University of Twente Student Theses


Analysis and comparison of switch-based frequency converters

Soer, Michiel (2007) Analysis and comparison of switch-based frequency converters.

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Abstract:Among radio amateurs a variation of the sampling mixer with 25% duty cycle is used, which is known under several names: Tayloe Product Detector, van Graas Detector or Quadrature Sampling Detector. Although the circuit has been in use for several years no thorough analysis of its properties has been made and it has not been noticed in professional scientific literature. The experimental data suggests that the circuit has low conversion loss and noise figure, while having a high linearity. The goal of this Master Thesis is to investigate the precise properties of this mixer and to compare its performance with better known mixer circuits. The outcome is to be verified using circuit simulations. Also the feasibility of designing a RF receiver front end in 65 nm CMOS using this mixer should be explored. A comparison has been made between the topologies of the switching, sampling and Tayloe mixer. A model topology has been found that describes all three mixers, called the frequency converter model. This model has been analyzed using Linear Periodically Time-Variant theory and closed form expressions for the periodic transfer function have been derived. From these expressions, properties like conversion gain, noise figure and baseband bandwidth can be derived. Also an approximation of the periodic transfer function has been formulated for narrowband channels, which directly translates the duty cycle parameter to conversion gain and Noise Figure, and the bandwidth parameter to the baseband bandwidth. It was concluded that a double balanced Tayloe mixer with 25% duty cycle provides the best balance between noise figure and conversion loss. Using these results a RF receiver front end was designed and simulated in 65 nm CMOS. The channel was chosen at 1 GHz with 20 MHz bandwidth. A conversion gain of 10.5 dB was achieved with a noise figure of 5.0 dB. Furthermore, the IIP3 is +12 dBm and the -1dB compression point is -5 dBm. Therefore, it can be concluded that a receiver front end with high linearity and moderate noise figure can be implemented using the Tayloe mixer.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology
Programme:Electrical Engineering MSc (60353)
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