Research On GaAs MMIC Wideband Mixer

Mixer is the key component of microwave circuits and systems. With the rapid development of the wideband, miniaturization and integration of the communication and electronic systems, the wideband MMIC mixer with good performance has become one of the research challenges. Wideband passive double balanced mixers covering 2-18 GHz have been designed by theoretical analysis, parameterized modeling, simulation and optimization.In this paper, a wideband Marchand balun chip and three wideband passive double balanced mixer chips have been implemented in Win’ GaAs PD25 process. Main contents are listed as follows:1) With electromagnetic simulation, the parameterized equivalent circuits model of spiral transformer based on GaAs PD25 process have been developed and the design efficiency have been improved.2) By using even- and odd-mode method, analytical solution for amplitude and phase balance conditions of ideal balun are derived.3) A wideband Marchand balun is implemented and the design approach for wideband Marchand balun is presented. According to the restrictions which are derived by even-and odd-mode method before, an open stub in the center of the balun is added to improve the balance of the balun. An amplitude balance less than ±1.5 dB from 4～24 GHz and phase balance less than 10 degrees from 2-22 GHz were achieved. The measured results agree well with the simulated ones.4) The design approach for passive mixer is presented. Three wideband passive double balanced mixers are implemented. According to the traditional version of double balanced mixer, dual-core version is employed to expand the bandwidth of the mixer and novel IF extraction structure version is employed to improve the ripple of the conversion loss and the isolation from RF to IF. Tht wideband passive double balanced mixer covering 2-18 GHz is designed, which demonstrates the conversion loss less than 10 dB, the isolation from LO to IF more than 15 dB, the isolation from RF to IF more than 15 dB and the isolation from LO to RF more than 25 dB.