A proposal of antenna topologies for 5g communication systems
- Autores: Vedaprabhu Basavarajappa
- Directores de la Tesis: José Basterrechea Verdeja (dir. tes.)
- Lectura: En la Universidad de Cantabria ( España ) en 2018
- Idioma: inglés
- Títulos paralelos:
- Propuesta de topologías de antena para sistemas de comunicaciones 5G
- Tribunal Calificador de la Tesis: Belén Galocha Iragüen (presid.), Vicent Miquel Rodrigo Peñarrocha (secret.), Susana Loredo Rodriguez (voc.)
- Materias:
- Enlaces
- Resumen
- español
En línea con la previsión de crecimiento de varios órdenes de magnitud del tráfico celular para 5G en los próximos cinco años como se detalla en el informe CISCO VNI 2017, en esta Tesis se proponen tres topologías de antena operativas a 14, 28 y 31 GHz – orientas a aplicaciones Massive MIMO, Single RF MIMO y Millimeter-Wave. Se presenta un nuevo elemento cuasi-óptico de bajo perfil y con respuesta longitudinal, un subarray 4x4 del mismo operando con un nuevo esquema de conmutación de haces múltiples para su empleo en Massive MIMO junto con su adaptación para su empleo en sistemas Single RF MIMO. Por otra parte, para aplicación en celdas de reducido tamaño en bandas milimétricas, se propone una antena mutihaz de lente en guía, completamente metálica, que proyecta varios haces direccionales de aproximadamente 15 dBi en dos bandas centradas a 28 y 31 GHz. Los tres prototipos fabricados han sido validados experimentalmente y su aplicación puede extenderse a varios casos de uso en 5G.
- English
Methodologies for meeting the requirements of 5G by a structured and simplified design of antennas are proposed in this thesis for frequencies centred at 14 GHz, 28 GHz and 31 GHz.
Using a unique method for the refractive index retrieval, employed over S parameters, a special arrangement of parasitics was used to design and realize a directional, low-profile quasi-optic end fire antenna element with a gain around 5.5 dBi with a bandwidth of 1.5 GHz around 14 GHz. Experimental validation of the antenna element asserted its suitability for use in the 4x4 sub-array for Massive MIMO antenna array.
The 4x4 subarray antenna was designed with an interelement spacing of 0.8λ and was solved for individual element patterns using a full wave solver before applying postprocessing on it. The measured active reflection coefficient over a selected element is distributed over the range 13.5 GHz to 14.5 GHz with an Snn < -15 dB. The mutual coupling between the ports for the best case is -31 dB and for the worst case is -25 dB. The 4x4 subarray employs two phasing networks that were designed to generate the two-phase states of 0° and 180° required for the beamswitching. The proposed multiple beamswitching scheme was applied on the antenna array and there was a good agreement between the simulated and measured antenna pattern for the different beamstates. For the generation of the boresight pattern a Co-polar gain varying around 18 dBi centred around 14 GHz was measured. The Cross-polar discrimination is around 20 dB around 14 GHz. For the generation of four beams a Co-polar gain of around 8 dBi at each beam and a Cross-polar discrimination varying from 10 to 20 dB is seen over the frequency band 13 to 15 GHz. Measurements made on other beamstates along other directions also agreed well with the simulations.
A novel two-phase state multibeam switching scheme proposed and applied over the designed 4x4 sub-array enables realization of multibeams along predefined directions spread over five selected validated beam states, though other beamstates can be obtained through the switching scheme. The scheme significantly reduces beamswitching latency generally associated with switching networks owing to the only-two-phase state proposition and that the switching is between multiple simultaneous beams rather than between single beams. This multibeam simultaneous beam footprint drastically reduces the switching time required for beam transition in conventional switching networks that need to hop between single beams.
Spatial modulation is a way of realizing Single RF MIMO. Spatial modulation harnesses pattern diversity to transmit implicit information over antenna patterns, where the implicitness comes from the selection of the antenna index to transmit the pattern. This requires the generation of beampatterns with low correlation coefficients (< 0.4) or ones that are orthogonal or non-overlapping to each other. A reconfigurable antenna beamswitching configuration that rotates a paired split beam over the azimuth for the range {0°< φ < 360°} in steps of 45° can be implemented on the subarray of a Massive MIMO array. The sub array can be 3x3 or 4x4 depending on the number of antennas in the Massive MIMO array. Recent interest in Massive MIMO antennas has been on 64 and 128 antennas, therefore it follows to have a subarray of 4x4 to act as the subarray beamswitching building block of the 64-antenna array.
The proposed beamswitching scheme employs electronic phase tethering that locks antenna elements or groups of antenna elements so that a control over the beam is attained which can be mapped onto simple geometric relations. Such a switching scheme was applied over the 4x4 array and paired split beam patterns spread over the azimuth in time in steps of 45° were measured. A good agreement between the simulated and measured results was observed. A gain of around 8 dBi and an XPD of more than 10 dB is seen over these patterns between 13.5 GHz to 14.5 GHz. These patterns share the same phase centre which introduces an additional degree of normalization over the varied paired split beams formed when employed as a reconfigurable antenna array for spatial modulation purposes. The beamswitching scheme proposed incorporates pattern reconfigurability that introduces dual functionality into the array: Use in large scale arrays such as Single RF MIMO and the use in Spatial Modulation to transmit implicit information through antenna index.
For application in small cell scenarios at Millimeter Wave band, an all-metal multibeam waveguide lens antenna is proposed that projects multiple high directional beams of the order of 15 dBi over two bands centred at frequency of 28 GHz and 31 GHz. Experimental validation of the antenna confirms the phase extraction and compensation method proposed for simplifying the design process. The designed beam angles directed towards pointed three beam distributions over a 120° sector of a small cell can be used in millimeter wave based 5G LMDS small cell scenarios. These antennas are conceptualized, designed and tested with due considerations to current 5G requirements and therefore are 5G-ready. The thesis presents a detailed treatise on these antennas.
- español
