Pi-type attenuator based on microstrip matching, signal test system and communication system

Abstract

The invention discloses an n-shaped attenuator based on microstrip matching, a signal test system and a communication system, and aims to solve the problems of parasitic effect and unstable performance of a traditional attenuator in high-frequency application, the n-shaped attenuator comprises a first resistor, a second resistor and a matched microstrip line, the two ends of the matched microstrip line are connected with the first resistor and the second resistor respectively, and the first resistor is connected with the second resistor. The length of the matched microstrip line is lambda / 4, lambda is the wavelength corresponding to the center frequency of the attenuator, and the resistance values of the first resistor and the second resistor are equal. A microstrip line is used for replacing a traditional series resistor, the parasitic effect is remarkably reduced, the high-frequency performance is improved, the applicable frequency band of the attenuator is expanded, the stability and consistency of the attenuator under the high-frequency condition are improved, the bandwidth is expanded by optimizing the resistance value and impedance parameters, and the design flexibility and applicability of the attenuator are ensured. Compared with the prior art, the structure is simple, the manufacturing process is more simplified, the antenna is suitable for various circuit systems of microwave high frequency bands and other frequency bands, and the antenna has wide application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of attenuators, and in particular to a Π-type attenuator based on microstrip matching, a signal testing system, and a communication system. Background Art

[0002] In traditional microwave integrated circuits, attenuators are the core components for signal power regulation, and their topological structure directly affects the high-frequency performance and applicable range of the system. In basic circuit design, T-type and π-type attenuators have become classic choices because of their simple structure and easy calculation. Taking the π-type attenuator as an example, its core design concept is to achieve energy dissipation and impedance balance through a resistor network. In a typical structure, two parallel resistors are located at the input and output ports respectively, and a series resistor is connected in the middle to form a layout similar to the Greek letter "π". This symmetrical structure shows significant advantages in the low or medium frequency range: by adjusting the resistance ratio of the parallel and series resistors, the attenuation amplitude of the signal can be accurately controlled, and the impedance matching of the input and output ports can be maintained, thereby reducing the impact of signal reflection on system stability.

[0003] However, as the application scenarios evolve towards high frequency and integration, the limitations of the Π-type attenuator are gradually exposed. In thin-film circuits or microwave high-frequency circuits (such as millimeter wave bands), the parasitic effects of traditional resistors have become a bottleneck that cannot be ignored. The lead inductance and distributed capacitance of the resistor element will couple with the high-frequency signal, causing the actual impedance characteristics of the attenuator to deviate from the theoretical model. This non-ideality is particularly prominent in the high-frequency band, which will not only cause additional insertion loss fluctuations, but also destroy the impedance matching state, causing the return loss to deteriorate significantly. In addition, in the pursuit of miniaturized microwave integrated circuits, the physical size of discrete resistors is not compatible with the integration of microstrip lines, making it difficult to meet the requirements of high-density packaging. At the same time, limited by the power tolerance of the resistor material, this type of structure is prone to performance drift or even device failure due to heat accumulation in high-power scenarios. These inherent defects have caused the traditional Π-type attenuator to be gradually replaced by new topological structures in modern systems such as 5G communications and phased array radars that have strict requirements for broadband, high frequency, and high integration. Its main disadvantages and shortcomings are:

[0004] 1) The two ground resistors of the Π-type attenuator have large resistance and long length, and the parasitic effect is significant under high-frequency conditions, resulting in uneven signal attenuation and poor frequency response, affecting the performance of the overall circuit.

[0005] 2) As the frequency increases, the attenuation value of the π-type attenuator is no longer as stable as it is at low frequencies. Due to the distribution effect in the circuit, the actual performance of the π-type attenuator deviates greatly from the design calculation and cannot achieve the expected attenuation value.

[0006] 3) The resistor in the middle has extremely high precision requirements and has a great impact on the attenuation value. A slight deviation will cause the attenuation value to not meet the design requirements, increasing manufacturing difficulty and cost. Summary of the invention

[0007] The purpose of the present invention is to provide a new type of attenuator based on two resistors and a microstrip line, which has the advantages of simple structure, flexible design, compact structure, etc., and can meet the application requirements of high frequency bands. Compared with traditional attenuators, the design of the present invention not only has higher performance stability, but also can effectively reduce the volume and adapt to more stringent space constraints. This new attenuator can be widely used in various circuits and systems that require precise attenuation, including wireless communications, radar, radio frequency measurement and other high-frequency electronic equipment fields, especially in the microwave high frequency band, and can effectively overcome a series of difficulties encountered in high-frequency applications in the prior art, such as uneven attenuation and unstable frequency response.

[0008] In addition, the attenuator of the present invention has good adaptability and scalability, and can be flexibly adjusted to meet the needs of different frequency bands, thereby providing a new solution for the development of microwave and millimeter wave technology. Its design method is simple and easy to implement, the manufacturing process is not complicated, the cost is low, and it has high production efficiency. At the same time, the attenuator can accurately control the attenuation by adjusting the resistance value and the geometric parameters of the microstrip line, which greatly improves the flexibility and reliability of the design.

[0009] The technical solution of the present invention is: a Π-type attenuator based on microstrip matching, comprising a first resistor, a second resistor and a matching microstrip line, wherein both ends of the matching microstrip line are respectively connected to the first resistor and the second resistor, the length of the matching microstrip line is λ / 4, λ is the wavelength corresponding to the center frequency of the attenuator, and the resistance values ​​of the first resistor and the second resistor are equal.

[0010] Furthermore, the matching microstrip line is a section of microstrip line, and two ends of the microstrip line are respectively connected to the first resistor and the second resistor.

[0011] Furthermore, the connection point between the microstrip line and the first resistor is a voltage amplitude point; and the connection point between the microstrip line and the second resistor is a voltage wave node.

[0012] Furthermore, the resistance values ​​of the first resistor and the second resistor and the impedance of the microstrip line are determined by the following formula:

[0013] First, the proposed attenuator is analyzed according to the equivalent circuit, where Z in represents the input impedance, Z L represents the load impedance, Z 0 For a known attenuator port impedance, to ensure the best impedance matching between the input and output ports, the following conditions must be met:

[0014] ZL =Z 0 =Z in

[0015] When calculating the input impedance, first determine the second resistor and Z 0 The parallel combination of the λ / 4 microstrip line is then added to the series impedance, and the result is connected in parallel with the first resistor, where R 1 is the resistance of the first resistor and the second resistor, so the input impedance Z in It can be expressed as:

[0016]

[0017] The insertion loss IL can be calculated based on the input power P in And the output power P out After calculation, the mathematical expression of IL is as follows:

[0018]

[0019] P in / P out It can also be calculated from the input and output voltages and further expressed in terms of load impedance as follows:

[0020]

[0021] Furthermore, the matching microstrip line is a three-section matching microstrip line, which are a first microstrip line, a second microstrip line and a third microstrip line. The first microstrip line, the second microstrip line and the third microstrip line are connected in sequence. The left end of the first microstrip line is connected to the first resistor, and the right end of the third microstrip line is connected to the second resistor.

[0022] Furthermore, a connection point between the first microstrip line and the first resistor is a voltage amplitude point; and a connection point between the third microstrip line and the second resistor is a voltage wave node.

[0023] Furthermore, the resistance values ​​of the first resistor and the second resistor and the impedances of the first microstrip line, the second microstrip line and the third microstrip line are determined by the following formulas:

[0024] According to the optimal impedance transformation condition of the multi-section matching structure, the relationship between the three-section matching microstrip lines is obtained:

[0025]

[0026] Also according to the equivalent circuit analysis, where Z in represents the input impedance, Z L represents the load impedance, Z 0 is the known attenuator port impedance. To ensure the best impedance matching between the input and output ports, the following conditions must be met:

[0027] ZL =Z 0 =Z in

[0028] For three-section matching, the input impedance Z in It can be expressed as follows:

[0029]

[0030] Where R 1 is the resistance of the first resistor and the second resistor, Z 2 is the impedance of the first microstrip line, Z 3 is the impedance of the second microstrip line, Z 4 is the impedance of the third microstrip line.

[0031] The insertion loss IL can be calculated based on the input power P in And the output power P out After calculation, the mathematical expression of IL is as follows:

[0032]

[0033] P in / P out It can also be calculated from the input and output voltages and further expressed in terms of load impedance as follows:

[0034]

[0035] Furthermore, the lengths of the first microstrip line, the second microstrip line and the third microstrip line are all λ / 4; and the widths of the first microstrip line, the second microstrip line and the third microstrip line increase in sequence.

[0036] The present invention further provides a signal testing system, which adopts the above-mentioned Π-type attenuator based on microstrip matching.

[0037] The present invention can also provide a communication system, which adopts the above-mentioned Π-type attenuator based on microstrip matching.

[0038] Compared with the prior art, the present invention has at least the following beneficial effects:

[0039] 1) Reduce parasitic effects and improve high-frequency performance: The present invention successfully reduces the interference of parasitic effects on signal transmission by replacing the series resistor in the traditional Π-type attenuator with a microstrip line structure. The microstrip line structure can effectively control the propagation path of the signal, thereby reducing the additional loss caused by the traditional resistor element and significantly improving the performance of the attenuator in the high-frequency band. This improvement improves the performance degradation problem caused by parasitic effects and unstable frequency response of traditional attenuators when working in the microwave and millimeter wave frequency bands.

[0040] 2) Expand the applicable frequency band and improve high-frequency stability and reliability: Compared with traditional resistor elements, the microstrip line structure can maintain stable working performance in a wider frequency range. By optimizing the geometric design of the microstrip line, the attenuator of the present invention can adapt to the high-frequency application requirements of the microwave and millimeter wave frequency bands, especially under high-frequency conditions, its performance is outstanding. Compared with the prior art, the present invention can effectively expand the applicable frequency band of the attenuator, enhance its stability and reliability in high-frequency environments, and ensure stable operation even in complex signal environments.

[0041] 3) Simplify the manufacturing process, improve consistency and production efficiency: After using microstrip lines to replace traditional resistor elements, the manufacturing process of the attenuator has been significantly simplified. Microstrip lines can be made through standardized PCB (printed circuit board) processes, reducing complex assembly processes and reducing production costs. At the same time, the design of the microstrip line structure can achieve precise size control, thereby ensuring the consistency of performance of each attenuator product. This provides a more feasible solution for large-scale mass production of attenuators, improves production efficiency, ensures high product consistency, and reduces errors in the production process.

[0042] In summary, the present invention reduces parasitic effects and significantly improves high-frequency performance by replacing the series resistor in the traditional Π-type attenuator with a microstrip line structure, expands the applicable frequency band of the attenuator, and improves its stability and reliability under high-frequency conditions. At the same time, it simplifies the manufacturing process and enhances product consistency and the feasibility of mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 It is a schematic diagram of a first embodiment of the attenuator in the present invention;

[0044] Figure 2 This is an example of attenuator impedance calculation for the first embodiment of the attenuator in the present invention;

[0045] Figure 3 It is a schematic diagram of the simulation and measured curves of the attenuator of the first embodiment of the attenuator in the present invention;

[0046] Figure 4 It is a schematic diagram of a second embodiment of the attenuator in the present invention;

[0047] Figure 5 This is an example of attenuator impedance calculation for the second embodiment of the attenuator in the present invention;

[0048] Figure 6 It is a schematic diagram of attenuator simulation and measured curves of the second embodiment of the attenuator in the present invention;

[0049] In the figure, 1-first resistor, 2-second resistor, 3-microstrip line, 4-first microstrip line, 5-second microstrip line, 6-third microstrip line. DETAILED DESCRIPTION

[0050] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0051] In the description of the present invention, it should be understood that the terms "left", "right", "one end", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0052] Embodiment 1, Figure 1 This is a schematic diagram of the first embodiment of the attenuator in the present invention. The attenuator provided by the present invention includes a first resistor 1, a second resistor 2 and a microstrip line 3. The two ends of the microstrip line 3 are respectively connected to the first resistor 1 and the second resistor 2. The length of the microstrip line 3 is λ / 4, where λ is the wavelength corresponding to the center frequency of the attenuator. The resistance values ​​of the first resistor 1 and the second resistor 2 are equal. A symmetrical Π-type network is formed, and the resistance values ​​of the first resistor and the second resistor are equal, ensuring symmetrical impedance matching of the input / output ports. By selecting a microstrip line of appropriate length and width and a resistor value, the load impedance of the resistor is converted into a target characteristic impedance using the impedance transformation formula of a λ / 4 transmission line, and the microstrip line shares part of the power loss, reduces the thermal load of the resistor, and improves the overall power capacity; by integrating the microstrip line to directly achieve impedance matching and simplify the layout, the attenuator of the present invention can achieve good frequency response and attenuation effects, especially in the microwave and millimeter wave frequency bands, its attenuation characteristics are stable and uniform, and impedance matching is easy to achieve; in addition, the microstrip line and the resistor can be integrated on the same substrate to reduce the number of discrete components, which is suitable for compact RF module design, and achieves high-precision attenuation, low reflection loss and impedance matching effects at the center frequency, and is particularly suitable for narrowband high-frequency systems.

[0053] Furthermore, the connection point between the microstrip line 3 and the first resistor 1 is a voltage amplitude point; and the connection point between the microstrip line 3 and the second resistor 2 is a voltage node.

[0054] Set the attenuator port impedance to Z 0 , Z 0is a known quantity, for example, 50Ω, and the attenuation of the attenuator is IL. In order to determine the resistance values ​​of the first resistor 1 and the second resistor 2 and the impedance of the microstrip line 3, according to Figure 2 The attenuator impedance calculation diagram of the first embodiment of the attenuator of the present invention is analyzed, wherein Z in represents the input impedance, Z L represents the load impedance, Z 0 is the known attenuator port impedance. To ensure the best impedance matching between the input and output ports, the following conditions must be met:

[0055] Z L =Z 0 =Z in

[0056] When calculating the input impedance, we must first determine the second resistor 2 and Z 0 The parallel combination of the λ / 4 microstrip line is then added, and the result is connected in parallel with the first resistor 1, where R 1 is the resistance of the first resistor 1 and the second resistor 2, so the input impedance Z in It can be expressed as:

[0057]

[0058] The insertion loss IL can be calculated based on the input power P in And the output power P out After calculation, the mathematical expression of IL is as follows:

[0059]

[0060] P in / P out It can also be calculated from the input and output voltages and further expressed in terms of load impedance as follows:

[0061]

[0062] According to the above equation, the resistance values ​​R of the first resistor 1 and the second resistor 2 can be determined 1 And the initial value Z of the impedance of microstrip line 3 1 .

[0063] As an example, set Z 0 =50Ω, center frequency f 0 =13GHz, attenuation IL = 3dB, the resistance value R is obtained according to the formula 1 and Z 1 According to the initial value of resistance R 1 and Z 1 The initial value of is modeled and optimized, and the first embodiment of the attenuator in the present invention is simulated and measured. The results are as follows Figure 3As shown, the attenuation flatness is maintained within 0.6dB over its entire operating frequency range, which indicates that it has a significant stability advantage over the traditional π-type attenuator. In addition, the proposed design achieves a reflection loss of less than -14dB over the entire frequency band, surpassing the typical performance of traditional π-type attenuators, which usually exhibits a reflection loss of more than -10dB. Therefore, this microstrip matching design has obvious advantages in impedance matching and overall performance.

[0064] Embodiment 2, Figure 4 This is a schematic diagram of the second embodiment of the attenuator in the present invention. In order to further expand the bandwidth, Figure 1 The microstrip line 3 in the figure can be replaced by three sections of matching microstrip lines, namely the first microstrip line 4, the second microstrip line 5 and the third microstrip line 6. The first microstrip line 4, the second microstrip line 5 and the third microstrip line 6 are connected in sequence, wherein the left end of the first microstrip line 4 is connected to the first resistor 1, and the right end of the third microstrip line 6 is connected to the second resistor 2. By adopting a three-section matching microstrip line structure, the frequency characteristics and impedance matching of the attenuator can be designed more flexibly to meet the needs of a wider frequency band. The multi-section structure is less sensitive to the size error of a single section. Through the step impedance transformation and the coordination of distributed parameters, the bandwidth, matching accuracy and frequency response flatness of the attenuator are significantly improved, which is suitable for the stringent requirements of multi-frequency compatibility and stability in broadband wireless systems. In addition, the same topology can be reused in different frequency bands by adjusting the length or impedance of a certain section of the microstrip line.

[0065] The connection point between the first microstrip line 4 and the first resistor 1 is a voltage amplitude point; the connection point between the third microstrip line 6 and the second resistor 2 is a voltage wave node.

[0066] The lengths of the first microstrip line 4 , the second microstrip line 5 and the third microstrip line 6 are all λ / 4; the widths of the first microstrip line 4 , the second microstrip line 5 and the third microstrip line 6 increase in sequence.

[0067] Also let the attenuator port impedance be Z 0 , Z 0 is a known quantity, for example, 50Ω, and the attenuation of the attenuator is IL. In order to determine the resistance values ​​R of the first resistor 1 and the second resistor 2 1 As well as the impedances of the first microstrip line 4, the second microstrip line 5 and the third microstrip line 6, the relationship between the three matching microstrip lines is first determined according to the optimal impedance transformation condition of the multi-section matching structure:

[0068]

[0069] According to Figure 5 The attenuator impedance calculation diagram of the second embodiment of the attenuator of the present invention is analyzed, wherein Z in represents the input impedance, Z L represents the load impedance, Z0 is the known attenuator port impedance. To ensure the best impedance matching between the input and output ports, the following conditions must be met:

[0070] Z L =Z 0 =Z in

[0071] For three-section matching, the input impedance Z in It can be expressed as follows:

[0072]

[0073] Where R 1 is the resistance of the first resistor 1 and the second resistor 2, Z 2 is the impedance of the first microstrip line, Z 3 is the impedance of the second microstrip line, Z 4 is the impedance of the third microstrip line.

[0074] The insertion loss IL can be calculated based on the input power P in And the output power P out After calculation, the mathematical expression of IL is as follows:

[0075]

[0076] P in / P out It can also be calculated from the input and output voltages and further expressed in terms of load impedance as follows:

[0077]

[0078] According to the above equation, the resistance values ​​R of the first resistor 1 and the second resistor 2 can be determined 1 And the initial value Z of the impedance of the first microstrip line 4 2 , the initial value Z of the impedance of the second microstrip line 5 3 and the initial value Z of the impedance of the third microstrip line 6 4 .

[0079] Setting R 0 =50Ω, center frequency f 0 =13GHz, attenuation IL = 6dB, according to the formula, R 1 , Z 2 , Z 3 , and Z 4 The initial value of R 1 , Z 2 , Z 3 , and Z 4 The initial value of is modeled and optimized, and the second embodiment of the attenuator in the present invention is simulated and measured. The results are as follows Figure 6As shown, the passband range is 5 GHz to 20 GHz, the attenuation flatness of the attenuator is maintained within 0.5 dB, and the in-band return loss is maintained below -14 dB. Compared with the one-section matching attenuator of the first embodiment, the three-section matching attenuator of the second embodiment further improves the stability and impedance matching performance of the attenuator.

[0080] Through the above embodiments, the attenuator in the present invention has the characteristics of compact structure and simple design, can achieve accurate attenuation in microwave and millimeter wave high frequency bands, and has excellent impedance matching performance. The design of using microstrip lines to replace traditional resistor elements enables the present invention to exhibit good frequency response and low loss characteristics in high-frequency applications, and successfully solves the problems of large parasitic effects and unstable frequency response in the existing attenuator in the high frequency band. Therefore, the attenuator of the present invention is very suitable for use in various high-frequency circuits and systems that need to attenuate signals, especially in the microwave and millimeter wave bands.

[0081] Based on the attenuator provided in the above embodiment, the present invention can also be applied to a signal test system. The above-mentioned Π-type attenuator based on microstrip matching can provide effective protection for devices such as network analyzers and signal generators. During the test process, the attenuator can ensure that the signal strength does not exceed the tolerance range of the device, and avoid high-power signals being directly transmitted to the device and causing damage. Especially when measuring high-power signals, the attenuator can effectively adjust the signal strength, ensure the safety of the device, and maintain the accuracy and stability of the measurement.

[0082] In addition, the present invention can also be applied to communication systems, especially microwave and radio frequency communication systems. In these systems, signal power control is crucial because an overly strong signal may cause distortion, interference or equipment damage. By adopting the microstrip matching-based Π-type attenuator of the present invention, the signal power in the system can be effectively adjusted to avoid the negative impact of an overly strong or weak signal. For example, in a base station or satellite communication system, the attenuator can appropriately attenuate the signal at different links, thereby ensuring the quality of the communication signal, avoiding signal distortion or interference, and ensuring the stable operation of the system.

[0083] The attenuator of the present invention can not only be used for power regulation in communication systems, but also provide important technical support in other high-frequency applications. In high-frequency circuits, accurate regulation of signal power is one of the key factors to ensure efficient and stable operation of equipment. Through reasonable power control, the attenuator of the present invention can provide a more reliable and stable signal regulation solution in complex high-frequency systems, and has broad application prospects and commercial value.

[0084] The above embodiment is only one of the implementation methods that can realize the technical solution of the present invention. The scope of protection claimed by the present invention is not limited only to this embodiment, but also includes changes, replacements and other implementation methods that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention.

Claims

1. A Π-type attenuator based on microstrip matching, characterized in that: The invention comprises a first resistor (1), a second resistor (2) and a matching microstrip line, wherein two ends of the matching microstrip line are respectively connected to the first resistor (1) and the second resistor (2), the length of the matching microstrip line is λ / 4, λ is the wavelength corresponding to the center frequency of the attenuator, and the resistance values ​​of the first resistor (1) and the second resistor (2) are equal.

2. The Π-type attenuator based on microstrip matching according to claim 1, characterized in that: The matching microstrip line is a section of microstrip line (3), and two ends of the microstrip line (3) are respectively connected to the first resistor (1) and the second resistor (2).

3. The Π-type attenuator based on microstrip matching according to claim 2, characterized in that: The connection point between the microstrip line (3) and the first resistor (1) is a voltage amplitude point; and the connection point between the microstrip line (3) and the second resistor (2) is a voltage wave node.

4. The Π-type attenuator based on microstrip matching according to claim 2, characterized in that: The resistance values ​​of the first resistor (1) and the second resistor (2) and the impedance of the microstrip line (3) are determined by the following formula: Among them, Z in is the input impedance, Z L is the load impedance, Z0 is the known attenuator port impedance, R1 is the resistance value of the first resistor (1) and the second resistor (2), Z1 is the impedance of the microstrip line (3), IL is the attenuation of the attenuator given in advance, P in is the input power, P out is the output power.

5. The Π-type attenuator based on microstrip matching according to claim 1, characterized in that: The matching microstrip line comprises three sections of matching microstrip lines, namely a first microstrip line (4), a second microstrip line (5) and a third microstrip line (6). The first microstrip line (4), the second microstrip line (5) and the third microstrip line (6) are connected in sequence. The left end of the first microstrip line (4) is connected to the first resistor (1), and the right end of the third microstrip line (6) is connected to the second resistor (2).

6. The Π-type attenuator based on microstrip matching according to claim 5, characterized in that: The connection point between the first microstrip line (4) and the first resistor (1) is a voltage amplitude point; and the connection point between the third microstrip line (6) and the second resistor (2) is a voltage wave node.

7. The Π-type attenuator based on microstrip matching according to claim 5, characterized in that: The resistance values ​​of the first resistor (1) and the second resistor (2) and the impedances of the first microstrip line (4), the second microstrip line (5) and the third microstrip line (6) are determined by the following formula: Among them, Z in is the input impedance, Z L is the load impedance, Z0 is the known attenuator port impedance, R1 is the resistance value of the first resistor (1) and the second resistor (2), Z2 is the impedance of the first microstrip line (4), Z3 is the impedance of the second microstrip line (5), Z4 is the impedance of the third microstrip line (6), IL is the attenuation of the attenuator given in advance, P in is the input power, P out is the output power.

8. The Π-type attenuator based on microstrip matching according to claim 1, characterized in that: The lengths of the first microstrip line (4), the second microstrip line (5) and the third microstrip line (6) are all λ / 4; the widths of the first microstrip line (4), the second microstrip line (5) and the third microstrip line (6) increase in sequence.

9. A signal testing system, characterized in that: A Π-type attenuator based on microstrip matching as described in any one of claims 1 to 8 is adopted.

10. A communication system, characterized in that: A Π-type attenuator based on microstrip matching as described in any one of claims 1 to 8 is adopted.

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