Wearable Microstrip Patch Ultra Wide Band Antenna

Wearable Microstrip Patch Ultra Wide Band Antenna for Breast Cancer Detection Fawzy Alsharif1, and Çetin Kurnaz2 1,2

Department of Electrical and Electronics Engineering Ondokuz Mayis University Samsun, Turkey 1 [email protected], [email protected]

Abstract— This paper illustrates a novel design for a wearable microstrip patch ultra-wide band (UWB) antenna with improved bandwidth design to be used in breast cancer detection. The operating frequency of the proposed antenna ranges from 1.6 GHz to 11.2 GHz. The antenna consists of a rectangular radiating patch fed by a rectangular feed line. This antenna design will be part of a wearable device for women to detect breast cancer early. To support wearable property, 100% cotton has been utilized as the substrate with dielectric constant 1.6, while the transmitting component patch and ground planes are composed of copper as the conductive material. The analysis of the antenna and breast models was carried out using CST Microwave Studio. Simulated results in terms of return loss, bandwidth, radiation pattern, and gain and efficiency are presented to validate the usefulness of the proposed design, and different bending conditions are presented. Keywords—UWB Antenna; Wearable Bending; Breast cancer detection; CST.

antenna;

Antenna

I. INTRODUCTION Breast cancer influences numerous women and has deadly consequences on the chance that it isn’t cured effectively. Early detection is the most critical parameter to identify and halt the progression of malignant tissue. Traditional techniques used for breast cancer discovery are X-ray mammogram, magnetic resonance imaging (MRI) and ultrasound, but they have a few restrictions. For instance, between 4% and 34% of all breast cancers are missed as a result of poorly detected cell/normal malignancy tissue differentiate. Microwave imaging (MI) to recognize breast cancer is a promising technique [1]. MI utilizing a microstrip antenna has advantages such as comfort, potentially low cost, and being a nonionizing, safe alternative. The working guideline of MI methods depends on the dielectric contrast between the dangerous tumor tissues and the healthy ones. The electrical properties of conductivity and dielectric parameters of involved tissue are utilized for pathological recognition between normal and defected tissue through difference appropriation maps. The essential thought of utilizing the MI system for breast cancer detection is that the transmitting antenna transmits electromagnetic waves through the breast and a receiving antenna receives the scattered waves [2, 3]. Microwave tomography and radar-based MI techniques have been investigated in cancer detection [4-7]. In medical imaging, ultra-wide band (UWB) antennas were utilized, and these antenna types should be planar, compact, with high

radiation efficiency and strength stability over the whole activity band. The greater part of UWB antennas discussed in previous designs show omni-directional radiation designs with low pick up. A few sorts of receiving wires can be utilized, for instance, smaller scale strip, Vivaldi, Bowtie and Circular antennas [8-11]. One of the prevailing examination factors in antennas for body-driven correspondences is wearability. A wearable antenna is intended to be a piece of the apparel utilized for correspondence purposes, which incorporates following and route, mobility and safety. Wearable antenna apparatus necessities for all new application require light weight, minimal cost, nearly repair free and no establishment [12, 13]. In this paper, the proposed design aims to detect breast cancer early by using MI and supporting wearability that can be integrated as part of garment and worn on the body, with the ability to extend wireless range that use ultra-wide bands in addition to the low frequency. The rest of the paper is organized as follows: Section II presents antenna design and operation, and Section III discusses simulation results. In Section IV, bending conditions of wearable antenna are discussed, Section V describes cancer detection, and Section VI illustrates the simulation results of cancer detection. Section VII contains the conclusion. II. ANTENNA DESIGN The position of the safety planar antenna can be incorporated into attire. A recognizable topology of the microstrip antenna apparatus is favored. This guarantees that radiation is kept far from the body with adequate data transmission for a decent scope [4]. The proposed antenna (70mm x 60mm) has a permittivity of (1.6) and thickness of 1.6 mm for the substrate. 100% cotton material is utilized as the dielectric substrate with a εr value of 1.6. Copper in the patch is used as the radiating surface with a thickness of 0.1 mm; Table I shows the dimensions of the patch and ground planes. The antenna is fed through a 50Ω miniature adapter (MMCX) connector. As stated previously, the dimensions of this antenna have been obtained using CST Microwave studio [14]. Fig. 1 shows the step by step development of the antenna structure used for simulation in the next section.

TABLE I. DIMENSION OF THE DESIGNED ANTENNAS

Parameter

Dimension (mm)

Parameter

Dimension (mm)

L W LF S1 S2 S3

30 36 26 11 4 9

S4 S5 S6 LG WG SG

4 4 6 25.7 25.25 10

B. Radiation Pattern 2D radiation patterns (polar) in free space at different frequencies 2.5 GHz, 4.5 GHz, 6.8 GHz, 9.8 GHz when using 100% cotton for substrate and copper for the conductive material are shown in Fig. 3. The antenna exhibits a broadside directional radiation pattern with a peak gain of 6.17 dBi, and the total efficiency is (ηt=93%) at 9.8GHz.

Fig. 3. Polar radiation pattern a) 2.5 GHz, b) 4.5 GHz, c) 6.8 GHz, d) 9.8 GHz. Fig. 1. Geometry of the proposed antenna a) Structure 1, b) Structure 2, c) Structure 3, d) Ground plane is the same for all structures.

III. SIMULATIONS RESULTS A. Return loss As shown in Fig. 2, the -10 dB return loss (S11) bandwidth expands from 1.6 GHz to more than 11.2 GHz, with bandwidth 9.6 GHz achieved by Structure 3. The designed antenna covers the required bandwidth to detect most types of breast cancers [15, 16]. The measured and simulated results are similar, validating the antenna specifications.

C. Substrate Material Selection for Wearability The material’s permittivity is normally offered with respect to that of free space, which is known as relative permittivity or dielectric steady εr. Diverse substrates with distinctive dielectric constants influence the radio wire execution in different methods as shown in Table II; Fig. 4 shows a comparison between return losses of different substrate materials. TABLE II. DIFFERENT TYPES OF SUBSTRATE MATERIALS FOR DESIGNING

Material Panama fabric Fleece Dacron Pure Cotton

Fig. 2. Simulated return loss of the various structures.

Permittivity (F/m) 2.12 2.22 3 1.6

Thickness (mm) 1.6 1.524 1.524 1.6

Panama fabric has excellent absorbency, durability, and resilience, and is popular in clothing; it is also less flammable. Fleece material has many properties, such as being pleasant to touch and warm. It dries quickly, never loses its properties when used, looks appealing, and is hygroscopic. The properties of Dacron material are high rigidity, high protection from stretching, strength and extraordinary electrical properties. Unadulterated 100% cotton material is chosen for a firm, smooth surface, and it is reasonable for wearable applications.

V. CANCER DETECTION

Fig. 4. Comparison between return losses of different substrate materials.

IV. BENDING OF ANTENNA

A breast model has been designed using CST software shown in Fig. 7. The breast model is an approximate replica of a human breast. The model was designed as a half sphere with a skin layer of thickness 3 mm and outer radius of 25 mm. A fibro glandular breast fatty tissue layer of radius 22 mm is situated inside the skin layer. A plane wave is made incident through the z axis towards the model, and the field is situated at 4 mm. The breast model is excited by plane wave stimulation. The plane wave is passed through the model and then received by the field. Different characterizations of the model are shown. A defected cell is situated inside the fibro glandular breast fatty tissue layer as a sphere with diameter 10 mm, as shown in Fig. 7. The dielectric constants and conductivity of each layer of the breast model are shown in Table III [17-20].

The wearable antenna bends continuously due to human body movements, and to guarantee the antenna execution, applications are up to check, particularly when the antenna is connected to adjusted parts of the body. Based on the analysis, the proposed design antenna has been tested under several conditions to examine its ability to keep its operating bandwidth in a desirable range; the antenna has been bent with different modes (vertical and horizontal) at 45 degrees as shown in Fig. 5. Fig. 7. Breast model with tumor. TABLE III. BREAST MODEL PARAMETERS FOR THE NORMAL BREAST TISSUE, THE DEFECTED AND THE SKIN

Dielectric medium

Fig. 5. Simulation bending of antenna with two different modes a) vertical, b) horizontal.

Fig. 6 shows the measured results of the return loss when different bending situations are applied to the proposed antenna; the return loss parameter is still almost UWB, and no major differences occur. Therefore, the antenna will be able to operate within the desired frequency range.

Fig. 6. Return loss of different bending modes.

Skin Normal tissue Defected tissue

Dielectric constant (F/m) 46.7 9 50

Conductivity (S/m) 1.1 0.15 0.7

VI. SIMULATION RESULTS OF CANCER DETECTION In the proposed antenna system, the transmitter antenna sends signals and then illuminates the breast phantom model, and the receiver antenna collects the backscattered waves from the breast phantom model. In order to achieve a higher amplitude for enhancement of the tumor signal, the end fire direction for the antenna position is introduced as shown in Fig. 8. In the proposed breast cancer imaging system, horizontal end fire antennas are placed with 180 degrees between the transmitter and receiver antenna at 5 mm away from the skin fat interface. Fig. 9 shows a comparison between transmitted signal, received signal when the breast model contains tumor cells and received signal for the breast model without tumor cell. Alignment steps rely on the presumption that the signs recorded at various antenna sites have comparable episode heartbeat and skin backscatter content [21, 22]. The tumor signal is different in amplitude and time as a result of multipath propagation and different tumor antenna distance. This variation is observed (e.g., from 0.8 ns to 3 ns) as the tumor response is observed.

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Fig. 8. Breast model with tumor and (Tx, Rx) antennas.

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[12] Fig. 9. Received signals from reflection from breast without tumor and breast contains tumor.

VII. CONCLUSION This study analyzed a wearable microstrip UWB antenna intended to perform microwave imaging to detect breast cancer early. The antenna structure working at 1.6 GHz -11.2 GHz is simulated with basic 3D breast structure. Various antenna structures are assessed by changing the top plane and bottom plane of the microstrip; many types of substrate materials were also utilized to test the best return loss parameter to support wearability. Likewise, the material substrate utilized as a part of this proposed antenna is 100% cotton, which retains water as needed. The execution was changed to be approved for future improvement. The designed antenna has the benefits of UWB, conservative size, minimal cost, good directional radiation patterns with acceptable gain of 6.17 dBi with a total efficiency above 93%, wearability, and it functions under different bending conditions. Because of that, this work acquires better outcomes when compared with other works in literature. REFERENCES [1]

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