Frequency Tripler Design by Using Dual-Mode Hybrid Coupler for High-Isolation Wireless Sensing

A frequency tripler is designed based on a dual-mode hybrid coupler for wireless sensing applications. The dual modes of a hybrid coupler are analyzed according to the odd-even mode theory, whose S-parameters are simulated in the advanced design system. Due to the nonlinearities of two diodes at the direct and coupled ports, 3rd harmonics are generated, and entirely coupled to the isolation port while the input port maintains isolated. Two quarter-wavelength short stubs are implemented to reflect all 2nd harmonics with an enhancement of 3rd-harmonic generation. The frequency carrier detuning effect is evaluated from 1.95 to 2.05 GHz, which indicates that the frequency tripler can have more than 100 MHz bandwidth. Theory analysis and simulations have both validated the proposed frequency tripler design for wireless sensing applications.