Microstrip lines are a type of electrical transmission line used to guide microwave signals. They consist of a thin conducting strip on top of a dielectric substrate, with a ground plane beneath. This structure allows for efficient signal transmission with minimal loss, making them popular in various applications, including antennas and integrated circuits. The design of microstrip lines can be adjusted by changing the width of the strip and the thickness of the dielectric material. This flexibility enables engineers to tailor the line's characteristics, such as impedance and bandwidth, to meet specific requirements in devices like radar systems and mobile phones.