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Feasibility study of frequency doubling using an anxor-gate method

Ma, Song (2013) Feasibility study of frequency doubling using an anxor-gate method.

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Abstract:The performance of integrated Frequency Synthesizers relies on a clean fixed reference frequency, which is usually derived from a crystal. Unfortunately, commercial low cost crystal oscillators are limited in the range of 20-50MHz. In general, a higher reference frequency results in better noise performance for Frequency Synthesizers. Therefore it is desired to be able to multiply the reference frequency and at the same time to preserve the clean crystal properties. This work examines the feasibility of a low power and low noise CMOS Frequency Doubler in CMOS IC-technology. Main target specifications are: -151 dBc/Hz phase noise floor, 10kHz flicker noise corner frequency and precise 50% duty cycle rate within a power budget of approximately 4mW. Within this scope a known analog method has been analyzed, which has been proven to be sub-optimal. A digital method has been proposed using an XOR-gate. The basis idea is that the frequency of the input clock is doubled at the output of an XOR-gate if the two input clock signals have 90° phase shift. The advantages are that it is a highly digital circuit which implies low power dissipation and that phase noise floor is 10dBc/Hz lower than for the analog method at the cost of power less than 2uW at 20MHz, which is a factor of hundred lower power than for the analog method. However, the major drawback of this approach is that static timing errors, due to the different transition times of NMOS transistors and PMOS transistors, spoil the duty cycle rate—it is not 50% anymore. A duty cycle correction circuit is therefore added to detect the error and correct this duty cycle error. The system has been analyzed on system level and implemented and simulated on circuit level.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology
Programme:Electrical Engineering MSc (60353)
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