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Open Access Publications from the University of California

Scholarly Works (4 results)

  • Thesis
  • Peer Reviewed
UCLA Electronic Theses and Dissertations (2015)

Metamaterial transmission lines are able to control the phase response in the circuit, thereby making it possible to achieve multi-band characteristic in guided structures and full beam scanning ability in leaky-wave antenna applications. Isolation circuits use multi-band trait of a metamaterial transmission line for having infinite impedance at multiple frequencies. With isolation circuits, it is possible to connect microwave filters for having unique property, so called multiplexing functionality. This new approach provides unique advantageous features beneficial to system designer. For instance, there is no need to modify the components (filters and multiplexers) used in the system. Also, the design process is straightforward.

Substrate integrated waveguide (SIW) is a novel guided-wave structure developed in recent years in microwave and millimeter wave areas. It can be synthesized on a planar substrate with linear periodic arrays of metallic vias by planar circuit processes. SIW has significant advantages such as low insertion loss, low cost and strong integration ability with other planar circuits. Based on the SIW technique and the metamaterial transmission line concept, circular polarized SIW leaky-wave antennas are designed and presented. The proposed frequency scanning antennas provide circular polarized fields using a single radiating transmission line, which can avoid the complexity of conventional approach.

    Cover page: Multiplexers and Antennas Based on Metamaterial Transmission Line
    • Article
    • Peer Reviewed
    UCLA Previously Published Works (2014)
    Several types of multiplexers based on isolation circuits have been introduced and investigated. Combining method of two filtering circuits (CMTC) is one way to make multiplexers based on isolation circuits. This method fits well for designing contiguous channel triplexers. A triplexer based on CMTC consists of a conventional transmission line (TL) connected to a diplexer and a composite right/left-handed (CRLH) TL connected to a filter. The triplexer based on CMTC has two significant advantages. One is that it is not necessary to modify the design of a stand-alone filter and diplexer and there is freedom in the choice of filtering circuits. In addition, a designer does not need to perform three-dimensional full-wave optimization, because of a simple and straightforward design concept. In this paper, a triplexer prototype having 1, 1.125, and 1.25 GHz center frequencies, is designed and fabricated. The measured results show good agreement with the simulation results. © Cambridge University Press and the European Microwave Association 2014.
      Cover page: Study and analysis of contiguous channel triplexer based on combining method of two filtering circuits using CRLH and RH isolation circuits
      • Article
      • Peer Reviewed
      UCLA Previously Published Works (2014)
      In this letter, a novel dipole antenna based on substrate integrated waveguides (SIWs) is presented. The dipole antenna radiates through the equivalent magnetic current loops on the top and bottom annular ring slot that is excited by the fundamental mode of the SIW cavity. Therefore, the proposed dipole possesses a vertical polarization perpendicular to the metallic plane. Moreover, thanks to normal electric field, the proposed dipole is less affected by the ground plane size and surrounding metal. The proposed antenna topology provides a very easy way to realize vertical dipole antenna by just using planar circuits and is promising to be used as a fundamental element to realize antenna arrays. © 2002-2011 IEEE.
        Cover page: Magnetic-Current-Loop-Induced Electric Dipole Antenna Based on Substrate Integrated Waveguide Cavity
        • Article
        • Peer Reviewed
        UCLA Previously Published Works (2015)
        A circularly polarized (CP) CRLH-inspired leaky-wave antenna (LWA) based on substrate-integrated waveguide (SIW) and microstrip delay line is presented. The unit-cell of the proposed periodic antenna consists of two conventional CRLH SIW cells and two quarter-wavelength microstrip lines. The interdigital slots on the CRLH SIW are rotated at +45° and -45° with respect to the wave propagation direction and separated by 90° to create circular polarization. Utilizing the microstrip line instead of the SIW delay section, the total size of the five unit-cell antenna is reduced by 24.4% in comparison to the previous single radiator CP LWA. Furthermore, microstrip lines provide improved matching for broadside radiation as well as better CP purity. The unitcell characteristics are investigated in detail through dispersion and Bloch impedance analysis. In addition, space harmonic analysis is carried out to explain the radiation mechanism of the proposed antenna. The proposed CRLH-inspired SIW CP antenna operates from 4.2 to 4.85 GHz and frequency scans from -25° to 26° along the elevation angle. Axial ratio is maintained below 3 dB throughout the operating frequency. The measured results show good agreement with the simulated results.
          Cover page: A Compact Single Radiator CRLH-Inspired Circularly Polarized Leaky-Wave Antenna Based on Substrate-Integrated Waveguide
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