Mixed Dual-Band Impedance Transformer with Embedded Transmission Zero

Dual-and multi-band impedance transformers are important components in radio frequency (RF) and microwave circuits for contemporary communication systems. This work presents a mixed transmission zero embedded dual-band impedance transformer that consists of transmission lines and lumped elements, operates at two uncorrelated frequencies. The proposed impedance transformer is appropriate for a load with frequency-dependent complex impedance. The presented transformer has the advantages of compact size and the absence of extremely high or low impedance transmission lines and stubs. In addition, the values of the transformer parameters are determined using the presented closed-form design formula. The proposed structure is validated through simulations and measurements.