Sharif Digital Repository

Modern communication and space systems such as satellite communication devices, radars, SAR and radio astronomy interferometers are realized with large antenna arrays since this kind of radiating systems are able to generate radiation patterns with high directivity and resolution. In such a framework, conventional arrays with uniform inter-element spacing could be not satisfactory in terms of costs and dimensions. An interesting alternative is to reduce the array elements obtaining the so called ‘ thinned arrays’. Large thinned arrays have been exploited because of their advantages in terms of weight,consumption, hardware complexity, and cost over the... 

In this thesis, an X band vector modulator chip in CMOS .18 um technology is designed, implemented and measured. The receiver with two RF signal path includes differential amplifier, hybrid, attenuaters, variable gain amplifiers (VGA) and power combiner blocks respectively. Capability of gain and phase control is provided by 14 digital bit. 6 bits are used to control gain of each RF path, so that changing the phase and gain of the output signal in a trigonometric quarter shall be possible. The trigonometric quarter is selected by two single pole double throw switch. Cascode structure is utilized in amplifiers stages for its stability and isolation feature. Furthermore, in order to to enhance... 

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... 

New applications such as high data rate telecommunications, millimeter-wave imaging systems, positioning systems, wall, and ground-penetrating radars, and vital sign monitoring radars require specifications of heavy-duty systems. In summary, in advanced applications with high bandwidth, having multiple inputs and multiple outputs, phased arrays, and optimal energy efficiency are in demand and desirable. Despite the diverse applications of these radars, commercial products in this field are very rare, expensive, and bulky. Therefore, research work in this area is justified from an applied perspective. Increasing the power amplifier's efficiency results in the creation of a smaller, more... 

In the recent decades, the estimation of direction of arrival has been an active area and some high resolution direction finding methods like MUSIC and ESPIRIT have been developed. These methods suffer from factors like mutual coupling. Direction of arrival estimation in presence of mutual coupling is a widely studied problem. In order to resolve this problem, many array calibration algorithms have been developed. However it may be impossible or difficult to set some calibration source in some situation. In this work we show that the effect of mutual coupling can be dynamically compensated by the inherent mechanism. First we show that how mutual coupling can degrades the performance of... 

In this project, issues related to designing and fabricating active phase shifter blocks on the silicon substrate have been examined. Phase shifter circuits are designed in a way that have the most bandwidth and the less sensitivity to process characteristics changes and environmental conditions. The purpose of this research, is designing an active 6 bits phase shifter. The active phase shifter synthesizes the required phase using a phase interpolation process by adding quadrature phased input signals. It uses a new quadrature all-pass filter for quadrature signaling with a wide bandwidth. Also substitute structure has been suggested to this filter which is the main block in determining... 

Today, phased array antennas have important role in wireless communication systems. Utilizing optimum channel capacity, having better signal to noise ratio and, high data rate are the most important features of these systems. These systems are composed of several thousands of separated transceivers which provide possibility of directional electromagnetic radiation by changing the phase and the amplitude of the signal in each transceiver independently. So, the main components of such a system are amplifiers, phase shifters and, amplitude controllers. Also a high resolution phased array military radar system is another vital applications of these systems at frequency band of 9-10 GHz. The... 

Phase shifters are commonly used in the implementation of phased-array antenna systems.The function of these systems is highly dependent on the performance of phase shifters. In addition, phase shifter circuits are used in some applications such as antenna test and regulation, power amplifier linearization, and QAM modulator implementation, to name but a handful. In this project, design of phase shifter blocks, as well as limitations of fabrication on silicon substrate, is studied and these blocks are designed for maximum bandwidth and minimum sensitivity based on fabrication characteristics and environmental conditions. Design of a 6-bit phase shifter based on vector-sum method is the... 

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... 

Nowadays millimeter wave imaging technology has found various applications in industry, medical and security systems. From one side the capability of penetration of this frequency spectrum into non-metal objects, and being harmless to humankind on the other side, has made this spectrum an appropriate alternative instead of dangerous spectrums such as X-ray. Recently, development of millimeter wave electronic circuits and antenna arrays has made the optimal design and implementation of millimeter wave imaging systems feasible. Among actions which have been taken in industry, medical and security systems until now, we can refer to efforts for detection of defects in production line,... 

In order to improve the performance of radar systems, encouraging the movement towards multifunctional applications, wider frequency span is required to be considered for phased array systems constituting radars. The conventional approach of phase shifting is not applicable to wideband phased array system, and the need for phased array systems based on time delay is apparent. In active phased array systems where a transceiver module is placed before each radiating element, the task of controlling the delay and gain variation of each path is assigned to individual core chips residing in the transceiver modules. A typical core chip consists of several amplifying blocks along, with delay and...