Enabling Ridge Waveguide Technology for Wideband Millimeter-Wave Decoys

Manafi, Sara

Graduate Thesis Or Dissertation

Enabling Ridge Waveguide Technology for Wideband Millimeter-Wave Decoys Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/3x816m825

Abstract

Emerging high power millimeter wave applications such as RF decoy repeaters require transmission line technologies operating over a wide bandwidth with the ability to carry hundreds of watts of continuous wave (CW) power. To develop such repeaters an enabling technology for integration of components such as dual-polarized antennas, filters, couplers, bends, and twists is needed. This thesis presents the analysis, design, and measurements of novel passive components for such repeaters in V- and W- bands. At these high frequencies, traditional techniques of design and fabrication are challenging due to small size, losses, and wide bandwidth.A high-power capable wideband 45 ‒ 110 GHz double-ridge waveguide (WRD45110) transmission line with low loss, low dispersion, and high theoretical power-handling is demonstrated first. Then, utilizing the designed cross-section a suite of passive waveguide components required for a typical decoy repeater system such as straight transmission lines, E- and H- plane bends, 90° twists, and termination loads are developed. A quad-ridge horn antenna with consistent broadside gain and stable E- and H- plane radiation patterns over the desired frequency band is also demonstrated. All components are carefully designed across different physics-based domains (RF, thermal, air-breakdown, etc.) and fabricated with either a direct metal laser sintering (DMLS) 3D printing or a conventional CNC machining with special care taken to allow for easy interconnecting.The design of a dual polarized high power capable system over 45 ‒ 110 GHz band is also presented. To combine two polarizations into the same radiating aperture, an Orthomode Transducer (OMT) based upon WRD45110 is developed. In order to fabricate this prototype through DMLS process, this OMT is devised with all the guidelines of 3D metal printing.Also, in system level, a preliminary system integration of a decoy repeater is discussed. To enhance the isolation between the TX and RX antennas in a decoy repeater, reactive impedance surfaces (RIS) with 1D RIS (corrugations), and 2D RIS (mushroom structure) are designed and built. In addition, a switched-beam phased array system that uses a perforated gradient index flat lens for beam scanning in ±30° elevation and 0° ‒ 360° azimuth is demonstrated over the entire 45 ‒ 110 GHz frequency range.

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