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Several studies have shown that friction and wear properties are the limiting factors to the performance and the reliability of nanoelectromechanical systems (NEMS). In reality, many NEMS devices work at high sliding speeds (m/s), e.g. the I/O-head of a hard disk. However, due to the limitation of the piezoelectric driving stage, the maximum sliding velocity we can get by using a conventional AFM is less than 1 mm/s. Therefore, the study of the nanotribology at relative high speeds requires an alternative approach. Because of the piezoelectric effect, quartz crystal resonators have been widely used in research. By studying the impedance as a function of the cycling frequency, one can determine the resonance frequency. However, the measurements of the oscillation amplitudes are not as easy as that of the resonance frequencies, because the amplitude is unique for each piezo, dependent on the oscillation frequency and the applied voltage. Laserinterferometric vibrometry is a classical method to detect mechanical vibrations. Such a method is ideal for thickness oscillations but not for shear oscillation. Therefore, we designed a setup to measure shear oscillation amplitudes under high resonance frequencies. With the new laser apparatus we can successfully measure the oscillation amplitude at the edge of the electrode on a quartz crystal with a resolution of 2 pm at MHz frequencies. Yet, this method is not apt for measuring oscillations at the center of the electrode. In this thesis, we will present how to directly measure the oscillation amplitude of a quartz crystal via AFM and perform friction measurements at the same time. As the oscillation speed at the center of the quartz crystal is up to 4 m/s, friction measurements under high speeds are achieved with the modified setup.
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Frequency estimation
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Oscillators, electric... Radio frequency... Voltage-controlled oscillators... Oscillators, audio-frequency... Frequency dividers
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High-frequency-rheology in rheometer... Real frequency rheology
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A U-band VCO and a V-band push-push frequency doubler are designed in a 0.25 mym SiGe:C BiCMOS technology. The VCO oscillates from 48 GHz to 55 GHz, with an output power of around - 1 dBm and a phase noise of - 84 dBc/Hz at 1 MHz offset. The push-push frequency doubler has a minimum loss of 12 dB at 50 GHz for an input power of 6 dBm. It achieves an output power of - 2.4 dBm at 50 GHz and - 5.8 dBm at 75 GHz for an input power of 10 dBm. The VCO is biased at 4 V consuming 36 mA, and the push-push doubler draws 9.4 mA from a 2 V supply.
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Oscillator based ADC
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This paper presents a 64-84 GHz phase-locked loop (PLL) realized in a low-cost 80-GHz HBT technology. The circuit consists of a wide tuning-range voltage-controlled oscillator, a push-push frequency doubler, a divide-by-32 frequency divider, a phase detector and an active loop filter. The measured phase noise at 1 MHz offset is -106 dBc/Hz. The output power is -2.5 dBm at 64 GHz, and it slowly decreases to -8.1 dBm at 84 GHz, with a maximum dc power consumption of 517 mW. To the authors’ knowledge, the circuit achieves the widest frequency tuning range and its in-band phase noise is the lowest among the fully integrated V/W-band PLLs reported to date.
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The recent significant performance improvement of SiGe Heterojunction Bipolar Transistors has opened the way to the millimeter-wave domain. In the future, this will allow the development of new exciting consumer-oriented applications such as high-data-rate wireless systems or high resolution automotive radar. However, with the aggressive scaling of device dimensions and the implementation of new advanced features, the cost of Si-based technologies becomes a major issue. The possible solutions are, first, to use and combine efficient design techniques to reach higher frequencies for a given technology with relaxed lateral scaling. A second approach consists in using a circuit, once the design has been successful, as a foundation for future designs, thus drastically reducing the required time for a design cycle and its cost. These two approaches have been investigated in this work. The four main RF blocks of a typical RF front-end (Low Noise Amplifier, Voltage Controlled Oscillator, Downconverter Mixer and Frequency Divider) have been successfully designed and achieve very good results beyond one third of the transistor transit frequency. Furthermore, by slightly modifying the design topology (mostly the reactive elements), the ICs have been redesigned to operate at higher frequencies and demonstrate very good performance.
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One common problem of frequency modulated continuous wave radar is leakage from the transmitter to the receiver. The leakage power is orders of magnitude larger than the target return power and appears as a very strong signal in the first few range bins. Additionally, the residual phase noise density of the local oscillator occurs around the leakage signal, which often raises the noise floor and limits the dynamic range of a radar system at the close proximity of the sensor. In this paper a novel system concept that cancels the phase noise around the dominating leakage path is proposed, mathematically derived, and proven by radar measurements with a radar demonstrator at 77 GHz.,acceptedVersion,
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