High-gain, flat, miniaturized broadband electric field probe based on a three-stage transition structure

Abstract

The present invention discloses a high-gain, flat, 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 in the coupling portion, a symmetrical bevel transition structure in the transmission portion, and a gradually transitioned improved coplanar waveguide in the output portion. The improved sensing tip, composed of the symmetrical arc transition structure and the circular detection structure, can effectively increase the coupling capacitance between the electric field probe and the device under test, improving the transmission gain of the electric field probe in the low-frequency band. The symmetrical bevel transition structure can more concentratedly transmit the desired energy of the sensing signal to the output portion, suppressing resonance, ringing-like ripples, and surge ripples in the electric field probe in the mid- and high-frequency bands, thereby improving the gain flatness in the mid- and high-frequency bands. The gradually transitioned improved coplanar waveguide ensures that the characteristic impedance of the contact portion between its center conductor and the micro-coaxial connector is 50Ω.

Description

Technical field

[0001] The present invention relates to a high-gain flatness miniaturized broadband electric field probe based on a three-stage transition structure, which is used to accurately capture 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, operating frequencies are trending higher and higher, leading to a dramatic increase in product complexity. Near-field testing technology is widely used to locate, track, and visualize interference sources. Near-field probes, as key components of near-field testing technology, play an important role. Gain flatness, a key specification for near-field probes, determines the level of several electromagnetic performance indicators, such as operating frequency band, probe calibration factor (CF), sensitivity, and test error. Currently, the frequency response of most broadband electric field probes exhibits a significant drop in gain within their higher frequency bands, and they exhibit significant resonance, ringing-like ripple, and surge ripple, making it difficult for the probes to maintain a stable gain value within their operating frequency band. For example, the electric field probe described in the Chinese invention patent application "A Broadband Miniature Near-Field Electric Field Test Probe" (Application No.: 201610214913.2) exhibits a rapid decrease in frequency response amplitude after 10 GHz, with the value at 20 GHz being approximately 13 dB lower than that at lower frequencies. In addition, the overall size of many current probes is large, especially the coupling part at the bottom. During actual testing, electronic engineers have found that due to the physical size limitations of the probes, it is difficult to apply the probes to the testing of products with high integration. [Summary of the invention]

[0003] In order to solve the above technical difficulties 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. The purpose is to effectively suppress the resonance, ringing-like ripples and surge ripples of the near-field electric field probe, improve the gain flatness of the electric field probe, maintain good spatial resolution and other electromagnetic characteristic indicators, realize accurate measurement of radiated electric field signals, assist electronic engineers in completing fault diagnosis of radio frequency electronic equipment, and provide 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, flat, 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 stack structure, wherein the stack structure comprises a bottom layer, a middle layer 1, a middle layer 2, and a top layer.

[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 sensing tip is located in the coupling portion of the electric field probe and consists of a symmetrical arc transition structure and a circular detection structure. The improved sensing 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 the lower frequency band.

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

[0010] The symmetrical bevel transition structure is located below the transmission portion of the electric field probe, cascading the coupling portion and the transmission portion of the electric field probe. The purpose 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 portion, suppress the ringing-like ripples and surge ripples of the electric field probe in the medium and high frequency bands, and thus improve the gain flatness of the electric field probe; the symmetrical bevel transition structure has an "inverted trapezoidal" shape, 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, achieving miniaturization;

[0011] The desired energy of the induced signal flows along the stripline center conductor through the signal via to the tapered transition improved coplanar waveguide and the micro-coaxial connector, and is finally output to the receiving device. The center conductor of the tapered transition improved coplanar waveguide is shaped like a "normal trapezoid" after undergoing a trapezoidal-like gradient treatment, in order to ensure that the characteristic impedance of the contact portion between the center conductor of the tapered transition 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 transitioned 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 operating 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] The present invention designs a high-gain flatness miniaturized broadband electric field probe based on a three-stage transition structure, which 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 practical application scenarios of the electric field probe; the electric field probe described in the present invention takes into account the practicality in engineering in the design of the scheme, and the overall structure implementation scheme is simple, which makes it 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 structure 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, flat, miniaturized broadband electric field probe based on a three-stage transition structure.

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

[0019] Figure 5 The figure shows the frequency characteristics simulation and test results 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 tapered transition, 2-5: Micro coaxial connector, 3-1: Bottom layer shield, 3-2: Stripline center conductor, 3-3: Circular probing structure, 3-4: Impedance reference plane in middle layer 2, 3-5: Signal via, 3-6: Center conductor of improved coplanar waveguide with tapered transition, 3-7: Top layer shield, 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] To facilitate understanding of the present application, the present application will be described in more detail below with reference to the accompanying 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 pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0025] It should be noted that the terms "top", "bottom", "up", "down" 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 One embodiment shown provides a high-gain, flat, miniaturized, broadband electric field probe based on a three-stage transition structure designed according to the present invention. From bottom to top, the printed circuit board laminate structure comprises a bottom layer 1-1, a middle layer 1-2, a middle layer 2 1-3, and a top layer 1-4. In this embodiment, the copper thickness of the bottom layer 1-1 and the top layer 1-4 of the four-layer printed circuit board is 1 oz, while the copper thickness of the middle layer 1-2 and the middle layer 2 1-3 is 0.5 oz. A 0.34 mm thick copper-clad Rogers 4003C sheet serves as the top layer 1-4, a 0.238 mm thick copper-clad Rogers 4003C sheet serves as the bottom layer 1-1, and a 0.19 mm thick copper-clad Rogers 4450F sheet serves as the prepreg. The four-layer laminate structure employed in the present invention has a small number of layers and a simple structure, facilitating processing and promoting the invention.

[0027] In this embodiment, Figure 2 The present invention provides a high-gain, flat, miniaturized, broadband electric field probe based on a three-stage transition structure. The sensing signal generated by the improved sensing tip 2-1 passes through the symmetrical bevel transition structure 2-2 and along the transmission section 2-3 to the output section. The desired energy of the sensing signal is then transmitted through a signal via 3-5 to a tapered-transition improved coplanar waveguide 2-4. Finally, the signal is output to the receiving device via a micro-coaxial connector 2-5. The micro-coaxial connector 2-5 is a press-fit connector, which offers low insertion loss, excellent frequency characteristics, and accurate signal output.

[0028] In this embodiment, the circular detection structure 3-3 and the symmetrical arc transition structure 3-8 together constitute the 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, with a vertical distance of 0.26mm, and the arc transition radius ranges from 0.2-0.5mm. Then, the line width of 0.6mm is maintained and the linear extension is continued to be finally inserted into the circular detection structure 3-3, with an extension distance of 3.6mm, wherein 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 this embodiment is listed here.

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

[0030] In this embodiment, the transmission section 2-3 primarily consists of a well-matched 50Ω stripline. The stripline center conductor 3-2 is located in the middle layer 1-2, and the impedance reference planes are the bottom shield layer 3-1 and the top shield layer 3-7. In the symmetrical bevel transition structure 2-2, the width of the probe transmission section 2-3 transitions from 10mm to 3mm from top to bottom. The vertical distance between the upper and lower horizontal edges is 5mm, and the width ratio is approximately 3.3. The bevel transition section has an overall "inverted trapezoidal" shape, cascading the coupling section and transmission section. Its function is to suppress the common-mode surface currents excited by the induced electric field generated by the sensing tip, thereby suppressing resonance, ringing-like ripple, and surge ripple in the electric field probe's mid- 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 sudden changes in the probe structure during the transmission of the induced signal, suppress the desired energy of the induced signal from dispersing and dissipating in all directions, and centrally transmit the desired energy in the induced signal along the stripline center conductor 3-2 to the output portion. The symmetrical bevel transition structure 2-2 can miniaturize the electric field probe 4-5, making the electric field probe 4-5 suitable for use in testing scenarios with higher integration and more complex environments. It should be noted that the values ​​of the various widths, transition distances, etc. of the symmetrical bevel transition structure 2-2 described herein are not fixed and can be changed according to the specific application requirements of the probe. Only one case in this embodiment is listed here.

[0031] In this embodiment, the output portion includes a signal via 3-5 and a gradually transitioned improved coplanar waveguide 2-4, wherein the center conductor of the gradually transitioned improved coplanar waveguide 2-4 is located on the top layer 1-4, and the middle two-layer impedance reference plane 3-4 and the top shielding layer 3-7 serve as the impedance reference planes 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 together. The center conductor 3-6 of the gradually transitioned improved coplanar waveguide is subjected to a trapezoidal gradient treatment, with the ratio of the width of the upper horizontal side to the lower horizontal side ranging from 0.5 to 1, and the vertical distance being 2 mm. In this embodiment, its line width gradually transitions from 0.47 mm to 0.58 mm from top to bottom. The center conductor 3-6 of the tapered-transition improved coplanar waveguide is shaped like a regular trapezoid. This ensures a characteristic impedance of 50Ω at the contact portion between the center conductor 3-6 and the micro-coaxial connector 2-5. It should be noted that the line widths and transition distances of the center conductor 3-6 of the tapered-transition improved coplanar waveguide described herein are not fixed and are merely examples of this embodiment.

[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 testing, a standard two-port calibration is performed on the vector network analyzer 4-1. A calibration microstrip line 4-6 serves as a calibration component to provide electric field information. Port 1 4-2 of the vector network analyzer 4-1 is connected to one end of the calibration microstrip line 4-6 via a coaxial line 4-4 via a micro-coaxial connector. Port 2 4-3 of the vector network analyzer 4-1 is connected to the electric field probe 4-5 via a micro-coaxial connector via a coaxial line 4-4. The other end of the calibration microstrip line 4-6 is connected to a 50Ω matched 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 directly above the center of the calibration microstrip line 4-6.

[0033] In this embodiment, the symmetrical arc transition structure 3-8 of the coupling section, the symmetrical beveled transition structure 2-2 of the transmission section, and the gradually transitioned improved coplanar waveguide 2-4 of the output section together constitute the three-stage transition structure. This three-stage transition structure enables the electric field probe 4-5 to accurately detect the normal electric field component, reducing test errors and significantly improving the gain flatness of the electric field probe. This enables the probe to output accurate, high-quality electric field signals while maintaining good spatial resolution. Furthermore, the symmetrical beveled transition structure 2-2 reduces the overall size of the electric field probe, significantly expanding its application scenarios.

[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 high gain value in the low frequency band, a stable amplitude in the mid- and high-frequency bands, no resonance, obvious ringing-like ripples, and surge ripples. The effective operating frequency band is 9kHz-20GHz, the average gain value is approximately -27.6dB, the maximum fluctuation value is approximately 2.1dB, and the average fluctuation value is approximately 1.45dB. The test result curve is highly consistent with the simulation result curve. Multiple actual measurement results of this embodiment show that when the bottom of the electric field probe 4-5 is 0.3mm from the surface of the center conductor of the calibration microstrip line 4-6, the measured spatial resolution is 1mm, demonstrating that the electric field probe 4-5 can distinguish different adjacent test paths.

[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, flat, miniaturized, broadband electric field probe based on a three-stage transition structure. The probe is designed and fabricated based on a four-layer printed circuit board stack, comprising a bottom layer, a first middle layer, a second middle layer, and a top layer. The probe is characterized by: 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 in 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 under test, thereby improving the transmission gain of the electric field probe in the low frequency band; The transmission part is mainly composed of a well-matched 50 Ω stripline, the center conductor of the stripline is located in the middle layer, and the impedance reference plane is the top and bottom layers; 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 the shape of an "inverted trapezoid"; The improved coplanar waveguide with gradual transition is located at the output part of the electric field probe, the 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 subjected to gradual transition processing; The micro coaxial connector is a press-fit connector, which is press-fit connected to the gradually transition improved coplanar waveguide.

2. The 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 consists of an arc transition structure and a straight extension structure, the purpose of which 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, flat, 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, and the straight extension structure and the circular detection structure in the symmetrical arc transition structure are only covered by the dielectric material layer. Their orthographic projections on the planes where the bottom and top layers are located are outside the range of the bottom and top layers.

4. The 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. The 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 gradient process, presenting a "normal trapezoidal shape", 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 50 Ω.

6. The 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.

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