Microstrip Dual-Band Transformer of Complex Load Impedances into Complex Input Impedances with Different Values in Frequency Bands

The article is devoted to the development of a microwave dual-band transformer of complex load impedances into specified values of the complex input impedance and a method for calculating the electrical parameters of the elements in its composition. The proposed circuit consists of three segments of single transmission lines and a reactive element, which is connected in parallel to the junction of the first from the input side and the second segments and is realized by an open or shorted at the end line segment. To avoid the restrictions on the permissible values of the complex input and load impedances, which are generally different in different frequency bands, the circuit can be supplemented with additional line segments and parallel stubs on the input and load sides, the parameters of which are chosen arbitrarily. To verify the proposed transformer circuit and the method of its calculation, two examples were computer simulated: a dual-band complex impedance transformer with a large frequency ratio equal to 6 and a dual-band transformer for matching the input of a patch antenna with the output of an amplifier.