Microwave Integrated I/Q Quadrature Modulator

Direct modulator converts baseband signal to RF signal without upconvertion. The system design is relatively simple compared to upconversion. So direct modulator provides adventages of compact size, low cost and low spurious response.Error Vector Magnitude(EVM) and Adjacent Channel Power Leakage(ACPL) are two important considerations of direct modulation. This paper clarifies the theory of I/Q modulation, elaborates EVM and ACPL, and analyzes the effect of amplitude and phase imbalance and DC offset on EVM. Even harmonic mixer can suppress even-order mixing products and carrier leakage(), and associated EVM when it is used as modulator. Subharmonic mixer simplifies LO design. So it is much suitable for millimeter-wave transceivers.The subharmonic mixing modulator is modeled, simulated and designed using ADS(Advanced Design System) software. The simulation results are in close agreement with theoretical results on the whole, so the circuit scheme is workable.