Transmission-line modelling of microstrip antennas and their application in fixed-frequency beam steering

Planar antennas are paramount in today's world because they can be embedded easily into portable devices such as laptops, mobile phones, etc. Beam or the radiation with directivity is important beacause it gives a suitable range advantage than omnidirectionally radiating antennas with the same power. Steerability can provide the flexibility of the omnidirectional antenna and the benefit of a directional antenna; provided that multiplexing is possible. Reconfigurable antennas that can radiate multiple patterns at a single frequency or a single spectrum are necessary for modern telecommunication systems. The requirements for increased functionalities like direction finding, beam steering, radar, control and command, within a confined volume place a greater burden on today's transmitting and receiving systems. Reconfigurable antennas offer an exceptional solution to this complex engineering problem. This thesis contains the design of two particular fixed frequency beam-steerable antennas. The antennas are cost effective from the industrial perspective, and reliable for long term maintenance free use. The first one is a fixed frequency active phased array antenna. The relevant chapter showcases the layouts and results for two 1 x 2 variants and one 2 x 2 variant. Initial development of accurate transmission line models gave the insight of developing a fixed frequency active phased array antenna. Initial chapters outline the transmission-line modelling of single tunable and reconfigurable rectangular microstrip antenna elements. Analytically obtained values reasonably agree with the results achieved from measurements and simultaions, for numerous designs based on multiple substrates. The active phased array antenna can steer its beam up to 25°. The limitations of the phased array antennas led to the design of the second fixed frequency beam-steerable antenna. The second beanm-steerable relies on a switchable ground plane that can reflect or transmit electromagnetic waves. The second antenna has a steerable beam that radiates either in the broadside or endfire region. The antenna can cove up to 133° in the H-plane. Later chapters in this thesis discuss the transmission-line modelling of the reconfigurable surface with numerous examples, and its operation as a surface waveguide. The examples for the transmission-line model demonstrate reasonable agreement with simulation results for different substrate thickness and with or without a dielectric cover. The thesis presents a comprehensive overview of simulation and measurement results for multiple antenna designs backed by a reliable transmission-line model insight. Substantial area coverage is possible with the proposed antennas. Behavioural modelling software can benefit from the models discussed to create quick design solutions without wasting time for full-wave numerical calculations.