University of Twente Student Theses


Interference Nulling via a Resistor-Weighted Op-Amp Vector Modulator

Ende, Frederik van den (2011) Interference Nulling via a Resistor-Weighted Op-Amp Vector Modulator.

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Abstract:In order to perform interference nulling (through beamforming), for an in- terferer with variable angular position, the radiation pattern of an array antenna has to be adjusted electronically. This thesis deals with a beamforming algorithm that rotates the beams of a Butler Matrix beamforming network (BFN), such that one of the beams is able to 'capture' an interferer. This beam is strongly attenuated, such that the interferer is nulled out. In this way the signal-to-interference ratio (SIR) is improved. Subsequently, a vector modulator performs phase shifting in order to optimize the signal-to-noise ratio (SNR). Based on an existing platform, a circuit level implementation, using Op- Amps and resistors, is proposed to verify the nulling performance of the beamforming algorithm. Circuit simulations demonstrate, for low resolutions, a minimum rejection of 17.56 dB, such that the SIR is improved by this number.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:54 computer science
Programme:Computer Science MSc (60300)
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