Design Considerations for Using Dual-Band Real-to-Complex Impedance Transformers Consisting Only of Transmission Line Sections

Dual-band real-to-complex impedance transformers consisting of three transmission line sections are designed and used as input and output impedance matching circuits of a dual-band low-noise amplifier. A simple design method of these type of impedance transformers is presented, as well as a short analysis on the allowed complex impedances. The simulated results obtained for the dual-band amplifier confirm the design accuracy of the impedance transformers.