| As the main vehicle nowadays,automobile is more and more closely related to people's life.Anti-collision radar is important for automobile safety protection,and it is also paid more and more attention.As the front of anti-collision radar,antennas are vital parts,which not only relate to the detection range of radar,but also play an important role in the detection accuracy.Current anti-collision radar has millimeter-wave bands,such as 24 GHz,77 GHz and 94 GHz.The high frequency band makes the antenna have better accuracy and resolution,and is more suitable for automobile anti-collision radar.The antenna form of anti-collision radar is mostly microstrip array,which can meet different beam and gain requirements.In this paper,24 GHz and 77 GHz microstrip series-fed array antennas with narrow beams and low sidelobes are studied,which are suitable for automotive anti-collision radar antennas.In this paper,microstrip array antennas are designed according to the actual project requirements.Firstly,a single antenna unit fed in series is designed,which is equivalent to a two-port network under the requirement of frequency and phase.Then the energy relationship of each stage patch is calculated by using the relationship between the S parameters and the energy transfer of the two-port network.These relationships are integrated into a MATLAB program.The program calculates the direction of the array by using the product theorem of the pattern.The pattern is optimized to meet the requirements.Finally,the impedance matching of the antenna is carried out with ADS.An 8-element linear array is designed by using the two-port network equivalence method to verify the validity.On this basis,24 GHz and 77 GHz array antennas are designed respectively.The working frequency band of 24 GHz array antenna is 24-24.25 GHz,and the gain is above 20 d Bi.The antenna is designed as a 4×16 antenna array.The feeding mode of each linear array is series feeding,and linear arrays is analyzed according to the two-port network.Then,four linear arrays are formed by power divider.According to the current ratio,a power divider with a power-to-power ratio of 1:3:3:1 is designed.The impedance matching is simulated by ADS and HFSS.Finally,the antenna is manufactured and measured by microwave anechoic chamber.The results show that the antenna has the characteristics of high gain and low sidelobe.77 GHz array antenna is divided into two antennas,antenna 1 is receiving and antenna 2 is transmitting.The antenna is designed as a 1×6 linear array with gain of 14.4 d Bi.The beam width basically meets the requirements.The elevation angle is about 14.3 degrees and the azimuth angle is about 80 degrees.The waveform is fan-shaped,and the working frequency is 77-81 GHz,which is consistent with the demands.Antenna 2 is a transmitting antenna,which requires the elevation angle and azimuth angle to be 14 degrees.Therefore,it is designed to be a 6×6 array.The E-plane direction is fed in series,and the H-plane direction is fed in parallel by power splitter.The impedance matching is still simulated by ADS and HFSS.The final result is that the antenna works at 76.47-81.5 GHz,and the sidelobe level is below-15 d B on both elevation and azimuth planes.The corresponding angle is also about 14 degrees,which basically meets the requirements. |
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