Research On E-band Broadband Mixer And Application In Down Conversion System

The working frequency band of E-band covers 60GHz-90 GHz,among which 71GHz-76 GHz and 81GHz-86 GHz expand the tight spectrum resources of wireless transmission,and have a broad application and development prospect.This paper aims to achieve a high performance in up-down converter system with low cost,wide bandwidth and low loss of the E-band,utilizing the low cost commercial Schottky diode MA4E1310,the E-band low-intermediate frequency fundamental mixer,E-band high-intermediate frequency fundamental mixer,E-band fourth harmonic mixer and V-band tripler as local oscillator are developed,E-band and V-band waveguide cavity filters with high selectivity are also developed.The main research progress of this dissertation includes the following contents:1.An E-band low IF mixer is designed based on the Schottky barrier diode MA4E1310 delivered by MACOM company.Based on the principle of 90° phase-shift structure,this mixer is designed for the purpose of down conversion.The waveguide to microstrip transition probe,3dB microstrip directional coupler,IF ground loop,IF lowpass filter,Schottky diode and its matching circuits are designed by HFSS software.The parameters of the circuit structure are optimized by ADS software and HFSS software.The experimental results show that the conversion loss of mixer is 7.8dB-10.8dB and the flatness is better than ±1.5dB in the frequency range of 74GHz-88 GHz with fixed IF frequency of 5MHz.The minimum conversion loss is 7.8dB at 82 GHz.2.Based on the same model of the Schottky diode,a 180° phase shift E-band high intermediate frequency fundamental mixer is designed.A 180° hybrid network is formed by adding a 90° phase shift line to the output arm near the LO end of the 3dB microstrip directional coupler.The 180°phase shift mixer can be used for up-down conversion.By adding short circuit on the input and output arms of the coupler,the bandwidth of the coupler is expanded,an E-band high IF fundamental mixer is designed.The 180° hybrid network,Schottky diode and its matching circuits,IF lowpass filter,IF ground loop are designed and combined by HFSS software.A complete 3D electromagnetic model of mixer is established in HFSS software.The model is optimized by the method of electromagnetic simulation and harmonic balance circuit simulation.The test results show that the fixed IF frequency is 15.7GHz,in the frequency range of 66GHz-76 GHz,the conversion loss of down conversion is 9.7dB-12.2dB,the optimal LO power is about 15 dBm,the1 dB compression point of RF signal is larger than 3dBm.The conversion loss of up conversion is8.9dB-12.1dB,The LO-RF isolation of mixer is over 12 dB in the frequency range of50GHz-76 GHz.The mixer has excellent characteristics of wide band and low conversion loss,which can be applied to E-band superheterodyne down-conversion system.3.Based on the same model of Schottky diode,a V-band unbalanced tripler is designed.The diode pair is connected to the circuit in antiparallel connection(APDP).The input lowpass filter,output waveguide to microstrip probe transition,Schottky diode and its matching circuits are designed and simulated by HFSS.A complete 3D model is established,and the match circuit of V-band tripler is optimized by the field-circuit method of HFSS and ADS.Measured results demonstrated that the input power is 20 dBm,the typical output power of the tripler is 4.5dBm,the power fluctuation range is less than ±0.75 dBm,and the conversion loss of the tripler is less than16 dB and the typical value is 15.5dB in the frequency range of 50.3GHz-60.3GHz.The measured results are similar to the simulation results.The V-band tripler can be used as a part of local oscillator of E-band high-intermediate frequency mixer to construct E-band superheterodyne down-conversion system.Based on waveguide inductive diaphragm structure,E-band and V-band cavity bandpass filter are designed respectively in the HFSS software.The experimental results show that the typical value of insertion loss of E-band bandpass filter is 0.5dB in the frequency range of 66GHz-76 GHz.The suppression is greater than 25 dB at 80 GHz and 62 GHz.The typical value of insertion loss of V-band bandpass filter is 0.5dB in the frequency range of 50.3GHz-60.3GHz,the suppression is greater than 20 dB at 64.3GHz and 48.3GHz.4.The E-band superheterodyne down-conversion system is constructed.The system is mainly composed of E-band high IF mixer and its local oscillator module,Ku-band down-conversion module and its local oscillator module.The developed E-band high IF fundamental mixer,E-band and V-band bandpass filter,V-band tripler are applied in E-band superheterodyne down-conversion system.E-band high IF fundamental mixer is used to realize the first down conversion;V-band tripler is used as the local oscillator of E-band high IF fundamental mixer with X-band hopping signal source module and doubler module;The E-band and V-band bandpass filter can filter out the spurious in the E-band high IF mixer's RF side signal as well as the LO side signal,improve the purity of the down conversion output spectrum.The experimental results show that RF frequency in the range of 66GHz-74 GHz,the flatness of IF output power is better than ±1.5dB after the second frequency conversion.5.Based on the same model of Schottky diode,an E-band fourth harmonic mixer is designed,which the antiparallel diode pair structure(APDP)is adopted.LO input bandpass filter,RF output waveguide to microstrip transition probe,LO and RF recycling network,IF lowpass filter,Schottky diode and its matching circuits are designed and simulated by HFSS software.The IF lowpass filter utilizes an improved three stage CMRC structure,which has a smaller size and broader stopband compared with the conventional step impedance lowpass filter.The suppression of the entire LO band is above 60 dB,and effectively improves the isolation between the LO port and IF port.The mixer is simulated and optimized by combining with the field analyze method of HFSS and circuit analyze method of ADS.The E-band fourth harmonic mixer is fabricated.The experimental results show that the conversion loss of RF in the frequency range of 72GHz-84 GHz is 13 dB-19.5dB and the flatness is less than ±3.3dB when the fixed IF frequency is 1GHz.The mixer has a good application prospect in the design of low-cost and miniaturized E-band receiver system.