Design of broadband amplifiers for microwave transmitters via real frequency techniques

The evolution of wireless communication, led by notable figures including Maxwell, Marconi, Hertz, and Tesla, had a major impact on technology from the late 19th century. As radio technology advanced in the early 20th century, wireless communication became widespread and played a crucial role in various sectors, including civil, industrial, military, and medical applications. Antennas and power amplifiers are vital components within wireless communication systems, grounded in the fundamental principles of EM wave propagation. The rise of commercial communication systems such as Wi-Fi and WiMax and the ongoing development of 5G and 6G technologies have expanded the market for antennas and power amplifiers. These technologies are integral to today's commercial landscape and extend their impact on space research and technologies, underscoring the versatile applications of antennas and microwave power amplifiers. The diverse landscape of existing and emerging wireless communication systems necessitates continuously advancing antennas and power amplifiers with unique features. Microwave engineers find the study of antenna and power amplifier design particularly intriguing due to the various modulation types and frequency bands. In practical applications, antenna design emphasizes crucial factors, including bandwidth, beamwidth, polarization, and gain. The power amplifier design process begins with selecting the antenna and power transistor for the amplifier, considering specific design parameters like power gain, output power, efficiency, and amplifier bandwidth. The design of broadband antennas and power amplifiers is significant as a research focus, particularly for systems that integrate communication across different wavelengths for diverse purposes. Designing wideband antennas and amplifiers poses challenges, especially when dealing with microstrip patch antennas that typically have a single resonance frequency. A double-matching network between the transistor output and antenna input was employed to address these challenges and enable resonance across multiband frequencies. The design approach involved using the new model of RFT-LS (Real Frequency Technics), known as Unified Real Frequency Techniques, for double-matching problems. A chapter in the work is dedicated to the Real Frequency Technique (RFT) method, specifically SRFT (Simplified Real Frequency Technique). This method is particularly useful for designing broadband microwave amplifiers. In this method, a lossless equalizer is characterized through its unit-normalized scattering parameters, and computations are performed using the scattering parameters of the blocks to be matched. The SRFT method is faster and more accessible than other computer-aided design (CAD) algorithms. It's inherently suitable for designing broadband microwave amplifiers. The method optimizes the system's transducer power gain (TPG) to be matched. However, more than gain optimization is needed to ensure successful matching networks. For instance, an amplifier engineered to achieve a specific flat gain level may demonstrate inadequate input and/or output reflection characteristics. To address this, the work emphasizes the integration of optimization goals for input/output reflections along with TPG in the SRFT method. Customized objective functions optimize multiple performance metrics, ensuring achieving various goals and specifying optimization priorities. The proposed technique goes beyond the conventional SRFT method, where input/output matching circuits are typically created separately, leading to a time-consuming iterative design sequence. The proposed method optimizes scattering parameters based on derived equations for the entire amplifier block, enabling the simultaneous design of the input/output matching circuit. The approach is implemented via package programs written in MATLAB, providing a comprehensive design tool for microwave engineers. Another chapter in the work explores the Unified Real Frequency Techniques (U-RFT) method, divided into three main parts: Basic Concepts of Unified RFT, Assessment of GBWL (Gain-Bandwidth Limit) via Uni RFT, and Building Models for Network Functions. The effort to achieve wideband resonance involved testing various geometric shapes of antennas, including Conical and Horn antennas and, later, the microstrip patch antenna. However, regular Microstrip antenna structures are limited to achieving the desired wideband resonance (100-200MHz). Therefore, alternative approaches were explored, leading to the testing of monopole antenna structures and their variations, which were simulated to assess their performance. The Power Amplifier (PA) underwent simulations with different transistors during the design process. Initially, simulations were based on the small signal analysis of Mini-Circuits SAV581+ transistor; later, MACOM`s CGH40010 transistor operating in the range of DC-6GHz was used. However, the final design work shifted towards simulation and design based on MACOM`s CG2H40010F Power Amplifier HEMT Gallium Nitride – GaN Transistor. This comprehensive exploration of antenna models and power amplifiers, combined with Unified Real Frequency Techniques, demonstrates a systematic approach to achieving wideband resonance and optimizing the performance of microwave systems.