Wideband Low Side Lobe Aperture Coupled Patch Phased Array Antennas

Low profile printed antenna arrays with wide bandwidth, high gain, and low Side Lobe Level (SLL) are in great demand for current and future commercial and military communication systems and radar. Aperture coupled patch antennas have been proposed to obtain wide impedance bandwidths in the past. Aperture coupling is preferred particularly for phased arrays because of their advantage of integration to other active devices and circuits, e.g. phase shifters, power amplifiers, low noise amplifiers, mixers etc. However, when designing such arrays, the interplay between array performance characteristics, such as gain, side lobe level, back lobe level, mutual coupling etc. must be understood and optimized under multiple design constraints, e.g. substrate material properties and thicknesses, element to element spacing, and feed lines and their orientation and arrangements with respect to the antenna elements. The focus of this thesis is to investigate, design, and develop an aperture coupled patch array with wide operating bandwidth (30%), high gain (17.5 dBi), low side lobe level (20 dB), and high Forward to Backward (F/B) ratio (21.8 dB). The target frequency range is 2.4 to 3 GHz given its wide application in WLAN, LTE (Long Term Evolution) and other communication systems. Notwithstanding that the design concept can very well be adapted at other frequencies. Specifically, a 16 element, 4 by 4 planar microstrip patch array is designed using HFSS and experimentally developed and tested. Starting from mutual coupling minimization a corporate feeding scheme is designed to achieve the needed performance.To reduce the SLL the corporate feeding network is redesigned to obtain a specific amplitude taper. Studies are conducted to determine the optimum location for a metallic reflector under the feed line to improve the F/B. An experimental prototype of the antenna was built and tested validating and demonstrating the performance levels expected from simulation predictions. Finally, simulated beam scanning in several angles of the array is shown considering specific phases for each antenna element in the array

Three-Dimensional Printed Dielectric Substrates for Radio Frequency Applications

Engineered porous structures are being used in many applications including aerospace, electronics, biomedical, and others. The objective of this paper is to study the effect of three-dimensional (3D)-printed porous microstructure on the dielectric characteristics for radio frequency (RF) antenna applications. In this study, a sandwich construction made of a porous acrylonitrile butadiene styrene (ABS) thermoplastic core between two solid face sheets has been investigated. The porosity of the core structure has been varied by changing the fill densities or percent solid volume fractions in the 3D printer. Three separate sets of samples with dimensions of 50 mm × 50 mm × 5 mm are created at three different machine preset fill densities each using LulzBot and Stratasys dimension 3D printers. The printed samples are examined using a 3D X-ray microscope to understand pore distribution within the core region and uniformity of solid volumes. The nondestructively acquired 3D microscopy images are then postprocessed to measure actual solid volume fractions within the samples. This measurement is important specifically for dimension-printed samples as the printer cannot be set for any specific fill density. The experimentally measured solid volume fractions are found to be different from the factory preset values for samples prepared using LulzBot printer. It is also observed that the resonant frequency for samples created using both the printers decreases with an increase in solid volume fraction, which is intuitively correct. The results clearly demonstrate the ability to control the dielectric properties of 3D-printed structures based on prescribed fill density

Three-Dimensional Printed Dielectric Substrates for Radio Frequency Applications

Engineered porous structures are being used in many applications including aerospace, electronics, biomedical, and others. The objective of this paper is to study the effect of three-dimensional (3D)-printed porous microstructure on the dielectric characteristics for radio frequency (RF) antenna applications. In this study, a sandwich construction made of a porous acrylonitrile butadiene styrene (ABS) thermoplastic core between two solid face sheets has been investigated. The porosity of the core structure has been varied by changing the fill densities or percent solid volume fractions in the 3D printer. Three separate sets of samples with dimensions of 50 mm × 50 mm × 5 mm are created at three different machine preset fill densities each using LulzBot and Stratasys dimension 3D printers. The printed samples are examined using a 3D X-ray microscope to understand pore distribution within the core region and uniformity of solid volumes. The nondestructively acquired 3D microscopy images are then postprocessed to measure actual solid volume fractions within the samples. This measurement is important specifically for dimension-printed samples as the printer cannot be set for any specific fill density. The experimentally measured solid volume fractions are found to be different from the factory preset values for samples prepared using LulzBot printer. It is also observed that the resonant frequency for samples created using both the printers decreases with an increase in solid volume fraction, which is intuitively correct. The results clearly demonstrate the ability to control the dielectric properties of 3D-printed structures based on prescribed fill density