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Feasibility study for a clock-controlled analog beamforming frontend

Ruiter, M. (2010) Feasibility study for a clock-controlled analog beamforming frontend.

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Abstract:In this work, a beamforming receiver system is presented that applies amplitude and phase adjustment by a passive mixer concept. A passive mixer is very linear and therefore suitable for canceling strong interference (nulling). In a concept proposed by Farzaneh et al. called 'A novel amplitude-phase weighting for analog microwave beamforming', amplitude and phase adjustment are realized by adjusting the pulse width and phase of a square wave LO (local oscillator) driving the mixer. This way of implementing amplitude and phase adjustment within a passive (switching) mixer relies on timing, which can perfectly exploit the benefits of CMOS technology: digital timing, very good switching capabilities and relatively low-costs. In this work two important equations are derived: the first equation predicts the maximum possible null depth as a function of the number of bits with which the pulse width is controlled. The second equation predicts the maximum possible null depth as a function of the bandwidth of interferers, angular uncertainty of the interferers and the number of nulls that are working together. Furthermore a beamforming circuit level design is proposed that is able to generate a LO clock at 1 GHz with variable phase and variable pulse width. With this LO clock, gains between 0.38 and 1 can be made together with phase shifts between 0 and 360 degrees. According to the derived equations and assuming that there are enough antenna elements, the system is expected to suppress interferers at least 20 dB. The system is able receive signals between 500 MHz and 1 GHz.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology
Programme:Electrical Engineering MSc (60353)
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