Low-SAR folding screen mobile phone antenna based on reconfigurable parasitism

Abstract

The invention discloses a low-SAR folding screen mobile phone antenna based on reconfigurable parasitism. The problems that in the prior art, an antenna is large in size, and the use scene of the low-SAR characteristic of the antenna is single are mainly solved. According to the scheme, an antenna comprising an initial antenna structure and a reconfigurable parasitic structure is arranged at the lower right corner of a metal frame in an unfolded state of a folding screen mobile phone model, and an auxiliary frame parasitic branch knot and a plastic frame are arranged at the lower left corner and correspond to the initial antenna structure and the reconfigurable parasitic structure in position; wherein the initial antenna structure comprises an upper branch knot and a lower branch knot and is additionally provided with a matching circuit, and the working bandwidth of the initial antenna structure can cover two frequency bands; a reconfigurable parasitic branch knot is introduced on the basis of an initial antenna, and parasitics of different frequency bands are enabled to act respectively through switching of a switch. According to the invention, the size of the folding screen mobile phone antenna is significantly reduced, dual-band coverage can be realized, and the folding screen mobile phone antenna has low SAR performance in two states and can be used for 5G wireless communication.

Description

Technical Field

[0001] The present invention belongs to the field of antenna technology, and further relates to low SAR antenna technology, specifically a folding screen mobile phone antenna with low electromagnetic wave absorption ratio SAR (Specific Absorption Rate) based on reconfigurable parasitics, which can be used for 5G wireless communication. Background Art

[0002] With the continuous evolution of terminal devices, product designers are constantly optimizing smartphone form factors to meet user demands for larger screens and greater portability. This has led to the emergence of foldable phones, whose portability and large screens offer a superior user experience. Foldable phones are commonly available in two forms: unfolded and folded. During use, the constant shift in the phone's form causes the distance between the antenna and the human body to change, significantly altering the amount of electromagnetic energy absorbed by the human body. The latest 2020 guidelines from the International Commission on Non-Ionizing Radiation Protection (ICNIRP) stipulate that the 10g tissue peak-average SAR (SAR) must not exceed 2.0W / kg for the head and 4.0W / kg for the torso. When foldable phones are used close to the human body, the increased risk of electromagnetic exposure directly impacts the user's health and safety. Therefore, effectively reducing SAR values ​​to protect user health has become a pressing technical challenge in mobile phone antenna design.

[0003] Researchers have proposed many solutions for the design of low-SAR mobile phone antennas. For example, Zhang HH et al. proposed the concept of reverse current in their paper "Design of low-SAR mobile phone antenna: theory and applications" published in the journal IEEE Transactions on Antennas and Propagation, 69(2): 698-707, 2021, to reduce the radiation field of the antenna at the air-tissue interface, thereby reducing the SAR value of the human body. Based on the concept of reverse current, a metal frame mobile phone antenna was designed. The designed antenna's -6dB bandwidth can cover 830MHz-1040MHz and 1670MHz-2730MHz, and the measured normalized peak head SAR and human body SAR are both less than 2.0W / kg. However, although this antenna can reduce the SAR value of the entire LTE frequency band, it occupies a large space in the mobile phone, and the antenna form is limited to straight-screen smartphones, with a single usage scenario, and is not suitable for foldable screen mobile phones. Summary of the Invention

[0004] The purpose of the present invention is to address the shortcomings of the above-mentioned existing technologies and propose a low-SAR foldable screen mobile phone antenna based on reconfigurable parasitics, which mainly solves the problems of large size and single usage scenarios of existing foldable screen mobile phone antennas. First, an initial antenna is designed at the main frame position of the foldable screen mobile phone. Then, based on the working principle of the initial antenna in different frequency bands, a reconfigurable parasitic branch is introduced. By switching, the parasitics of different frequency bands are activated separately. Ultimately, while achieving antenna miniaturization, it can also cover dual frequency bands and ensure low SAR performance in both the unfolded and folded states of the foldable screen mobile phone.

[0005] To achieve the above objectives, the technical solutions of the present invention include the following:

[0006] A low-SAR foldable phone antenna based on reconfigurable parasitics includes a foldable phone model consisting of a metal floor 11, a dielectric substrate 12, and a metal frame 13. When the foldable phone model is unfolded, a final antenna comprising an initial antenna structure 5 and a reconfigurable parasitic structure 6 is disposed at the lower right corner of the metal frame 13. A sub-frame parasitic branch 10 and a plastic frame 9 are disposed at the lower left corner, corresponding to the initial antenna structure 5 and the reconfigurable parasitic structure 6, respectively. A clearance area W3 is provided between the final antenna and the metal floor 11.

[0007] The initial antenna structure 5 includes an upper branch and a lower branch, wherein the lower branch is provided with a feeding port 1 and a grounding port 2, and a first inductor element L1 and a first capacitor element C1 are connected in series at the feeding port 1, and a second capacitor element C2 is connected in parallel, and a second inductor element L2 and a third capacitor element C3 are connected in series at the grounding port 2;

[0008] The reconfigurable parasitic structure 6 includes an intermediate frequency parasitic stub 7, an intermediate frequency parasitic ground port 3, a high frequency parasitic stub 8, and a high frequency parasitic ground port 4. When the intermediate frequency parasitic ground port 3 is grounded, the high frequency parasitic ground port 4 is disconnected, and the intermediate frequency parasitic stub 7 takes over. When the intermediate frequency parasitic ground port 3 is disconnected, the high frequency parasitic ground port 4 is connected in series with a fourth capacitor element C4, and the high frequency parasitic stub 8 takes over.

[0009] The distance between the initial antenna structure 5 and the reconfigurable parasitic structure 6 is W4, and the distance between the initial antenna structure 5 and the metal frame is W2, and W2>W4.

[0010] Compared with the prior art, the present invention has the following advantages:

[0011] First, since the present invention is based on a folding screen mobile phone model, a slit design is performed on the frame to obtain a U-shaped antenna structure. By utilizing the upper and lower branches of the U-shaped structure, the antenna structure can cover dual frequency bands while achieving miniaturization.

[0012] Second, the present invention fully utilizes the advantages of the large frame of the foldable screen mobile phone. When the foldable screen mobile phone is in the folded state, the parasitic influence of the sub-frame on the antenna on the main frame is reduced by adopting a slit treatment on the sub-frame at the position corresponding to the antenna on the main frame. By analyzing the working principle of the antenna itself, reconfigurable parasitic branches are introduced and switched by a switch, so that the antenna has low SAR characteristics in both the open and folded states of the foldable screen mobile phone. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Schematic diagram of the structure of the initial antenna part of the present invention;

[0014] Figure 2 is a matching circuit diagram of the initial antenna in the present invention;

[0015] Figure 3 Schematic diagram of the overall structure of the final antenna in the present invention;

[0016] Figure 4 The diagram is a matching circuit diagram of the final antenna switch switching in the present invention; wherein (a) and (b) represent the intermediate frequency parasitic matching circuit and the high frequency parasitic matching circuit respectively;

[0017] Figure 5 Schematic diagrams of the position structure of the foldable screen mobile phone in different states of the present invention; (a) and (b) respectively represent the position structure schematic diagrams of the foldable screen mobile phone in the unfolded and folded states, and (c) represents the partial structure schematic diagram of the antenna part of the foldable screen mobile phone in the unfolded state;

[0018] Figure 6 is a return loss characteristic curve diagram of the initial antenna according to an embodiment of the present invention;

[0019] Figure 7 A graph showing the return loss characteristic curve of the final antenna provided by an embodiment of the present invention; (a) and (b) are the return loss parameter simulation results of the final antenna in the unfolded and folded states of a foldable screen mobile phone, respectively;

[0020] Figure 8 A total efficiency curve diagram of the final antenna provided by an embodiment of the present invention; (a) and (b) are simulation results of the total efficiency parameters of the final antenna in the unfolded and folded states of a foldable screen mobile phone, respectively;

[0021] Figure 9 Simulated SAR distribution diagrams of the final antenna provided by an embodiment of the present invention in different states of a foldable screen mobile phone. (a) and (b) respectively represent the simulated SAR distribution diagrams of the foldable screen mobile phone in the unfolded and folded states, when placed 5mm from a body model.

[0022] Figure 10Current distribution diagrams of the final antenna provided by an embodiment of the present invention at different frequency points; (a) and (b) represent the current distribution diagrams of the antenna at 1.75 GHz and 2.5 GHz frequencies, respectively. DETAILED DESCRIPTION

[0023] The present invention will be further described below with reference to the accompanying drawings.

[0024] Example 1: Refer to the attached Figure 1-5 The present invention proposes a low-SAR folding screen mobile phone antenna based on reconfigurable parasitics, including a folding screen mobile phone model composed of a metal floor 11, a dielectric substrate 12 and a metal frame 13; when the folding screen mobile phone model is unfolded, a final antenna including an initial antenna structure 5 and a reconfigurable parasitic structure 6 is set at the lower right corner of the metal frame 13; a sub-frame parasitic branch 10 and a plastic frame 9 are set at the lower left corner, and correspond to the positions of the initial antenna structure 5 and the reconfigurable parasitic structure 6 respectively; a clearance area W3 is provided between the final antenna and the metal floor 11, and the value of W3 in this embodiment is 1.5mm-2mm.

[0025] The above-mentioned initial antenna structure 5 includes an upper branch and a lower branch, wherein the lower branch is provided with a feeding port 1 and a grounding port 2, and a first inductor element L1 and a first capacitor element C1 are connected in series at the feeding port 1, and a second capacitor element C2 is connected in parallel, and a second inductor element L2 and a third capacitor element C3 are connected in series at the grounding port 2; in this embodiment, the length of the lower branch of the initial antenna structure 5 is 18mm-19.5mm, and the length of the upper branch is 61mm-61.3mm; the above-mentioned L1 and L2 are inductor elements of 9.1nH-9.15nH and 5.4nH-5.58nH respectively, and C1, C2 and C3 are capacitor elements of 0.6pF-0.7pF, 1.5pF-1.57pF and 1pF-1.11pF respectively; the above-mentioned C4 is a capacitor element of 1.1pF-1.2pF.

[0026] The above-mentioned reconfigurable parasitic structure 6 includes an intermediate frequency parasitic branch 7, an intermediate frequency parasitic ground port 3, a high frequency parasitic branch 8 and a high frequency parasitic ground port 4; wherein, when the intermediate frequency parasitic ground port 3 is grounded, the high frequency parasitic ground port 4 is disconnected, and the intermediate frequency parasitic branch 7 plays a role; when the intermediate frequency parasitic ground port 3 is disconnected, the high frequency parasitic ground port 4 is connected in series with the fourth capacitor element C4, and the high frequency parasitic branch 8 plays a role; in this embodiment, the length range of the intermediate frequency parasitic branch 7 in the above-mentioned reconfigurable parasitic structure 6 is set to 31.5mm-32mm; the length range of the high frequency parasitic branch 8 is set to 21mm-21.5mm; the functions of the intermediate frequency parasitic branch 7 and the high frequency parasitic branch 8 are to reduce the SAR values ​​of the initial antenna intermediate frequency and high frequency, respectively.

[0027] The distance between the initial antenna structure 5 and the reconfigurable parasitic structure 6 is W4, and the distance between the two and the metal frame is W2, and W2> W4. In this embodiment, the distance W4 is 1mm-1.5mm, and the distance W2 is 1.5mm-2mm.

[0028] The folding screen mobile phone model in this embodiment adopts a model with a length of L3, a width of W1, and a frame height of H3, where the value ranges of L3, W1 and H3 are 144.8mm-145mm, 162mm-163mm and 6.3mm-6.5mm respectively; the metal floor 11 of the folding screen mobile phone model has a spacing of 1.75mm-2mm when the mobile phone is in the folded state.

[0029] Example 2: The overall structure of the folding screen mobile phone antenna proposed in this example is the same as that of Example 1. Figure 1-5 , set preferred parameters, and give examples to further describe the present invention in detail.

[0030] Reference Figure 1 、 Figure 2 , Figure 1 The initial antenna structure designed for the present invention includes an antenna structure 5 , a feed port 1 and a ground port 2 . Figure 2 As the matching circuit of the initial antenna, an inductor element L1 of 9.15 nH and a capacitor element C1 of 0.7 pF are connected in series at the feeding port 1, and a capacitor element C2 of 1.57 pF is connected in parallel. An inductor element L2 of 5.58 nH and a capacitor element C3 of 1.11 pF are connected in series at the grounding port 2.

[0031] Reference Figure 3 The antenna structure finally realized by the present invention includes two parts, namely the initial antenna structure 5 and the reconfigurable parasitic structure 6; the reconfigurable parasitic structure 6 includes the intermediate frequency parasitic branch 7 and the intermediate frequency parasitic ground port 3, the high frequency parasitic branch 8 and the high frequency parasitic ground port 4.

[0032] Reference Figure 4 ,based on Figure 2 The matching circuit of the antenna of the present invention is given as the final matching circuit. Figure 4 (a) shows that when the ground port 3 is grounded, the ground port 4 is disconnected, and the intermediate frequency parasitic branch 7 is active; Figure 4 In (b), when the ground port 3 is disconnected, a capacitor element C4 of 1.2 pF is connected in series with the ground port 4 for grounding, and the high-frequency parasitic branch 8 comes into play.

[0033] Reference Figure 5 , describes the geometric structure and size of the antenna of the present invention in the unfolded and folded states of the folding screen mobile phone. Figure 5(a) and (b) are schematic diagrams of a foldable phone model in the unfolded and folded states, respectively. The phone model includes a metal floor 11, a metal frame 13, and a dielectric substrate 12. The dielectric constant of the dielectric substrate is In the unfolded state, the length L3 of the mobile phone model is 144.8mm, the width W1 is 162mm, and the frame height H3 is 6.3mm. In the folded state, the spacing W2 between the two metal floors is 2mm. The structure at the symmetrical position of the frame of the initial antenna structure 5 in the main frame is the secondary frame parasitic branch 10, and the structure at the symmetrical position of the frame of the parasitic branches 7 and 8 is the plastic frame 9. The dielectric constant of the plastic frame is is 3.5. Figure 5 (c) in the figure describes the specific dimensions of the antenna of the present invention. The antenna of the present invention comprises an initial antenna structure 5 and a reconfigurable parasitic stub 6. The length of the lower stub L6 of the initial structure is 19.5 mm, the length of the upper stubs (L7, L8, and L9) of the initial antenna structure is 61.3 mm, and the antenna clearance W3 is 2 mm. The length L4 of the intermediate frequency parasitic stub 7 is 32 mm, and the length L5 of the high frequency parasitic stub 8 is 21.5 mm. The spacing W2 between the initial antenna structure 5 and the reconfigurable parasitic stub 6 and the metal frame is 2 mm, and the spacing W4 between the initial antenna structure 5 and the reconfigurable parasitic stub 6 is 1 mm.

[0034] The effects of the present invention will be further described below in conjunction with simulation experiments.

[0035] 1. Simulation conditions:

[0036] Simulation 1. Using the commercial software CST Microwave Studio, the return loss parameters of the initial antenna in the above embodiment 2 are simulated and calculated. The results are as follows: Figure 6 shown.

[0037] from Figure 6 It can be seen that, with return loss < -6 dB as the standard, the bandwidth of the initial antenna in the present invention can cover the mid-frequency band of 1.7 GHz to 1.9 GHz and the high-frequency band of 2.3 GHz to 2.7 GHz.

[0038] Simulation 2. The return loss parameters of the antenna designed in the second embodiment are simulated and calculated using the commercial software CST Microwave Studio. The results are as follows: Figure 7 As shown, where:

[0039] Figure 7 (a) and (b) are the simulation results of the return loss parameters of the final antenna in the unfolded and folded states of the foldable screen mobile phone respectively; Figure 7It can be seen that with the return loss <-6dB as the standard, the bandwidth of the foldable screen mobile phone of the present invention in the unfolded state can cover the mid-frequency band of 1.7GHz-1.92GHz and the high-frequency band of 2.1GHz-2.65GHz respectively; the bandwidth in the folded state can cover the mid-frequency band of 1.71GHz-1.85GHz and the high-frequency band of 2.2GHz-2.6GHz.

[0040] Simulation 3. The total efficiency of the final antenna in the above embodiment is simulated and calculated using the commercial software CST Microwave Studio. The results are as follows: Figure 8 As shown, where:

[0041] Figure 8 (a) and (b) are the simulation results of the total efficiency parameters of the final antenna in the unfolded and folded states of the foldable screen mobile phone respectively; it can be seen from the figure that in the unfolded state of the foldable screen mobile phone, after calculation, the average total efficiency of the present invention in the two frequency bands of mid-frequency band 1.7GHz-1.92GHz and high-frequency band 2.1GHz-2.65GHz are 87.6% and 87.9% respectively; in the folded state, after calculation, the average total efficiency of the present invention in the two frequency bands of mid-frequency band 1.71GHz-1.85GHz and high-frequency band 2.2GHz-2.6GHz can reach 51.3% and 79% respectively.

[0042] Simulation 4. Using the commercial software CST Microwave Studio, the antenna in the second embodiment is simulated at a distance of 5 mm from the body model at 10 g in both the unfolded and folded states of the foldable screen mobile phone. The results are as follows: Figure 9 As shown, where: Figure 9 (a) shows the simulated distribution of SAR values ​​of the final antenna at 1.75 GHz. Figure 9 (b) in the figure is the simulated distribution result of the SAR value of the final antenna at 2.5 GHz. It can be seen from this that the SAR of the three surfaces (back, side, and bottom) of the final antenna are close to human tissue in the two states of the folding screen mobile phone. The simulation results of the 10g body SAR distribution at 1.75 GHz and 2.5 GHz in the two states of the folding screen mobile phone of the present invention are obtained.

[0043] Will Figure 9The SAR distribution simulation results for (a) and (b) were normalized, and the normalized SAR values ​​are summarized in Table 1. In the unfolded state, the present invention achieved a maximum normalized SAR of 1.058 W / kg at an intermediate frequency of 1.75 GHz and 1.503 W / kg at a high frequency of 2.5 GHz. In the folded state, the present invention achieved a maximum normalized SAR of 1.289 W / kg at an intermediate frequency of 1.75 GHz and 1.246 W / kg at a high frequency of 2.5 GHz. The normalized SAR value at 10g of body weight is well below 2 W / kg, meeting international SAR standards. The final designed antenna exhibits low SRA characteristics.

[0044] Table 1 summarizes the normalized SAR values ​​of the foldable screen mobile phone of the present invention when placed at a distance of 5 mm from the body model in both the unfolded and folded states. The details are as follows:

[0045] Table 1

[0046]

[0047] Simulation 5. The current distribution of the final antenna in the above embodiment 2 at the medium and high frequency bands is simulated using the commercial software CST Microwave Studio. Figure 10 As shown, where: Figure 10 (a) is the final antenna current distribution at 1.75 GHz; Figure 10 (b) is the final current distribution of the antenna at 2.5 GHz;

[0048] from Figure 10 As can be seen, in the IF parasitic operating mode, the current in the IF parasitic branch is in the opposite direction to the current in the upper branch of the initial antenna. These opposite currents cancel each other out. In the HF parasitic operating mode, the current in the HF parasitic branch is in the same direction as the current in the lower branch of the initial antenna. As can be seen from the figure, the unidirectional current in the HF parasitic branch evens out the current hotspots on the initial antenna, reducing the concentration of current hotspots on the initial antenna and achieving a more uniform current distribution on the initial antenna, thereby reducing the high-frequency SAR value.

[0049] The above simulation analysis demonstrates the correctness and effectiveness of the proposed method. The proposed low-SAR foldable phone antenna based on a reconfigurable parasitic design not only miniaturizes the antenna but also enables dual-band operation. Most importantly, it maintains low SAR performance in both foldable phone states.

[0050] Any portions of the present invention not described in detail are common knowledge among those skilled in the art. The foregoing is merely an embodiment of the present invention and does not constitute any limitation thereto. It is apparent that, after understanding the content and principles of the present invention, those skilled in the art may make various modifications and alterations in form and detail without departing from the principles and structure of the present invention. However, such modifications and alterations based on the concepts of the present invention remain within the scope of protection of the claims of the present invention.

Claims

1. A low SAR folding screen mobile phone antenna based on reconfigurable parasitics, comprising a folding screen mobile phone model consisting of a metal floor (11), a dielectric substrate (12) and a metal frame (13), characterized in that: In the unfolded state of the folding screen mobile phone model, a final antenna including an initial antenna structure (5) and a reconfigurable parasitic structure (6) is provided at the lower right corner of the metal frame (13); a sub-frame parasitic branch (10) and a plastic frame (9) are provided at the lower left corner, and correspond to the positions of the initial antenna structure (5) and the reconfigurable parasitic structure (6) respectively; a clearance area W3 is provided between the final antenna and the metal floor (11); The initial antenna structure (5) comprises an upper branch and a lower branch, wherein the lower branch is provided with a feeding port (1) and a grounding port (2), and a first inductance element L1 and a first capacitance element C1 are connected in series at the feeding port (1), and a second capacitance element C2 is connected in parallel, and a second inductance element L2 and a third capacitance element C3 are connected in series at the grounding port (2); The reconfigurable parasitic structure (6) comprises an intermediate frequency parasitic branch (7), an intermediate frequency parasitic grounding port (3), a high frequency parasitic branch (8) and a high frequency parasitic grounding port (4); wherein, when the intermediate frequency parasitic grounding port (3) is grounded, the high frequency parasitic grounding port (4) is disconnected, and the intermediate frequency parasitic branch (7) takes over; when the intermediate frequency parasitic grounding port (3) is disconnected, the high frequency parasitic grounding port (4) is connected in series with a fourth capacitor element C4, and the high frequency parasitic branch (8) takes over; The distance between the initial antenna structure (5) and the reconfigurable parasitic structure (6) is W4, and the distance between the initial antenna structure (5) and the metal frame is W2, and W2>W4.

2. The mobile phone antenna according to claim 1, characterized in that: The folding screen mobile phone model adopts a model with a length of L3, a width of W1, and a frame height of H3, where the value ranges of L3, W1 and H3 are 144.8mm-145mm, 162mm-163mm and 6.3mm-6.5mm respectively.

3. The mobile phone antenna according to claim 1, characterized in that: The metal floor (11) of the folding screen mobile phone model has a spacing of 1.75 mm to 2 mm when the mobile phone is in the folded state.

4. The mobile phone antenna according to claim 1, wherein: The antenna clearance is W3, which is 1.5mm-2mm.

5. The mobile phone antenna according to claim 1, characterized in that: In the initial antenna structure (5), the length of the lower branch is 18 mm to 19.5 mm; the length of the upper branch is 61 mm to 61.3 mm.

6. The mobile phone antenna according to claim 1, characterized in that: The L1 and L2 are inductance elements of 9.1nH-9.15nH and 5.4nH-5.58nH respectively, and the C1, C2 and C3 are capacitance elements of 0.6pF-0.7pF, 1.5pF-1.57pF and 1pF-1.11pF respectively; the C4 is a capacitance element of 1.1pF-1.2pF.

7. The mobile phone antenna according to claim 1, characterized in that: In the reconfigurable parasitic structure (6), the length of the intermediate frequency parasitic branch (7) is 31.5 mm to 32 mm, and the length of the high frequency parasitic branch (8) is 21 mm to 21.5 mm.

8. The mobile phone antenna according to claim 1, characterized in that: The intermediate frequency parasitic branch (7) and the high frequency parasitic branch (8) respectively play the role of reducing the SAR values ​​of the intermediate frequency and high frequency of the initial antenna.

9. The mobile phone antenna according to claim 1, characterized in that: The distance W4 between the initial antenna structure (5) and the reconfigurable parasitic structure (6) is 1 mm to 1.5 mm, and the distance W2 between the initial antenna structure (5) and the metal frame is 1.5 mm to 2 mm.

Images