Design of Small Circular Polarized Antenna With Ring Descriptive Loading for Biomedical Applications

A small circular polarized antenna for biomedical applications is designed, which can be used for signal transmission of implantable medical devices or capsule endoscopes. By introducing the ring characteristic loading array, the high electromagnetic energy is aggregated, and the electrical size of the antenna is reduced effectively while the impedance bandwidth is widened. Under the same bandwidth requirement, the antenna size is reduced by about 18 %, and the antenna volume is 80.7 mm3. The circular polarization performance of the antenna is generated and adjusted by adding annular slots between the outer ring and the ring descriptive loaded array to generate geometric perturbations. The sensitivity of the complete antenna model to implant in different parts of human body and ingestion of different digestive organs is studied. The biological compatibility, radiation characteristics and safety of the antenna are evaluated. The gain values are −16.8 dBi and −15.6 dBi. The performances of the antenna are tested in pork and simulated digestive tissue solutions. The impedance bandwidths are 24.7 % (2.23 ~ 2.86 GHz) and 20.2 % (2.25 ~ 2.76 GHz) respectively, and the effective communication distance is 11.8m in space. The designed antenna has wide working frequency band, small size, anti-interference and good electromagnetic compatibility, which can meet the working requirements of biological medical equipment after ingestion in digestive organs or implantation in human body.

SECTION I. Introduction

With the rapid development of wireless communication and electronic technology, more advanced and intelligent microsystems are constantly applied to implantable or ingested wireless biomedical devices. Implantable or ingested antennas play an important role in wireless biomedical devices. The structural forms of implantable or ingested antennas mainly include monopole antenna, microstrip antenna, ring antenna, spiral antenna, conformal patch antenna and MIMO antenna, etc [1], [2], [3], [4]. In order to reduce the size of the antenna, the dielectric substrate with high relative dielectric constant is selected, the meandering technology with slots or gaps on the surface of the radiation patch and the capacitive loading technology which can offset the inductive impedance are adopted. In order to obtain a wide bandwidth, some literatures adopt fractal technology, multi-resonance coupling structure, multi-layer stacking structure and other methods by reducing the Q value of equivalent resonant circuit [5], [6], [7], [8], [9]. Implantable or ingested antennas work in the human body, and the strong coupling between the human body and the antenna affects the electromagnetic characteristics of the antenna. Linearly polarized antenna has weak anti-interference ability in human body, while circularly polarized antenna can suppress multipath interference, transmit and receive without influence of angle, can improve the efficiency of information transmission, and make up for the lack of adaptability of linearly polarized antenna to human environment effectively [10], [11], [12]. In order to achieve the circular polarization and axial ratio performance, the aperture coupling feeding method is usually adopted, which introduces geometric disturbance structure or slit of specific structure into the radiation patch, feeds and introduces slice resistance on the diagonal of the radiation patch, and adopts complementary open resonant structure or slow wave structure, etc [14], [15], [16], [17]. Monolayer antenna has the advantages of simple structure, easy processing, stable performance and small size, and it has become the focus of implantable or ingested antenna research. In [18], a single-layer structure is adopted, a rectangular ring groove is opened in the center of the radiation element, and the power is fed through a coplanar waveguide. In [19], the cross-groove is etched in the center of the radiating patch antenna, the arc groove is etched in the edge of the radiating patch antenna, which can achieve circular polarization performance. In [20], two capacitive loads are added to the top and left side of the radiation unit as load capacitors to improve impedance matching. A rectangular slit is cut in the circular floor to further widen the bandwidth. In [21], by setting two slots on the radiation patch to adjust the circular polarization characteristics, the pins loaded around can improve the antenna gain effectively.

This paper presents an antenna with small size and wide frequency band. The outer ring of the radiation element is slotted to form a meandering element to reduce the resonant frequency. A ring descriptive loading array is introduced in the center of the radiation element to aggregate higher electromagnetic energy and reduce the antenna’s electrical size while broadening the impedance bandwidth effectively. A ring slot is added between the outer ring and the ring descriptive loading array to generate geometric perturbation, thereby adjusting the circular polarization performance of the antenna.

SECTION II. Design of the Antenna

In this design, rectangular slots with the same size and uniform distribution are opened on the outer ring of the radiation unit to form a meander unit and reduce the resonant frequency. A ring descriptive loading array is introduced in the center of the radiation element to aggregate high electromagnetic energy, which can reduce the antenna electrical size effectively while broadening the impedance bandwidth. Ring slots with different sizes are symmetrically added between the outer ring and the ring description loading array to generate geometric perturbation, so as to form two degenerate modes with equal amplitude, orthogonal polarization and phase difference of 90 degrees, realizing and adjusting the circular polarization characteristics. The impedance matching can be improved by adjusting the size of the circular patch in the center of the radiation element. Two short-circuit probes are loaded on the outer ring of the radiation element to broaden the impedance bandwidth further. The two short-circuit probes are symmetrical about the center of the radiation element, and the floor is a complete circular metal patch structure, which can reduce the interference of the antenna to other electronic components effectively, so as to improve the electromagnetic compatibility. The dielectric substrate is Rogers RO3010, the thickness H is 0.635 mm, the dielectric constant $\varepsilon _{r}$ is 10.2, and the loss tangent tan$\delta$ is 0.0035. The radiation unit is covered with a layer of dielectric substrate to prevent contact with skin or digestive tissue. The structure of the antenna is shown in Fig. 1.

FIGURE 1.

Structure of the antenna (a) Frontal structure and (b) Backside structure.

A. Initial Simulation Environment and Structural Parameters of Antenna

Fig. 2 shows the model diagram of the antenna implantation in three-layer human tissue. The three-layer human tissue model includes the skin layer ($\varepsilon _{r}$ is 37.88, $\sigma$ is 1.44 S/m), the fat layer ($\varepsilon _{r}$ is 5.3, $\sigma$ is 0.1 S/m) and the muscle layer ($\varepsilon _{r}$ is 52.7, $\sigma$ is 1.7 S/m). The size of the three-layer human tissue is 80 mm $\times80$ mm $\times30$ mm, the electrical characteristics are consistent with the human skin tissue, the electrical conductivity is 1.44 S/m, the dielectric constant $\varepsilon _{r}$ is 37.88. The antenna is placed in the center of the simulation environment, 4 mm away from the upper surface of the model. After optimized design, the antenna size is $\pi \times$ (4.5)$^{2}\,\,\times0.635$ mm³ (a cylinder with a radius of 4.5 mm and a height of 0.635 mm), and the parameters of each part are shown in Table 1.

TABLE 1 The Parameters of the Proposed Antenna

FIGURE 2.

Antenna simulation environment.

B. The Influence Analysis of Antenna Structure on the Performance

Fig. 3 shows the design process of the radiation unit. Fig. 3 (a) shows the initial structure of the annular patch antenna. Rectangular slots are cut inside and outside the ring. Fig. 3 (b) introduces two short-circuit probes symmetrically on the ring, Fig. 3 (c) loads a circular patch through the ring branch in the center of the radiation unit. The circular patch is replaced by four groups of ring descriptive loaded arrays in Fig. 3(d). The influence of antenna structure change on reflection coefficient is shown in Fig. 4. The following conclusions can be drawn: (1) Rectangular slots can produce capacitance effects that reduce the resonant frequency. (2) By introducing two short-circuit probes, the resonant frequency of the antenna can be reduced from 3.19 GHz to 2.84 GHz. (3) The circular patch loaded through the annular branch increases the inductance and capacitance distribution of the radiating patch, further reduces the resonant frequency of the antenna, and decreases the resonant point from 2.84 GHz to 2.58 GHz. (4) By introducing four groups of ring descriptor loaded arrays, high electromagnetic energy is aggregated, impedance matching is improved, impedance bandwidth is increased, and the electrical size is reduced effectively. Under the same bandwidth requirement, the antenna size is reduced by about 18 %. Fig. 5 shows the reflection coefficient and axial ratio of the optimized antenna, as a function of frequency. Impedance bandwidth and axial ratio bandwidth are 2.24 ~ 2.73 GHz and 2.28 ~ 2.62 GHz respectively.

FIGURE 3.

The design process of the radiation unit: (a) Case 1, (b) Case 2, (c) Case 3 and (d) Case 4.

FIGURE 4.

The influence of antenna structure change on reflection coefficient.

FIGURE 5.

The reflection coefficient and axial ratio of the optimized antenna, as a function of frequency.

C. Analysis of Circular Polarization Characteristics of Antenna

Two short-circuit probes are symmetrically introduced on the ring, and a certain phase difference is generated in Fig. 3(b). However, due to the limited size of the ring, a phase difference of 90 degrees can not be achieved by changing the positions of the two short-circuit probes. By adding annular slots between the outer ring and the capacitive loaded array in Fig. 3 (c), geometric perturbation is generated, thus forming two degenerate modes with equal amplitude, orthogonal polarization and 90 degree phase difference, resulting in circular polarization characteristics. The two groups of annular slots are different in size, and the circular polarization purity of the antenna can be improved by adjusting the Angle of the annular slots. In order to further expand the axial ratio bandwidth, a ring descriptive loading array is introduced in Fig. 3 (d), which can concentrate stronger electromagnetic energy and excite additional circular polarization modes that are close to the resonant frequency of the main mode and have the same rotation direction, thus expanding the axial ratio bandwidth. Fig. 6 shows that at 2.45GHz, the surface current distribution of the antenna radiation patch in different phases: 0°, 90°, 180°, 270°. The red arrow indicates the direction of the dominant current in four different phases. It can be seen that the dominant current on the antenna radiation patch flows in two orthogonal directions and rotates clockwise for a period of time, so the antenna is left-handed circular polarization.

FIGURE 6.

At 2.45GHz, the surface current distribution of the antenna radiation patch in different phases: 0°, 90°, 180°, 270°.

SECTION III. Sensitivity and Safety Evaluation of Antenna Complete Model

A complete antenna model is constructed, in which all electronic devices and antenna components are set, including sensors, batteries, optical systems, PCB (Printed Circuit Board) boards, DSP (Digital Signal Processor), antennas, wireless transmission modules, etc. In the study of complete model, most literatures only disclose one of implantable medical devices or ingested medical devices, but this paper studies both of them. Implantable medical devices are mainly implanted into skin or muscle, such as continuous blood glucose monitoring, electrical neurostimulator and cardiac pacemaker. The complete antenna model is shown in Fig.7 (a), while the ingested medical device is ingested into human digestive organs, such as capsule endoscope, and the complete antenna model is shown in Fig.7 (b). The dimensions of the implantable antenna complete model are $\pi \times 52\times16$ mm³, and those of the ingestion antenna complete model are $16\times 10\times3$ mm³. The antenna is implanted or ingested into different human and digestive tissues, to test the performance of the antenna and evaluate the sensitivity of the antenna.

FIGURE 7.

Simulated working environment (a)Implantable continuous glucose monitoring and (b) Ingestion capsule endoscope.

A. Evaluation of Antenna Sensitivity in Different Implanted Environments

The implantable continuous glucose monitoring model is implanted into the head, arm and chest of the CST human tissue model, as shown in Fig. 8. Reflection coefficient and axial ratio of the proposed antenna according to the implanted location is shown in Fig. 9. The antenna is implanted into the chest, because the dielectric constant of muscle layer is greater than that of skin layer, the resonant frequency is shifted to low frequency. The antenna is implanted into the arm, because the dielectric constant of the fat layer is much smaller than that of the skin layer, the overall effective dielectric constant of the arm position is lower than that of the skin model, resulting in a shift of the resonant frequency to the high frequency. The antenna is implanted into the head, because the dielectric constant of the chest and the head is close, the simulation results in the two models have little change. From the above sensitivity analysis, it is concluded that in the complete model, the designed antenna has good stability. When the human body dielectric constant $\varepsilon$ , conductivity $\sigma$ and implantation depth change, the antenna can still meet the working requirements.

FIGURE 8.

The antennas are implanted in different models of human tissue.

FIGURE 9.

Reflection coefficient and axial ratio of the proposed antenna according to the implanted location.

B. Evaluation of Antenna Sensitivity in Different Ingested Environments

The ingestion capsule endoscope model is placed in the stomach, small intestine and colon of the CST human digestive tissue model, as shown in Fig. 10. Test the antenna’s sensitivity in the human digestive tissue environment. Among them: $\varepsilon _{r}=62.16$ , $\sigma$ = 2.21 S/m in the stomach, $\varepsilon _{r}=54.43$ , $\sigma$ = 3.18 S/m in the small intestine, $\varepsilon _{r}=53.88$ , $\sigma$ = 2.04 S/m in the colon [16], [20]. The influences of three different digestion environments on impedance bandwidth and axial ratio bandwidth are analyzed, as shown in Fig. 11. The three ingestion environments have little influence on the resonant frequency. With the increase of the dielectric constant of the ingestion environment, the impedance matching is improved to a certain extent, indicating that the resonant frequency is not sensitive to the ingestion environment. With the increase of the electrical conductivity of the ingestion environment, the optimal axial ratio performance moves to the low-frequency direction, indicating that the axial ratio bandwidth is sensitive to different ingestion environments. The antenna maintains a wide impedance bandwidth and axial ratio bandwidth in the three ingestion environments, which can meet the communication requirements of ingestion medical devices.

FIGURE 10.

The ingestion capsule endoscope model is placed in the stomach, small intestine and colon of the CST human digestive tissue model.

FIGURE 11.

Evaluation of antenna sensitivity to stomach, small intestine and colon.

C. Biocompatibility Analysis of Antenna Complete Model

The complete antenna model is coated with a layer of Parylene-C, PEEK and Alumina biocompatibility film respectively, the coating thickness is 0.02 mm and the simulation results are shown in Fig. 12. Wrapped in three biocompatible materials, the antenna’s working bandwidth and resonant frequency can meet the working requirements, and the circular polarization performance is good. When Alumina is used for the antenna, the optimum point of axial ratio and resonant frequency offset are small. Therefore, the designed complete antenna model is encapsulated in Alumina to make it have biological compatibility.

FIGURE 12.

Influence of different biocompatible films on antenna performance.

Alumina is used to wrap the antenna, and the influence of different coating thickness on antenna performance is analyzed. As shown in Fig. 13, the simulation results show that when the coating thickness is 0.02 mm, the antenna can maintain good impedance bandwidth and circular polarization performance. With the increase of the thickness of the coating layer, the optimal point of the resonant frequency and axial ratio performance of the antenna will shift slightly to the high frequency direction. Therefore, the thickness of the biocompatible material should be included in the design optimization during the study of biocompatibility.

FIGURE 13.

Comparison of effects of different coating thicknesses on antenna performance.

D. Gain and SAR Analysis in Different Environments

In order to evaluate the radiation performance of the antenna in the implanted environment, Fig. 14 shows the simulation test gain at 2.45 GHz. The test environment is a three-layer human tissue model, with the main pole converted to left-handed circular polarization and the cross pole to right-handed circular polarization, which is consistent with the results verified in Fig. 6. The antenna has good directivity. The maximum radiation direction is along the Z-axis, towards the outside of the human body. The maximum gain value is −16.8 dBi. The smaller rear lobe and secondary lobe can reduce radiation damage to the human body. The Cross Polarization Discrimination in the main radiation direction is about −27.6 dBi, which indicates that the antenna has good cross polarization rejection.

FIGURE 14.

Radiation pattern of antenna in plane E and plane H at 2.45GHz (a) E plane and (b) H plane.

In order to analyze the influence of the antenna ingestion position and environment on the radiation characteristics, the circularly polarized antenna is placed in the stomach, small intestine and colon for comparison and test. The gain and axial ratio curves are shown in Fig. 15. As can be seen from it, the optimal axial ratio angle at 2.45 GHz are 36 °, 12 ° and $-28\,\,^{\circ }$ , and the maximum gain are −15.6 dBic, −23.2 dBic and −30.6 dBic respectively. The maximum gain of the antenna decreases gradually with the change of the ingestion position, because different digestive tissues cause different dielectric loss, and different ingestion depth affects the electromagnetic energy loss.

FIGURE 15.

Gain and axial ratio curves of antenna ingestion in stomach, small intestine, and colon (a) stomach, (b) small, intestine and (c) colon.

Considering the safety issues after implantation or ingestion, the SAR value is evaluated to calculate whether the intensity of energy absorbed or dissipated by the human model exceeds the safe range. The implantable antenna is placed on the arm of the mannequin, as shown in Fig. 16 (a) and (b), and the ingestion antenna is placed in the stomach of the mannequin, as shown in Fig. 16 (c) and (d). By providing 1 W input signal to the antenna, the simulation results show that the maximum average SAR value of 1g and 10g in the arm are 276.5 W/kg and 28.5 W/kg, and that in the stomach are 316.8 W/kg and 42.6 W/kg. Because the implant depth in the arm is much less than that in the stomach, the maximum average SAR value in the arm is also less than that in the stomach, and the electromagnetic energy absorbed by the arm is relatively less. In order to meet the safety standards of IEEEC95.1 - 1999 and IEEEC95.1 - 2005 at the same time [10], the maximum allowable input power of the implantable antenna at the arm under different standards is 5.83 mW and 71.2 mW, respectively. The maximum allowable input power of the ingestion antenna into stomach under different standards is 4.92 mW and 53.1 mW. In order to meet the IEEE standard for SAR, the input power of the antenna should be lower than 4.92 mW and 53.1 mW. Since the output power of the general medical transmitter is -14 dBm, the power range of the transmitter is much smaller than the maximum allowable input power of the antenna. Therefore, the electromagnetic radiation generated by the antenna is safe and harmless to human tissues.

FIGURE 16.

Average value of SAR in the arm and the stomach (a) 1 g average SAR value distribution at the arm, (b) 10 g average SAR value distribution at the arm, (c) 1 g average SAR value distribution in the stomach and (d) 10 g average SAR value distribution in the stomach.

SECTION IV. Analysis of Measured Results

A. Performance Test of Implantation Environment

The radiation unit is made by chemical etching, and the antenna and covering layer are bonded by adhesives. Fabrication of the antenna and the finished product of integrating the antenna into an implantable, ingested device is shown in Fig. 17. The antenna system is connected with vector grid analyzer through coaxial cable and implanted into pork for testing. Pork is composed of skin, fat and muscle. The actual test environment is shown in Fig. 18. A linearly polarized antenna is used as an external receiving antenna, and a circularly polarized antenna designed is used as a transmitting antenna. By receiving the orthogonal position of the linearly polarized antenna, that is, when the azimuth of the linearly polarized antenna is measured to be 0 ° and 90 °, Whether $\vert ~\text{S}_{21}~\vert$ fluctuation is more than 3 dB, indirect test antenna polarization characteristics. The impedance bandwidth and axis ratio of the antenna tested in practice are compared with the simulation and the results are shown in Fig. 19. The measured impedance bandwidth is 2.23 ~ 2.86 GHz (24.7 %), the resonant point is located at 2.47 GHz, and the axial ratio bandwidth is 2.30 ~ 2.79 GHz (19.3 %). There is little difference between the measured results and the simulation results. Compared with the simulation results, the measured impedance bandwidth and axial ratio bandwidth are increased, mainly due to the loss caused by the penetration of pork tissue, the measurement error of antenna processing and the different dielectric constant in the simulated and measured environment. The test results of circular polarization performance are shown in Fig. 20. Within the working frequency band, $\vert ~\text{S}_{21}\vert$ difference is less than 3 dB, the biggest difference is about 1.1 dB, which shows that the designed antenna has good circular polarization performance.

FIGURE 17.

Fabrication of the antenna and the finished product of integrating the antenna into an implantable, ingested device.

FIGURE 18.

Circular polarization antenna test diagram.

FIGURE 19.

The impedance bandwidth and axis ratio of the antenna tested in practice are compared with the simulation results.

FIGURE 20.

Circular polarization performance test results.

B. Ingestion Environment Performance Test

The antenna is placed in the simulated human digestive tissue solution, the actual test diagram is shown in Fig. 18. The solution ratio are 61.2 % (percentage by weight) of de-ionized water, 33.9 % of Triton X - 100 (Polyethylene glycol mono phenyl ether) and 4.9 % of diethylene glycol butyl ether (DGBE). The electrical properties at 2.45 GHz are $\varepsilon _{r} =53.88$ , $\sigma$ = 2.04 S/m. The receiving antenna adopts circular polarization antenna, impedance bandwidth is 2.39 ~ 2.51 GHz, axial ratio bandwidth is 2.27 ~ 2.55 GHz, the distance of the transceiver antenna is 150 mm. Comparisons between measured impedance bandwidth and simulation results are shown in Fig. 21. The measured impedance bandwidth is 2.25 - 2.76 GHz (20.2 %). The measured results of the designed antenna are in good agreement with the simulation results, and some frequency offset occurs, which is mainly caused by the coupling effect of the transceiver antenna and the measurement position error.

FIGURE 21.

Comparison between measured impedance bandwidth and simulation results.

C. Antenna Communication Link Evaluation

By evaluating the communication capability of the antenna, the effective communication distance is determined. The designed antenna is used as the transmitting antenna, the circularly polarized and linearly polarized antennas are used as the receiving antennas respectively. Assuming that there is no impedance loss and the gain is 2.15 dBi. In order to meet the limit of 10g SAR value and EIPR value [8], the maximum input power of the antenna is 33.8 mW (15.3 dbm). Therefore, the input power is set as −30 dBm. Table 2 shows the detailed parameters used to calculate the allowance of antenna communication link. The margin of communication link is calculated according to the formula given in [13].

TABLE 2 Parameter Table for Calculating the Allowance of Antenna Communication Link

For far-field wireless communication, the formula for calculating link margin is:

$$\begin{align*} &\hspace {-.2pc}\text {Link} \text {margin} (\text {dB}) \\ &= {\it Link\, C}/N_{0}-{\textit{Required}} C/N_{0} \\ &= P_{t}+ G_{t}- L_{f}+ G_{r}- N_{0} - E_{b}/N_{0} - 10\text {log}10B_{r} \\ &\quad + G_{c} - G_{d} \tag{1}\end{align*}$$

In formula (1), $P_{t}$ is the transmitting power, $G_{t}$ is the transmitting antenna gain, $L_{f}$ is the path loss in free space, $G_{r}$ is the receiving antenna gain, and $N_{0}$ is noise power density.

Path loss in free space can be expressed as:

$$\begin{equation*} L_{f} (\text {dB}) = 20\text {log} (4\pi d/\lambda) \tag{2}\end{equation*}$$

The impedance mismatch formula is:

$$\begin{equation*} \text {Limp} (\text {dB}) = - 10\text {log}(1 - \vert \Gamma \vert ^{2}) \tag{3}\end{equation*}$$

The relationship between the margin of communication link and distance is shown in Fig. 22. In order to meet the communication requirements, the designed antenna communication link is considered as reliable communication when the margin is 0 dB. It can be seen from the calculation results that when the receiving antenna adopts omnidirectional circularly polarized antenna, the effective communication distance is 11.8 m. When the receiving antenna adopts dipole wire-polarized antenna, the effective communication distance is 8.2 m, indicating that the effective communication distance of circularly polarized receiving antenna is longer. Both types of receiver antennas can meet the communication needs of the implanted environment.

FIGURE 22.

The curve of communication link allowance as a function of communication distance.

In this paper, a small circularly polarized antenna is proposed, and its performance is compared with that of implantable or capsule endoscope antennas in published literature, as shown in Table 3. Compared with literature [18], this antenna has smaller volume and wider axial ratio bandwidth. Compared with literature [19], the proposed antenna has wider impedance bandwidth and higher radiation efficiency. Compared with literature [20], this antenna axis has wider specific bandwidth and higher radiation efficiency. Compared with literature [21], the proposed antenna has a compact structure, wider impedance bandwidth and axial ratio bandwidth. Therefore, compared with the above antennas, although the antenna proposed in this paper is not the best in terms of performance, it has a higher degree of miniaturization, wider working bandwidth, longer communication distance and wider application range, which is suitable for implantable or ingested medical devices.

TABLE 3 Comparison of proposed antenna to prior art.

SECTION V. Conclusion

In this paper, a small circularly polarized antenna with ring descriptive loading is proposed for biomedical applications. A ring descriptive loading array is introduced in the center of the radiation element to aggregate high electromagnetic energy, which can reduce the electrical size of the antenna effectively while broadening the impedance bandwidth. Circular grooves with different sizes are symmetrically added between the outer ring and the ring descriptive loading array to generate geometric perturbation and achieve and adjust the circular polarization characteristics. The performance and parameters of the antenna are optimized by simulation in a three-layer human tissue model. The sensitivity of the complete antenna model to implant in different parts of the human body and ingest different digestive systems is studied, and the biocompatibility and radiation characteristics in different environments are evaluated. The proposed antenna is manufactured, and the performances of the antenna in the pork and human digestive tissue are actually tested, and the simulation results are further verified. The communication link is evaluated by an external antenna. Compared with the existing literature, the capacitive loaded array can aggregate higher electromagnetic energy, reduce the antenna size by about 18 % under the same bandwidth requirements, which is easy integration and compatible with wireless medical devices. In future research, the antenna can be integrated into biological medical systems such as physiological parameter monitoring of living organisms or capsule endoscope, so that the wireless biological medical system can establish a reliable connection with external receiving devices. At the same time, accurate animal experiments will be carried out to test key parameters such as transmission efficiency, optimal operating frequency and communication link.