A Research Of 6-10 GHz MMIC IQ Mixer

Due to the development of microwave circiut and processing,miniaturization and high integration have become the development trend of modern communication system.Bacause of the advantages of small size,low cost and high stability and so on,MMIC becomes the research hotspot.So it is more and more widely used in military field and civil field.As a very impotant part in the research of MMIC,the mixer has important significance.To effectively suppress the image signals is a research focus in single side band wireless system.As one kind of image rejection mixer,IQ mixer can efficiently inhibit image signal,its performance has great impact on wireless system.The mixer employs lumped-element quadrature coupler instead of the traditional Lange bridge,which reduced the chip size remarkably.After analysis the principle of lumped-element quadrature coupler,its one-stage structure is derived by even-and odd-mode method.A suitable two-stage structure can be achieved.when connecting two one-stage structure.The designed mix based on design formul has great amplitude balance and phase balance,which makes the IQ mixer's ability of inhibiting image signals be improved significantly.To improve isolation and bandwidth of circuit,double balance structure is ued.In the design of Balun,spiral Balun insteads of traditonal MarchandBalun.Because double balanced mixer is difficuit to achieve wideband matching,a new structure is used.One capacitor works as a parallel capacitor with the primary coil and another one works as a series capacitor connecting the primary coil to the ground,which forms a T network.This structure can insteads of LC matching circuit,besides performs well in wideband matching.A 6-10 GHz MMIC IQ mixer is implemented using WIN 0.15mm Ga As p HEMT process,whose size is1.5×1.15mm~2.The test results presents that,in the band of 6-10 GHz,the typical value of conversion loss is 7 dB,the typical value of image rejection is 30 dB,the typical value of isolation between LO to RF is 36 dB,the typical value of isolation between LO to IF is 20 dB,the typical value of isolation between RF to IF is 36 dB,the IF bandwidth is DC-3.5GHz,the IP1dB is larger than 13dBm.