Design method of one-to-four filtering power divider applied to low frequency band

Abstract

The invention discloses a design method of a one-to-four filtering power divider applied to a low frequency band. The design method comprises the following steps: designing a Wilkinson power divider prototype; calculating order, source end impedance and load impedance which need to be matched by using a multi-section stepped impedance matching theory; calculating the impedance transformation ratio of the Chebyshev low-pass filtering impedance matching network; designing a Chebyshev low-pass filtering impedance matching network, and calculating a lumped element parameter value in the Chebyshev low-pass filtering impedance matching network; lumped element parameter values in the Chebyshev low-pass filtering impedance matching network are converted into parameter values corresponding to distributed parameters; and verifying whether the distributed parameters are reasonable or not, and if yes, forming design parameters of the one-to-four filtering power divider. The method has the remarkable effects that the functions of performing power distribution on signals and filtering clutters can be realized, mutual interference among the signals is reduced, and wireless communication resources are optimized.

Description

Technical Field

[0001] The present invention relates to the field of microwave radio frequency technology, and particularly to a design method of a one-to-four filtering power divider applied in a power distribution system of a 6G low-frequency wireless communication base station. Background Art

[0002] With the evolution of wireless communication technology towards the 6G standard, as a core subsystem of the radio frequency front end, the multi-dimensional performance indicators of the power distribution network are facing intergenerational leap requirements. In typical 6G scenarios such as Massive MIMO arrays, ultra-dense networking, and full-spectrum access, the power distribution system needs to achieve joint optimization of multi-dimensional resources (spectrum / space / energy) while meeting the stringent requirements of ultra-low profile, wideband reconfiguration, and high power tolerance.

[0003] Based on the base station radio frequency indicators defined in the 3GPP TS 38.141 V17 specification, modern power distribution architectures need to solve three core contradictions: First, the balance problem between topological complexity and space efficiency; second, the collaborative design problem of broadband impedance matching and out-of-band rejection; third, thermal stability and intermodulation distortion suppression under high power density.

[0004] To address the above problems, the present invention proposes a heterogeneous integrated one-to-four filtering power divider based on the concept of hybrid-domain collaborative design. By transforming the Chebyshev low-pass prototype into a distributed structure through the generalized Richards transformation, and constructing an N-order low-pass impedance transformation network through the expansion formula of Chebyshev polynomials, the lumped-distributed hybrid mapping technology is innovatively adopted to achieve a double breakthrough in functional integration and structural compactness. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a design method of a one-to-four filtering power divider for low-frequency applications. Based on the Wilkinson power divider, this method uses the combined ladder impedance matching theory and Chebyshev low-pass filter impedance matching network to achieve the functions of power distribution of signals and filtering out clutter, so as to reduce the mutual interference between signals and optimize the resources of wireless communication.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A design method of a one-to-four filtering power divider for low-frequency applications, which is characterized in that it includes the following steps:

[0008] Step 1, design the Wilkinson power divider prototype;

[0009] Step 2, based on the Wilkinson power divider prototype, use the multi-section ladder impedance matching theory to calculate the number of stages, source impedance, and load impedance to be matched;

[0010] Step 3: Calculate the impedance transformation ratio of the Chebyshev low-pass filter impedance matching network using the source impedance and load impedance calculated in Step 2;

[0011] Step 4: Design the Chebyshev low-pass filter impedance matching network using the insertion loss method according to the design requirements, and calculate the lumped element parameter values in the Chebyshev low-pass filter impedance matching network;

[0012] Step 5: Convert the lumped element parameter values in the Chebyshev low-pass filter impedance matching network into the corresponding parameter values of distributed parameters;

[0013] Step 6: Verify whether the distributed parameters are reasonable. If so, form the design parameters of a one-to-four filter power divider; otherwise, return to Step 5.

[0014] Further, the specific steps for designing the Wilkinson power divider prototype in Step 1 are as follows:

[0015] Based on the input port power P1 of the Wilkinson power divider under ideal conditions and the power P2 and P3 of the two output ports, calculate the load impedances Z1 and Z2 between the input port and the two output ports respectively;

[0016] Based on the load impedances Z1 and Z2, according to the formula Calculate the characteristic impedance Z0 of the Wilkinson power divider to obtain the Wilkinson power divider prototype.

[0017] Further, the specific steps for calculating the number of matching stages, source impedance, and load impedance that need to be matched using the multi-section stepped impedance matching theory in Step 2 are as follows:

[0018] According to the load impedance Z1 between the input port and the first output port of the Wilkinson power divider prototype and the characteristic impedance Z0 of the Wilkinson power divider, calculate the characteristic impedance difference Z Δ ;

[0019] Based on the characteristic impedance difference Z Δ between the source impedance and the load impedance, and the number of matching stages n of the source and load ends, calculate the characteristic impedance difference Z δ of each matching stub;

[0020] According to the characteristic impedance Z0 of the Wilkinson power divider and the characteristic impedance difference Z δ of each matching stub, calculate the characteristic impedance value of each matching stub;

[0021] Use the characteristic impedance of the previous matching stub of the matching stub as the source impedance of the Chebyshev low-pass filter impedance matching network and its own impedance as the load impedance of the Chebyshev low-pass filter impedance matching network to design the Chebyshev low-pass filter impedance matching network.

[0022] Further, the characteristic impedance difference Z of each matching stub δ is calculated by the formula:

[0023]

[0024] where Z Δ is the characteristic impedance difference between the source impedance and the load impedance, and n is the number of matching sections at the source and load ends.

[0025] Further, the formula for calculating the characteristic impedance value of each matching stub according to the characteristic impedance Z0 of the Wilkinson power divider and the characteristic impedance difference Z δ of each matching stub is:

[0026]

[0027] where Z 11 to Z 1n , Z 21 to Z 2n are the characteristic impedance values of each matching stub on the two output ports respectively.

[0028] Further, the formulas for calculating the lumped element parameter values in the Chebyshev low-pass filter impedance matching network in step 4 are as follows:

[0029]

[0030] where L and C are the inductance and capacitance values of the lumped elements in the Chebyshev low-pass filter impedance matching network, ω c is the angular frequency of the cut-off frequency, Z0 represents the characteristic impedance of the Wilkinson power divider, and g L , g c are the normalized values of the lumped elements.

[0031] Further, the specific process of converting the lumped element parameter values in the Chebyshev low-pass filter impedance matching network into the corresponding distributed parameter values in step 5 is as follows:

[0032] Set a distributed parameter microstrip low-pass filter on the basis of the Chebyshev low-pass filter impedance matching network;

[0033] Equivalent the high-impedance microstrip line in the microstrip low-pass filter to an inductor, and the low-impedance microstrip line to a capacitor;

[0034] Calculate the length L oh corresponding to the high-impedance line and the length L ol corresponding to the low-impedance line;

[0035] According to the characteristic impedance of each matching stub microstrip line, calculate the line widths of the high-impedance line and the low-impedance line corresponding to each matching stub.

[0036] Further, the length L corresponding to the high-impedance line oh is calculated according to the following formula:

[0037]

[0038] The length L corresponding to the low-impedance line ol is calculated according to the following formula:

[0039]

[0040] where Z oh is the characteristic impedance of the high-impedance microstrip line, Z ol is the characteristic impedance of the low-impedance microstrip line, ε is the dielectric constant of the dielectric substrate, c is the speed of light, and C and L are the equivalent capacitance value and the equivalent inductance value respectively.

[0041] Further, the dielectric substrate used in the one-to-four filter power divider is an FR4 epoxy resin board, the resistor used is a thin-film resistor, and before welding the resistor, the copper-clad parts on both sides of the dielectric substrate are subjected to tin spraying for anti-oxidation treatment.

[0042] The remarkable effect of the present invention is:

[0043] Based on the improved Wilkinson architecture, the present invention adopts a low-cost FR4 epoxy resin substrate to achieve a high-cost performance solution. This design constructs an Nth-order low-pass filter impedance matching network through the Chebyshev polynomial expansion, and innovatively adopts the lumped-distributed hybrid mapping technology: at the same time, it transforms the traditional lumped-parameter low-pass filter prototype into a distributed microstrip structure with impedance transformation function, that is, transforms the LC filter network into a distributed microstrip stub structure through the Richard transformation, and introduces a graded stepped impedance unit (Graded SIR), and innovatively constructs the collaborative design of the stepped impedance resonant unit and the multi-stage impedance transformation network, realizing the adjustment of the wide-range impedance transformation ratio from 1:4 to 1:8. The measured results show that the device presents an equivalent insertion loss (IL) of 9.9 dB at the cut-off frequency of 1.2 GHz, the return loss in the passband is better than 15 dB, and the voltage standing wave ratio (VSWR) ≤ 1.7. The isolation degree between the output ports in the passband is below 15 dB, and the out-of-band rejection characteristic still maintains a roll-off slope of 35 dB at 7.2 GHz, and its power distribution imbalance degree ≤ ±0.6 dB. The overall structural size is 0.68×0.57 (λg×λg, λg is the guided wavelength). Description of the Drawings

[0044] Figure 1 is the flowchart of the method of the present invention

[0045] Figure 2 is a schematic diagram of a Wilkinson power divider;

[0046] Figure 3 is a schematic diagram of stepped impedance;

[0047] Figure 4 is a schematic diagram of a Chebyshev low-pass filter impedance matching network;

[0048] Figure 5 is a schematic diagram of the structure of the one-to-four filter power divider obtained by the present invention. Detailed implementation manners

[0049] The following further describes in detail the specific implementation manners and working principles of the present invention with reference to the accompanying drawings.

[0050] As Figure 1 shown, a design method for a one-to-four filter power divider applied in a low-frequency band is as follows:

[0051] Step 1: Design a Wilkinson power divider prototype;

[0052] In this example, the design diagram of the Wilkinson power divider is as Figure 2 shown. When in an ideal situation, the input port power P1 and the two output port powers P2 and P3 of the Wilkinson power divider satisfy formulas (1) and (2):

[0053] P1 = P2 + P3 (1)

[0054]

[0055] According to formula (2), it can be obtained that:

[0056]

[0057] Therefore, the characteristic impedance Z0 of the Wilkinson power divider can be calculated and obtained:

[0058]

[0059] where U is the voltage applied to the Wilkinson power divider, and Z is the equivalent impedance of the Wilkinson power divider; it can be seen from formula (3) that when performing power distribution in different ratios, the output load impedance of each output port of the Wilkinson power divider is inversely proportional to the power distribution ratio.

[0060] Therefore, in this embodiment, a Wilkinson power divider prototype is designed through formulas (1), (2), (3), and (4).

[0061] Step 2: Based on the Wilkinson power divider prototype, calculate the number of matching stages, source impedance, and load impedance required according to specific design requirements using the multi-section stepped impedance matching theory.

[0062] Specifically, to achieve better impedance matching between Z0 and Z1, a section of Z is added in between. 01 Stepped matching is performed, as shown in Figure 3 . Among them, Z0, Z1, and Z 01 satisfy:

[0063]

[0064] To meet the requirement of the in-bandwidth of the power divider, the number of impedance matching network sections can be increased. The more matching stages there are, the better the matching effect between the source end and the output end.

[0065] Step 2.1: Calculate the characteristic impedance difference Z between the source impedance and the load impedance based on the load impedance Z1 between the input port and the first output port of the Wilkinson power divider prototype and the characteristic impedance Z0 of the Wilkinson power divider: Δ :

[0066] Z V = Z1 - Z0 (6)

[0067] Step 2.2: Based on the characteristic impedance difference Z between the source impedance and the load impedance and the number of matching stages n between the source end and the load end, calculate the characteristic impedance difference Z of each matching stub: Δ : δ :

[0068]

[0069] Step 2.3: Calculate the characteristic impedance value of each matching stub according to the characteristic impedance Z0 of the Wilkinson power divider and the characteristic impedance difference Z of each matching stub. The calculation formula is: δ :

[0070]

[0071] Among them, Z Δ is the characteristic impedance difference between the source impedance and the load impedance, n is the number of matching stages between the source end and the load end, and Z 11 ~Z 1n , Z 21 ~Z 2n are the characteristic impedance values of each matching stub on the two output ports respectively. Therefore, the characteristic impedance values of each matching stub can be calculated through formulas (6)-(9).

[0072] Step 2.4: Take the characteristic impedance of the matching stub in the previous section as the source impedance of the Chebyshev low-pass filter impedance matching network, and its own impedance as the load impedance of the Chebyshev low-pass filter impedance matching network, and design the Chebyshev low-pass filter impedance matching network.

[0073] Step 3: Calculate the impedance transformation ratio of the Chebyshev low-pass filter impedance matching network using the source impedance and load impedance calculated in Step 2.

[0074] In this example, the characteristic impedance value calculated by the stepped impedance matching is used as the characteristic impedance for the design of the Chebyshev low-pass filter matching network, and the impedance transformation ratio of the Chebyshev low-pass filter matching network is determined. Design according to the required bandwidth and in-band ripple requirements by looking up the Chebyshev low-pass filter impedance matching network table, and determine the impedance transformation ratio K through Equation (10):

[0075]

[0076] Step 4: Design the Chebyshev low-pass filter impedance matching network using the insertion loss method according to the design requirements, and calculate the lumped element parameter values in the Chebyshev low-pass filter impedance matching network.

[0077] In this example, design the Chebyshev low-pass filter impedance matching network using the insertion loss method according to the specific design requirements. Obtain the corresponding normalized element g values by looking up the Chebyshev low-pass filter impedance matching network table. The prototype of the Chebyshev low-pass filter impedance matching network designed by lumped elements is as Figure 4 shown.

[0078] Therefore, the lumped element parameter values in the Chebyshev low-pass filter impedance matching network can be calculated by the following formula:

[0079]

[0080] where L and C are the inductance and capacitance values of the lumped elements in the Chebyshev low-pass filter impedance matching network, ω c is the angular frequency of the cut-off frequency, Z0 represents the characteristic impedance of the Wilkinson power divider, and g L , g c are the normalized values of the lumped elements obtained from the table.

[0081] Calculate the inductance value through Equation (12), and then the second is the capacitance, and so on for inductance and capacitance. For details, please refer to Figure 4 shown.

[0082] Step 5: Convert the lumped element parameter values in the Chebyshev low-pass filter impedance matching network into the corresponding distributed parameter values.

[0083] Step 5.1: Set a microstrip low-pass filter with distributed parameters on the basis of a Chebyshev low-pass filter impedance matching network;

[0084] Step 5.2: Equivalent the high-impedance microstrip line in the microstrip low-pass filter to an inductor, and the low-impedance microstrip line to a capacitor;

[0085] Step 5.3: Calculate the length L corresponding to the high-impedance line oh and the length L corresponding to the low-impedance line ol , and the calculation formula is:

[0086]

[0087] where Z oh is the characteristic impedance of the high-impedance microstrip line, Z ol is the characteristic impedance of the low-impedance microstrip line, ε is the relative permittivity of the dielectric substrate, c is the speed of light, C and L are the equivalent capacitance value and equivalent inductance value respectively.

[0088] Step 5.4: According to the characteristic impedance of each section of the matching stub microstrip line, use the characteristic impedance calculation tool to calculate the line width of the high-impedance line and low-impedance line corresponding to each section of the matching stub.

[0089] Step 6: Verify whether the distributed parameters are reasonable. If so, form the design parameters of a one-to-four filter power divider; otherwise, return to Step 5.

[0090] In this embodiment, for the one-to-four filter power divider, a common FR4 board is used as the dielectric substrate. The FR4 board has extremely high insulation and heat resistance during use, can work in a high-temperature and high-pressure environment for a long time, can resist electromagnetic interference and radiation interference, and at the same time has excellent acid and alkali resistance and corrosion resistance. Moreover, due to its good processing performance, it is more flexible in layout design. The double-sided substrate method is used during production, and the specific dielectric substrate parameters are shown in Table 1.

[0091] Table 1. Substrate parameter settings

[0092]

[0093] The described one - to - four filter power divider includes an input port / source end, four output ports / load ends, and the impedance of each port is 50Ω. It is designed using microstrip lines. To improve the port isolation between the output ports, the resistors soldered on the board are commercially available 0805 metal - film resistors. The resistor body is formed by vacuum evaporation. This thin - film resistor has a high precision value, low current noise, and a low temperature coefficient, and has excellent stability in actual use. The corresponding resistance values are R1 = 180Ω, R2 = 220Ω, R3 = 470Ω. Necessary optimizations are carried out in the design environment to compensate for the impedance matching of the gaps between the resistors and the elbow soldering. Also, since tin dioxide has excellent antioxidant properties during the soldering process, the physical object is subjected to tin spraying anti - oxidation treatment at the copper - clad areas on both sides of the substrate. The conductivity of tin is much worse than that of copper, and tin dioxide formed after oxidation in the air can protect the copper - clad area, which can increase the service life of the device.

[0094] After the above - mentioned treatment, during subsequent use, only the source end of this power divider needs to be connected to the port that requires power distribution and signal processing, and then the processed signal can be output through the output ports.

[0095] After the above steps, the obtained one - to - four filter power divider is as Figure 5 shown, and its specific parameters are: W1 = 2.73, W2 = 3.27, W3 = 14, W4 = 18, W5 = 1.6, W6 = 0.26, L1 = 1.74, L2 = 3.07, L3 = 2.03, L4 = 2.73, L5 = 20, L6 = 8, L7 = 23, L8 = 17, L9 = 5 (all units are mm).

[0096] In summary, using the design method of this invention patent to design a power divider, with the Wilkinson power divider shown in Figure (2) as the prototype, the Wilkinson power divider prototype is designed through formulas (1), (2), (3), (4); then, with Figure (3) as the prototype, according to specific design requirements, the number of matching orders, source - end impedance, and load impedance are calculated using formulas (5), (6), (7), (8) by applying the stepped - impedance matching theory; then, the characteristic impedance values calculated by the stepped - impedance theory are used for calculating the impedance transformation ratio of the Chebyshev low - pass filter impedance matching network, and the source - end impedance and load impedance calculated by the stepped - impedance matching theory are used to calculate the impedance transformation ratio of the Chebyshev low - pass filter impedance matching network using formula (10); then, with Figure (4) as the design prototype, the lumped - element parameter values of the Chebyshev low - pass filter impedance matching network are calculated through formulas (11), (12); then, formulas (13), (14) are used to convert the lumped elements in the Chebyshev low - pass filter impedance matching network into the corresponding parameter values of distributed parameters; finally, after verifying the rationality of the parameter values, the design parameters of the one - to - four filter power divider are obtained.

[0097] As can be seen, the present invention is based on an improved Wilkinson architecture and adopts a low-cost FR4 epoxy resin substrate (ε_r = 4.4, tanδ = 0.02) to achieve a high cost-effective solution. This design constructs an N-order Chebyshev low-pass filter impedance matching network through the Chebyshev polynomial expansion, and innovatively adopts a lumped-distributed hybrid mapping technology: simultaneously transforming the traditional lumped-parameter low-pass filter prototype into a distributed microstrip structure with impedance transformation function, that is, transforming the LC filter network into a distributed microstrip stub structure through Richard transformation, and introducing a graded stepped impedance unit (Graded SIR), innovatively constructing a collaborative design of a stepped impedance resonant unit and a multi-stage impedance transformation network, realizing a wide-range impedance transformation ratio adjustment from 1:4 to 1:8. The measured results show that the device exhibits an equivalent insertion loss (IL) of 9.9 dB at the cut-off frequency of 1.2 GHz, the return loss in the passband is better than 15 dB, and the voltage standing wave ratio (VSWR) ≤ 1.7. The output port isolation in the passband is below 15 dB, and the out-of-band rejection characteristic still maintains a roll-off slope of 35 dB at 7.2 GHz, and its power distribution imbalance ≤ ±0.6 dB. The overall structure size is 0.68×0.57 (λg×λg, λg is the guided wavelength).

[0098] The technical solutions provided by the present invention have been introduced in detail above. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A design method of a one-to-four filtering power divider for low-frequency band applications, characterized in that It includes the following steps: Step 1: Design the Wilkinson power divider prototype; Step 2: Based on the Wilkinson power divider prototype, use the multi-section stepped impedance matching theory to calculate the number of matching sections, the source impedance, and the load impedance; Step 3: Use the source impedance and the load impedance calculated in Step 2 to calculate the impedance transformation ratio of the Chebyshev low-pass filter impedance matching network; Step 4: Design the Chebyshev low-pass filter impedance matching network using the insertion loss method according to the design requirements, and calculate the lumped element parameter values in the Chebyshev low-pass filter impedance matching network; Step 5: Convert the lumped element parameter values in the Chebyshev low-pass filter impedance matching network into the corresponding parameter values of distributed parameters; Step 6: Verify whether the distributed parameters are reasonable. If so, form the design parameters of the one-to-four filter power divider; otherwise, return to Step 5.

2. The design method of the one-to-four filtering power divider for low-frequency band applications according to claim 1, characterized in that: The specific steps for designing the Wilkinson power divider prototype in Step 1 are as follows: Based on the input port power P1 of the Wilkinson power divider and the two output port powers P2 and P3 under ideal conditions, calculate the load impedances Z1 and Z2 between the input port and the two output ports respectively; Based on the load impedances Z1 and Z2, according to the formula calculate to obtain the characteristic impedance Z0 of the Wilkinson power divider, and obtain the Wilkinson power divider prototype.

3. The design method of the one-to-four filtering power divider for low-frequency band applications according to claim 1, characterized in that: The specific steps for calculating the number of matching sections, the source impedance, and the load impedance using the multi-section stepped impedance matching theory in Step 2 are as follows: Calculate the characteristic impedance difference Z between the source impedance and the load impedance based on the load impedance Z1 between the input port and the first output port of the Wilkinson power divider prototype and the characteristic impedance Z0 of the Wilkinson power divider Δ ; Based on the characteristic impedance difference Z between the source impedance and the load impedance Δ and the number of matching sections n at the source end and the load end, calculate the characteristic impedance difference Z of each matching stub δ ; According to the characteristic impedance Z0 of the Wilkinson power divider and the characteristic impedance difference Z of each matching stub δ , the characteristic impedance value of each matching stub is calculated; Take the characteristic impedance of the matching stub of the previous section of the matching stub as the source impedance of the Chebyshev low-pass filter impedance matching network and its own impedance as the load impedance of the Chebyshev low-pass filter impedance matching network to design the Chebyshev low-pass filter impedance matching network.

4. The design method of the one-to-four filter power divider for low-frequency band applications according to claim 3, characterized in that: The characteristic impedance difference Z of each matching stub δ is calculated by the following formula: Among them, Z Δ is the characteristic impedance difference between the source impedance and the load impedance, and n is the number of matching sections at the source end and the load end.

5. The design method of the one-to-four filtering power divider for low-frequency band applications according to claim 3, characterized in that: The characteristic impedance Z0 of the Wilkinson power divider and the characteristic impedance difference Z of each matching stub are used to calculate the characteristic impedance value of each matching stub, and the calculation formula is as follows: δ , and the calculation formula for calculating the characteristic impedance value of each matching stub is: Among them, Z 11 to Z 1n , Z 21 to Z 2n are the characteristic impedance values of each matching stub on the two output ports respectively.

6. The design method of a one-to-four filter power divider for low-frequency band applications according to claim 1, characterized in that: The calculation formulas for the lumped element parameter values in the Chebyshev low-pass filter impedance matching network in Step 4 are as follows: where L and C are the inductance and capacitance values of the lumped elements in the Chebyshev low-pass filter impedance matching network, ω c is the angular frequency of the cut-off frequency, Z0 represents the characteristic impedance of the Wilkinson power divider, g L and g c are the normalized values of the lumped elements.

7. The design method of the one-to-four filtering power divider for low-frequency band applications according to claim 1, characterized in that: The specific process for converting the lumped element parameter values in the Chebyshev low-pass filter impedance matching network into the corresponding parameter values of distributed parameters in Step 5 is as follows: Set a microstrip low-pass filter with distributed parameters based on the Chebyshev low-pass filter impedance matching network; Equivalent the high-impedance microstrip line in the microstrip low-pass filter to an inductor and the low-impedance microstrip line to a capacitor; Calculate the length L corresponding to the high-impedance line oh and the length L corresponding to the low-impedance line ol ; According to the characteristic impedance of each section of the matching stub microstrip line, calculate the line widths of the high-impedance line and the low-impedance line corresponding to each section of the matching stub.

8. The design method of the one-to-four filtering power divider for low-frequency band applications according to claim 7, characterized in that: The length L corresponding to the high impedance line oh has the following calculation formula: The length L corresponding to the low-impedance line ol The calculation formula is as follows: Among them, Z oh is the characteristic impedance of the high-impedance microstrip line, Z ol is the characteristic impedance of the low-impedance microstrip line, ε is the dielectric constant of the dielectric substrate, c is the speed of light, and C and L are the equivalent capacitance value and the equivalent inductance value respectively.

9. The design method of the one-to-four filtering power divider for low-frequency band applications according to any one of claims 1-8, characterized in that: The dielectric substrate used for the one-to-four filter power divider is an FR4 epoxy resin board, and the resistor used is a thin-film resistor. Before soldering the resistor, spray tin on the copper-clad parts on both sides of the dielectric substrate to prevent oxidation.

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