Electromagnetic compatibility connection device and apparatus

Abstract

The application relates to the field of electromagnetic compatibility, in particular to an electromagnetic compatibility connecting device and equipment. The device comprises a printed circuit board, a coaxial cable and a shielded radio frequency connector; the coaxial cable is used for transmitting radio frequency signals and differential signals simultaneously; the shielded radio frequency connector has a shell and a center signal pin; a shielding layer of the coaxial cable is electrically connected with the shell, and a core wire of the coaxial cable is electrically connected with the center signal pin; the shielded radio frequency connector is installed on the printed circuit board, the shell is electrically connected with a grounding system of the printed circuit board; a signal separation and filtering network is integrated on the printed circuit board, which is used for separating mixed signals from the coaxial cable into radio frequency signals and differential signals, and providing a high-frequency grounding path for the shielding layer of the coaxial cable. The radio frequency signals and the differential signals are simultaneously transmitted by using a single coaxial cable, and electromagnetic interference is reduced.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic compatibility, and more specifically to an electromagnetic compatibility connection device and equipment. Background Technology

[0002] Electromagnetic compatibility (EMC) design is required for equipment in many fields. For example, CS114 in GJB 152A-1997 "Measurement of Electromagnetic Emissions and Susceptibility of Military Equipment and Subsystems" is a commonly used test item. When the output RF cable of a product needs to transmit both L-band RF signals and differential signals with a communication rate of 460800bps, common methods include... Figure 1 As shown, however, when performing EMC CS114 testing, the signal originally output by the product on the network analyzer was as follows: Figure 2 As shown, because this product transmits both radio frequency (RF) and differential signals simultaneously through the outer sheath and core of a coaxial cable, the RF cable sheath cannot be directly connected to the cavity via an RF connector. This prevents the product from forming a shielded cavity to prevent electromagnetic interference, resulting in severe signal interference. The effect of electromagnetic interference is as follows: Figure 3 As shown. Summary of the Invention

[0003] The purpose of this invention is to provide an electromagnetic compatibility connection device and equipment, which solves the problems in the prior art.

[0004] This invention is achieved through the following technical solution:

[0005] In a first aspect, embodiments of the present invention provide an electromagnetic compatibility connection device, including a printed circuit board, a coaxial cable, and a shielded radio frequency connector;

[0006] The coaxial cable is used to transmit radio frequency signals and differential signals simultaneously;

[0007] The shielded RF connector has a housing and a center signal pin;

[0008] The shielding layer of the coaxial cable is electrically connected to the outer shell, and the core wire of the coaxial cable is electrically connected to the center signal pin.

[0009] The shielded RF connector is mounted on the printed circuit board, and the housing is electrically connected to the grounding system of the printed circuit board;

[0010] The printed circuit board integrates a signal separation and filtering network to separate the mixed signal from the coaxial cable into radio frequency signals and differential signals, and to provide a high-frequency grounding path for the shielding layer of the coaxial cable.

[0011] Preferably, the housing of the shielded RF connector is electrically connected to the top RF ground on the printed circuit board, and the center signal pin is electrically connected to the bottom pad on the printed circuit board.

[0012] Preferably, the signal separation and filtering network includes a radio frequency signal extraction branch, a radio frequency reference ground loop, and a differential signal extraction branch.

[0013] Preferably, the radio frequency signal extraction branch includes a first capacitor connected between the center signal pin and the radio frequency output terminal of the shielded radio frequency connector.

[0014] Preferably, the RF reference ground loop includes a filter circuit connected between the housing of the shielded RF connector and the common ground of the printed circuit board.

[0015] Preferably, the filter circuit includes a first inductor and a second capacitor connected in series.

[0016] Preferably, the differential signal extraction branch includes:

[0017] The first branch is used to extract the differential positive terminal signal, and the first branch is connected between the center signal pin and the differential positive input terminal of the shielded RF connector;

[0018] The second branch is used to extract the differential negative input signal, and the second branch is connected between the housing of the shielded RF connector and the differential negative input.

[0019] Preferably, a third inductor is connected in series in the first branch; and a fourth inductor is connected in series in the second branch.

[0020] Preferably, the radio frequency signal is an L-band signal, and the communication rate of the differential signal is 460800bps.

[0021] Secondly, embodiments of the present invention provide an electronic device including the electromagnetic compatibility connection device described in the first aspect.

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

[0023] By connecting the shielding layer of the coaxial cable to the grounding system of the printed circuit board using a shielded RF connector, and by specifically designing an RF reference ground loop composed of inductors and capacitors, a low-impedance discharge path is provided for common-mode interference currents introduced by the cable shielding layer, especially in the RF band. This allows externally injected interference energy to be effectively dissipated into the PCB ground plane rather than intruding into the internal signal processing circuitry.

[0024] By employing RF signal extraction branches and differential signal extraction branches containing specific capacitors and inductors, the significant spectral differences between RF and differential signals are utilized to separate them from the shared transmission channel and process them along different physical paths. The RF signal is guided to the RF path through capacitive coupling, ensuring the continuity of its high-frequency response; the differential signal is extracted through a symmetrical branch containing a filter inductor, suppressing common-mode noise while maintaining the amplitude and phase balance of the signal pair.

[0025] This approach distributes connection points (casing and center pin) to different layers of the PCB (top RF ground and bottom pads) and integrates filtering components in the signal separation network, managing noise paths from both spatial layout and frequency characteristics perspectives. This reduces coupling between high-current ground loops and sensitive signal paths, and further cancels out residual common-mode interference that cannot be fully discharged through the inherent common-mode rejection capability of the differential architecture. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0027] Figure 1 A schematic diagram illustrating the conventional use of coaxial cable for transmitting radio frequency signals and differential signals, provided by the present invention;

[0028] Figure 2 A schematic diagram of normal operation of the product provided by this invention before electromagnetic compatibility CS114 testing;

[0029] Figure 3 A schematic diagram illustrating interference encountered when performing electromagnetic compatibility CS114 testing on the product provided by this invention;

[0030] Figure 4 A schematic diagram of the electromagnetic compatibility connection device provided by the present invention;

[0031] Figure 5 This is a schematic diagram illustrating the CS114 test results using an electromagnetic compatibility connection device provided by the present invention. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0033] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0034] It should be noted that all actions involving the acquisition of signals, information, or data in this invention are carried out in compliance with the relevant data protection laws and regulations of the locality and with authorization from the owner of the relevant device.

[0035] Example 1

[0036] Please see Figure 4 This invention provides an electromagnetic compatibility connection device, including a printed circuit board, a coaxial cable, and a shielded radio frequency connector.

[0037] The coaxial cable is used to transmit radio frequency signals and differential signals simultaneously;

[0038] The shielded RF connector has a housing and a center signal pin;

[0039] The shielding layer of the coaxial cable is electrically connected to the outer shell, and the core wire of the coaxial cable is electrically connected to the center signal pin.

[0040] The shielded RF connector is mounted on the printed circuit board, and the housing is electrically connected to the grounding system of the printed circuit board;

[0041] The printed circuit board integrates a signal separation and filtering network to separate the mixed signal from the coaxial cable into radio frequency signals and differential signals, and to provide a high-frequency grounding path for the shielding layer of the coaxial cable.

[0042] Specifically, a coaxial cable is a transmission line with a central conductor, insulating medium, shielding layer, and outer sheath. It can transmit high-frequency electromagnetic energy with low loss, while suppressing signal radiation and external interference through the outer shielding structure. This coaxial cable is configured to carry two different types of signals within the same internal transmission path: radio frequency signals, which can refer to continuous or modulated waves with frequencies in the range of 1 GHz to 2 GHz, such as L-band communication or radar signals; and differential signals, which are a pair of electrical signals with equal amplitude and opposite phase, commonly used in digital communication to enhance anti-interference capabilities, such as serial data with communication rates up to 460,800 bps. This multiplexing design reduces the number of external connection lines, contributing to structural simplification and weight reduction, but it also brings new technical challenges: how to maintain the integrity of both signals within the same physical channel and avoid mutual interference, especially when strong external electromagnetic fields are injected.

[0043] A shielded RF connector is a mechanical interface used to achieve high-frequency electrical connection between a coaxial cable and a circuit board while maintaining electromagnetic shielding integrity. It consists of a metal housing and a central conductor, or center signal pin, supported by insulating material and passing through it. The housing can be connected to the cable's shielding layer and the equipment's grounding system, forming a continuum of electromagnetic shielding; the center signal pin is responsible for transmitting the main signal carried by the cable core. In this structure, the connector not only provides physical connection and signal conduction, but the housing, as an extension of the cable shielding layer inside the equipment, also provides the necessary physical access point for subsequent high-frequency grounding.

[0044] The core wire of the coaxial cable is electrically connected to the center signal pin. This connection can be established through welding, crimping, or threading, ensuring a low-impedance electrical connection between the cable's braided mesh or aluminum foil shield and the connector housing, while simultaneously establishing a reliable signal path between the cable's center conductor and the connector's center signal pin. This completes the signal transition from the cable to the connector. Furthermore, it transforms the cable's shield from part of the external transmission line into a node in the device's internal grounding system, laying the foundation for further processing on the printed circuit board. If the shield fails to achieve effective grounding at this point, the cable sheath will become an antenna for introducing or radiating interference, especially in cable bundle injection interference tests such as the CS114, where interference current will be directly coupled to the internal circuitry.

[0045] The mounting methods for electrically connecting the connector housing to the grounding system of the printed circuit board include, but are not limited to, through-hole soldering, surface mounting, or flange and screw fixing. The grounding system of the printed circuit board can consist of one or more copper foil planes dedicated to potential reference and current return, which may include RF-specific ground planes, digital ground planes, or analog ground planes. Electrically connecting the connector housing to this grounding system means that any common-mode interference current or induced charge from the cable shield can be discharged with low impedance to the ground plane of the circuit board through this connection point, rather than entering sensitive signal processing circuitry. This connection essentially establishes a pre-defined high-frequency current discharge path between the cable shield and the circuit board ground, thus constituting the first level of electromagnetic interference suppression at the physical interface.

[0046] A signal separation and filtering network is a circuit composed of passive or active electronic components that distinguishes and guides composite electrical signals based on differences in signal frequency, amplitude, or mode. In this application scenario, the network needs to process mixed signals that simultaneously contain high-frequency continuous carrier waves and low-frequency differential digital pairs. Its implementation can include channel separation using frequency selectivity, such as setting a bandpass path for RF signals and a low-pass or baseband path for differential signals. Simultaneously, the network also needs to include specific impedance management for the cable shield access point, such as a combination of series inductors and parallel capacitors, aiming to present low impedance to ground at high frequencies to effectively bypass interference, while presenting high impedance to the useful signal frequency to avoid signal energy loss. Through the collaborative design of this network, on the one hand, effective separation and separate routing of the two signals are achieved, ensuring the normal operation of their respective subsequent processing circuits; on the other hand, it provides an optimized grounding terminal for the interference spectrum at the circuit board level after the connector access point of the cable shield, allowing common-mode interference current introduced from the cable to be effectively absorbed and dissipated, rather than circulating within the circuit, thereby improving the robustness of the entire connection structure in complex electromagnetic environments.

[0047] In some embodiments, the housing of the shielded RF connector is electrically connected to the top RF ground on the printed circuit board, and the center signal pin is electrically connected to the bottom pad on the printed circuit board.

[0048] Specifically, the shielded RF connector, acting as an interface between the coaxial cable and the printed circuit board (PCB), has its outer shell fixed and electrically connected to the dedicated RF grounding copper foil area on the top layer of the PCB, i.e., the top-layer RF ground, via soldering or conductive adhesive. This top-layer RF ground is a continuous or grid-like conductor plane optimized for high-frequency signals, located on the outermost layer of the PCB. Its main function is to provide a low-inductance return path for signal current flowing through the surface layer and to serve as a reference potential for the top-layer wiring components. Simultaneously, the connector's center signal pin passes through a pre-drilled mounting hole on the PCB, forming a mechanical and electrical connection with a specific pad located on the bottom layer of the PCB. The bottom-layer pad is a metallized contact area located on the back of the PCB and can be adjacent to the bottom signal wiring layer and the RF ground plane. This connection configuration achieves physical separation of the signal path and decoupling of the reference plane. The RF signal and its associated return current are primarily guided to the bottom layer of the printed circuit board (PCB), with the bottom RF ground as a reference. This helps control the impedance continuity of the RF path and reduces radiated coupling to the top layer circuitry. Meanwhile, the top RF ground connected to the connector housing provides a direct and independent discharge plane for common-mode interference currents introduced by the cable shield, preventing interference currents from flowing through the sensitive bottom signal reference ground. By distributing the grounding point of the cable shield and the access point of the center signal pin on different PCB layers, this structure spatially separates potential high-noise ground loops from critical signal paths. It utilizes the PCB's own layered structure to create a natural isolation barrier, thereby enhancing the overall connection structure's ability to suppress common-mode interference coupled through the cable without relying on additional metal shielding cavities.

[0049] In some embodiments, the signal separation and filtering network includes a radio frequency signal extraction branch, a radio frequency reference ground loop, and a differential signal extraction branch.

[0050] Specifically, the RF signal extraction branch is responsible for separating the target RF component from the composite electrical signal introduced by the connector center pin. This branch may contain passive or active circuitry with frequency selectivity, designed to present a low insertion loss path for the RF band and a high impedance for low-frequency differential signal components, thereby achieving effective separation in the frequency domain.

[0051] The purpose of setting up an RF reference ground loop is to provide a low-impedance path to ground optimized for the RF interference spectrum for the access point of the housing connected to the cable shield. This loop can include a combination of inductor and capacitor elements, whose parameters are configured to exhibit low impedance characteristics near the target RF operating frequency. This effectively guides RF common-mode noise that intrudes along the shield to the grounding system of the printed circuit board for dissipation, while avoiding short circuits to useful differential signals.

[0052] The differential signal extraction branch is used to recover clean differential digital signal pairs from the composite signal. This branch can contain two symmetrical or balanced signal processing channels, processing the positive and negative components of the signal respectively. The design of these two channels must ensure a high common-mode noise rejection ratio. This can be achieved by using circuit structures such as common-mode chokes, balanced transmission lines, or differential amplifiers, aiming to extract the effective signal of the differential mode and suppress common-mode interference introduced during transmission.

[0053] These three branches are strategically laid out and electrically connected on the printed circuit board, forming a complete signal processing front end: the RF signal extraction branch ensures lossless transmission of high-frequency carrier signals; the RF reference ground loop provides a dedicated channel for interference discharge, protecting the quiet environment of internal circuits; and the differential signal extraction branch ensures the integrity of digital communication. Through this partitioned processing architecture, the network can differentiate and manage signals and noise of different natures and sources in terms of physical space and electrical characteristics. This systematically solves the problems of crosstalk between signals and external electromagnetic interference intrusion under the constraint of single-cable multiplexing transmission, achieving high-fidelity transmission and high-reliability reception of mixed signals.

[0054] In some embodiments, the radio frequency signal extraction branch includes a first capacitor (C3) connected between the center signal pin and the radio frequency output terminal of the shielded radio frequency connector.

[0055] Specifically, the first capacitor mainly functions as a coupling or DC blocking element in the circuit. Its capacitance value is selected to present a sufficiently low impedance to the target radio frequency band (e.g., L-band) so that the radio frequency signal energy can pass through efficiently. However, for the differential signal fundamental frequency and its main harmonic components, which are much lower than radio frequency, the capacitor presents a high impedance, thereby blocking the differential signal components outside the branch and achieving preliminary frequency domain separation.

[0056] In some embodiments, the radio frequency reference ground loop includes a filter circuit connected between the housing of the shielded radio frequency connector and the common ground of the printed circuit board.

[0057] Specifically, the filter circuit is a passive network designed to address the common-mode interference spectrum characteristics introduced by the cable shielding layer. Its core function is to provide a controllable, low-impedance discharge path for high-frequency interference currents to the common ground plane of the printed circuit board, while avoiding adverse effects on useful low-frequency or DC signal paths. The common ground can be a large-area, low-inductance copper foil layer or network inside the printed circuit board, serving as a common potential reference point for various circuits in the system.

[0058] In some embodiments, the filter circuit includes a first inductor (L1) and a second capacitor (C1) connected in series.

[0059] Specifically, the series connection of the first inductor and the second capacitor constitutes a series resonant circuit, which exhibits theoretically the lowest impedance at a specific frequency, while the impedance gradually increases as it deviates from the resonant frequency. This resonant frequency is determined by the inductance of the first inductor and the capacitance of the second capacitor.

[0060] In some embodiments, the differential signal extraction branch includes:

[0061] The first branch is used to extract the differential positive terminal signal, and the first branch is connected between the center signal pin and the differential positive input terminal of the shielded RF connector;

[0062] The second branch is used to extract the differential negative input signal, and the second branch is connected between the housing of the shielded RF connector and the differential negative input.

[0063] Specifically, the first branch connects between the center signal pin and the differential positive input terminal of the shielded RF connector, and the second branch connects between the housing of the shielded RF connector and the differential negative input terminal. The center signal pin carries the raw mixed signal from the coaxial cable core, which includes the RF signal, the differential positive input signal component, and any common-mode noise. The differential positive input terminal can be the positive input port of subsequent processing circuits such as differential receivers or comparators. The function of the first branch is to effectively transmit the differential positive input signal component from the mixed signal to this port, while suppressing the RF signal component and handling common-mode noise. The second branch uses the connector housing as a reference extraction point for the differential negative input signal. This is because in the coaxial cable transmission model, the shielding layer not only performs shielding and grounding functions, but its potential change also contains information about the differential negative input signal when multiplexing differential signals. The differential negative input terminal is the negative input port of the differential receiver circuit. The task of the second branch is to extract the clean differential negative input signal component from the housing and transmit it to this port.

[0064] In some embodiments, a third inductor (L3) is connected in series in the first branch; and a fourth inductor (L2) is connected in series in the second branch.

[0065] Specifically, a third inductor and a fourth inductor are introduced into the first and second branches, respectively, to isolate crosstalk of the differential channel from radio frequency interference and to enhance the suppression of common-mode noise from the circuit structure. This design enables the differential signal extraction branch to more reliably extract weak differential signal components in complex electrical environments containing strong radio frequency signals and external electromagnetic interference, providing cleaner input conditions for subsequent digital signal recovery.

[0066] In some embodiments, the radio frequency signal is an L-band signal, and the communication rate of the differential signal is 460800bps.

[0067] This embodiment, through systematic circuit and layout design, achieves the technical effect of simultaneously transmitting radio frequency signals and differential signals using a single coaxial cable and stably passing electromagnetic interference tests such as CS114. Specifically:

[0068] By connecting the shielding layer of the coaxial cable to the grounding system of the printed circuit board using a shielded RF connector, and by specifically designing an RF reference ground loop composed of inductors and capacitors, a low-impedance discharge path is provided for common-mode interference currents introduced by the cable shielding layer, especially in the RF band. This allows externally injected interference energy to be effectively dissipated into the PCB ground plane rather than intruding into the internal signal processing circuitry.

[0069] By employing RF signal extraction branches and differential signal extraction branches containing specific capacitors and inductors, the significant spectral differences between RF and differential signals are utilized to separate them from the shared transmission channel and process them along different physical paths. The RF signal is guided to the RF path through capacitive coupling, ensuring the continuity of its high-frequency response; the differential signal is extracted through a symmetrical branch containing a filter inductor, suppressing common-mode noise while maintaining the amplitude and phase balance of the signal pair.

[0070] This approach distributes connection points (casing and center pin) to different layers of the PCB (top RF ground and bottom pads) and integrates filtering components in the signal separation network, managing noise paths from both spatial layout and frequency characteristics perspectives. This reduces coupling between high-current ground loops and sensitive signal paths, and further cancels out residual common-mode interference that cannot be fully discharged through the inherent common-mode rejection capability of the differential architecture.

[0071] In summary, this embodiment, without relying on an external overall shielding cavity, solves the electromagnetic compatibility vulnerability caused by the grounding conflict of the cable shielding layer in single-cable multiplexing transmission scenarios by optimizing the interface circuit from the connector to the PCB and the collaborative design of the internal signal processing front end. This enables the system to maintain dual transmission quality and reliability of RF and differential digital signals in environments with strong electromagnetic interference. The effect of using this embodiment in a CS114 test is shown in the figure below. Figure 5 As shown.

[0072] Example 2

[0073] This embodiment also provides an electronic device, including the electromagnetic compatibility connection device of Embodiment 1.

[0074] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. An electromagnetic compatibility connection device, characterized in that, This includes printed circuit boards, coaxial cables, and shielded RF connectors; The coaxial cable is used to transmit radio frequency signals and differential signals simultaneously; The shielded RF connector has a housing and a center signal pin; The shielding layer of the coaxial cable is electrically connected to the outer shell, and the core wire of the coaxial cable is electrically connected to the center signal pin. The shielded RF connector is mounted on the printed circuit board, and the housing is electrically connected to the grounding system of the printed circuit board; The printed circuit board integrates a signal separation and filtering network to separate the mixed signal from the coaxial cable into radio frequency signals and differential signals, and to provide a high-frequency grounding path for the shielding layer of the coaxial cable.

2. The electromagnetic compatibility connection device according to claim 1, characterized in that, The housing of the shielded RF connector is electrically connected to the top RF ground on the printed circuit board, and the center signal pin is electrically connected to the bottom pad on the printed circuit board.

3. The electromagnetic compatibility connection device according to claim 1 or 2, characterized in that, The signal separation and filtering network includes a radio frequency signal extraction branch, a radio frequency reference ground loop, and a differential signal extraction branch.

4. The electromagnetic compatibility connection device according to claim 3, characterized in that, The radio frequency signal extraction branch includes a first capacitor connected between the center signal pin and the radio frequency output terminal of the shielded radio frequency connector.

5. The electromagnetic compatibility connection device according to claim 3, characterized in that, The RF reference ground loop includes a filter circuit connected between the housing of the shielded RF connector and the common ground of the printed circuit board.

6. The electromagnetic compatibility connection device according to claim 5, characterized in that, The filter circuit includes a first inductor and a second capacitor connected in series.

7. The electromagnetic compatibility connection device according to claim 3, characterized in that, The differential signal extraction branch includes: The first branch is used to extract the differential positive terminal signal, and the first branch is connected between the center signal pin and the differential positive input terminal of the shielded RF connector; The second branch is used to extract the differential negative input signal, and the second branch is connected between the housing of the shielded RF connector and the differential negative input.

8. The electromagnetic compatibility connection device according to claim 7, characterized in that, A third inductor is connected in series in the first branch; a fourth inductor is connected in series in the second branch.

9. The electromagnetic compatibility connection device according to claim 1, characterized in that, The radio frequency signal is an L-band signal, and the communication rate of the differential signal is 460800bps.

10. An electronic device, characterized in that, Includes the electromagnetic compatibility connection device as described in any one of claims 1 to 9.

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