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Tesis:

RF- Front-End Non-Linear coupling cancellation = Cancelación de acoplo no lineal en frontales de RF

  • Autor: ARAMBASIC, Igor

  • Título: RF- Front-End Non-Linear coupling cancellation = Cancelación de acoplo no lineal en frontales de RF

  • Fecha: 2008

  • Materia: Tecnología electrónica y de las comunicaciones

  • Escuela: E.T.S. DE INGENIEROS DE TELECOMUNICACION

  • Departamentos: SEÑALES, SISTEMAS Y RADIOCOMUNICACIONES

  • Acceso electrónico: http://oa.upm.es/1836

  • Director/a 1º: CASAJÚS DE QUIRÓS, Francisco Javier

  • Resumen: Abstract In order to extend the communication range, improve reliability and achieve higher bit rates recent trends in communication industry include the use of multiple antennas in transmitter and at the receiver. At the same time the dimensions of mobile terminals are getting smaller incrementing the level of electronic interferences in their interior. The closeness of data metallic wires and many electronic circuits creates rather hostile environment which, among other dis¬tortions, stimulates the appearance of undesirable energy transfers between physical mediums. This signal distortion, also known as multiantenna radio-frequency (RF) front-end coupling is analyzed throughout the thesis, and as a result three coupling cancellation procedures are developped and later tested in simulated coupling environments. The coupling phenomena depends on many variables, starting with the selection of electronic elements and RF front-end design, up to the transmission system working conditions. Since the complexity of coupling distortion discards simple linear models, nonlinear modelling based on polynomials, limited to third order, is implemented. The coupling model proposed in this thesis is consistent with the analog electronic elements and follows the nonlinear behaviour experienced in many RF front end imperfections. The coupling cancellation approach is based on nonlinear software decoupling module located at the output of analog-to-digital (AD) converter. The advantage of this location is that it deals directly with sampled physical data avoiding any dependency on specific signal type. Hence the decoupling module can be easily implemented in wide range of transmission systems. Inside the module, signal enhancement is achieved with the approximation of inverse nonlinear coupling function based on the sum of two independent polynomials modelling the inverse function of coupling between two antennas. The adequate decoupling surface is obtained with three different search methods: Simulated Annealing (SA), Improved Fast Simulated Annealing (IFSA) and Guided Multi-Level (GML) search. The thesis is divided into eight chapters. The first two correspond to technological back¬ground and RF front end description, respectively. In chapter three, nonlinear coupling model is developed with emphasis on receiver's RF front-end based on I/Q downconverter. Chapter four introduces the inverse coupling function and develops the adequate approximation surface model used for coupling cancellation. The three approaches used for the corresponding surface search are than analyzed in chapter five. The following two chapters first simplify the surface 3 form in noiseless conditions, and afterwords the performance of adopted search methods is an¬alyzed in environment with AWGN noise during the calibration. The last chapter corresponds to conclusion and possible future applications of decoupling module. 4