**3. Simulation**

A 2D image is obtained by using inversion Fast Fourier Transformation:

images when the sensor array plane is placed at different heights (H):

~

∬

, *l*, *m*) = *d I*

/*dz* = ( *I* ~ *Zn* − *I* ~ *Zn*−<sup>1</sup>

*V*(*u*, *v*)*ej*2*π*(*ul*+*vm*)

(*l*, *m*) ∙ (1 − *l*

The 2D image difference between each two 2D images is computed by differentiating 2D

**Figure 3.** (a) Geometry of two detectors, (b) scattering characterization scheme from different receiving height [24].

~

*dldm* (7)

<sup>2</sup> − *m*2)/*dz* (8)

)/(*Zn* − *Zn*−1) (9)

~ (*l*, *m*) =

130 Emerging Microwave Technologies in Industrial, Agricultural, Medical and Food Processing

*I*

*I*(*H* = *zn*

*d I*

A numerical system was developed under MATLAB environment to investigate the proposed theory and system for diagnosing concealed MFOs. An array of 16 open-ended waveguide antennas with one element for transmitter and others for receivers. The target object was located at *z* = 0 mm and it was assumed to be fully contained in a rectangle imaging domain with length of 300 mm. The sensor array plane was placed at *z* = −200 m. Five models (see **Figure 4**) were developed using the published dielectric properties to evaluate the 3D HMMW [27].

Model I was made of two metallic spheres (10 mm in diameter, x1 = 0, *y*<sup>1</sup> = 0, *z*<sup>1</sup> = 35, x2 = 50, *y*<sup>2</sup> = 0, *z*<sup>2</sup> = 35) embedded in a cylindrical tank (240 mm in diameter and 70 mm in height) filled of clothing material; Model II was made of two wood spheres (5 mm in diameter, x1 = 0, *y*<sup>1</sup> = 0, *z*<sup>1</sup> = 35) embedded in a cylindrical tank; Model III was made of two wood

**Figure 4.** (a) Model I, (b) Model II, (c) Model III, (d) Model IV, (e) Model V (*A* 1: matching medium, *A* 2: cloth, *A* 3: metallic object, *A* 4: skin, *A* 5: skull, *A* 6: fat).

spheres (10 mm in diameter, x1 = 0, *y*<sup>1</sup> = 0, *z*<sup>1</sup> = 35, x1 = 20, *y*<sup>1</sup> = 0, *z*<sup>1</sup> = 35) embedded in a cylindrical tank; Model IV was made of one metallic sphere (10 mm in diameter, x1 = 0, *y*<sup>1</sup> = 0, *z*<sup>1</sup> = 35) embedded in a cylindrical tank.

To investigate the feasibility of on body conceded weapon detection using the proposed imaging method, a Model V includes human phantom was developed using published dielectric properties of various tissues, and a series of simulations were carried out on a personal computer by the developed computer model. **Figure 4(e)** shows the Model V, where the multimedia dielectric object (cylinder) was located at z = 0 mm and it was assumed to be fully contained in a rectangle imaging domain with length 100 cm. This multimedia object simulates human body (contains skin, skull and fat), clothing and metallic object. The scale values of the published dielectric properties of real tissues were applied (see **Table 1**).

**Figure 5** shows the reconstructed images of Model I at different frequencies in water. Both cylindrical box and two metallic objects are clearly identified in the frequency range of 20–25 GHz, but only metallic object is identified when frequency out of this range.

**Figure 6** shows the reconstructed images of Model II when the two objects located at different distance with frequency of 23 GHz in free-space. Results show that two small wood spheres are successfully identified when the distance between the two items great than 3 mm.

**Figure 7** shows the 3D reconstructed images of Model III and Model IV when the sensor array plane moved from *z* = −650 mm to *z* = −600 mm in 50 equal steps at frequency of 23 GHz.

To simulate on body weapon detection using the HMMW approach, the image measuring system was set-up in free-space with operating of frequency at 96 GHz, a 16-element antenna array plane was placed at the bottom of the model with a distance of 65 cm. A small four-band patch RF antenna was designed as transmitter and receiver and it was simulated using HFSS software with operating frequency of 50–120 GHz. **Figure 8** shows the return loss of the four-band patch antenna, which has the ability to receive good result at 96–116 GHz.

**Figure 9** shows the 2D reconstructed images of Model V at operating frequency of 96 GHz. The rectangle imaging region contains the dielectric object (human model with clothing) and the steel stainless object. Simulation result demonstrates that the metallic object underneath


wof human model's clothing has been successfully imaged, and structures of the tested human model are clearly identified with operation frequency of 96 GHz. Color bar plots signal energy on a linear scale, normalized to the maximum in the image space and values

**Figure 6.** Reconstructed images of Model II when the distance between two wood spheres is: (a) 0 mm, (b) 1 mm,

**Figure 5.** Reconstructed images of Model I with operating frequency of (a) 19 GHz, (b) 20 GHz, (c) 21 GHz, (d) 22 GHz,

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below 0.1 are rendered as blue.

(c) 2 mm, (d) 3 mm, (e) 4 mm, (f) 5 mm, (g) 6 mm, (h) 7 mm.

(e) 23 GHz, (f) 24 GHz, (g) 25 GHz, (h) 26 GHz.

**Table 1.** Dielectric properties of human body [26].

3D Holographic Millimeter-Wave Imaging for Concealed Metallic Forging Objects Detection http://dx.doi.org/10.5772/intechopen.73655 133

spheres (10 mm in diameter, x1 = 0, *y*<sup>1</sup> = 0, *z*<sup>1</sup> = 35, x1 = 20, *y*<sup>1</sup> = 0, *z*<sup>1</sup> = 35) embedded in a cylindrical tank; Model IV was made of one metallic sphere (10 mm in diameter, x1 = 0,

To investigate the feasibility of on body conceded weapon detection using the proposed imaging method, a Model V includes human phantom was developed using published dielectric properties of various tissues, and a series of simulations were carried out on a personal computer by the developed computer model. **Figure 4(e)** shows the Model V, where the multimedia dielectric object (cylinder) was located at z = 0 mm and it was assumed to be fully contained in a rectangle imaging domain with length 100 cm. This multimedia object simulates human body (contains skin, skull and fat), clothing and metallic object. The scale values of the published dielectric properties of real tissues were applied

**Figure 5** shows the reconstructed images of Model I at different frequencies in water. Both cylindrical box and two metallic objects are clearly identified in the frequency range of

**Figure 6** shows the reconstructed images of Model II when the two objects located at different distance with frequency of 23 GHz in free-space. Results show that two small wood spheres

**Figure 7** shows the 3D reconstructed images of Model III and Model IV when the sensor array plane moved from *z* = −650 mm to *z* = −600 mm in 50 equal steps at frequency of 23 GHz. To simulate on body weapon detection using the HMMW approach, the image measuring system was set-up in free-space with operating of frequency at 96 GHz, a 16-element antenna array plane was placed at the bottom of the model with a distance of 65 cm. A small four-band patch RF antenna was designed as transmitter and receiver and it was simulated using HFSS software with operating frequency of 50–120 GHz. **Figure 8** shows the return loss of the four-band patch antenna, which has the ability to receive good result at

**Figure 9** shows the 2D reconstructed images of Model V at operating frequency of 96 GHz. The rectangle imaging region contains the dielectric object (human model with clothing) and the steel stainless object. Simulation result demonstrates that the metallic object underneath

*ε<sup>r</sup> σ* **(S/m)** *ε<sup>r</sup>* **σ (S/m)**

**No Region Dielectric properties Scale value of dielectric properties**

A4 Skin 41 4 0.5125 0.4 A5 Skull 25 2 0.31 0.2 A6 Fat 5 0.4 0.06 0.04

20–25 GHz, but only metallic object is identified when frequency out of this range.

are successfully identified when the distance between the two items great than 3 mm.

*y*<sup>1</sup> = 0, *z*<sup>1</sup> = 35) embedded in a cylindrical tank.

132 Emerging Microwave Technologies in Industrial, Agricultural, Medical and Food Processing

(see **Table 1**).

96–116 GHz.

**Table 1.** Dielectric properties of human body [26].

**Figure 5.** Reconstructed images of Model I with operating frequency of (a) 19 GHz, (b) 20 GHz, (c) 21 GHz, (d) 22 GHz, (e) 23 GHz, (f) 24 GHz, (g) 25 GHz, (h) 26 GHz.

**Figure 6.** Reconstructed images of Model II when the distance between two wood spheres is: (a) 0 mm, (b) 1 mm, (c) 2 mm, (d) 3 mm, (e) 4 mm, (f) 5 mm, (g) 6 mm, (h) 7 mm.

wof human model's clothing has been successfully imaged, and structures of the tested human model are clearly identified with operation frequency of 96 GHz. Color bar plots signal energy on a linear scale, normalized to the maximum in the image space and values below 0.1 are rendered as blue.

**4. Experimental validation**

**Figure 10.** (a) HMMW measurement setup; (b) sensor array; (c) target object.

box (100 × 100 × 40) mm3

detailed above).

An experimental study was conducted to evaluate the 3D HMMW system for concealed MFO detection (see **Figure 10**). A concealed steel ball (10 mm in diameter) embedded in a plastic

ended waveguide antennas with one element for transmitter and others for receivers. The plastic box was placed at *z* = 0 mm, and the sensor array plane was moved from *z* = −600 mm to *z* = −560 mm in 40 equal steps during data collection. During data collection, the VNA excited MMW signals to each transmitter located on the sensor array at frequency of 23 GHz. The scattered signals from the target object were measured by each detector. 2D and 3D images of the target object were reconstructed using the proposed imaging algorithms (as

that filled of emulsifying wax (see **Figure 10(c)**). An array of 16 open-

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**Figure 7.** (a) 3D reconstructed image of Model III, (b) 3D reconstructed image of Model IV.

**Figure 8.** Simulated S11 value of the designed 4-band patch antenna.

**Figure 9.** Reconstructed 2D image of Model V.
