Matlab-HFSS interface. HFSS simulations show that the second layer has a wide tuning ability with the appropriate state formed through optimization. As a proof of concept, the pixel grid on the second layer is initially made of a metal conductor. A state corresponding to a resonant frequency of 3.5GHz is selected and the antenna is constructed using conventional photolithography. The measured reflection coefficients are shown to be in good agreement with HFSS simulations, successfully demonstrating the ability to dramatically tune the antenna with a second pixel grid.

Plasmonic waveguide coupling at terahertz frequencies

Two approaches for coupling terahertz radiation to surface plasmonic waveguides are proposed and simulated. The first approach utilizes a rectangular waveguide with a tapered plasmonic feed, which allows for the gradual confinement of terahertz waves into a plasmonic structure. The second method employs a ribbon dielectric waveguide, which edge couples terahertz radiation onto a surface plasmonic structure. Coupling designs are presented along with simulation results.