The Millimeter Wave Radar Receiver Is Designed With A Mixer

The high resolution,high precision and wide bandwidth of millimeter wave radar make it popular in the military applications.However,due to the high frequency of millimeter wave and large space transmission loss,great challenges exist in the development of radar equipment operating in this frequency band.The receiver is a key component of a millimeter wave radar system,and as such,considering the massive deployment of novel military carriers such as drones,which is becoming more and more popular and whose combating technical indices are constantly improving,the enhancement of receiver performance and integration is also imminent.As one of the core modules for the receiver system,the mixer can convert the received high-frequency signal into an intermediate frequency signal that is easier to process.The performance of the mixer directly affects the key performance indices,such as linearity of the receiver.Therefore,the mixers have always been a hot topic in the field of millimeter wave receiver development all over the world.35 GHz is on the low end of millimeter wave,which is a very important "atmospheric window" for millimeter wave,that is,the electromagnetic wave in this frequency band has stronger atmospheric penetration capability than those in other frequency bands.Correspondingly,this frequency band has become the most widely adopted millimeter wave band,and it is the focus of academic and industrial arenas.In this dissertation,the 35 GHz millimeter wave harmonic mixer is investigated,with the millimeter wave radar receiver for a certain model of drone under development as its targeted application.The main contents of this dissertation include:(1)The characteristics of millimeter wave and the development of millimeter wave radar are discussed,and the research background and significance of millimeter wave mixer are expounded,which justify the topic selection of the dissertation;(2)The more common receiver schemes,as well as their advantages and disadvantages are discussed in depth.Considering the design indices of the project,the chain modeling and simulation of the super-heterodyne receiver architecture for 34~36 GHz band are carried out,and the feasibility of the receiver architecture is verified,on the basis of which,the performance indices of each module of the receiver are determined,providing the basis for the subsequent mixer design;(3)The design method of Ka-band fourth harmonic mixer is studied emphatically.The diode pair of model MA4E2039 is selected as the core mixing component,and a fourth harmonic mixer with an RF frequency of 34~36 GHz and a local oscillator frequency of 7.5~9.5 GHz was designed based on microstrip structure.After the simulation and analysis of the performance are accomplished,the prototype is fabricated and assembled with in a specialized house;(4)As the mixer is a three-port device,the frequency of its input signal and the output signal are not the same,which brings challenges to the test.In this dissertation,the applicability of two commonly used mixer test methods is discussed.Considering the actual situation,the test method based on vector network analyzer is selected to test the mixer prototype,and good test results are obtained.The results show that the mixer has a conversion loss of approximately 10.3 dB and an isolation greater than 25 dB,which verifies the feasibility of the mixer design and simulation scheme.The major innovation of the dissertation include: 1)The idea of collaborative design and analysis for the receiver and the mixer is implemented during the design,which is beneficial to improve the design efficiency;2)by comprehensive considering the effects of substrate materials,filters,and processability on the performance of the mixer components,a collaborative design idea that effectively reduces the device volume while ensuring the performance of the mixer is proposed.Overall,the work of this dissertation provides strong support for the development of targeted millimeter-wave radar application.