Sharif Digital Repository

In this thesis, the design of a fully-integrated Millimeter-wave Broadband power amplifier in TSMC 0.18 µm CMOS technology is studied. The Darlington cell with cascode topology was adopted as the power cell to improve the maximum available gain of transistors in standard 0.18 µm CMOS technology to make it eligible of operating at Ka band. Furthermore, by proposing a new topology as an improved Darlington-cascode with intermediate inductor in the Darlington pair, the improvement in flat power gain at Ka band and more importantly, in available power gain of active element at high frequencies of the Ka band is achieved. The proposed power amplifier is a two stage structure with the driver stage... 

In this thesis, a low-power low-phase-noise 28 GHz voltage-controlled oscillator for 5G applications is presented. At first, to select the best structure in terms of FoM, various types of inductors and transformers have been designed and EM simulated. The class-C structure which leads to the highest FoM is chosen eventually. In order to increase oscillation amplitude and reduce phase noise while preserving FoM, a high-frequency noise filter is presented. This filter which is based on a λ/8 microstrip transmission line has solved the conventional filter problems e.g. narrow bandwidth, coupling with oscillator inductor and practical implementation issues.The oscillator is designed, EM... 

The blood pressure (BP) is one of the most vital signs to monitor human health. Hypertension is a major public health problem that is associated with morbidity and mortality. In the past decades, the number of people with hypertension disease has been increased. According to Ministry of Health, 54 percent of hypertensive patients are unaware of this health threat. Therefore, accurate and continuous measurement of BP is essential for its prevention and treatment. Traditional non-invasive methods of BP monitoring use an inflatable cuff, which causes discomfort due to occlusion of the artery and can not be used continuously. Numerous studies have attempted to present methods without using a... 

In this study، a novel frequency multiplier chain for wideband millimeter-wave applications at 28 GHz is presented. Millimeter-wave imaging systems require high frequency and wide bandwidth to accurately detect hidden objects. Various methods have been proposed to increase the frequency of generated signals, but in the meantime، frequency multiplier structures exhibit better performance in terms of bandwidth، power consumption and, harmonic rejection. These circuits are widely used in High-frequency telecommunication systems such as 5th generation mobile services. To design a frequency quadrupler، two multiplier stages based on the improved quadrature Gilbert structure were used. Generating... 

Design of a 28GHz phased array receiver front-end for 5G applications in CMOS 0.18um technology in the frequency band from 27.5 to 28.3 GHz is presented in this thesis. We use an RF phase shifting structure which consists of a low-noise amplifier, a phase shifter and a power combiner. The low-noise amplifier is designed using common-source cascode topology with a transformer-based gm-boosting technique in order to enhance the power gain and reduce the noise figure. A vector sum phase shifter is then designed to further enhance the gain. A Wilkinson power combiner with lumped elements is designed as the power combiner. The results of simulating a single RX chain shows a maximum of 15 dB... 

This thesis presents a four-antenna phased-array transceiver front-end for 5G applications. The designed front-end uses RF architecture and time division duplexing mode and operates in the 26~30 (GHz) band. In our design procedure, we have used a four-stage inductively degenerated common source LNA, a differential three-stage PA, and a vector-sum phase shifter. Circuit blocks are connected using traditional architecture, and an SPDT switch is used to determine the Tx/Rx mode of the system. A switching current reference is designed, which enables us to control the circuit gain over different process corners and temperatures.Each transmitter chain produces 13.42 (dBm) power at its operating... 

With the expansion of wireless communication technology and the advent of the fifth generation of mobile communication, there is a growing need for broadband systems. Consequently, RF engineers are currently focusing their attention on broadband transceiver systems. The low noise amplifier (LNA) is a critical component in the receiver of a telecommunication system. In this research, the design of a broadband LNA in the K and Ka frequency band (18 ~ 40 GHz) is presented. The main challenge in designing a broadband LNA lies in achieving simultaneous power matching and noise matching through the input impedance matching network. Various types of broadband impedance matching networks have been... 

On the demand of higher directivity, higher throughput and less interference, phased array systems and MIMO have become attractive to reach these goals. The advantages of phased array systems include the ability to perform electronic beam steering and arbitrary pattern synthesis. Phase shifters and variable gain amplifiers are used to reach these advantages. In this thesis, a ‘’ C‘’ band (4.8 GHz-6.2 GHz) vector-sum phase shifter using HMIC technology for realizing a phased array receiver is designed. This phase shifter can change the signal phase and amplitude. The main blocks of this phase shifter are low-insertion phase and low-noise variable gain amplifier, which consists of current... 

Today, by emerging wearable technologies and digital health, it is possible to constantly monitor vital signals of people without time-consuming and costly referrals to medical centers. Applications of wearable sensors for health monitoring include electrocardiograms (ECG), blood pressure measurement, and blood sugar measurement, etc. One of the important fields of health monitoring is cardiac arrhythmia detection. Cardiac arrhythmia is any kind of anomalies in heart beat rhythm that can lead to serious damage to vital organs of the body. It is estimated that between 750 thousand to 1.5 million people are facing cardiac arrhythmia in Iran. Therefore, early detection of cardiac arrhythmia is... 

Nowadays, frequency synthesizers are widely used in many modern devices due to the ever-increasing growth of electronic circuits and their applications in various aspects of life. Imaging devices with security applications in the millimeter-wave frequency band is one of the mentioned applications. To prevent crowds at checkpoints and facilitate traffic, these devices need to monitor people's security at the highest possible speed. Furthermore, significant bandwidth is required to increase image quality. Therefore, using frequency generators with high-speed frequency sweep ability is a great advantage. In this thesis, a digital frequency generating chip with 1GHz bandwidth is designed using... 

Power harvesters are used to generate energy for electronic devices. These electrical energy generators consist of three main parts: energy source, power electronic converter and energy storage. In order to minimize some of the weaknesses of these devices, including low power density and low reliability, the hybrid power harvesting method can be utilized. In this thesis, we design and build a hybrid energy harvester considering the advantages of simultaneous usage of solar and thermal energies for a wearable sensor, focusing on "efficiency enhancement" and "availability improvement". In the designed device, both solar and thermal energy harvesting units operate independently. In the solar... 

Today's millimeter imaging has been widely used in the field of security and medicine. With increasing security threats, there is a need for improved security equipment. Millimetric waves not only have the ability to penetrate dielectric materials, but also the ability to separate them to detect hazardous materials. Also, the millimeter-field imagery is capable of detecting different materials from each other, which is an advantage in detecting hidden cases. Unlike X-ray imaging, millimeter waves do not have the ability to ionize the cells of the body, which reduces the risk of creating radios for imaging. In this project, an array antenna with two orthogonal poles is designed. Macrostrip... 

An inseparable problem from human daily life is stress that causes problems such as heart disease and depression, so stress management and control is essential for the health of the individual and society. This thesis explores the possibility of stress detection using vital signs and machine learning algorithms. First, by examining the potential of unsupervised learning algorithms for stress detection, a general method is developed and the accuracy of the algorithm is evaluated with the ECG signals of a smart wristband made in Sharif University of Technology Biosen group as well as WESAD data set. The self-organizing map structure is created based on stress-related features and final result... 

The most important feature of the fifth generation of mobile telecommunications is the increase of information transfer rate and together with it the increase of the capacity of telecommunication channels in comparison with the previous generation. One solution is to increase the frequency toward millimeter-wave frequencies. Currently, the most suitable option for the millimeter-wave frequency band is the 28 GHz band, which has received a lot of attention due to its availability and the possibility of implementing cheap integrated circuits using CMOS technology in this band. In addition to the features that this frequency band has; This band has limitations such as high emission losses and... 

This thesis is in the field of electroulography sensor technology and with the main goal of designing and manufacturing electroulography sensor for use in various applications including human-machine communication and biomedical technology. The research method used includes a comprehensive review of the existing literature to understand the current state of this technology and to identify its major advances and shortcomings. In the next step, an experimental approach is chosen to evaluate the performance of the sensor in recording and interpreting electrical signals related to biological processes, which includes the design and execution of controlled experiments using prepared biological... 

In synthetic aperture radar (SAR) satellites, the nadir echo is defined as the backscattered signal from the point directly below the satellite on the earth surface. If the timing of the radar is such that the nadir echo arrives at the receiver while the receiver is turned on for receiving the desired signal, it could damage the receiver or disrupt the resulting SAR image, unless it is suppressed enough by proper design of antenna radiation pattern. In current SAR satellites, ”avoiding” this phenomenon is associated with two problems: 1) limiting the swath width, 2) imposing stringent restrictions on the selection of pulse repeatition frequency (PRF). Therefore, ”suppressing” the nadir echo,... 

In this thesis, study of some kinds of dual band transmission lines and structures are investigated. Attention to 3 important kinds, CRLH, SCRLH and the equal phase line are introduced and the formulations of each one are derived and considered. Also the method of designing these lines are attached. These lines form a complete category that makes the ability of designing all kind of dual band line with arbitrary frequencies and result phases with arbitrary non-integer ratio less or more than 1. Also an important attention is paid for the designing these lines in the microstrip configuration. Various kinds of Dual band structures are proposed at the last part of the introducing each lines.... 

Ever increasing demand for higher data rate in wireless communication in the face of limited or underutilized spectral resources has motivated the introduction of cognitive radio for dynamic access to spectrum. In dynamic spectrum access a new type of users called secondary users measure the spectrum to see if it is occupied by licensed users (primary users or PU). When channel is empty secondary users can use it to transmit signal. This approach is called spectrum sensing. Hidden PU problem can severely defect detection ability of non-cooperativ spectrum sensing systems. Cooperative spectrum sensing (CSS) uses spatial diversity of spectrum sensors to tackle this problem. There are two kinds... 

The significant growth in wireless data traffic over the past few years has necessitated the use of new frequency bands for wireless communications. With the advent of the fifth-generation mobile network (5G), millimeter wave band will be widely employed for the purpose of wireless data transmission, increasing in channel bandwidth and data rate. Due to high propagation loss, severe vulnerability to blockage and poor reflection in millimeter wave frequencies, beamforming for antenna arrays is being considered a key enabler for millimeter wave applications in 5G. Beamforming contributes significantly to maintaining channel stability and capacity through enhancing Signal-to-Noise-Ratio (SNR)... 

Millimeter-wave imaging is used in a vast applications like security, medical and non-destrcutive testings. Frequency scanning antenna is one of the optimum solution in mm-wave imaging systems, because of its accuracy, agility and low cost. In this method, changing the frequency plays the main role and leads the main beam to scan the space. In this thesis, by observing different frequency scanning structures, like microstrip antenna, slotted waveguide antenna array, substrate integrated waveguide leaky-wave antenna, different structures are designed and simulated. The antenna, which results in the best performance for an imaging system is selected for fabrication and measurement. The...