Design strategies for electrically small antennas, actively matched with non-foster elements

• Autores: Luis Fernando Albarracin Vargas
• Directores de la Tesis: Daniel Segovia Vargas (dir. tes.)
• Lectura: En la Universidad Carlos III de Madrid ( España ) en 2017
• Idioma: español
• Tribunal Calificador de la Tesis: Milos Mazanek (presid.), Luis Enrique García Muñoz (secret.), Marco Antoniades (voc.)
• Programa de doctorado: Programa de Doctorado en Multimedia y Comunicaciones por la Universidad Carlos III de Madrid y la Universidad Rey Juan Carlos
• Materias:
  • Física
    • Electrónica
      • Circuitos
  • Ciencias tecnológicas
    • Ingeniería y tecnología eléctricas
    • Tecnología electrónica
      • Antenas
    • Tecnología de las telecomunicaciones
• Enlaces
  • Tesis en acceso abierto en: e-Archivo
• Resumen

  • During the last years, some researchers have been working on the active matching or on non-Foster matching networks for electrically small antennas (ESAs) in response to the vertiginous increase in demand for compact devices working in multiband platforms. The inclusion of non-Foster networks allows broad bandwidths at lower frequencies, overcoming the inherent limitations derived from the high-quality factor (Q) property of ESAs. Thus, the development of multiband antennas with an engineered lower broadband obtained by embedding an active non- Foster matching network (MN) is one of the primary objectives addressed in this work. Such non-Foster MNs are implemented by using Negative Impedance Converters (NICs), introduced many years ago to realize negative capacitors or negative inductors that disobey Foster's reactance theorem.

    In this sense, an integral design methodology of actively matched ESAs with embedded non-Foster elements is proposed and developed. This design method takes into account the operating parameters inherent to a radiating element, such as efficiency and radiation pattern, impedance matching, realizability, and stability. A new parameter (called Sens) on the sensitivity of the ESA when loaded with a non-Foster form, is presented. This sensitivity analysis will allow us to choose what kind of antennas can be properly matched with non-Foster networks and their position in order to optimize the performance of the design. The design methodology can be easily extended to any type of antenna, disregarding its electrical size.

    Two electrically small antennas are presented as design examples in which the proposed design strategy is applied. First, a printed small semiloop antenna, which is resonant at 1200 MHz, is loaded with an embedded MOSFET-based NIC, resulting in fractional bandwidth (FBW) of 119% (centered at 117 MHz). Second, a blade-type monopole, whose resonant frequency is around 300 MHz, is loaded with an embedded non-Foster MN, resulting in an FBW of 82% (centered at 85 MHz). The outstanding results in terms of impedance bandwidth and miniaturization level encouraged us to keep seeking for solutions for radiation pattern changes and added noise issues. Finally, the proposed design strategy is applied to few-element antenna arrays to obtain a multiband performance, keeping unchanged the natural response of the host structure (i.e. around its resonant frequency).