Research On Millimeter-wave Components Based On RF Cancellation Technology

Millimeter continuous wave radar has many kinds of advantages,such as high range resolution,simple construction and high receiving sensitivity,compared with pulse wave radar.But because of the characteristic of continuous wave,the transmitter of radar leaks signal to the receiver.So the difficulty is how to improve the isolation between the transmitting and receiving channel.All kinds of methods to solve the problem have been proposed.Inside them,radio frequency cancellation technology based on millimeter-wave is a direction,which is worth to lucubrate.Under the background,this paper researches millimeter-wave cancellation system comprehensively.First,this paper briefly introduces the research background and points out the matters and solutions in practical application.According to the requirement of the system,the closed-loop cancellation project is applied and the system framework is established.loop-control module,feed-through module and error detection module in millimeter-wave cancellation system are designed.And ADS is used to create system model and verify in simulation.The result shows that the design scheme of this paper is feasible.Secondly,the most important part in the cancellation system is the vector modulator,which is analyzed theoretically,and adopts p HEMT named VMMK-1225 according to the requirement of the system.The paper uses the balanced structure to solve the inherent problem of parasitic parameters,which is verified in ADS.The orthogonal mixer in the error detected module is HMC8191,a kind of I/Q orthogonal mixer.The operational amplifier OP37 is used to design the loop-control module and the power supply of the modulator.The passive parts in every block,such as: the coupler,the in-phase power divider and the waveguide to probe,are simulated and optimized by HFSS.And the system is design as an integrated block.Then,the vector modulation and the millimeter-wave closed-loop cancellation system are tested,the test result indicates the cancellation ratio of the system can reach about 12 d B,in point-frequency mode and sweep-frequency mode.After the compensation of DC-offset,the ratio can be 15 d B.And the closed-loop system is tested with whole radar system,proved that it can offer 15 d B isolation.Finally the whole work and the fault of this paper are summarized and induced,and the future direction of work is prospected.