Minimally invasive planar ablation antenna

Abstract

The application discloses a minimally invasive planar ablation antenna, which comprises a microstrip line, an SICL structure and a radiator; the microstrip line is connected with the SICL structure through a first via hole, and the SICL structure is matched with the radiator through a pi matching network; and the radiator is in a serpentine wiring structure. The application designs a planar ablation needle with a very small cross-sectional area, which is different from an ablation needle based on a coaxial line structure and has the advantage of low cost based on PCB processing. The application proposes a method for constructing a pi matching network in the planar ablation antenna, and directly matches the radiator with the SICL, so that the ablation needle has a free length.

Description

Technical Field

[0001] This invention belongs to the field of ablation needle design technology, specifically relating to a minimally invasive planar ablation needle. Background Technology

[0002] In recent years, as traditional surgical tumor resection methods are not suitable for some patients, relatively low-cost microwave ablation technology has been rapidly developed and applied. Microwave ablation therapy involves inserting rigid, semi-rigid, or flexible antennas subcutaneously into the patient's body and releasing microwave power in a local area to cause cell necrosis at high temperatures, thereby eliminating the tumor. Compared with radiofrequency ablation, microwave ablation is less prone to tissue springing and has a theoretically wider power density field and a correspondingly larger active heating area.

[0003] The key to invasive microwave hyperthermia lies in the design of the ablation antenna. An ablation antenna needs to possess the following characteristics: a localized ablation area, a miniature size, and low return loss. Coaxial baluns are widely used in monopole, dipole, or slot antennas to generate high impedance at the far end to suppress current on the outer conductor surface, thereby enhancing the concentration of ablation. However, coaxial baluns increase the antenna's outer diameter and invasiveness, which is not suitable for minimally invasive surgery. Therefore, balun-less spiral antennas have been proposed, including monopole spiral antennas and dipole spiral antennas. The monopole spiral antenna operates at the second resonant frequency of the spiral, causing the current minimum to occur at the feed point, achieving high feed impedance. Simultaneously, to achieve impedance matching and suppress return loss, this antenna also employs a matching method that constructs a pi network internally. The dipole spiral antenna extends the outer and inner conductors of the coaxial line to three-quarters and one-quarter of the wavelength, respectively. The current direction of the spiral aligns with the current in the extended inner conductor at one-quarter of the wavelength at the feed point, resulting in relatively low input impedance and thus suppressing current on the outer conductor. However, helical antennas based on coaxial structures are characterized by complex manufacturing, high cost, and unsuitability for mass production. Therefore, helical antennas based on SICL (Substrate Integrated Coaxial Line) have been proposed. These utilize printed circuit board technology and offer advantages such as small size and low cost. However, both types of antennas employ a back-end matching method, using a microstrip line or grounded coplanar waveguide to match the portion of the SICL with a high virtual impedance to the antenna end with a 50-ohm characteristic impedance coaxial line. While this matching method is effective, it lacks theoretical support, reducing the degree of freedom in antenna design.

[0004] In an existing microwave ablation antenna, the structure is as follows: It has a body comprising an inner conductor, which is sequentially covered by a dielectric, an outer conductor, and a shell. The body extends axially, with one end for connecting to a coaxial cable and the other end serving as the antenna end. At the antenna end, the outer conductor and inner conductor protrude from the dielectric and are welded together. Three circumferential slits are cut into the outer conductor near the antenna end. A dielectric perforated section and a thickened outer conductor extending inward from the outer conductor are sequentially arranged axially on the dielectric in the middle of the body. The disadvantages of this ablation antenna are: integrating a pi matching section structure into a coaxial-based ablation antenna is complex, costly, and unsuitable for mass production; the thinner the inner conductor, the higher the required processing precision, hindering antenna miniaturization; and the design freedom is limited by manufacturing conditions.

[0005] Another existing microwave ablation antenna includes a substrate-integrated coaxial cable structure, a matching structure, a radiating structure, and a protective sleeve structure. The matching structure is connected to the radiating structure via the substrate-integrated coaxial cable structure, and the protective sleeve structure surrounds both the substrate-integrated coaxial cable structure and the radiating structure. The disadvantages of this type of ablation needle are: its cross-sectional area is relatively large, reaching a width of 3.5 mm, which is too large for its length, making it unsuitable for minimally invasive surgery; while using microstrip lines to match the antenna front end in the ablation needle design is effective, it lacks analytical methods, limiting the design freedom. Furthermore, matching difficulties may arise when the length of the ablation needle changes. Summary of the Invention

[0006] In view of the above-mentioned shortcomings in the prior art, the minimally invasive planar ablation antenna provided by the present invention solves the problems of limited length of freedom, complex processing, and unfavorable miniaturization of existing ablation antenna designs.

[0007] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows: a minimally invasive planar ablation antenna, comprising a microstrip line, a SICL structure, and a radiator;

[0008] The microstrip line is connected to the SICL structure through a first via, and the SICL structure is matched to the radiator through a pi matching network.

[0009] The radiator has a serpentine wiring structure.

[0010] Furthermore, the ablation antenna is a laminated structure, comprising a first metal layer, a second metal layer, a third metal layer, a fourth metal layer, a first FR4 plate, a second FR4 plate, and a curing sheet;

[0011] The first and second FR4 layers are bonded together using a curing sheet.

[0012] The first metal layer is disposed on the upper side of the first FR4 plate, the second metal layer is disposed between the first FR4 plate and the cured sheet, the third metal layer is disposed between the cured sheet and the second FR4 plate, and the fourth metal layer is disposed on the lower side of the second FR4 plate.

[0013] Furthermore, for the SICL structure, the first metal layer and the fourth metal layer constitute the upper wall and the lower wall of the SICL structure. Two rows of second vias are provided on both the first metal layer and the fourth metal layer. The two rows of second vias constitute the two side walls of the SICL structure. The side walls, the upper wall and the lower wall together constitute the outer conductor of the SICL structure.

[0014] The second metal layer and the third metal layer constitute the three-segment structure of the SICL structure, including a standard transmission line segment, a capacitor segment, and an inductor segment; wherein, the third metal layer portion to the left of the second metal layer serves as the standard transmission line segment, the second metal layer serves as the capacitor segment, and the third metal layer portion to the right of the second metal layer serves as the inductor segment.

[0015] The third metal layer serves as the inner conductor of the SICL structure;

[0016] The capacitor segment and the inductor segment constitute the pi matching network.

[0017] Furthermore, the SICL structure serves as the transmission line of the ablation antenna, and its characteristic impedance is:

[0018] Z = (L / C) 1 / 2

[0019] In the formula, L is the line inductance of the transmission line, and C is the line capacitance of the transmission line;

[0020] in, L1, L2, and L3 are the component inductances related to the upper and lower walls of the transmission line and the SICL structure, respectively, as well as the component inductances of the side walls of the SICL structure. Their calculation formulas are as follows:

[0021]

[0022]

[0023]

[0024] The line capacitance C is:

[0025]

[0026] In the formula, g1 and g2 are the distances from the inner layer trace of the rectangular transmission line to the upper board and the distance from the inner layer trace of the rectangular transmission line to the lower board, respectively; μ is the permeability; w is the width of the inner layer trace of the rectangular transmission line; d is the distance from the inner layer trace of the rectangular transmission line to the sidewall; π is pi; ε is the dielectric constant; and t is the thickness of the inner layer trace of the rectangular transmission line.

[0027] Furthermore, the serpentine trace structure of the radiator is disposed on the third metal layer, including lateral traces, serpentine traces, and extended traces;

[0028] One end of the lateral trace extends from the inner conductor of the SICL structure, and the other end is connected to one end of the serpentine trace, the other end of which is connected to the extension trace.

[0029] Furthermore, the unfolded length of the radiator is λ / 2.

[0030] Furthermore, the microstrip line is connected to the third metal layer of the SICL structure through a first via;

[0031] A cylindrical cavity is provided between the first via and the fourth metal layer of the SICL structure;

[0032] A rectangular cavity is provided between the microstrip line and the first metal layer of the SICL structure.

[0033] Furthermore, the microstrip line and the first via of the ablation antenna are disposed in a detachable aluminum cavity, and an SMA probe is provided to connect with the SICL structure. The SICL structure and the radiator of the ablation antenna are covered with heat shrink tubing.

[0034] The beneficial effects of this invention are as follows:

[0035] (1) The matching method of integrating the pi network in the planar ablation needle of this invention is in line with the characteristics of PCB structure, which is simple and easy to implement without additional processing costs. At the same time, since the processing of coaxial cable requires laser cutting technology, the smaller the antenna size, the more difficult it is to process. However, in the PCB structure, the reduction of line width will not significantly increase the cost. Therefore, it is possible to design an extremely small ablation needle that can be used for small animal experiments.

[0036] (2) This invention is the first to apply the pi matching section to a planar ablation antenna, and the matching is performed at the far end of the antenna. It has analytical method support, which enables the ablation antenna to ensure ideal return loss at any design length and has a very high degree of design freedom in terms of size.

[0037] (3) The ablation antenna of the present invention has an extremely small insertion outer diameter of 1.8mm×0.6mm, which is in line with the characteristics of minimally invasive surgery. As a disposable ablation needle, it has the advantage of being suitable for mass production. Attached Figure Description

[0038] Figure 1 The overall structure diagram of the ablation antenna provided by the present invention.

[0039] Figure 2 This is a schematic diagram of the ablation antenna laminate structure provided by the present invention.

[0040] Figure 3 This is a cross-sectional view of the single eccentric coaxial line provided by the present invention.

[0041] Figure 4 The segmented SICL structure diagram provided by the present invention.

[0042] Figure 5 This is a structural diagram of the radiator provided by the present invention.

[0043] Figure 6 This is a structural diagram of the transition section provided by the present invention.

[0044] Figure 7 A physical diagram of the ablation antenna provided by this invention.

[0045] Figure 8 The simulation results of S11 under different SICL degrees provided by this invention.

[0046] Figure 9 Simulation and measurement results of antenna S11 provided by this invention.

[0047] Figure 10 Isothermal curves for ablation at different times provided by the present invention.

[0048] Figure 11 The diagram shows the actual ablation effect provided by this invention.

[0049] The components are: 1. First metal layer; 2. Second metal layer; 3. Third metal layer; 4. Fourth metal layer; 5. First FR4 board; 6. Cured sheet; 7. Second FR4 board; 8. Horizontal trace; 9. Serpentine trace; 10. Vertical edge of serpentine trace; 11. Horizontal edge of serpentine trace; 12. Transition arc; 13. Extension trace; 14. Second via; 15. Standard transmission line segment; 16. Capacitor segment; 17. Inductor segment; 18. Microstrip line; 19. SICL structure; 20. Radiator; 21. First via; 22. Cylindrical cavity; 23. Rectangular cavity; 24. Aluminum cavity; 25. SMA probe; 26. Heat shrink tubing. Detailed Implementation

[0050] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0051] This invention provides a minimally invasive planar ablation antenna, such as... Figure 1 As shown, it includes a microstrip line 18, a SICL structure 19, and a radiator 20;

[0052] The microstrip line 18 is connected to the SICL structure 19 through the first via 21, and the SICL structure 19 is matched to the radiator 20 through the pi matching network;

[0053] The radiator 20 has a serpentine wiring structure.

[0054] In this embodiment of the invention, the ablation antenna is a laminated structure, such as... Figure 2 As shown, it includes a first metal layer 1, a second metal layer 2, a third metal layer 3, a fourth metal layer 4, a first FR4 board 5, a second FR4 board 7, and a cured sheet 6;

[0055] The first FR4 board 5 and the second FR4 board 7 are bonded together by a curing sheet 6.

[0056] The first metal layer 1 is disposed on the upper side of the first FR4 plate 5, the second metal layer 2 is disposed between the first FR4 plate 5 and the cured sheet 6, the third metal layer 3 is disposed between the cured sheet 6 and the second FR4 plate 7, and the fourth metal layer 4 is disposed on the lower side of the second FR4 plate 7.

[0057] In this embodiment, the ablation antenna formed by the above-mentioned laminated structure operates at a frequency of 2.45 GHz. Based on this, the thickness of the first to fourth metal layers is 0.035 mm, the thickness of the first RF4 plate and the second RF4 plate is 0.2 mm, and the thickness of the curing sheet is 0.13 mm. RF4 is a common flame-retardant laminate material made of glass fiber. In the composition of the above-mentioned laminated structure, the dielectric constant of the electrolyte is 4.3, and the tangent loss is 0.02.

[0058] Based on the composition of the above-mentioned laminated structure, the design of the ablation antenna in this embodiment includes the following steps:

[0059] Step 1: Design the radiator by using a planar serpentine path to simulate a three-dimensional spiral. The fundamental purpose is to make the monopoles extending from SICL more compact at the front end, thereby making the radiation area more concentrated.

[0060] Step 2: Design the feed structure and matching section. SICL structure 19 is used as the transmission line for the feed, and its characteristic impedance is determined to be 50Ω. The matching section needs to impedance match the transmission line with the antenna, using a pi network.

[0061] Step 3: Transition section design. Add a microstrip line 18 to the back end of the SICL and connect it to the inner conductor of the SICL structure 19 through the first via 21 to determine the overall structure of the antenna.

[0062] Specifically, in the implementation of this invention, in the structural design of the SICL structure 19, the first metal layer 1 and the fourth metal layer 4 constitute the upper wall and lower wall of the SICL structure 19. Two rows of second vias 14 are provided on both the first metal layer 1 and the fourth metal layer 4. The two rows of second vias 14 constitute the two side walls of the SICL structure 19. The side walls, the upper wall and the lower wall together constitute the outer conductor of the SICL structure 19. The third metal layer 3 serves as the inner conductor of the SICL structure 19.

[0063] Based on the above SICL structure 19 design, when designing the feed structure and matching section, the SICL structure 19 is used as a transmission line, and its characteristic impedance is determined to be 50Ω. The matching section requires impedance matching between the transmission line and the antenna. In this embodiment, a pi matching network is selected for matching. Figure 3 As shown, the SICL structure 19 used in the ablation antenna is essentially a single-eccentric rectangular line (symmetrical left and right but asymmetrical up and down), and its characteristic impedance is:

[0064] Z = (L / C) 1 / 2

[0065] In the formula, L is the line inductance of the transmission line, and C is the line capacitance of the transmission line;

[0066] in, L1, L2, and L3 are the component inductances related to the upper and lower walls of the transmission line and the SICL structure, respectively, as well as the component inductances of the side walls of the SICL structure. Their calculation formulas are as follows:

[0067]

[0068]

[0069]

[0070] The line capacitance C is:

[0071]

[0072] In the formula, g1 and g2 are the distances from the inner layer trace of the rectangular transmission line to the upper board and the distance from the inner layer trace of the rectangular transmission line to the lower board, respectively; μ is the permeability; w is the width of the inner layer trace of the rectangular transmission line; d is the distance from the inner layer trace of the rectangular transmission line to the sidewall; π is pi; ε is the dielectric constant; and t is the thickness of the inner layer trace of the rectangular transmission line.

[0073] In this embodiment, as Figure 4 A top view of the inner metal layers of a three-segment SICL structure 19 is shown. The second metal layer 2 and the third metal layer 3 constitute the three-segment structure of the SICL structure 19, including a standard transmission line segment 15, a capacitor segment 16, and an inductor segment 17. The left side of the third metal layer of the second metal layer 2 serves as the standard transmission segment 15, the second metal layer 2 serves as the capacitor segment 16, and the right side of the third metal layer 2 serves as the inductor segment 17. The capacitor segment 16 and the inductor segment 17 constitute the pi matching network.

[0074] Specifically, using the above formula, the standard characteristic impedance Z of the standard transmission segment 15 is determined to be 50Ω. At this time, the line width of the third metal layer 3 trace (i.e., the inner conductor of SICL) is 0.187mm. A short transmission line with low input impedance is equivalent to a parallel capacitor. Therefore, when setting the capacitor segment 16, a rectangular copper sheet with the same width as SICL and a length of 9.98mm is added to the second metal layer 2, reducing the value of g1 and thus increasing the line capacitance. A short transmission line with high input impedance is equivalent to a series inductor. When designing the inductor segment 17, the width of the third metal layer 3 trace is reduced from 0.187mm to 0.107mm, increasing its characteristic impedance and achieving the effect of an inductor. The length of the inductor segment 17 is 16.19mm. The antenna impedance can be matched to 50Ω using a pi matching network composed of capacitors and inductors, consistent with the characteristic impedance of the transmission line.

[0075] In this embodiment of the invention, the design of the radiator 20 is as follows: Figure 5 As shown, the serpentine trace structure of the radiator 20 is disposed on the third metal layer 3, including lateral traces 8, serpentine traces 9 and extension traces 13; one end of the lateral trace 8 extends from the inner conductor of the SICL structure 19, and the other end is connected to one end of the serpentine trace 9, and the other end of the serpentine trace 9 is connected to the extension trace 13.

[0076] In this embodiment, in the structure of the radiator 20, the length of the transverse trace 8 is 2.8 mm, the serpentine trace 9 simulates a three-dimensional spiral, the fundamental purpose of which is to make the monopole extending from the SICL structure 19 more compact at the front end, thereby making the radiation area more concentrated. The length of the longitudinal side 10 of the serpentine trace is 1.6 mm, the length of the transverse side 11 of the serpentine trace is 0.5 mm, the radius of the transition arc 12 is 0.187 mm, and the length of the extension trace 13 is 0.7 mm.

[0077] In this embodiment, the unfolded length of the radiator 20 is ensured to be λ / 2, corresponding to its second resonant frequency. The high impedance suppresses the return current on the outer conductor, thereby eliminating the comet tail effect.

[0078] In this embodiment of the invention, the design of the transition section is as follows: Figure 6 As shown, the microstrip line 18 and the first via 21 form a transition section, wherein the microstrip line 18 is connected to the third metal layer 3 of the SICL structure 19 through the first via 21.

[0079] A cylindrical cavity 22 is provided between the first via 21 and the fourth metal layer 4 of the SICL structure 19;

[0080] A rectangular cavity 23 is provided between the microstrip line 18 and the first metal layer 1 of the SICL structure 19.

[0081] In this embodiment, the length of the microstrip line 18 is 14.5 mm, the diameter of the first via is 0.4 mm, and the diameter of the cylindrical cavity 22 is 1 mm to achieve electrical isolation and prevent short circuits; at the same time, the microstrip line 18 and the first metal layer 1 are also electrically isolated by a matrix cavity.

[0082] In this embodiment, the microstrip line 18 only serves to facilitate the connection between the antenna and the coaxial adapter and to fix it to the cavity; it does not participate in impedance matching, therefore its characteristic impedance must also be 50Ω. In practical applications, the antenna needs to be connected to the microwave source via a coaxial line. The transmission structure between the antenna and the source consists of a coaxial line, a coaxial adapter, a microstrip line, and a SICL. Since the characteristic impedance of each part is 50Ω, this transmission structure can be approximated as a continuous transmission line. As long as the material strength allows, the lengths of the SICL and the microstrip line can be freely chosen, and the cross-sectional area of ​​the finally designed antenna is only 1.8mm × 0.6mm.

[0083] In this embodiment of the invention, the formed ablation antenna structure is as follows: Figure 7As shown, the ablation antenna is disposed in the detachable aluminum cavity 24, and the SMA probe 25 is connected to the SICL structure 19. The exposed part of the ablation antenna is covered with heat shrink tubing 26. Specifically, the microstrip line 18 and the first via 21 are disposed in the detachable aluminum cavity 24, and the exposed part of the ablation antenna, including the SICL structure 19 and the radiator 20, is covered with heat shrink tubing 26.

[0084] Specifically, due to the advantages of PCB mass production, its unit cost is very low. To facilitate the grounding of the antenna's outer conductor, a detachable aluminum cavity 24 is fabricated and an SMA probe 25 is fixed therein, enabling it to connect to the coaxial cable. At the same time, a PET heat shrink tubing 26 is fitted over the exposed part of the ablation antenna to prevent heat flow from flowing back along the metal wall, thus avoiding unnecessary tissue thermal damage. It also serves to simulate the adhesion between the metal and tissue after heating, facilitating removal after ablation.

[0085] Example 2:

[0086] This invention provides a simulation example of the ablation antenna in Embodiment 1:

[0087] The reflection coefficient (S11) of the antenna was simulated in ANSYS HFSS. To verify the effect of antenna length on return loss, the S11 curve was tested under different values ​​of SICL length. (See attached image) Figure 8 As shown in the figure, the length of SICL and the length of the microstrip line have almost no impact on the antenna performance. In the simulation results, S11 is stable below 30dB.

[0088] Appendix Figure 9 The simulated and actual measured S11 curves are shown, where the SICL structure length is 50 mm, the microstrip line length is 14.5 mm, and the dielectric constant of the pig liver material is 45.2 at 37 degrees Celsius. The figure shows that the simulated S11 value at 2.45 GHz is -30.48 dB, while the actual antenna's S11 measured by a vector network analyzer is -20.73 dB. Due to unavoidable errors in antenna manufacturing, the expected frequency of S11 deviates slightly, but the return loss at 2.45 GHz is still below 20 dB, meaning that over 99% of the energy output from the microwave source enters the antenna.

[0089] The isotherm curves obtained from COMSOL Multiphysics are as follows: Figure 10 As shown, the ablation region of the antenna model is spherically symmetrical and concentrated at the antenna front end. To further verify its effectiveness, a physical test was conducted, with a microwave source feeding 10W of power and heating for 300 seconds. The actual ablation effect is shown in the attached figure. Figure 11 As shown.

[0090] In the description of this invention, it should be understood that the terms "center," "thickness," "upper," "lower," "horizontal," "top," "bottom," "inner," "outer," and "radial," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying the relative importance or the number of technical features implicitly specified. Therefore, a feature defined by "first," "second," and "third" may explicitly or implicitly include one or more of that feature.

[0091] Specific embodiments have been used to illustrate the principles and implementation methods of this invention. The descriptions of the embodiments above are only for the purpose of helping to understand the method and core ideas of this invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this invention. Therefore, the content of this specification should not be construed as a limitation of this invention.

[0092] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A minimally invasive planar ablation antenna, characterized by, Including microstrip lines (18), SICL structures (19), and radiators (20); The microstrip line (18) is connected to the SICL structure (19) through a first via (21), and the SICL structure (19) is matched to the radiator (20) through a pi matching network; The radiator (20) has a serpentine wiring structure; The ablation antenna is a laminated structure, including a first metal layer (1), a second metal layer (2), a third metal layer (3), a fourth metal layer (4), a first FR4 plate (5), a second FR4 plate (7), and a curing sheet (6). The first FR4 board (5) and the second FR4 board (7) are bonded together by a curing sheet (6). The first metal layer (1) is disposed on the upper side of the first FR4 plate (5), the second metal layer (2) is disposed between the first FR4 plate (5) and the curing sheet (6), the third metal layer (3) is disposed between the curing sheet (6) and the second FR4 plate (7), and the fourth metal layer (4) is disposed on the lower side of the second FR4 plate (7); For the SICL structure (19), the first metal layer (1) and the fourth metal layer (4) constitute the upper wall and the lower wall of the SICL structure (19). Two rows of second vias (14) are provided on the first metal layer (1) and the fourth metal layer (4). The two rows of second vias (14) constitute the two side walls of the SICL structure (19). The side walls, the upper wall and the lower wall together constitute the outer conductor of the SICL structure (19). The second metal layer (2) and the third metal layer (3) constitute the three-segment structure of the SICL structure (19), including a standard transmission line segment (15), a capacitor segment (16) and an inductor segment (17); wherein, the third metal layer portion on the left side of the second metal layer (2) serves as the standard transmission line segment (15), the second metal layer (2) serves as the capacitor segment (16), and the third metal layer portion on the right side of the second metal layer (2) serves as the inductor segment (17). The third metal layer (3) serves as the inner conductor of the SICL structure (19); The capacitor segment (16) and the inductor segment (17) constitute the pi matching network; The SICL structure serves as the transmission line for the ablation antenna, and its characteristic impedance is: wherein is the line inductance of the transmission line, is the line capacitance of the transmission line; in, , The inductances of the components related to the transmission line and the upper and lower walls of the SICL structure, as well as the inductances of the components on the side walls of the SICL structure, are calculated using the following formulas: The line capacitance for: In the formula, These represent the distances from the inner layer trace of the rectangular transmission line to the upper board and the distances from the inner layer trace of the rectangular transmission line to the lower board, respectively. Permeability, This refers to the width of the inner layer trace of the rectangular transmission line. This represents the distance from the inner layer trace of the rectangular transmission line to the sidewall. Pi Where is the dielectric constant. This represents the thickness of the inner layer trace of the rectangular transmission line.

2. The minimally invasive planar ablation antenna according to claim 1, characterized in that, The serpentine trace structure of the radiator (20) is disposed on the third metal layer (3), including lateral traces (8), serpentine traces (9) and extended traces (13). One end of the lateral trace (8) extends from the inner conductor of the SICL structure (19), and the other end is connected to one end of the serpentine trace (9), the other end of which is connected to the extension trace (13).

3. The minimally invasive planar ablation antenna of claim 2, wherein, The spread length of the radiator (20) is .

4. The minimally invasive planar ablation antenna of claim 1, wherein, The microstrip line (18) is connected to the third metal layer (3) of the SICL structure (19) through a first via (21); A cylindrical cavity (22) is provided between the first via (21) and the fourth metal layer (4) of the SICL structure (19). A rectangular cavity (23) is provided between the microstrip line (18) and the first metal layer (1) of the SICL structure (19).

5. The minimally invasive planar ablation antenna of claim 1, wherein, The microstrip line (18) and the first via (21) of the ablation antenna are set inside the detachable aluminum cavity (24), and the SMA probe (25) is connected to the SICL structure (19). The SICL structure (19) and the radiator (20) of the ablation antenna are covered with heat shrink tubing (26).

Images