Figure 15 is a block diagram of the antenna and distribution network. The fabricated prototype is shown in Figure 16. Based on the relationship between the system receive power and the detection distance in the system link analysis, the test distance is determined to be 0.35 m. The radiant flux of the mmWave equipment is one thousandth of the radiant flux of mobile phones.

Figure 15 Block diagram of the antenna and distribution network.

Figure 16 Prototype mmWave antenna and distribution network.

Based on the uniform distribution error analysis of the array elements, the processing precision of the array elements and the motion precision of the scanning frame are controlled to 0.2*dx. The linearity of the signal source is better than 5*e⁻⁴.

IMAGE ANALYSIS

The prototype system is first tested by determining the its ability to image objects on a test plate (see Figure 17) as compared with optical images. Figure 17a shows the optical images. Figure 17b shows the MMW images. The expanded view (see Figure 17c) shows distinct 5 mm round holes in the test plate and even a blurry image of 3 mm round holes.

Next, a human body is scanned (see Figure 18). These two images (Figures 18a and b) are from the same array, with the same processing accuracy, linearity and spectral error. The difference is motion accuracy. Figure 18b is the result of higher motion accuracy in the mechanical frame. It shows a vivid outline of the human body, including smooth muscle lines and 10 fingers, with a mobile phone visible in the hip pocket.

 

Figure 18 Human body images: coarse motion accuracy (a) and fine motion accuracy (b).

CONCLUSIONS

A high-performance security check MMW imaging system for detection of objects on the human body is described. The results show suitable sensitivity and resolution at a conventional detection distance between 0 and 0.5 m. Through analysis and simulation, the distribution error of antenna array and the linearity of signal emitter minimize ISLRs. An optimized prototype demonstrates imaging with a resolution approaching 5 mm.

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