High-gain flatness miniaturized broadband electric field probe based on three-stage transition structure

Abstract

The invention discloses a high-gain flatness miniaturized broadband electric field probe based on a three-stage transition structure. The three-stage transition structure is composed of a symmetrical arc transition structure of a coupling part, a symmetrical bevel edge transition structure of a transmission part and a gradually-changed transition improved coplanar waveguide of an output part. The improved induction tip formed by the symmetrical arc transition structure and the circular detection structure can effectively increase the coupling capacitance between the electric field probe and a to-be-detected piece and improve the transmission gain of the electric field probe at a low frequency band. The symmetrical bevel edge transition structure can enable expected energy of an induction signal to be transmitted to the output part in a more concentrated manner, restrain resonance, ringing-like ripples and surge ripples of the electric field probe in a middle-high frequency band, and improve gain flatness of the middle-high frequency band. The gradual transition improved coplanar waveguide ensures that the characteristic impedance of the contact part of the central conductor and the miniature coaxial connector is 50 ohms.

Description

[Technical field]

[0001] The present invention relates to a high-gain flatness miniaturized broadband electric field probe based on a three-level transition structure, which is used for accurately capturing electric field information generated by integrated circuit radiation, and belongs to the technical field of electromagnetic compatibility and electromagnetic field near-field testing. [Background technology]

[0002] With the increasing demand for electronic products in contemporary society, their operating frequencies are developing towards a higher and higher trend, and the complexity of products is increasing dramatically. In order to locate, track and visualize interference sources, near-field testing technology is widely used. As a key component of near-field testing technology, near-field probes play an important role. Gain flatness, as a key indicator of near-field probes, determines the level of multiple electromagnetic performance indicators of near-field probes, such as operating frequency band, probe calibration factor (CF), sensitivity and test error. At present, the frequency response of most broadband electric field probes has a significant decrease in gain value in its higher frequency band, and there are obvious resonance, ringing ripple and surge ripple problems, making it difficult for the probe to maintain a stable gain value in the operating frequency band. For example, the electric field probe in the Chinese invention patent application "A broadband miniature near-field electric field test probe" (application number: 201610214913.2) has a frequency response amplitude value that decreases rapidly after 10GHz, and the value at 20GHz is about 13dB lower than that in the lower frequency band. In addition, the overall size of many current probes is large, especially the coupling part at the bottom. Electronic engineers have found in actual testing that due to the limitation of the physical size of the probe, it is difficult to apply the probe to the testing of products with high integration. [Summary of the invention]

[0003] In order to solve the above technical problems and meet the development needs of the electronics industry, the present invention designs a high-gain flatness miniaturized broadband electric field probe based on a three-level transition structure, with the aim of effectively suppressing the resonance, ringing-like ripples and surge ripples of the near-field electric field probe, improving the gain flatness of the electric field probe, maintaining good spatial resolution and other electromagnetic characteristic indicators, achieving accurate measurement of radiated electric field signals, assisting electronic engineers in completing fault diagnosis of radio frequency electronic equipment, and providing a favorable testing method for improving the electromagnetic performance of electronic systems.

[0004] In order to meet the above purpose, the scheme of the present invention is as follows:

[0005] A high-gain flatness miniaturized broadband electric field probe based on a three-stage transition structure, the design and processing of the electric field probe is based on a four-layer printed circuit board laminate structure, wherein the laminate structure is a bottom layer, a middle layer 1, a middle layer 2 and a top layer in sequence;

[0006] The dielectric materials in the laminated structure are Rogers 4003C and Rogers 4450F;

[0007] The electric field probe is composed of at least a coupling part, a transmission part, an output part and a micro coaxial connector; the symmetrical arc transition structure of the coupling part, the symmetrical bevel transition structure of the transmission part and the gradually transition improved coplanar waveguide of the output part of the electric field probe together constitute the three-level transition structure;

[0008] The improved inductive tip is located at the coupling part of the electric field probe, and is composed of a symmetrical arc transition structure and a circular detection structure. The improved inductive tip can significantly increase the coupling capacitance between the electric field probe and the device under test, reduce the parasitic capacitance of the probe itself, and improve the gain flatness of the frequency response curve of the electric field probe in a lower frequency band;

[0009] The transmission part is mainly composed of a well-matched 50Ω stripline, the central conductor of the stripline is located in the middle layer, and the impedance reference plane is the top layer and the bottom layer;

[0010] The symmetrical bevel transition structure is located below the transmission part of the electric field probe, and cascades the coupling part and the transmission part of the electric field probe, with the purpose of suppressing the common-mode surface current excited by the induced electric field generated by the improved induction tip, ensuring that the energy of the induced signal is more concentratedly distributed in the transmission part, suppressing the ringing-like ripples and surge ripples of the electric field probe in the medium and high frequency bands, thereby improving the gain flatness of the electric field probe; the symmetrical bevel transition structure is in the shape of an "inverted trapezoid", and the ratio of the width of the upper horizontal side to the lower horizontal side of the "inverted trapezoid" is greater than 1 and less than or equal to 5; the symmetrical bevel transition structure can reduce the overall size of the electric field probe and achieve miniaturization;

[0011] The expected energy of the induction signal flows along the stripline center conductor through the signal via to the gradually transitioned improved coplanar waveguide and the micro coaxial connector, and is finally output to the receiving device; the center conductor of the gradually transitioned improved coplanar waveguide is shaped like a "normal trapezoid" after being subjected to a trapezoidal-like gradual treatment, in order to ensure that the characteristic impedance of the contact portion between the center conductor of the gradually transitioned improved coplanar waveguide and the micro coaxial connector is 50Ω;

[0012] The symmetrical arc transition structure of the coupling part, the symmetrical bevel transition structure of the transmission part and the gradually transition improved coplanar waveguide of the output part together constitute the three-level transition structure. Under the action of the three-level transition structure, the gain flatness and working bandwidth of the electric field probe are improved, and the electric field probe can accurately measure the radiated electric field.

[0013] The beneficial effects of the high-gain flatness miniaturized broadband electric field probe based on the three-stage transition structure of the present invention are:

[0014] A high-gain flatness, miniaturized, broadband electric field probe based on a three-stage transition structure designed by the present invention has the advantages of high gain flatness, miniaturization, and wide bandwidth, and can significantly suppress the resonance, ringing-like ripples, and surge ripples of the frequency response curve of the electric field probe, thereby improving the gain flatness, reducing the test error, and expanding the working bandwidth; at the same time, under the action of the symmetrical bevel transition structure of the transmission part, the overall size of the electric field probe is small, suitable for narrower and more complex test environments, and greatly expands the actual application scenarios of the electric field probe; the electric field probe described in the present invention takes into account the practicability in engineering in the design of the scheme, and the overall structure implementation scheme is simple, which is easy for engineering personnel and R&D personnel to master the design scheme of the electric field probe in the present invention and promote its use in engineering.

Brief Description of the Drawings

[0015] Figure 1 The printed circuit board stackup diagram of a high-gain, flat, miniaturized broadband electric field probe based on a three-stage transition structure.

[0016] Figure 2 This is the overall structural diagram of a high-gain, flat, miniaturized broadband electric field probe based on a three-stage transition structure.

[0017] Figure 3 The 3D layered structure diagram of a high-gain flatness miniaturized broadband electric field probe based on a three-level transition structure.

[0018] Figure 4 This is a calibration test diagram of a high-gain flatness miniaturized broadband electric field probe based on a three-stage transition structure.

[0019] Figure 5 This is a graph showing the simulation and test results of the frequency characteristics of a high-gain, flat, miniaturized broadband electric field probe based on a three-stage transition structure.

[0020] Description of Figure Numbers:

[0021] 1-1: bottom layer, 1-2: middle layer 1, 1-3: middle layer 2, 1-4: top layer, 2-1: improved sensing tip, 2-2: symmetrical bevel transition structure, 2-3: transmission section, 2-4: improved coplanar waveguide with gradual transition, 2-5: micro coaxial connector, 3-1: bottom shield layer, 3-2: stripline center conductor, 3-3: circular detection structure, 3-4: middle layer 2 impedance reference plane, 3-5: signal via, 3-6: center conductor of improved coplanar waveguide with gradual transition, 3-7: top shield layer, 3-8: symmetrical arc transition structure, 4-1: vector network analyzer, 4-2: port 1, 4-3 port 2, 4-4: coaxial line, 4-5: electric field probe, 4-6: calibration microstrip line, 4-7: 50Ω matched load. [Specific implementation method]

[0022] Combined with the accompanying drawings, the specific structure of a high-gain flatness miniaturized broadband electric field probe based on a three-stage transition structure, the positional relationship of each component structure and the function of each component are further explained.

[0023] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0025] It should be noted that the terms "top", "bottom", "upper", "lower" and similar expressions used in this article are based on the orientation or relative position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description.

[0026] like Figure 1 An embodiment shown provides a printed circuit board laminate structure of a high-gain flatness miniaturized broadband electric field probe based on a three-stage transition structure designed by the present invention, which includes a bottom layer 1-1, a middle layer 1-2, a middle layer 2 1-3 and a top layer 1-4 from bottom to top. In this embodiment, the copper thickness of the bottom layer 1-1 and the top layer 1-4 in the four-layer printed circuit board is 1oz, and the copper thickness of the middle layer 1-2 and the middle layer 2 1-3 is 0.5oz. A 0.34mm thick copper-clad Rogers 4003C plate is used as the top layer 1-4, a 0.238mm thick copper-clad Rogers 4003C plate is used as the bottom layer 1-1, and a 0.19mm thick copper-clad Rogers 4450F plate is used as a prepreg. The four-layer laminate structure used in the design scheme of the present invention has a small number of laminates and a simple structure, which is conducive to processing and promotion of the present invention.

[0027] In this embodiment, Figure 2 The present invention provides an overall structure of a high-gain flatness miniaturized broadband electric field probe based on a three-stage transition structure. The induction signal obtained by the improved induction tip 2-1 passes through the symmetrical bevel transition structure 2-2 and reaches the output part along the transmission part 2-3. The desired energy of the induction signal is transmitted to the gradually transitioned improved coplanar waveguide 2-4 through the signal via 3-5, and finally output to the receiving device through the micro coaxial connector 2-5. The micro coaxial connector 2-5 adopts a press-fit connector, which has the advantages of low insertion loss and good frequency characteristics, and can accurately output signals.

[0028] In the present embodiment, the circular detection structure 3-3 and the symmetrical arc transition structure 3-8 together constitute an improved sensing tip 2-1, and are both located in the middle layer 1-2. The symmetrical arc transition structure 3-8 is composed of an arc transition structure and a straight extension structure, wherein the line width of the arc transition structure transitions from 0.296mm to 0.6mm from top to bottom, the vertical distance is 0.26mm, and the arc transition radius ranges from 0.2-0.5mm, and then maintains the 0.6mm line width and continues to extend linearly and finally inserts into the circular detection structure 3-3, the extension distance is 3.6mm, and the radius of the circular detection structure 3-3 is 1.5mm. It should be noted that the values ​​of the line width, transition distance and arc transition radius in the symmetrical arc transition structure 3-8 described here are not fixed, and only one case in the present embodiment is listed here.

[0029] In this embodiment, the linear extension structure and the circular detection structure 3-3 are only covered by the dielectric material layer, and the orthographic projections on the plane where the bottom layer 1-1 and the top layer 1-4 are located are outside the range of the bottom layer 1-1 and the top layer 1-4, and the arc transition structure in the improved sensing tip 2-1 is covered by the bottom layer 1-1 and the top layer 1-4. The improved sensing tip 2-1 can significantly improve the gain flatness of the electric field probe 4-5 in the lower frequency band and obtain better spatial resolution.

[0030] In this embodiment, the transmission part 2-3 is mainly composed of a well-matched 50Ω stripline, the stripline center conductor 3-2 is located in the middle layer 1-2, and the impedance reference plane is the bottom shielding layer 3-1 and the top shielding layer 3-7. In the symmetrical bevel transition structure 2-2, the width of the probe transmission part 2-3 transitions from 10mm bevel to 3mm from top to bottom, the vertical distance between the upper horizontal edge and the lower horizontal edge is 5mm, and the width ratio is about 3.3. The bevel transition part is an "inverted trapezoid" as a whole, cascading the coupling part and the transmission part, and its function is to suppress the common-mode surface current excited by the induced electric field generated by the inductive tip, suppress the resonance, ringing-like ripples and surge ripples of the electric field probe in the medium and high frequency bands, thereby improving the gain flatness of the electric field probe. The symmetrical bevel transition structure 2-2 can effectively reduce the high-order modes excited by the sudden change of the probe structure during the transmission of the induction signal, suppress the divergence and loss of the desired energy of the induction signal, and make the desired energy in the induction signal be concentrated along the stripline center conductor 3-2 and transmitted to the output part. The symmetrical bevel transition structure 2-2 can realize the miniaturization of the electric field probe 4-5, making the electric field probe 4-5 suitable for testing scenarios with higher integration and more complex environments. It should be noted that the values ​​of the width, transition distance, etc. of the symmetrical bevel transition structure 2-2 described here are not fixed and can be changed according to the application requirements of the specific probe. Only one case in this embodiment is listed here.

[0031] In this embodiment, the output part includes a signal via 3-5 and a gradually transitioned improved coplanar waveguide 2-4, wherein the central conductor of the gradually transitioned improved coplanar waveguide 2-4 is located at the top layer 1-4, and the middle 2-layer impedance reference plane 3-4 and the top shielding layer 3-7 serve as the impedance reference plane of the gradually transitioned improved coplanar waveguide 2-4. The gradually transitioned improved coplanar waveguide 2-4 and the micro coaxial connector 2-5 are connected and transmit signals by tightly pressing. The central conductor 3-6 of the gradually transitioned improved coplanar waveguide is subjected to a trapezoidal gradient treatment, and the ratio of the width of the upper horizontal side to the lower horizontal side is in the range of 0.5-1, and the vertical distance is 2mm. In this embodiment, its line width gradually transitions from 0.47mm to 0.58mm from top to bottom. The center conductor 3-6 of the gradually transitioned improved coplanar waveguide is in a "positive trapezoidal shape" to ensure that the characteristic impedance of the contact portion between the center conductor 3-6 of the gradually transitioned improved coplanar waveguide and the micro coaxial connector 2-5 is 50Ω. It should be noted that the values ​​of the line width and transition distance of the center conductor 3-6 of the gradually transitioned improved coplanar waveguide described here are not fixed, and only one case in this embodiment is listed here.

[0032] An embodiment of a high-gain flatness miniaturized broadband electric field probe based on a three-stage transition structure designed by the present invention is tested. The test calibration system is as follows: Figure 4 As shown. Before the test, the vector network analyzer 4-1 is subjected to a standard two-port calibration. The calibration microstrip line 4-6 is used as a calibration piece to provide electric field information. Port 14-2 of the vector network analyzer 4-1 is connected to one end of the calibration microstrip line 4-6 through a coaxial line 4-4 through a micro coaxial connector. Port 24-3 of the vector network analyzer 4-1 is connected to the electric field probe 4-5 through a coaxial line 4-4 through a micro coaxial connector. The other end of the calibration microstrip line 4-6 is connected to a 50Ω matching load 4-7. In this embodiment, the characteristic impedance of the calibration microstrip line 4-6 is 50Ω, and the electric field probe 4-5 is placed 0.3mm above the center of the calibration microstrip line 4-6.

[0033] In this embodiment, the symmetrical arc transition structure 3-8 of the coupling part, the symmetrical bevel transition structure 2-2 of the transmission part and the gradually transition improved coplanar waveguide 2-4 of the output part together constitute the three-stage transition structure. Under the action of the three-stage transition structure, the electric field probe 4-5 can accurately detect the normal electric field component, reduce the test error, greatly improve the gain flatness of the electric field probe, so that the electric field probe can output accurate and high-quality electric field signals to the outside, while maintaining good spatial resolution. In addition, under the action of the symmetrical bevel transition structure 2-2, the overall size of the electric field probe is small, which greatly expands the application scenarios of the electric field probe.

[0034] An embodiment of a high-gain flat miniaturized broadband electric field probe based on a three-stage transition structure, the frequency response simulation and test results are shown in FIG. Figure 5 As shown, the results show that the electric field probe has a higher gain value in the low frequency band, a stable amplitude in the medium and high frequency bands, no resonance, obvious ringing-like ripples and surge ripples, an effective working frequency band of 9kHz-20 GHz, an average gain value of about -27.6dB, a maximum fluctuation value of about 2.1dB, an average fluctuation value of about 1.45dB, and a high degree of agreement between the test result curve and the simulation result curve. The multiple actual measurement results of this embodiment show that when the height of the bottom of the electric field probe 4-5 from the surface of the central conductor of the calibration microstrip line 4-6 is 0.3mm, the measured spatial resolution is 1mm, proving that the electric field probe 4-5 can distinguish different adjacent paths to be measured.

[0035] It should be pointed out that the technical means and design methods disclosed in the present invention are not limited to the present invention, but are also applicable to other schemes, invention methods and invention products derived from the design ideas, invention methods, technical means and technical features described in the present invention. Therefore, these other derived schemes, invention methods and invention products should be regarded as within the scope of protection of the present invention.

Claims

1. A high-gain flatness miniaturized broadband electric field probe based on a three-stage transition structure, the design and processing of the electric field probe is based on a four-layer printed circuit board laminate structure, the laminate structure is sequentially a bottom layer, a middle layer 1, a middle layer 2 and a top layer, characterized in that: The electric field probe is composed of at least a coupling part, a transmission part, an output part and a micro coaxial connector; the symmetrical arc transition structure of the coupling part, the symmetrical bevel transition structure of the transmission part and the gradually transition improved coplanar waveguide of the output part of the electric field probe together constitute the three-level transition structure; The symmetrical arc transition structure and the circular detection structure together constitute the improved sensing tip of the electric field probe; the improved sensing tip is located at the coupling part of the electric field probe; the improved sensing tip can effectively increase the coupling capacitance between the electric field probe and the device to be tested, and improve the transmission gain of the electric field probe in the low frequency band; The transmission part is mainly composed of a well-matched 50Ω stripline, the central conductor of the stripline is located in the middle layer, and the impedance reference plane is the top layer and the bottom layer; The symmetrical bevel transition structure is located below the transmission part of the electric field probe and is cascaded with the coupling part; the symmetrical bevel transition structure is in an "inverted trapezoidal" shape, and its function is to suppress the common-mode surface current excited by the induced electric field generated by the improved sensing tip, ensure that the energy of the induced signal is more concentratedly distributed in the transmission part, suppress the ringing-like ripples and surge ripples of the electric field probe in the medium and high frequency bands, thereby improving the gain flatness of the electric field probe; The gradually transitioned improved coplanar waveguide is located at the output part of the electric field probe, and its central conductor is located at the top layer of the electric field probe. The impedance reference plane is the top layer and the middle two layers, and the line width of the central conductor is gradually transitioned, so as to reduce the parasitic capacitance generated by the press-fit connection between the central conductor of the gradually transitioned improved coplanar waveguide and the micro coaxial connector, thereby reducing the reflection and energy loss of the induced signal caused by the impedance mismatch, suppressing the ringing-like ripple and surge ripple in the high frequency band of the electric field probe, and improving the gain flatness of the electric field probe; The micro coaxial connector is a press-fit connector, which is press-fit connected to the gradually transition improved coplanar waveguide.

2. A high-gain flatness miniaturized broadband electric field probe based on a three-stage transition structure according to claim 1, characterized in that: The symmetrical arc transition structure is composed of an arc transition structure and a straight extension structure, and its purpose is to smoothly connect the central conductor of the strip line of the transmission part and the circular detection structure of the coupling part. The radius of the circular detection structure is 1.5 mm.

3. A high-gain flatness miniaturized broadband electric field probe based on a three-stage transition structure according to claim 1 or 2, characterized in that: The improved sensing tip is located in the middle layer 1, and the straight extension structure and the circular detection structure in the symmetrical arc transition structure are only covered by the dielectric material layer, and the orthographic projections on the planes where the bottom and top layers are located are outside the range of the bottom and top layers.

4. A high-gain flatness miniaturized broadband electric field probe based on a three-stage transition structure according to claim 1, characterized in that: The symmetrical bevel transition structure is in the shape of an "inverted trapezoid", and the ratio of the width of the upper horizontal side to the lower horizontal side of the "inverted trapezoid" is greater than 1 and less than or equal to 5.

5. A high-gain flatness miniaturized broadband electric field probe based on a three-stage transition structure according to claim 1, characterized in that: The central conductor of the gradually transitioned improved coplanar waveguide has its line width subjected to a trapezoidal gradual change process, presenting a "positive trapezoid", thereby ensuring that the characteristic impedance of the contact portion between the central conductor of the gradually transitioned improved coplanar waveguide and the micro coaxial connector is 50Ω.

6. A high-gain flatness miniaturized broadband electric field probe based on a three-stage transition structure according to claim 1, characterized in that: The overall structure of the electric field probe is bilaterally symmetrical about its central axis.

Images