Electromagnetic interference probe based on PCB through hole optimization

Abstract

The invention discloses an electromagnetic interference probe based on PCB through hole optimization, the electromagnetic interference probe is of a printed circuit board structure and comprises an output part, a transmission part and a detection part, the output part is of a combined structure of a coplanar waveguide and a strip line, and transition is carried out through a signal via hole; the transmission part is of a strip line structure, and via hole arrays are placed on the two sides of a signal line and used for shielding an electromagnetic field in the side face direction and optimizing the frequency response of the probe; the detection part is of an annular antenna structure. The magnetic field probe is high in sensitivity and can be used for magnetic field testing of an integrated circuit within 8GHz.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave engineering, and in particular relates to an electromagnetic interference probe based on PCB through-hole optimization. Background Art

[0002] With the rapid development of electronic process technology and integrated circuit technology, electronic equipment is moving towards miniaturization and high integration. Due to the reduced space and more complex functional modules within the electronic equipment system, more electromagnetic interference problems have emerged. For electronic equipment, the main source of internal electromagnetic interference problems is IC. Therefore, for IC, EMI has become one of the key indicators for evaluating circuit performance. Detecting and suppressing electromagnetic interference in IC is an effective way to solve electromagnetic interference problems. In order to achieve radiation diagnosis and source location of IC, near-field testing has received widespread attention. Near-field testing is a test technology that uses a near-field probe to test the distribution of electromagnetic fields near the circuit under test. The magnetic field probe probe is a key device in near-field testing, which can convert the magnetic field above the DUT into an electrical signal output to obtain the magnetic field value.

[0003] In 1964, The measurement effect of the loop antenna on the magnetic field was studied, and the recommended value of the ring structure size was given, which laid the foundation for the research of magnetic field probes. Most of the subsequent magnetic field probes were designed based on loop antennas. Early magnetic field probes were mainly wound by coaxial transmission lines. With the emergence of high-frequency circuits, the operating frequency of the probe must cover the operating frequency of the circuit. Therefore, it is very important to broaden the bandwidth of the magnetic field probe. Since the coaxial line is not suitable for working at high frequencies, the broadband magnetic field probe is mainly based on transmission line structures such as coplanar waveguides, strip lines, and microstrip lines.

[0004] In recent years, research on magnetic field probes has received extensive attention. Miniaturized high-frequency magnetic field probes based on stripline and coplanar waveguide structures have good frequency characteristics in a wide frequency band and can be used to test the magnetic field of high-frequency integrated circuits. Due to the large loss of low-cost dielectric materials, the performance of magnetic field probes will deteriorate at high frequencies. At the same time, in order to achieve high spatial resolution of magnetic field probes, it is usually necessary to reduce the size of the probe. Therefore, current magnetic field probes have the disadvantages of high cost and low sensitivity. Summary of the invention

[0005] Purpose of the invention: In order to overcome the deficiencies in the prior art, based on microwave engineering theory, in order to optimize the frequency characteristics of the magnetic field probe and improve the sensitivity of the magnetic field probe, an electromagnetic interference probe based on PCB through-hole optimization is provided.

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

[0007] An electromagnetic interference probe based on PCB through-hole optimization, the electromagnetic interference probe is a printed circuit board structure, including an output part, a transmission part and a detection part, the output part is a combination structure of a coplanar waveguide and a stripline, and the transition is made through a signal via. The transmission part is a stripline structure, and a via array is placed on both sides of the signal line to shield the electromagnetic field in the side direction and optimize the frequency response of the probe. The detection part is a ring antenna structure.

[0008] Preferably, the electromagnetic interference probe comprises a probe top layer, a dielectric layer 1, an impedance matching layer, a dielectric layer 2, a signal layer, a dielectric layer 3, and a probe bottom layer which are arranged in sequence, and the probe top layer, the signal layer, and the probe bottom layer are connected through metal vias.

[0009] Preferably: a square groove 1 is provided on the top layer of the probe, a slit 1 is provided on the square groove 1, and a circle of first via array 1 is provided around the square groove 1 to form a ring structure. A square groove 2 is provided on the bottom layer of the probe, a slit 2 is provided on the square groove 2, and a circle of second via array 1 is provided around the square groove 2 to form a ring structure. A signal line 2 of a stripline structure is provided on the signal layer. The first via array 1 is arranged opposite to the second via array 1, the first via array 1 is connected to the second via array 1, and the slit 1 is arranged opposite to the slit 2. The square groove 1, the slit 1, the first via array 1, the curved part of the signal line 2 of the stripline structure, the square groove 2, the slit 2, and the second via array 1 form a detection part.

[0010] Preferably: a first via array 2 is provided on the top layer of the probe, a second via array 2 is provided on the bottom layer of the probe, the first via array 2 is located on both sides of the straight portion of the stripline structure, and the second via array 2 is located on both sides of the straight portion of the stripline structure. The first via array 2 is arranged opposite to the second via array 2, and the first via array 2 is connected to the second via array 2. A portion of the first via array 2, a portion of the second via array 2, a portion of the straight portion of the signal line 2 of the stripline structure of the signal layer, and a portion of the second via array 2 form a transmission portion.

[0011] Preferably: the top layer of the probe is provided with a signal line 1 of a coplanar waveguide structure and a first via array 3, the first via array 3 is located on both sides of the signal line 1 of the coplanar waveguide structure, the bottom layer of the probe is provided with a second via array 3, the impedance matching layer is provided with an impedance matching structure, the first via array 3 is arranged opposite to the second via array 3, and the first via array 3 is connected to the second via array 3. The signal line 1 of the coplanar waveguide structure, the first via array 3, another part of the first via array 2, the impedance matching structure, another part of the signal line 2 of the stripline structure of the signal layer, the second via array 3, and another part of the second via array 2 form an output portion.

[0012] Preferably, the signal line 1 of the coplanar waveguide structure, the signal line 2 of the stripline structure and the bottom layer of the probe are connected through a central signal via hole.

[0013] Preferably, the relationship between the sensitivity of the electromagnetic interference probe and the loop area is as follows:

[0014] ;

[0015] in, represents the induced voltage, represents the imaginary unit, represents the angular frequency of the magnetic field through the ring plane, represents the magnetic permeability of the dielectric material in the middle part of the ring, represents the magnetic field component, Represents the area of ​​the circular loop.

[0016] Preferably: the resonant frequency of the magnetic field probe is:

[0017] ;

[0018] in, represents the resonant frequency of the magnetic field probe, , , represents the mode number of electromagnetic waves, represents the magnetic permeability, represents the dielectric constant, is the transmission line length, is the width of the ground on both sides of the transmission line, is the thickness of the transmission line.

[0019] The arrangement of vias needs to comply with the following requirements:

[0020] and ;

[0021] in, is the distance between adjacent vias, is the distance between the via and the transmission line, Indicates wavelength.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The magnetic field probe of the present invention has high sensitivity and can be used for Integrated circuit magnetic field testing within. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the equivalent circuit of the magnetic field probe of the present invention.

[0025] Figure 2 This is the basic structure of the magnetic field probe of the present invention.

[0026] Figure 3 This is the laminated structure of the magnetic field probe of the present invention.

[0027] Figure 4 It is a layered schematic diagram of the magnetic field probe of the present invention.

[0028] Figure 5 The magnetic field probe of the present invention Model..

[0029] Figure 6 Schematic diagram of the test of the magnetic field probe of the present invention.

[0030] Figure 7 Schematic diagram of S-parameter simulation results of the magnetic field probe of the present invention. DETAILED DESCRIPTION

[0031] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0032] An electromagnetic interference probe based on PCB through-hole optimization, such as Figure 4 As shown, the electromagnetic interference probe is a printed circuit board structure, including an output part, a transmission part and a detection part. The output part is a combination of a coplanar waveguide and a stripline structure, and the transition is made through a signal via. The transmission part is a stripline structure, and a via array is placed on both sides of the signal line to shield the electromagnetic field in the side direction and optimize the frequency response of the probe. The detection part is a loop antenna structure.

[0033] The electromagnetic interference probe includes a probe top layer 1, a dielectric layer 1, an impedance matching layer 2, a dielectric layer 2, a signal layer 3, a dielectric layer 3, and a probe bottom layer 4 which are arranged in sequence. The probe top layer 1, the signal layer 3, and the probe bottom layer 4 are connected through metal vias.

[0034] The top layer 1 of the probe is provided with a square groove 11, a slit 12 is provided on the square groove 11, and a circle of first via array 13 is provided around the square groove 11 to form a ring structure. The bottom layer 4 of the probe is provided with a square groove 2 41, a slit 2 42 is provided on the square groove 2 41, and a circle of second via array 1 43 is provided around the square groove 2 41 to form a ring structure. The signal layer 3 is provided with a signal line 2 31 of a stripline structure. The first via array 1 13 is arranged opposite to the second via array 1 43, the first via array 1 13 is connected to the second via array 1 43, and the slit 1 12 is arranged opposite to the slit 2 42. The square groove 1 11, the slit 1 12, the first via array 1 13, the curved part of the signal line 2 31 of the stripline structure, the square groove 2 41, the slit 2 42, and the second via array 1 43 form a detection part.

[0035] The probe top layer 1 is provided with a first via array 2 14, and the probe bottom layer 4 is provided with a second via array 2 44. The first via array 2 14 is located on both sides of the straight portion of the stripline structure, and the second via array 2 44 is located on both sides of the straight portion of the stripline structure. The first via array 2 14 and the second via array 2 44 are arranged opposite to each other, and the first via array 2 14 and the second via array 2 44 are connected. Part of the first via array 2 14, part of the second via array 2 44, part of the straight portion of the signal line 2 31 of the stripline structure of the signal layer 3, and part of the second via array 2 44 form a transmission portion.

[0036] The probe top layer 1 is provided with a signal line 16 of a coplanar waveguide structure and a first via array 3 15, the first via array 3 15 is located on both sides of the signal line 16 of the coplanar waveguide structure, the probe bottom layer 4 is provided with a second via array 3 45, the impedance matching layer 2 is provided with an impedance matching structure 21, the first via array 3 15 is arranged opposite to the second via array 3 45, and the first via array 3 15 is connected to the second via array 3 45. The signal line 16 of the coplanar waveguide structure, the first via array 3 15, another part of the first via array 2 14, the impedance matching structure 21, another part of the signal line 2 31 of the stripline structure of the signal layer 3, the second via array 3 45, and another part of the second via array 2 44 form an output part.

[0037] The signal line 1 16 of the coplanar waveguide structure, the signal line 2 31 of the stripline structure, and the probe bottom layer 4 are connected through a central signal via 16 .

[0038] like Figure 1 The equivalent circuit diagram of the magnetic field probe of the present invention is shown in FIG. Figure 2The basic structure of the magnetic field probe of the present invention is shown in the figure. It is essentially a loop antenna. When the magnetic flux passing through the loop changes, an induced voltage is generated. The induced voltage is processed to obtain the magnitude of the induced magnetic field. The time-varying magnetic field excites the induced voltage through the loop plane. First, the surface of the probe loop is integrated and brought into Maxwell's equations to obtain:

[0039] (1)

[0040] in, is the component of the electric field that passes through the plane of the ring, is the magnetic field component, S is the area of ​​the circular loop, is the direction vector pointing to the normal of the ring plane, is the magnetic permeability of the dielectric material in the middle of the ring. Applying Stokes' theorem on the left side of the above equation, we get the induced voltage V i :

[0041] (2)

[0042] in, is the circumference of the ring. On the right side of equation (1), replace :

[0043] (3)

[0044] in, is the angular frequency of the magnetic field passing through the ring plane. In the low frequency band, the wavelength of the magnetic field to be measured is large, and the loop size is much smaller than the wavelength. Combining equation (2) with equation (3), the relationship between the sensitivity of the electromagnetic interference probe and the loop area is obtained as follows:

[0045] (4)

[0046] in, represents the induced voltage, represents the imaginary unit, represents the angular frequency of the magnetic field through the ring plane, represents the magnetic permeability of the dielectric material in the middle part of the ring, represents the magnetic field component, Represents the area of ​​the circular loop.

[0047] It can be seen from the above formula that the induced voltage obtained by the magnetic field probe is proportional to the ring area and the angular frequency of the magnetic field passing through the ring. Therefore, for the test of the same scene, the larger the ring area of ​​the probe, the higher the sensitivity of the magnetic field probe.

[0048] like Figure 3The laminated structure of the magnetic field probe of the present invention is shown, the metal layer material is copper, the thickness is 0.017 mm, and the dielectric layer material is FR4, the thickness is 0.254 mm.

[0049] like Figure 4 The figure shows a layered schematic diagram of the magnetic field probe of the present invention. The overall size of the magnetic field probe is , the magnetic field probe is divided into output part according to its function , Transmission part and detection part , where the output part It is a combination of coplanar waveguide and stripline structure, with signal vias for transition and transmission part And the detection part All are stripline structures.

[0050] In order to optimize the frequency characteristics of the magnetic field probe, a via array is placed on both sides of the signal line, and a magnetic field probe with good performance is obtained by optimizing the arrangement and size of the vias. The resonant frequency of the magnetic field probe As shown below:

[0051] (5)

[0052] in, represents the resonant frequency of the magnetic field probe, , , represents the mode number of electromagnetic waves, represents the magnetic permeability, represents the dielectric constant, is the transmission line length, is the width of the ground on both sides of the transmission line, is the thickness of the transmission line.

[0053] The arrangement of vias needs to comply with the following requirements:

[0054] and (6)

[0055] in, is the distance between adjacent vias, is the distance between the via and the transmission line, Indicates wavelength. Detection part The whole structure is a ring antenna. The sensitivity of the probe is improved by appropriately increasing the ring area. The relationship between the sensitivity of the magnetic field probe and the ring area is shown in formula (4).

[0056] The optimization results of the circuit size are shown in the following table:

[0057] Table 1. Basic circuit parameters and dimensions

[0058] <![CDATA[l1]]> <![CDATA[l2]]> <![CDATA[l3]]> <![CDATA[l k ]]> <![CDATA[l f ]]> 15.9mm 30mm 3.98mm 0.9mm 0.1mm <![CDATA[w1]]> <![CDATA[w2]]> <![CDATA[w3]]> <![CDATA[w4]]> <![CDATA[w5]]> 15mm 4mm 10mm 0.56mm 0.39mm <![CDATA[w k ]]> <![CDATA[w f ]]> R <![CDATA[d1]]> <![CDATA[d2]]> 6mm 1.39mm 0.3mm 0.7mm 0.9mm <![CDATA[d3]]> 2.25mm

[0059] Output section of the magnetic field probe , Transmission part and detection part The widths are , and , the lengths are , and The widths of the signal lines of the coplanar waveguide structure and the stripline structure are and The length and width of the square slot in the probe detection part are and , the length and width of the gap below the square slot are and The radius of the probe hole is , the distance between the via and the signal line is , the distance between adjacent vias is , a coaxial via array is provided at the transition section between the coplanar waveguide structure and the stripline structure, and the distance between the edge via and the center signal via is ,

[0060] Ring microstrip line , , and The diameters are the same and are , where the ring microstrip line , and have the same width and are ; Among them, microstrip line The width is ; For symmetrically coupled microstrip lines, and and are the length and width of the coupled microstrip line, respectively. is the distance between the upper and lower conducting strips of the coupled microstrip line; and are the length and width of the two-port connection line respectively.

[0061] like Figure 5 The magnetic field probe is shown in the simulation software The simulation model in The proposed magnetic field probe is simulated and optimized, and the following results can be obtained: The basic parameters and dimensions of the magnetic field probe structure are shown.

[0062] like Figure 6 It is a test schematic diagram of the magnetic field probe, the input end of the microstrip line is port 1, the other end is connected to a 50Ω matching load, and the output port of the probe is port 2.

[0063] like Figure 7 The magnetic field probe is shown Simulation results show that the magnetic field probe is The S parameters are stable within the frequency range, and the reflection coefficient of the probe is Greater than , transmission coefficient Approx. , which can realize the test of broadband magnetic field of integrated circuit.

[0064] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An electromagnetic interference probe based on PCB through-hole optimization, characterized in that: The electromagnetic interference probe is a printed circuit board structure, including an output part, a transmission part and a detection part. The output part is a combination structure of a coplanar waveguide and a stripline, and the transition is made through a signal via. The transmission part is a stripline structure, and via arrays are placed on both sides of the signal line to shield the electromagnetic field in the side direction and optimize the frequency response of the probe. The detection part is a ring antenna structure.

2. The electromagnetic interference probe based on PCB through-hole optimization according to claim 1, characterized in that: The electromagnetic interference probe comprises a probe top layer (1), a dielectric layer 1, an impedance matching layer (2), a dielectric layer 2, a signal layer (3), a dielectric layer 3, and a probe bottom layer (4) which are arranged in sequence; the probe top layer (1), the signal layer (3), and the probe bottom layer (4) are connected via metal vias.

3. The electromagnetic interference probe based on PCB through-hole optimization according to claim 1, characterized in that: The probe top layer (1) is provided with a square groove (11), a gap (12) is provided on the square groove (11), and a circle of first via hole array (13) is provided around the square groove (11) to form a ring structure; the probe bottom layer (4) is provided with a square groove (41), a gap (42) is provided on the square groove (41), and a circle of second via hole array (43) is provided around the square groove (41) to form a ring structure; the signal layer (3) is provided with a strip line The invention relates to a signal line 2 (31) of the stripline structure; the first via array 1 (13) and the second via array 1 (43) are arranged opposite to each other, the first via array 1 (13) and the second via array 1 (43) are connected, and the slit 1 (12) and the slit 2 (42) are arranged opposite to each other; the square groove 1 (11), the slit 1 (12), the first via array 1 (13), the bent part of the signal line 2 (31) of the stripline structure, the square groove 2 (41), the slit 2 (42), and the second via array 1 (43) form a detection part.

4. The electromagnetic interference probe based on PCB through-hole optimization according to claim 1, characterized in that: The probe top layer (1) is provided with a first via array 2 (14), and the probe bottom layer (4) is provided with a second via array 2 (44); the first via array 2 (14) is located on both sides of the straight portion of the stripline structure, and the second via array 2 (44) is located on both sides of the straight portion of the stripline structure; the first via array 2 (14) and the second via array 2 (44) are arranged opposite to each other, and the first via array 2 (14) and the second via array 2 (44) are connected; a portion of the first via array 2 (14), a portion of the second via array 2 (44), a portion of the straight portion of the signal line 2 (31) of the stripline structure of the signal layer (3), and a portion of the second via array 2 (44) form a transmission portion.

5. The electromagnetic interference probe based on PCB through-hole optimization according to claim 1, characterized in that: The probe top layer (1) is provided with a signal line 1 (16) of a coplanar waveguide structure and a first via array 3 (15), the first via array 3 (15) being located on both sides of the signal line 1 (16) of the coplanar waveguide structure; the probe bottom layer (4) is provided with a second via array 3 (45), the impedance matching layer (2) is provided with an impedance matching structure (21), the first via array 3 (15) and the second via array 3 (45) are arranged opposite to each other, and the first via array 3 (15) and the second via array 3 (45) are connected; the signal line 1 (16) of the coplanar waveguide structure, the first via array 3 (15), another part of the first via array 2 (14), the impedance matching structure (21), another part of the signal line 2 (31) of the stripline structure of the signal layer (3), the second via array 3 (45), and another part of the second via array 2 (44) form an output portion.

6. The electromagnetic interference probe based on PCB through-hole optimization according to claim 1, characterized in that: The signal line 1 (16) of the coplanar waveguide structure, the signal line 2 (31) of the stripline structure, and the probe bottom layer (4) are connected via a central signal via hole (16).

7. The electromagnetic interference probe based on PCB through-hole optimization according to claim 1, characterized in that: The relationship between the sensitivity of the electromagnetic interference probe and the loop area is as follows: ； in, represents the induced voltage, represents the imaginary unit, represents the angular frequency of the magnetic field through the ring plane, represents the magnetic permeability of the dielectric material in the middle part of the ring, represents the magnetic field component, Represents the area of ​​the circular loop.

8. The electromagnetic interference probe based on PCB through-hole optimization according to claim 1, characterized in that: The resonant frequency of the magnetic field probe is: ； in, represents the resonant frequency of the magnetic field probe, , , represents the mode number of electromagnetic waves, represents the magnetic permeability, represents the dielectric constant, is the transmission line length, is the width of the ground on both sides of the transmission line, is the thickness of the transmission line; The arrangement of vias needs to comply with the following requirements: and ; in, is the distance between adjacent vias, is the distance between the via and the transmission line, Indicates wavelength.

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