| According to the significant difference between the millimeter-wave dielectric properties of normal tissues and diseased tissues,the millimeter-wave medical imaging technology forms a medical image of biological tissue with high spatial resolution by acquiring the scattered field information of the target to be measured,which can detect diseases such as skin cancer,breast cancer and burns in a noncontact manner,is widely favored for its non-invasiveness and high resolution.Antennas with ultra-wideband,high gain,small size,and directional radiation are the key to millimeter wave imaging systems to obtain high-resolution medical images.The performance of the antenna directly affects the imaging resolution and the accuracy of detection results.In order to better improve the broadband performance and radiation performance of the antenna,this paper proposes two types of ultrawideband antennas based on the Antipodal Vivaldi Antenna(AVA),the claw-shaped slot loading combined with the dielectric lens and the trapezoidal claw-shaped slot loading combined with the resistance.The problems of limited bandwidth and beam tilt of conventional AVA are improved,and the gain is high and the volume is small,which satisfies the application of burn detection.Aiming at the problems of limited bandwidth,low low-frequency gain,and beam tilt of conventional AVA,a claw-shaped AVA is firstly proposed,which combines patch loading,claw-shaped slot loading and dielectric lens loading technology.through the straight slot + oblique slot slotting method,the slotting path is extended as much as possible on the limited radiation arm,which expands the antenna bandwidth and increases the low-frequency gain by 2.5d Bi,and realizes high-gain directional radiation in the bandwidth of 22.5-39.78 GHz.To further improve the in-band mismatch and high-frequency radiation instability problems of claw-shaped AVA,a resistor-loaded ladder-shaped claw-shaped AVA is proposed.The trapezoidal clawshaped slot is only loaded on the radiation arm part,and the resistance loading technology is introduced to connect the patch load to the radiation arm with a resistor.By changing the current distribution on the radiating patch,the current backflow at the end of the antenna is prevented,the problem of in-band mismatch at the lowfrequency end is eliminated,and the phenomenon of high-frequency gain drop is improved,and the gain is 6-11.2d Bi in the bandwidth of 19.24-40.94 GHz.Compared with the conventional AVA,the bandwidth of the antenna is extended by nearly8.12 GHz,and the gain is increased by about 3d Bi on average,the pattern has stable directional radiation characteristics in the entire frequency band,and the size of the antenna is 33mm×15mm×0.508 mm.The simulated burn skin is simulated,and the skin simulation model is constructed according to the different dielectric constants of different tissues of human skin.By comparing and analyzing the complex reflection coefficients received by the antenna,the burn skin has lower real and imaginary parts,and it changes with the degree of burn,not only distinguishes healthy skin from burnt skin,but also distinguishes first-,second-,and third-degree burns.The S11 data is processed and imaged by the synthetic aperture imaging algorithm,and the imaging results are clear shows the burn site. |
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