Test tool and test method for crosstalk suppression of radio frequency microstrip line

Abstract

The invention discloses a radio frequency microstrip line crosstalk suppression test tool and a test method thereof, the test tool comprises a circuit board, an irrelevant microstrip line, an interference source microstrip line, a disturbed source microstrip line, a vector network analyzer, a nanometer shielding film and a packaging layer, the irrelevant microstrip line, the interference source microstrip line and the disturbed source microstrip line are arranged on the surface of the circuit board at intervals; one ends of the interference source microstrip line and the disturbed source microstrip line are connected with the vector network analyzer, and the other ends are connected with the standard terminal load; the surface of the interference source microstrip line or the disturbed source microstrip line is covered with a nanometer shielding film. The packaging layer is arranged on the surfaces of the circuit board, the irrelevant microstrip line, the interference source microstrip line, the disturbed source microstrip line and the nanometer shielding film. The device is simple in structure and does not occupy extra wiring space; the nano-film is easy to integrate and reuse, and the process compatibility is strong; through flexible adjustment of the film coverage position, directional shielding of the transmitting end and the receiving end is realized, the suppression effect is improved, and the applicability is wide.

Description

Technical Field

[0001] This invention pertains to test fixtures and methods, specifically a test fixture and method for suppressing crosstalk in radio frequency microstrip lines. Background Technology

[0002] With the widespread application of 5G / 6G communication, high-speed interconnects, and millimeter-wave chips, modern electronic systems place higher demands on signal integrity and electromagnetic compatibility. As circuit operating frequencies increase, capacitive and inductive coupling between adjacent traces becomes a key factor limiting bandwidth and causing crosstalk. According to interconnect design specifications, the traditional "3W rule" is used to suppress electromagnetic coupling by increasing the spacing between traces. Although this effectively reduces mutual capacitance and inductance, it also results in a 30% to 40% decrease in wiring density, which is detrimental to the miniaturization of devices.

[0003] Existing crosstalk testing solutions generally suffer from drawbacks such as simple structure, lack of material adaptability, limited evaluation dimensions, and low testing efficiency. Especially in high-frequency communication systems and multi-material integrated platforms, they struggle to meet the needs for rapid comparative verification of novel electromagnetic shielding materials and directional suppression structures. Summary of the Invention

[0004] Purpose of the invention: In order to overcome the shortcomings of the prior art, the purpose of this invention is to provide a test fixture for RF microstrip line crosstalk suppression that improves the signal integrity of RF transmission links and the anti-interference capability of the system. Another purpose of this invention is to provide a high-precision test method for RF microstrip line crosstalk suppression.

[0005] Technical Solution: The present invention provides a test fixture for suppressing crosstalk in radio frequency microstrip lines, comprising a circuit board, an unrelated microstrip line, an interfering source microstrip line, a disturbed source microstrip line, a vector network analyzer, a nano-shielding film, and an encapsulation layer. The unrelated microstrip line, interfering source microstrip line, and disturbed source microstrip line are spaced apart on the surface of the circuit board. One end of each interfering source microstrip line and disturbed source microstrip line is connected to the vector network analyzer, and the other end is connected to a standard terminal load. The surface of the interfering source microstrip line or disturbed source microstrip line is covered with a nano-shielding film, and the encapsulation layer is disposed on the surface of the circuit board, the unrelated microstrip line, the interfering source microstrip line, the disturbed source microstrip line, and the nano-shielding film.

[0006] Furthermore, the nano-shielding film is an Ag NWs / PLLA composite film. Preferably, the resistance of the nano-shielding film is <35Ω. It is ensured that the nano-shielding film adheres tightly to the surface of the interference source microstrip line, without wrinkles or suspended areas.

[0007] Furthermore, the encapsulation layer is made of epoxy resin and a transparent curing agent.

[0008] Furthermore, the ports connecting the interference source microstrip line to the standard terminal load and the ports connecting the disturbed source microstrip line to the standard terminal load are located on opposite sides of the circuit board.

[0009] Furthermore, the unrelated microstrip lines, the interfering source microstrip lines, and the disturbed source microstrip lines are completely identical, and the line width is less than three times the line width.

[0010] Furthermore, the spacing between the unrelated microstrip line and the interfering source microstrip line, and between the interfering source microstrip line and the disturbed source microstrip line, is greater than the width of the interfering source microstrip line.

[0011] The present invention discloses a test method for suppressing crosstalk in radio frequency microstrip lines, comprising the following steps:

[0012] Step 1: Connect the vector network analyzer to one end of the interfering source microstrip line, input the radio frequency signal, connect the vector network analyzer to one end of the disturbed source microstrip line, and connect the other ends of both the interfering source microstrip line and the disturbed source microstrip line to the standard terminal load.

[0013] Step two: Cover the interfering source microstrip line with the encapsulation layer, and use a vector network analyzer to perform multiple coupling tests on the input RF signal of the interfering source microstrip line. Obtain a stable reference crosstalk signal frequency response S before crosstalk suppression on the interfering source microstrip line. 41，ref ;

[0014] Step 3: Insert a nano-shielding film between the encapsulation layer and the interference source microstrip line. After ensuring a tight fit, record the frequency response S of the crosstalk signal under this configuration. 41，mat ;

[0015] Step 4, calculate S 41，ref and S 41，mat The difference is used to characterize the magnitude of crosstalk suppression.

[0016] Furthermore, in step two, the vector network analyzer inputs the radio frequency signal to the interfering microstrip line at a frequency of 2–18 GHz, preferably 4–8 GHz. Considering the characteristics of crosstalk variation with frequency in high-speed signal transmission of parallel microstrip lines, as well as the limitations of factors such as conductor spacing, length matching, and processing accuracy in circuit board fabrication, the selected signal frequency range is set to 2–18 GHz. In the low-frequency band (e.g., below 2 GHz), crosstalk is mainly electrostatic coupling with low energy coupling efficiency, making it difficult to significantly characterize frequency-related coupling behavior. In the high-frequency band (above 18 GHz), the electromagnetic field distribution between microstrip lines is complex, and the coupling path is limited by process bandwidth and increased dielectric loss, posing significant challenges to test structure design and detection accuracy. Therefore, the frequency range of 2–18 GHz can cover the main crosstalk behavior characteristics in typical high-speed interconnects while ensuring sufficient coupling strength.

[0017] Furthermore, the formula for calculating the crosstalk suppression amplitude is as follows:

[0018] .

[0019] Furthermore, the resistance of the standard terminal load is 50 Ω.

[0020] Test Principle: Based on a dual microstrip line structure simulating crosstalk coupling in a high-density wiring environment, this test focuses on evaluating the shielding and suppression effect of the nanofilm on RF crosstalk signals. A vector network analyzer (VNA) is used to measure the transmission parameters between the two microstrip lines, particularly the S-axis, which represents the coupling of the interfering line signal to the affected line. 41 Parameters. The frequency response S of the reference crosstalk signal was measured without nanofilm coverage. 41，ref A nanofilm was placed between a microstrip line and a covering medium, and the frequency response S of the crosstalk signal after the covering film was measured. 41，mat By comparing the two, the crosstalk suppression amplitude (in dB) is calculated:

[0021] .

[0022] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0023] 1. Wideband RF microstrip line crosstalk suppression is achieved using nanofilms, resulting in a simple device structure that does not require additional wiring space;

[0024] 2. Nanofilms are easy to integrate and reuse, and have strong process compatibility;

[0025] 3. By flexibly adjusting the film coverage position, directional shielding of the transmitter and receiver can be achieved, improving the suppression effect and making it widely applicable;

[0026] 4. The radio frequency microstrip line crosstalk suppression method is applicable to the frequency band from 2 GHz to 18 GHz. It can help testers determine the crosstalk suppression performance of different transmission lines isolated by nanofilm, significantly improve the accuracy and efficiency of crosstalk testing, and can be used for long-term stability testing. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the test fixture of the present invention;

[0028] Figure 2 This is a schematic diagram of the structure of the nano-shielding film 6 of the present invention;

[0029] Figure 3 This is a cross-sectional view of the nano-shielding film 6 covered by the present invention;

[0030] Figure 4 This is a top view of the nano-shielding film 6 of the present invention;

[0031] Figure 5 This is a graph showing the test results of the crosstalk suppression effectiveness of isolating interference sources in Embodiment 1 of the present invention;

[0032] Figure 6 This is a graph showing the changes in crosstalk suppression performance corresponding to the changes in thin film surface resistance in Examples 1-10 of the present invention. Detailed Implementation

[0033] like Figures 1-4 The surface of circuit board 1 is provided with an unrelated microstrip line 2, an interfering source microstrip line 3, and a disturbed source microstrip line 4. These three lines are identical in shape and material, each with a width of 3.5 mm. They are arranged side-by-side with a spacing of 5 mm between them. The middle line is the interfering source microstrip line 3, the right line is the disturbed source microstrip line 4, and the left line is the unrelated microstrip line 2. Together, they form a typical crosstalk test structure to simulate dual-path same-frequency crosstalk when transmitting high-frequency signals via parallel microstrip lines. Based on the frequency and power of the input signal to the interfering line during testing, the spacing between the two microstrip lines is adjusted to ensure that the output port of the disturbed line receives a clearly visible S0. 41 Crosstalk coupling value. Circuit board 1 is a PCB board with a length of 60 mm. Port 31 of the interfering source microstrip line 3 is connected to the vector network analyzer 5, and port 32 is connected to a 50 Ω standard terminating load. Port 41 of the affected source microstrip line 4 is connected to a 50 Ω standard terminating load, and port 42 is connected to the vector network analyzer 5. The surface of either the interfering source microstrip line 3 or the affected source microstrip line 4 is covered with a nano-shielding film 6. An encapsulation layer 7 is disposed on the surface of circuit board 1, unrelated microstrip line 2, interfering source microstrip line 3, affected source microstrip line 4, and nano-shielding film 6. The nano-shielding film 6 is an Ag NWs / PLLA composite film. The encapsulation layer 7 is made of epoxy resin and a transparent curing agent. The nano-shielding film 6, encapsulation layer 7, circuit board 1, unrelated microstrip line 2, interfering source microstrip line 3, and affected source microstrip line 4 can be perfectly integrated to prevent electromagnetic wave leakage. The size of the nano-shielding film 6 needs to completely cover the interference source microstrip line 3 or the disturbed source microstrip line 4, isolate the crosstalk coupling electromagnetic waves generated by the disturbed source microstrip line 4, and make it tightly attached to the circuit board 1 and the encapsulation layer 7 to avoid wave leakage.

[0034] Example 1

[0035] A test method for suppressing crosstalk in radio frequency microstrip lines includes the following steps:

[0036] Step 1: Connect the vector network analyzer 5 to port 31 of the interfering source microstrip line 3 in the middle of the PCB under test, and input an RF signal with a frequency range of 4~8 GHz. Connect the vector network analyzer 5 to port 42 of the affected source microstrip line 4 on the right side to receive crosstalk signals transmitted through the spatial coupling path. To ensure system impedance matching and reduce reflections, connect port 32 of the interfering source microstrip line 3 and port 41 of the affected source microstrip line 4 to a 50 Ω standard terminating load. This port configuration can stabilize the signal path and accurately reflect the coupling signal strength, i.e., S. 41 parameter.

[0037] Step 2: Prepare an encapsulation layer 7 with dimensions of 60 mm × 50 mm × 5 mm by mixing epoxy resin and polyamide curing agent at a mass ratio of 2:1, simulating a typical chip packaging form. Cover the microstrip line structure (unrelated microstrip line 2, interfering source microstrip line 3, disturbed source microstrip line 4, and circuit board 1) with this encapsulation layer 7, and record the S values ​​under this condition. 41 The value is used as a reference baseline when the nano-shielding film 6 is not present. This step is used to evaluate the shielding adaptability and actual effectiveness S of the nano-shielding film 6 under real packaging process conditions. 41,ref .

[0038] Step 3: Cut a 60 mm × 14 mm Ag NWs / PLLA composite film and insert it between the encapsulation layer 7 and the PCB board with the microstrip line, ensuring that the nano-shielding film 6 completely covers the top and sides of the interference source microstrip line 3. Keeping other test conditions unchanged, record the S values ​​under this configuration. 41 Data used to characterize the crosstalk suppression performance of the nano-shielding film after isolation. 41,mat Ensure that the nano-shielding film 6 is placed within the spacing range of the parallel microstrip lines (unrelated microstrip line 2, interfering source microstrip line 3, and disturbed source microstrip line 4), and that when testing the crosstalk suppression effect of isolating one of the microstrip lines, the nano-shielding film 6 must not contact the other untested microstrip line to avoid additional coupling paths or interference affecting the accuracy of the measurement results. The encapsulation layer 7 is fixed in a fixed position, located directly above the microstrip lines on the circuit board 1, forming a sandwich structure to ensure that the nano-shielding film 6 is tightly attached to the microstrip lines.

[0039] Step 4: Compare the S without the nano-shielding film 6 (baseline) with the S after the nano-shielding film 6 is attached. 41 The values ​​are calculated, and the difference is used to characterize the degree of crosstalk suppression. The nano-shielding film 6 obtained in steps 2 and 3 is placed before S 41,ref And after shielding S 41,mat Subtracting the data yields the far-end crosstalk suppression performance of the Ag NWs / PLLA composite film with a surface resistivity of 6 Ω when isolating interference sources.

[0040] Figure 5 The S obtained from the test by Vector Network Analyzer 5 41 The data comparison chart shows that the crosstalk suppression performance of the nano-shielding film 6 with a surface resistance of 6 Ω when isolating interference sources can be successfully obtained by calculating the data difference.

[0041] Example 2

[0042] A test method for suppressing crosstalk in radio frequency microstrip lines includes the following steps:

[0043] Step 1: Connect the vector network analyzer 5 to the interfering microstrip line 3 in the middle of the PCB under test, and input an RF signal with a frequency range of 4~8 GHz. Connect the vector network analyzer 5 to port 42 of the affected microstrip line 4 on the right side to receive crosstalk signals transmitted through the spatial coupling path. To ensure system impedance matching and reduce reflections, connect port 32 of the interfering microstrip line 3 and port 41 of the affected microstrip line 4 to a 50 Ω standard terminating load. This port configuration stabilizes the signal path and accurately reflects the coupling signal strength, i.e., S. 41 parameter.

[0044] Step 2: Prepare an encapsulation layer 7 with dimensions of 60 mm × 50 mm × 5 mm by mixing epoxy resin and polyamide curing agent at a mass ratio of 2:1, simulating a typical chip packaging form. This encapsulation layer 7 is then applied to the microstrip line structure (unrelated microstrip line 2, interfering source microstrip line 3, disturbed source microstrip line 4, and circuit board 1), and the S41 value under this condition is recorded as a reference baseline without the nano-shielding film 6. This step is used to evaluate the shielding adaptability and actual effectiveness S41 of the nano-shielding film 6 under real packaging process conditions. 41,ref .

[0045] Step 3: Cut a 60 mm × 14 mm Ag NWs / PLLA composite film and insert it between the encapsulation layer 7 and the PCB board with the microstrip line, so that the nano-shielding film 6 covers the disturbed source microstrip line 4. Keeping other test conditions unchanged, record the S under this configuration. 41 Data used to characterize the crosstalk suppression performance of the nano-shielding film after isolation. 41,mat .

[0046] Step 4: Compare the unattached nano-shielding film 6 (baseline) with the film-attached S. 41 The values ​​are calculated, and the difference is used to characterize the degree of crosstalk suppression. The nano-shielding film 6 obtained in steps 2 and 3 is placed before S 41,ref And after shielding S 41,mat Subtracting the data yields the far-end crosstalk suppression performance of the Ag NWs / PLLA composite film with a surface resistivity of 6 Ω when isolating the disturbed source.

[0047] Example 3

[0048] A test method for suppressing crosstalk in radio frequency microstrip lines includes the following steps:

[0049] Step 1: Connect the vector network analyzer 5 to the interfering microstrip line 3 in the middle of the PCB under test, and input an RF signal with a frequency range of 4~8 GHz. Connect the vector network analyzer 5 to port 42 of the affected microstrip line 4 on the right side to receive crosstalk signals transmitted through the spatial coupling path. To ensure system impedance matching and reduce reflections, connect port 32 of the interfering microstrip line 3 and port 41 of the affected microstrip line 4 to a 50 Ω standard terminating load. This port configuration stabilizes the signal path and accurately reflects the coupling signal strength, i.e., S. 41 parameter.

[0050] Step 2: Prepare an encapsulation layer 7 with dimensions of 60 mm × 50 mm × 5 mm by mixing epoxy resin and polyamide curing agent at a mass ratio of 2:1, simulating a typical chip packaging form. This encapsulation layer 7 is then applied to the microstrip line structure (unrelated microstrip line 2, interfering source microstrip line 3, disturbed source microstrip line 4, and circuit board 1), and the S41 value under this condition is recorded as a reference baseline without the nano-shielding film 6. This step is used to evaluate the shielding adaptability and actual effectiveness S41 of the nano-shielding film 6 under real packaging process conditions. 41,ref .

[0051] Step 3: Cut a 60 mm × 14 mm Ag NWs / PLLA composite film and insert it between the encapsulation layer 7 and the PCB board with the microstrip line, so that the nano-shielding film 6 covers the interference source microstrip line 3. Keeping other test conditions unchanged, record the S under this configuration. 41 Data used to characterize the crosstalk suppression performance of the nano-shielding film after isolation. 41,mat .

[0052] Step 4: Compare the unattached nano-shielding film 6 (baseline) with the film-attached S. 41 The values ​​are calculated, and the difference is used to characterize the degree of crosstalk suppression. The nano-shielding film 6 obtained in steps 2 and 3 is placed before S 41,ref And after shielding S 41,mat Subtracting the data, we obtain the far-end crosstalk suppression performance of the Ag NWs / PLLA composite film with a surface resistivity of 15 Ω when isolating the disturbed source.

[0053] Example 4

[0054] A test method for suppressing crosstalk in radio frequency microstrip lines includes the following steps:

[0055] Step 1: Connect the vector network analyzer 5 to the interfering microstrip line 3 in the middle of the PCB under test, and input an RF signal with a frequency range of 4~8 GHz. Connect the vector network analyzer 5 to port 42 of the affected microstrip line 4 on the right side to receive crosstalk signals transmitted through the spatial coupling path. To ensure system impedance matching and reduce reflections, connect port 32 of the interfering microstrip line 3 and port 41 of the affected microstrip line 4 to a 50 Ω standard terminating load. This port configuration stabilizes the signal path and accurately reflects the coupling signal strength, i.e., S. 41 parameter.

[0056] Step 2: Prepare an encapsulation layer 7 with dimensions of 60 mm × 50 mm × 5 mm by mixing epoxy resin and polyamide curing agent at a mass ratio of 2:1, simulating a typical chip packaging form. This encapsulation layer 7 is then applied to the microstrip line structure (unrelated microstrip line 2, interfering source microstrip line 3, disturbed source microstrip line 4, and circuit board 1), and the S41 value under this condition is recorded as a reference baseline without the nano-shielding film 6. This step is used to evaluate the shielding adaptability and actual effectiveness S41 of the nano-shielding film 6 under real packaging process conditions. 41,ref .

[0057] Step 3: Cut a 60 mm × 14 mm Ag NWs / PLLA composite film and insert it between the encapsulation layer 7 and the PCB board with the microstrip line, so that the nano-shielding film 6 covers the disturbed source microstrip line 4. Keeping other test conditions unchanged, record the S under this configuration. 41 Data used to characterize the crosstalk suppression performance of the nano-shielding film after isolation. 41,mat .

[0058] Step 4: Compare the unattached nano-shielding film 6 (baseline) with the film-attached S. 41 The values ​​are calculated, and the difference is used to characterize the degree of crosstalk suppression. The nano-shielding film 6 obtained in steps 2 and 3 is placed before S 41,ref And after shielding S 41,mat Subtracting the data, we obtain the far-end crosstalk suppression performance of the Ag NWs / PLLA composite film with a surface resistivity of 15 Ω when isolating the disturbed source.

[0059] Example 5

[0060] A test method for suppressing crosstalk in radio frequency microstrip lines includes the following steps:

[0061] Step 1: Connect the vector network analyzer 5 to the interfering microstrip line 3 in the middle of the PCB under test, and input an RF signal with a frequency range of 4~8 GHz. Connect the vector network analyzer 5 to port 42 of the affected microstrip line 4 on the right side to receive crosstalk signals transmitted through the spatial coupling path. To ensure system impedance matching and reduce reflections, connect port 32 of the interfering microstrip line 3 and port 41 of the affected microstrip line 4 to a 50 Ω standard terminating load. This port configuration stabilizes the signal path and accurately reflects the coupling signal strength, i.e., S. 41 parameter.

[0062] Step 2: Prepare an encapsulation layer 7 with dimensions of 60 mm × 50 mm × 5 mm by mixing epoxy resin and polyamide curing agent at a mass ratio of 2:1, simulating a typical chip packaging form. This encapsulation layer 7 is then applied to the microstrip line structure (unrelated microstrip line 2, interfering source microstrip line 3, disturbed source microstrip line 4, and circuit board 1), and the S41 value under this condition is recorded as a reference baseline without the nano-shielding film 6. This step is used to evaluate the shielding adaptability and actual effectiveness S41 of the nano-shielding film 6 under real packaging process conditions. 41,ref .

[0063] Step 3: Cut a 60 mm × 14 mm Ag NWs / PLLA composite film and insert it between the encapsulation layer 7 and the PCB board with the microstrip line, so that the nano-shielding film 6 covers the interference source microstrip line 3. Keeping other test conditions unchanged, record the S under this configuration. 41 Data used to characterize the crosstalk suppression performance of the nano-shielding film after isolation. 41,mat .

[0064] Step 4: Compare the unattached nano-shielding film 6 (baseline) with the film-attached S. 41 The values ​​are calculated, and the difference is used to characterize the degree of crosstalk suppression. The nano-shielding film 6 obtained in steps 2 and 3 is placed before S 41,ref And after shielding S 41,mat Subtracting the data, we obtain the far-end crosstalk suppression performance of the Ag NWs / PLLA composite film with a surface resistivity of 35 Ω when isolating the disturbed source.

[0065] Example 6

[0066] A test method for suppressing crosstalk in radio frequency microstrip lines includes the following steps:

[0067] Step 1: Connect the vector network analyzer 5 to the interfering microstrip line 3 in the middle of the PCB under test, and input an RF signal with a frequency range of 4~8 GHz. Connect the vector network analyzer 5 to port 42 of the affected microstrip line 4 on the right side to receive crosstalk signals transmitted through the spatial coupling path. To ensure system impedance matching and reduce reflections, connect port 32 of the interfering microstrip line 3 and port 41 of the affected microstrip line 4 to a 50 Ω standard terminating load. This port configuration stabilizes the signal path and accurately reflects the coupling signal strength, i.e., S. 41 parameter.

[0068] Step 2: Prepare an encapsulation layer 7 with dimensions of 60 mm × 50 mm × 5 mm by mixing epoxy resin and polyamide curing agent at a mass ratio of 2:1, simulating a typical chip packaging form. This encapsulation layer 7 is then applied to the microstrip line structure (unrelated microstrip line 2, interfering source microstrip line 3, disturbed source microstrip line 4, and circuit board 1), and the S41 value under this condition is recorded as a reference baseline without the nano-shielding film 6. This step is used to evaluate the shielding adaptability and actual effectiveness S41 of the nano-shielding film 6 under real packaging process conditions. 41,ref .

[0069] Step 3: Cut a 60 mm × 14 mm Ag NWs / PLLA composite film and insert it between the encapsulation layer 7 and the PCB board with the microstrip line, so that the nano-shielding film 6 covers the disturbed source microstrip line 4. Keeping other test conditions unchanged, record the S under this configuration. 41 Data used to characterize the crosstalk suppression performance of the nano-shielding film after isolation. 41,mat .

[0070] Step 4: Compare the unattached nano-shielding film 6 (baseline) with the film-attached S. 41 The values ​​are calculated, and the difference is used to characterize the degree of crosstalk suppression. The nano-shielding film 6 obtained in steps 2 and 3 is placed before S 41,ref And after shielding S 41,mat Subtracting the data, we obtain the far-end crosstalk suppression performance of the Ag NWs / PLLA composite film with a surface resistivity of 35 Ω when isolating the disturbed source.

[0071] Example 7

[0072] A test method for suppressing crosstalk in radio frequency microstrip lines includes the following steps:

[0073] Step 1: Connect the vector network analyzer 5 to the interfering microstrip line 3 in the middle of the PCB under test, and input an RF signal with a frequency range of 4~8 GHz. Connect the vector network analyzer 5 to port 42 of the affected microstrip line 4 on the right side to receive crosstalk signals transmitted through the spatial coupling path. To ensure system impedance matching and reduce reflections, connect port 32 of the interfering microstrip line 3 and port 41 of the affected microstrip line 4 to a 50 Ω standard terminating load. This port configuration stabilizes the signal path and accurately reflects the coupling signal strength, i.e., S. 41 parameter.

[0074] Step 2: Prepare an encapsulation layer 7 with dimensions of 60 mm × 50 mm × 5 mm by mixing epoxy resin and polyamide curing agent at a mass ratio of 2:1, simulating a typical chip packaging form. This encapsulation layer 7 is then applied to the microstrip line structure (unrelated microstrip line 2, interfering source microstrip line 3, disturbed source microstrip line 4, and circuit board 1), and the S41 value under this condition is recorded as a reference baseline without the nano-shielding film 6. This step is used to evaluate the shielding adaptability and actual effectiveness S41 of the nano-shielding film 6 under real packaging process conditions. 41,ref .

[0075] Step 3: Cut a 60 mm × 14 mm Ag NWs / PLLA composite film and insert it between the encapsulation layer 7 and the PCB board with the microstrip line, so that the nano-shielding film 6 covers the interference source microstrip line 3. Keeping other test conditions unchanged, record the S under this configuration. 41 Data used to characterize the crosstalk suppression performance of the nano-shielding film after isolation. 41,mat .

[0076] Step 4: Compare the unattached nano-shielding film 6 (baseline) with the film-attached S. 41 The values ​​are calculated, and the difference is used to characterize the degree of crosstalk suppression. The nano-shielding film 6 obtained in steps 2 and 3 is placed before S 41,ref And after shielding S 41,mat Subtracting the data, we obtain the far-end crosstalk suppression performance of the Ag NWs / PLLA composite film with a surface resistivity of 55 Ω when isolating the disturbed source.

[0077] Example 8

[0078] A test method for suppressing crosstalk in radio frequency microstrip lines includes the following steps:

[0079] Step 1: Connect the vector network analyzer 5 to the interfering microstrip line 3 in the middle of the PCB under test, and input an RF signal with a frequency range of 4~8 GHz. Connect the vector network analyzer 5 to port 42 of the affected microstrip line 4 on the right side to receive crosstalk signals transmitted through the spatial coupling path. To ensure system impedance matching and reduce reflections, connect port 32 of the interfering microstrip line 3 and port 41 of the affected microstrip line 4 to a 50 Ω standard terminating load. This port configuration stabilizes the signal path and accurately reflects the coupling signal strength, i.e., S. 41 parameter.

[0080] Step 2: Prepare an encapsulation layer 7 with dimensions of 60 mm × 50 mm × 5 mm by mixing epoxy resin and polyamide curing agent at a mass ratio of 2:1, simulating a typical chip packaging form. This encapsulation layer 7 is then applied to the microstrip line structure (unrelated microstrip line 2, interfering source microstrip line 3, disturbed source microstrip line 4, and circuit board 1), and the S41 value under this condition is recorded as a reference baseline without the nano-shielding film 6. This step is used to evaluate the shielding adaptability and actual effectiveness S41 of the nano-shielding film 6 under real packaging process conditions. 41,ref .

[0081] Step 3: Cut a 60 mm × 14 mm Ag NWs / PLLA composite film and insert it between the encapsulation layer 7 and the PCB board with the microstrip line, so that the nano-shielding film 6 covers the disturbed source microstrip line 4. Keeping other test conditions unchanged, record the S under this configuration. 41 Data used to characterize the crosstalk suppression performance of the nano-shielding film after isolation. 41,mat .

[0082] Step 4: Compare the unattached nano-shielding film 6 (baseline) with the film-attached S. 41 The values ​​are calculated, and the difference is used to characterize the degree of crosstalk suppression. The nano-shielding film 6 obtained in steps 2 and 3 is placed before S 41,ref And after shielding S 41,mat Subtracting the data, we obtain the far-end crosstalk suppression performance of the Ag NWs / PLLA composite film with a surface resistivity of 55 Ω when isolating the disturbed source.

[0083] Example 9

[0084] A test method for suppressing crosstalk in radio frequency microstrip lines includes the following steps:

[0085] Step 1: Connect the vector network analyzer 5 to the interfering microstrip line 3 in the middle of the PCB under test, and input an RF signal with a frequency range of 4~8 GHz. Connect the vector network analyzer 5 to port 42 of the affected microstrip line 4 on the right side to receive crosstalk signals transmitted through the spatial coupling path. To ensure system impedance matching and reduce reflections, connect port 32 of the interfering microstrip line 3 and port 41 of the affected microstrip line 4 to a 50 Ω standard terminating load. This port configuration stabilizes the signal path and accurately reflects the coupling signal strength, i.e., S. 41 parameter.

[0086] Step 2: Prepare an encapsulation layer 7 with dimensions of 60 mm × 50 mm × 5 mm by mixing epoxy resin and polyamide curing agent at a mass ratio of 2:1, simulating a typical chip packaging form. This encapsulation layer 7 is then applied to the microstrip line structure (unrelated microstrip line 2, interfering source microstrip line 3, disturbed source microstrip line 4, and circuit board 1), and the S41 value under this condition is recorded as a reference baseline without the nano-shielding film 6. This step is used to evaluate the shielding adaptability and actual effectiveness S41 of the nano-shielding film 6 under real packaging process conditions. 41,ref .

[0087] Step 3: Cut a 60 mm × 14 mm Ag NWs / PLLA composite film and insert it between the encapsulation layer 7 and the PCB board with the microstrip line, so that the nano-shielding film 6 covers the interference source microstrip line 3. Keeping other test conditions unchanged, record the S under this configuration. 41 Data used to characterize the crosstalk suppression performance of the nano-shielding film after isolation. 41,mat .

[0088] Step 4: Compare the unattached nano-shielding film 6 (baseline) with the film-attached S. 41 The values ​​are calculated, and the difference is used to characterize the degree of crosstalk suppression. The nano-shielding film 6 obtained in steps 2 and 3 is placed before S 41,ref And after shielding S 41,mat Subtracting the data, we obtain the far-end crosstalk suppression performance of the Ag NWs / PLLA composite film with a surface resistivity of 80 Ω when isolating the disturbed source.

[0089] Example 10

[0090] A test method for suppressing crosstalk in radio frequency microstrip lines includes the following steps:

[0091] Step 1: Connect the vector network analyzer 5 to the interfering microstrip line 3 in the middle of the PCB under test, and input an RF signal with a frequency range of 4~8 GHz. Connect the vector network analyzer 5 to port 42 of the affected microstrip line 4 on the right side to receive crosstalk signals transmitted through the spatial coupling path. To ensure system impedance matching and reduce reflections, connect port 32 of the interfering microstrip line 3 and port 41 of the affected microstrip line 4 to a 50 Ω standard terminating load. This port configuration stabilizes the signal path and accurately reflects the coupling signal strength, i.e., S. 41 parameter.

[0092] Step 2: Prepare an encapsulation layer 7 with dimensions of 60 mm × 50 mm × 5 mm by mixing epoxy resin and polyamide curing agent at a mass ratio of 2:1, simulating a typical chip packaging form. This encapsulation layer 7 is then applied to the microstrip line structure (unrelated microstrip line 2, interfering source microstrip line 3, disturbed source microstrip line 4, and circuit board 1), and the S41 value under this condition is recorded as a reference baseline without the nano-shielding film 6. This step is used to evaluate the shielding adaptability and actual effectiveness S41 of the nano-shielding film 6 under real packaging process conditions. 41,ref .

[0093] Step 3: Cut a 60 mm × 14 mm Ag NWs / PLLA composite film and insert it between the encapsulation layer 7 and the PCB board with the microstrip line, so that the nano-shielding film 6 covers the disturbed source microstrip line 4. Keeping other test conditions unchanged, record the S under this configuration. 41 Data used to characterize the crosstalk suppression performance of the nano-shielding film after isolation. 41,mat .

[0094] Step 4: Compare the unattached nano-shielding film 6 (baseline) with the film-attached S. 41 The values ​​are calculated, and the difference is used to characterize the degree of crosstalk suppression. The nano-shielding film 6 obtained in steps 2 and 3 is placed before S 41,ref And after shielding S 41,mat Subtracting the data, we obtain the far-end crosstalk suppression performance of the Ag NWs / PLLA composite film with a surface resistivity of 80 Ω when isolating the disturbed source.

[0095] After completing ten tests, the changes in crosstalk suppression effectiveness at a frequency of 6 GHz were analyzed, including isolating the interfering source microstrip line 3 or the affected source microstrip line 4, and altering the surface resistance of the nano-shielding film 6. Figure 6As shown, when the resistance of the nano-shielding film 6 is <35 Ω, a stable conductive network is formed, and the crosstalk suppression effect remains at 10~12dB, with no significant correlation to the resistance. However, when the resistance of the nano-shielding film 6 is ≥35 Ω, the conductive path is damaged, the local electromagnetic field diffusion is enhanced, and the suppression effect weakens significantly with increasing resistance. Therefore, when the line spacing is less than three times the linewidth, the optimal surface resistance of the film for crosstalk suppression should be <35Ω.

Claims

1. A test fixture for suppressing crosstalk in radio frequency microstrip lines, characterized in that: The system includes a circuit board (1), an unrelated microstrip line (2), an interference source microstrip line (3), a disturbed source microstrip line (4), a vector network analyzer (5), a nano-shielding film (6), and an encapsulation layer (7). The unrelated microstrip line (2), the interference source microstrip line (3), and the disturbed source microstrip line (4) are spaced apart on the surface of the circuit board (1). One end of the interference source microstrip line (3) and the disturbed source microstrip line (4) is connected to the vector network analyzer (5), and the other end is connected to a standard terminal load. The surface of the interference source microstrip line (3) or the disturbed source microstrip line (4) is covered with a nano-shielding film (6). The encapsulation layer (7) is disposed on the surface of the circuit board (1), the unrelated microstrip line (2), the interference source microstrip line (3), the disturbed source microstrip line (4), and the nano-shielding film (6).

2. The test fixture for suppressing crosstalk in radio frequency microstrip lines according to claim 1, characterized in that: The nano-shielding film (6) is an Ag NWs / PLLA composite film.

3. The test fixture for suppressing crosstalk in radio frequency microstrip lines according to claim 1, characterized in that: The encapsulation layer (7) is made of epoxy resin and polyamide curing agent.

4. The test fixture for suppressing crosstalk in radio frequency microstrip lines according to claim 1, characterized in that: The ports of the interference source microstrip line (3) connected to the standard terminal load and the ports of the interference source microstrip line (4) connected to the standard terminal load are located on opposite sides of the circuit board (1).

5. The test fixture for suppressing crosstalk in radio frequency microstrip lines according to claim 1, characterized in that: The unrelated microstrip line (2), the interference source microstrip line (3), and the disturbed source microstrip line (4) are completely identical, and the line spacing is less than three times the line width.

6. The test fixture for suppressing crosstalk in radio frequency microstrip lines according to claim 1, characterized in that: The spacing between the unrelated microstrip line (2) and the interference source microstrip line (3), and between the interference source microstrip line (3) and the disturbed source microstrip line (4) is greater than the width of the interference source microstrip line (3).

7. A test method for suppressing crosstalk in radio frequency microstrip lines, characterized in that, Includes the following steps: Step 1: Connect the vector network analyzer (5) to one end of the interference source microstrip line (3), input the radio frequency signal, connect the vector network analyzer (5) to one end of the interference source microstrip line (4), and connect the other ends of the interference source microstrip line (3) and the interference source microstrip line (4) to the standard terminal load. Step 2: Cover the interference source microstrip line (3) with the encapsulation layer (7), and use a vector network analyzer (5) to perform multiple coupling tests on the input RF signal of the interference source microstrip line (3). A stable reference crosstalk signal frequency response S before crosstalk suppression is obtained on the interference source microstrip line (4). 41，ref ; Step 3: Insert a nano-shielding film (6) between the encapsulation layer (7) and the interference source microstrip line (3). After the film is tightly bonded, record the frequency response S of the crosstalk signal under this configuration. 41，mat ; Step 4, calculate S 41，ref and S 41，mat The difference is used to characterize the magnitude of crosstalk suppression.

8. The test method for suppressing crosstalk in radio frequency microstrip lines according to claim 7, characterized in that: In step two, the vector network analyzer (5) inputs a radio frequency signal of 2~18GHz to the interference source microstrip line (3).

9. The test method for suppressing crosstalk in radio frequency microstrip lines according to claim 7, characterized in that: The formula for calculating the crosstalk suppression amplitude is as follows: 。 10. The test method for suppressing crosstalk in radio frequency microstrip lines according to claim 7, characterized in that: The resistance of the standard terminal load is 50Ω.

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