Research And Design Of Electrically Small Antennas Array For Automotive Collision Avoidance Radar

With the popularity of motor vehicles,traffic accidents caused everywhere,and traffic safety issues have become the focus of people’s attention.In this context,vehicle anti-collision radar has become a hot topic for car manufacturers and consumers.Presently,the microstrip antenna array used in the millimeter wave 24 GHz band and the 77 GHz band are widely investigated in the vehicle anti-collision radar system.However,the high frequency band module has high production cost,difficult manufacturing process,low practicability,longer wavelength and less loss in low-frequency band.This paper explores a micro-charged small-end antenna array operating at the 5.8GHz ISM universal low frequency band along the trend of miniaturized antenna research and development.The micro-charged small-end antenna was designed and the hfss simulation was carried out on the array model.The results met the requirements of the vehicle anti-collision radar for the antenna.The work done in this article is as follows:(1)The microstrip antenna unit is designed to be electrically small and meet the end-fire characteristics.There are only a few of such antennas at present,the commonly existing antennas achieved by meandering,high dielectric constant loading,and resistive loading,most of which are in omnidirectional form.The design of the microstrip end-fire antenna is mostly similar to the micro-band quasi-eight-wood structure.The design of the project is seriously constrained by the large size of balun.Therefore,choosing a balun that is not limited by the electrical size and can realize the function is a key and difficult point in the design of this paper.After demonstration and calculation,the final selected antenna element is in the form of a microstrip dipole antenna,which adopts a through-hole balun feed structure and realizes the electric small end-fire structure by bending the dipole arm.(2)For the high-gain,low side-lobe,narrow-beam requirements of the antenna for the vehicle anti-collision radar system,the traditional optimization method is combined with the simulation software HFSS.Since the feeding amplitude of each unit is different after adopting the weighting scheme,a large number of microstrip unequal power dividers are required.The array has designed seven one-two T-type splitters in the horizontal direction,and then connected the horizontal eight-line array with a vertical micro-band splitter to form an 8*8 area array.The final array gain is 16dB,the half-power beamwidth is 13°,the E-plane sidelobe level is-25dB,and the H-plane sidelobe level is-30dB,which meets the design needs.