| With the increase of people's consumption level,automobile consumption becomes more and more common,and road car congestion has become a common problem in the current society.The problem of car driving safety has also become more and more prominent and has been paid attention to,and the driver-less technology is also developing and becoming a hot technology.Millimeter-wave radar is one of high-resolution radars,which can achieve higher detection accuracy when using linear frequency modulated continuous wave(LFMCW)modulation,and has a more compact structure,higher ranging accuracy,and higher base band signal processing efficiency than other radar systems.as one of the core components of automobile safety control system and smart car driving technology,millimeter-wave radar has a broad market prospect,and it is of great significance for reducing traffic safety accidents and promoting the development of smart driving technology.This thesis takes the front part of the millimeter wave automotive anti-collision radar with77 GHz frequency as the main research content.a millimeter-wave radar front-end system integrated with a radio frequency circuit and a transceiver antenna is designed.The transmitting and receiving antenna adopts the structure of one-shot and two-receiving,which makes the transmitting antenna and receiving antenna have higher isolation and anti-interference ability,and can perform distance estimation,speed detection and angle measurement on multiple targets.The transmitting antenna has a shaped beam covering a long distance(150m)and a middle distance(60m),which enables simultaneous detection of targets in different field of views.The receiving antenna is a high gain and wide-beam array antenna.The transmitting and receiving antenna is a hybrid structure of a substrate-integrated wave guide(SIW)and a microstrip antenna,which is easy to integrate with a radio frequency(RF)circuit.MMIC chips are used in RF circuits.The transceiver chip integrates a triple frequency mixer and is driven by a local oscillator chip with25.5GHz.Each transceiver chip has two channels and supports multi-channel expansion.This compact structure is easy to miniaturize,and has a high practical value.The specific research work in this thesis has the following points:The common automotive anti-collision radar system solutions are compared.according to the actual application requirements and frequency-modulated continuous wave(FMCW)theory,the automotive anti-collision radar system indicators and various indicators of the radar front-end RF circuit and antenna are analyzed and determined.According to the antenna index requirements,the receiving and transmitting antennas are designed.In the design of the transmitting antenna,parameters of the shaped beam pattern function are determined by the array antenna theory and the MATLAB optimization solution,and these values are taken as the initial values of the antenna design in the following.Feed network,using SIW structure,can reduce the radiation loss,dielectric loss,and the effect on the side lobe of the pattern.A ten-element patch antenna that obeys the Dove-Chebyshev distribution is used in the antenna array elements,so that the pitch angle of the beam is narrowed to reduce the influence of spatial noise and reflected waves on the system performance.Receiving antennas use two channels to receive.Two ten-units patch antenna obeying the distributed by the Dove-Chebyshev are used in each channel.The middle column of the two receiving channels is common,so that the equivalent phase is less than one wavelength to prevent the grating lobes from appearing.Finally,an improved antenna structure based on SIW slot antenna was proposed to improve the performance of the antenna.Complete the RF circuit part.The main chip consists of a local oscillator chip,a transmitter chip and a receiver chip.The circuit structure is simple,small size and light weight.Because the double-layer plate structure is used in the circuit board,the GCPW-SIW conversion connector is designed to realized the signal transmission of the input and output microstrip lines of the transmitting and receiving chip to the antenna on the lower layer medium.Although this thesis proposes an achievable solution,many improvements can be made further,such as a simpler and more compact SIW slot antenna structure can be used for the transmit and receive antennas.Due to the unfamiliarity with the circuit board processing,the loss of the conversion joint is so great that the overall performance of the antenna is poor.With time pressure and lack of experience,there is no further work to be done.In the next,the overall plate layout,circuit board processing technology and dielectric plate selection can be used to improve the performance of the radar. |
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