Two-Tone Excited Hybrid-Coupler-Based Intermodulation Generator for High-Isolation Wireless Sensing Applications

An intermodulation generator is designed and presented with integration of a hybrid coupler and two identical Schottky diodes (i.e., D
₁
and D
₂
). The connection polarities of D
₁
and D
₂
to the direct and coupled ports of hybrid coupler are opposite for its rapid realization of balanced intermodulation generation. Due to the superior coupling characteristics of hybrid coupler, it can distribute an incident two-tone signal to the direct and coupled ports evenly for D
₁
and D
₂
, and deliver the balanced intermodulation generations to the isolation port highly insulated from its incident port. Two identical quarter-wavelength shorted stubs at the fundamental frequency are implemented by suppressing the second-order spectrums for an enhancement of the balanced intermodulation generations. Both theoretical analysis and experiments validate the presented intermodulation generator design, which can highly isolate its incidences (the two tones) and outputs (the intermodulation generations) for the future high-isolation wireless sensing applications.