Sharif Digital Repository

Low back pain (LBP) problems are of concern to many researchers specially physiologists, biomedical engineers and... .biomechanical models can help us to furthering our knowledge of the mechanical characteristics of the spine and its neural control to know more about potential mechanisms of injury. This thesis involves computational model of lumbar spine to generate and control its flexion-extension movement.
Model has involved 7 links: 5 lumbar vertebrae, pelvis and trunk. Desired trajectory has been generated for rhythmic and discrete motion by the central pattern generators (CPGs). And then controller has produced torque of joints to track desired trajectory. CPGs have been... 

Recent growth in wireless communications leads to higher demand for smaller and cheaper wireless products. This increasing demand for high speed wireless products and therefore development of new modulation techniques, results in higher sensitivity to phase deviations. This means that the voltage controlled oscillator or VCO circuit must has lower phase noise. VCO is an important part in Phase Lock Loop or PLL that has been used in most of transceivers. This thesis focuses on design of a Programmable VCO for DVB-H Application in 0.18um TSMC process. A VCO is an oscillator designed to be controlled in oscillation frequency by a voltage input. The frequency of oscillation is varied by the... 

In this thesis, the influence of nonideal boundary conditions on the vibration of a functionally graded beam excited by a moving oscillator on Pasternak-type viscoelastic foundation has been investigated. The beam has simply-supported boundary conditions and is assumed that the right-hand-side boundary conditions allows for small deflection, moment and axial force. The beam property gradient is assumed to be in the thickness direction and varies according to the power law distribution. The Hamilton's principle is utilized to obtain the governing equations of motion under the assumptions of Euler-Bernoulli beam theory. The equations of motion of the beam are solved using an... 

This thesis revises the conventional design of oscillators and presents new methods for shaping and improving the phase noise curve of the oscillators. These methods are based on the position of the zeros and poles of transfer functions in the S-plane and choosing their orders also. This thesis shows that the position of the zeroes and poles of the transfer functions can affect the phase noise performance of the oscillators. The basic idea is maximizing the slope of the phase of the transfer functions. It is proved that the maximizing the slope of the phase can expectedly reduce the phase noise of the oscillators. Increasing the order of the transfer functions with the proper selection of... 

We present a novel and simple method to calculate each Fourier series coefficient of ISFs in LC oscillators, analytically. This new approach explains the relationship between Fourier series coefficient of ISF and oscillator topology and parameters. This technique helps designers to obtain the great insight of how to decrease the output noise in oscillators. This method also can be used to derive the waveform of ISFs in time domain.Based on the features of our new technique and by presenting a general method to change the stationary noises to Cyclo-stationary ones, we suggest a step by step design guide which elucidates new ideas for designers to manipulate the oscillator parameters and... 

Oscillators in microwave communication systems play very important role. Therefore, designing an oscillator with a good performance, influences the final performance of the system. One of the parameters that determine the performance of an oscillator is the phase noise. This parameter in systems that have a large number of adjacent frequency channels, is causing many problems. Therefore, designing an oscillator with low phase noise improves the entire system performance.
Microwave oscillator phase noise is influenced by various factors, which one of the most important is the resonator. In microwave applications cavities have small sizes, thus it is difficult to use of them. Thus, in... 

In this thesis, at first, we study the active inductors have been reported in the literature. Then by choosing one of them and investigating its advantages and disadvantages, we changed the structure in a way to solve its problems. On the way by using this active inductor and a negative capacitor, we designed an oscillator in 1.5 GHz frequency that has -106 dBc/Hz phase noise at 1MHz offset and its FOM value is 160 dBc. Also this oscillator is capable of frequency tunability of oscillation from 500 MHz to 2.2 GHz. In this spectrum the phase noise is changing between -100 dBc/Hz and -110 dBc/Hz. In the second part, in the aim of improvement of phase noise of oscillator structures based on... 

One of the most important parameters of a smartphone is the ability to operate in a long time with a rechargeable battery. As a result, the design of radio frequency circuits which are used in these cell phones is a consistent challenge for designers. Bluetooth Low-Energy standard (BLE) which is the fourth edition of Bluetooth standard is recently introduced with the aim of transporting low volume data with minimum power consumption. The most important challenge of the design of an RF receiver in the BLE standard is the power consumption. In a typical receiver, the oscillator and the mixer are the most power hungry blocks. Therefore, decreasing the power consumption of these two blocks is... 

For decades Crystal Oscillators (XO) have been the unequaled references for stable and low noise frequency sources. This leadership is due to their high Q-factor. The resonant frequency of such crystal resonator is inversely proportional to the thickness of the quartz disk (the resonant cavity) and is today limited , by physical manufacturing constraints , to about 150 MHz . in order to avoid such limitation , the solution is to start with an oscillator at higher fundamental frequency. SAW technology on quartz offers this opportunity . with SAW the resonant cavity size is not linked to the thickness of the substrate and resonant frequencies up to the GHz range are achievable. In this thesis... 

A novel low noise quadrature voltage-controlled oscillator (QVCO) with differential N-path filter is proposed in 0.18-μm CMOS technology. The said QVCO benefits from a cross-coupled structure and a current-reuse technology to produce the quadrature signal and to save power consumption and area, respectively. The new architecture reduces the phase noise by 8dBc/Hz at a 1MHz offset frequency for 2.4GHz oscillation frequency. QVCO consumes 9.8mW from 1.8V power supply when operating at 2.4GHz. QVCO has a frequency tuning range from 2.4GHz to 3GHz and achieves a FOM of 191dB at 1MHz offset. Switches of N-path filter are controlled by outputs of QVCO, so the center frequency of N-path filter is... 

One of the most important parameters of an implanted device in the human body is its ability to operate for a long time to decrease the need for surgery in order to replace the battery. Therefore, the radio transceivers in these devices are designed in such a way to reduce the power consumption as much as possible. But, at the same time, it is crucial that the bit error rate be as small as possible to decrease the number of incorrect sent and received bits. Thus, the phase noise should also be as small as possible in order to reduce the bit error rate. In this thesis, a transmitter has been designed for Medical Implant Communications Service standard. In order to reduce the power... 

Phase noise is one of the important parameters in telecommunication systems and its measurement has always been considered. Digital phase noise measurement methods have a simpler implementation and calibration than analog types. Also, in digital methods, amplitude noise and phase noise can be separated and measured both at the same time. Comparing the phase noise of two oscillators with different frequencies is another major advantage of digital methods. The sensitivity of digital methods is limited to the noise of their analog-to-digital converters. Cross-correlation technique is used to reduce the minimum measurable level of phase noise. This method reduces the internal noise of the... 

A key point in designing class-C oscillators is maximizing the Figure-of-Merit (FoM). For this purpose, changing the oscillator’s structure or adjusting its bias current may be used. Previous literatures mostly limit their efforts to the first case, leaving the issue of determining the proper bias current almost untouched. In this work, a new approach recruiting DC voltage of the common source node of the switching pair transistors as an indicator has been presented. Using theoretical analysis, it has been shown that maximizing this voltage will optimize the oscillator in term of the FoM. The proposed indicator has the advantages of not introducing any loading effect to the output node, and... 

Wideband mm-wave radars are gaining popularity in automotive applications due to their superiority in harsh weather conditions, high distance resolution, precise velocity measurement, and superior spatial resolution. The primary purpose of this thesis is to design and implement a voltage-controlled oscillator for 77GHz automotive radar applications.Phase noise -as one of the most crucial specifications in VCO design- Phase noise improvement techniques as well as harmonic engineering methods are delineated. Also, an Ocean-based code for ISF simulation is introduced and developed to obviate the need for additional signal processing software so that simulation speed increases... 

In this thesis first of all we investigate phase noise and it's generation factors. Then we design and implement an ultra low phase noise oscillator. To do this, an ultra low phase noise oscillator which is tunable in 1-2GHz with 100MHz steps will be designed. The outline of the circuit is as follows: at the first we design a VCO which is ultra low phase noise and mechanically tunable in 1-2GHz by means of rotation of a handle. Then a phase locked loop will be built with the help of an ultra low phase noise OCXO at 100MHz and one SPD1 which generates harmonics of OCXO's output frequency. For the next, design and implementation of a 1.6GHz oscillator with fixed output frequency has been done....