A Novel Second Harmonic Separation Microwave Network

In this paper, a novel four-port microwave network is proposed to separate the second harmonic component. The even-odd mode analysis method is applied to find the electrical length and characteristics impedance of transmission lines determining frequency separation at second harmonic and power dividing ratio at fundamental frequency. It is found that only the electrical length of transmission lines controls the frequency separation. To prove the proposed design theory, a prototype device working at 800 MHz is fabricated and tested, and the second harmonic component 1600MHz is separated and guided to isolation port, which aligns with theory derivation.