Intrinsic safety system for wireless devices

Abstract

A system (200) for intrinsic safety in a wireless device is disclosed. The system includes a wireless communication module (110) powered by direct current (DC) power (116). Connected to the module is a radio frequency (RF) output circuit (120) including a series of filters (122, 124, 126) and an antenna (128). The system further includes a limiting unit (210) associated with the RF output circuit. The limiting unit includes a resistor (310) for limiting the DC power and a capacitor (320) for establishing a low impedance path for high frequency signals to ground, thereby ensuring overall safety and operational efficiency of the wireless device.

Description

Technical Field

[0001] This invention generally relates to the field of wireless communication, and more particularly to systems designed to ensure the intrinsic safety of wireless devices deployed in hazardous or explosive environments. Background Technology

[0002] The use of wireless devices across a wide range of sectors, including consumer electronics and commercial spaces, has fostered an ecosystem promising reliable data transmission, convenience, flexibility, and scalability. Compared to wired infrastructure, wireless communication offers numerous benefits, such as the absence of physical connectors and cables (meaning easier installation), dynamic network topologies, and reduced maintenance requirements. With the advent of Industry 4.0, there is a growing trend towards integrating wireless communication into industry. However, many industrial environments, such as the petrochemical, oil, gas, and mining sectors, are fraught with the risk of explosion. The volatile nature of materials handled or stored in these areas necessitates stringent safety protocols. Therefore, it becomes crucial that wireless devices used in such environments are intrinsically safe, ensuring they do not act as ignition sources due to sparks or any other factors.

[0003] Traditionally, industries have avoided using wireless devices in critical areas, relying instead on wired infrastructure. These wired devices, communicating via protocols such as 4-20mA, HART, Profibus, and Profinet, are considered more reliable and secure. Their inherent safety is typically achieved through design, ensuring energy levels remain below the ignition threshold. Some wireless devices used in industries with explosive zones are encased in robust, explosion-proof enclosures, often referred to as "Ex-d" enclosures. While effective, these enclosures are bulky, expensive, and typically relegate devices to less hazardous areas, such as Ex-Zone 2, keeping them away from more sensitive areas (Zone 1).

[0004] This traditional approach has many limitations. Reliance on wired equipment, for example, negates a major advantage of wireless systems: flexibility. Each new sensor or device added to the network requires additional wiring, increasing installation costs and complexity. Wireless devices, while robustly housed, have limitations in use. The bulky "Ex-d" housing adds significant weight and makes installation cumbersome. Furthermore, these housings often impede signal quality, reducing the device's effective communication range. Relegating these devices to less hazardous areas means the industry cannot utilize the full potential of wireless communication in areas where it may be most needed. While pragmatic, this protective approach is more of a stopgap measure than a solution, considering wireless communication but with significant trade-offs in cost, flexibility, and deployment area.

[0005] This invention seeks to overcome these challenges by providing an inherently safe system for wireless devices that addresses these limitations. The system ensures reliable communication while adhering to stringent safety standards for explosive zones. It is robust enough to meet evolving safety standards, anticipates worst-case scenarios, and proactively mitigates risks. Summary of the Invention

[0006] The present invention achieves its objectives through an intrinsically safe system for wireless devices. The system includes a wireless communication module powered by direct current (DC) power. The system also includes a radio frequency (RF) output circuit connected to the wireless communication module. The RF output circuit includes a series of filters and an antenna. The system further includes limiting units associated with the RF output circuit. The limiting units include resistors for limiting the DC power and capacitors for establishing a low-impedance path for high-frequency signals to ground.

[0007] In one or more embodiments, the system further includes a first ground plane associated with the wireless communication module and a second ground plane associated with the RF output circuitry. Here, the first ground plane and the second ground plane are implemented as a first printed circuit board (PCB) layer and a second PCB layer that are separate from each other.

[0008] In one or more embodiments, the limiting unit is connected between a first ground plane and a second ground plane.

[0009] In one or more embodiments, the capacitor of the limiting unit is composed of a first PCB layer, a second PCB layer, and an insulating material between the first PCB layer and the second PCB layer.

[0010] In one or more embodiments, the resistor of the limiting unit is implemented as a surface mount resistor connected to the first PCB layer and the second PCB layer through one or more vias.

[0011] In one or more embodiments, the resistors of the limiting unit are divided into a plurality of resistors distributed along the first PCB layer and the second PCB layer.

[0012] In one or more embodiments, the creepage distance between the first PCB layer and the second PCB layer is based on one or more intrinsically safe definition standards for wireless devices.

[0013] In one or more embodiments, the wireless communication module includes a system-on-a-chip (SoC) having a radio device with a transmitter and a receiver, and connected to a decoupling capacitor.

[0014] In one or more embodiments, the RF output circuitry includes a first PI filter for impedance transformation, a rejection filter for preventing spurious emissions, and a second PI filter for further impedance matching with the antenna.

[0015] In one or more embodiments, the wireless communication module is adapted for use in explosive environments and has an RF output circuit with an associated limiting unit.

[0016] The foregoing description of the invention is illustrative only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become clear from the accompanying drawings and the following detailed description. Attached Figure Description

[0017] The accompanying drawings, which are incorporated herein and constitute a part of this disclosure, illustrate exemplary embodiments and, together with the specification, serve to explain the disclosed principles. The same numerals are used throughout the drawings to refer to the same features and components, wherein: Figure 1 This is a schematic representation of a circuit used to implement a wireless communication module with radio frequency (RF) output circuitry; Figure 2 It is for implementing one or more embodiments of the present invention having Figure 1 A schematic representation of an intrinsically safe system for a wireless device with a circuit limiting unit; Figure 3 This is a schematic representation of a limiting unit according to an embodiment of the present invention; and Figure 4 This is a schematic representation of a limiting unit according to another embodiment of the present invention. Detailed Implementation

[0018] Various embodiments are described with reference to the accompanying drawings, wherein the same reference numerals are consistently used to refer to the same elements. In the following description, numerous specific details are set forth for purposes of explanation in order to provide a thorough understanding of one or more embodiments. It will be clear that such embodiments may be practiced without these specific details.

[0019] This document discloses examples of intrinsically safe systems for wireless devices. In the following description, numerous specific details are set forth for purposes of explanation in order to provide a thorough understanding of embodiments of the invention. However, it will be apparent to those skilled in the art that embodiments of the invention may be practiced without these specific details or using equivalent arrangements. In other instances, well-known structures and devices are shown in block diagram form to avoid unnecessarily obscuring embodiments of the invention.

[0020] Now for reference Figure 1 The diagram illustrates a schematic representation of a circuit (as indicated by reference numeral 100) for implementing a wireless communication module 110 with a radio frequency (RF) output circuit 120 according to an embodiment of the present invention. Circuit 100 is designed to optimally manage RF signals for both security and performance. Circuit 100 provides components and modules to ensure optimal signal transmission, reception, and processing. Circuit 100 is designed to handle a range of frequencies and signal strengths, making it suitable for various wireless communication needs. The components and modules within circuit 100 are arranged to minimize interference, reduce signal loss, and enhance clarity. Furthermore, circuit 100 incorporates features to prevent overheating and manage unexpected surges in power or signal strength.

[0021] In circuit 100, wireless communication module 110 acquires data to be transmitted (e.g., data from its associated sensors), converts it into RF signals, and then sends them to RF output circuit 120 for further processing. Similarly, when RF signals are received, wireless communication module 110 processes these signals, extracts data, and then sends it to the appropriate destination (e.g., a command to its associated sensor). Wireless communication module 110 is designed to work with a variety of wireless communication protocols, including Bluetooth, WLAN, GSM, or any other relevant standards, allowing circuit 100 to be versatile and available in a variety of applications. Therefore, regardless of specific communication requirements, wireless communication module 120 can be configured to handle them, ensuring that circuit 100 remains relevant and operational across different scenarios.

[0022] In this implementation, the wireless communication module 110 includes a system-on-chip (SoC) 112 with a radio device (not shown) including a transmitter and a receiver, an RF output (RF_OUT pin) 118, and a decoupling capacitor 114. In this document, the SoC integrates several components of the wireless communication module 110 into a single chip, which helps to reduce the footprint of the electronics and also enhances their efficiency and performance. The radio device is the communication component responsible for transmitting and receiving wireless signals. In the radio device, the transmitter is responsible for converting data into RF signals and broadcasting them wirelessly. The receiver, on the other hand, captures the incoming RF signals and converts them back into data for processing by the system associated with the wireless communication module 110. Electronic circuits, especially complex ones like the SoC 112, can sometimes experience small fluctuations in their power supply. If left unmanaged, these fluctuations can lead to performance problems or even potential damage. The decoupling capacitor 114 acts as a buffer, stabilizing the power supply to the SoC 114 by storing and releasing energy as needed. When SoC 114 requires a power burst, decoupling capacitor 114 provides it, and conversely, when excess energy is present, decoupling capacitor 114 absorbs it. This ensures that SoC 112 receives a stable power flow, thereby optimizing its performance and lifespan.

[0023] The wireless communication module 110 is powered by direct current (DC) power (as indicated by reference numeral 116 in the attached figure). DC power 116 is characterized by a constant voltage or current, providing a stable and uninterrupted energy supply to the electronic device. Using DC power 116, the wireless communication module 110 operates without power fluctuations. Such fluctuations could potentially introduce noise or distortion into the transmitted or received signals. Therefore, the wireless communication module 110 can maintain the integrity and clarity of the wireless signal, thereby ensuring accurate data transmission.

[0024] Furthermore, in circuit 100, RF output circuit 120 is responsible for processing RF signals, ensuring these signals have the correct frequency and amplitude. RF output circuit 110 includes various components such as filters (including inductors, capacitors, and / or any other components that can store energy) and amplifiers, which work together to ensure the RF signal is clear and robust. These components help reduce any unwanted signals or noise from the RF signal. As shown, RF output circuit 120 includes a series of filters and antenna 128. The series of filters includes a first PI filter 122, a suppression filter 124, and a second PI filter 126, each filter being specifically designed and placed to optimize the quality and safety of the transmitted and received RF signals.

[0025] Specifically, the RF output circuit 120 includes a first PI filter 122 for impedance transformation. In electronics and communications, impedance matching is required to ensure maximum power transfer from source to destination without unwanted reflections. The first PI filter 122 is configured to transform the impedance of, for example, an RF signal from the wireless communication module 110 to match the requirements of subsequent stages in circuit 100 (typically 50 Ohms). Following the first PI filter 122, the RF output circuit 120 includes a suppression filter 124 to prevent spurious emissions. In wireless communications, it is not uncommon for devices to emit unwanted frequencies or signals that can interfere with other devices or even violate regulatory standards. The suppression filter 124 is specifically designed to eliminate or significantly reduce these unwanted emissions, thereby ensuring that only the desired frequency band is transmitted or received. This is also necessary for radio certification according to FCC regulations or RED / EN300328. Furthermore, the RF output circuit 120 includes a second PI filter 126, which further refines the impedance matching process, specifically based on the connection to antenna 128.

[0026] Typically, antennas have specific impedance requirements, and any mismatch can lead to reduced transmitted power, signal distortion, or even potential damage to the system. The radio device of the wireless communication module 110 provides an output at RF output 118, which typically has a different impedance (usually a higher impedance) than the antenna 128. A second PI filter 126 ensures that the RF signals are impedance-matched to the antenna 128 before they are transmitted through it. This ensures optimal transmission range and overall performance.

[0027] Typically, each of the first PI filter 122, the suppression filter 124, and the PI filter 126 is connected to the ground plane, a common practice for achieving good RF performance. Grounding ensures minimal interference and distortion, thus maintaining the strength of the transmitted and received RF signals. From a safety perspective, particularly focusing on intrinsic safety, current evaluation methodologies consider such systems in their standard functional modes. This means that the evaluation is based on the premise of an undamaged system where all components operate as intended. The maximum RF power emitted from the corresponding SoC becomes a primary consideration. Importantly, this power is inherently limited by the design specifications of such SoC, such as its low power voltage, which may be, for example, 1.8 V. As long as such SoC does not incorporate an internal DC-DC converter, the system remains within parameters considered safe.

[0028] However, with the evolution of safety standards, particularly EN60079-11, it may be necessary to analyze the energy stored in each capacitor and coil of such a system to mitigate risks such as sparks. For example, refer to Figure 1The energy associated with coils such as F1 / L1, F2 / L1, and F3 / L1 in circuit 100 is not inherently limited. Theoretically, the current flowing through these coils could potentially be infinite, limited only by the inherent DC resistance of the coils. This resistance level, particularly for devices operating in DC power mode (such as circuit 100 using DC power 116), typically exceeds the inherent safety threshold of the device.

[0029] Those skilled in the art can envision several potential solutions to reduce excess energy stored in the coil. In one example, a resistor could be placed in series with the RF output 118 of the wireless communication module 110. While this reduces potential energy surges, it simultaneously degrades RF performance, making it an undesirable solution. In another example, a fuse could be placed in the line of the DC power 116 before the decoupling capacitor 114. However, this may not reduce the likelihood of energy within the decoupling capacitor 114 discharging into the coil. Instead, positioning the fuse after the decoupling capacitor 114 impairs its intended functionality, making this approach inefficient as well. In yet another example, a capacitor could be introduced in series with the RF output, effectively preventing the DC power 116 from reaching the coil without affecting RF power. However, such a capacitor must be inherently safe to prevent short circuits, as required by safety specifications. For this purpose, specialized failsafe capacitors (at least three) would be needed, an expensive and cumbersome method that often results in substandard behavior at high frequencies, impacting RF power. These conventional methods do not address the core issue of the potential risk of high energy being stored in the coil of the RF output circuit 120.

[0030] refer to Figure 2 This illustrates a schematic representation of a system 200 for intrinsically safe wireless devices. As shown, system 200 and... Figure 1 The system works in conjunction with circuit 100. System 200 is specifically designed to enhance and complement the functionality of circuit 100, thereby ensuring a comprehensive approach to secure wireless communication. Components and modules of system 200 are seamlessly integrated with components and modules of circuit 100, creating a holistic circuit optimized for both wireless performance and security.

[0031] As shown, the system 200 of this disclosure includes a limiting unit 210 associated with the RF output circuit 120 of circuit 100. The limiting unit 210 operates in conjunction with the RF output circuit 120 to ensure that the system 200 operates with increased safety, particularly in environments with potentially explosive conditions. Considering the potential risks associated with power surges or excessive energy storage, the integration of the limiting unit 210 acts as a protective measure, thereby ensuring that RF signals are processed, transmitted, and received within safe energy parameters. The primary function of the limiting unit 210 is to manage and regulate the power flow within the RF output circuit 120. The limiting unit 210 is configured to limit the power in the coil by cutting the ground plane of the RF output circuit 120 (the 'GND' of filters 122, 124, 126). In this case, RF output energy can be fed "to the air" through antenna 128 or through the limiting unit 210.

[0032] In an embodiment, such as Figure 3 As shown, limiting unit 210 includes a resistor 310 (also denoted as 'RL') for limiting DC power 116 and a capacitor 320 (also denoted as 'CL') for establishing a low-impedance path for high-frequency signals to ground. Specifically, resistor 310 is designed to regulate the DC power 116 flowing through RF output circuit 120. By introducing specific resistance, resistor 310 reduces excessive current, thereby ensuring that DC power remains within safe and predetermined limits. This resistance-based limiting protects components of system 200 from potential damage due to overcurrent. Furthermore, capacitor 320 in limiting unit 210 helps manage high-frequency signals. By design, the capacitor provides a low-impedance path for high-frequency signals, safely guiding them to ground. This function helps prevent potential feedback or interference that may be caused by stray high-frequency signals within system 200. Herein, capacitor 320 maintains the strength of these signals by ensuring that RF signals are effectively grounded.

[0033] In this configuration, the limiting unit 210, with resistor 310 and capacitor 320, provides safety against potential hazards. Herein, resistor 310 within the limiting unit 210 ensures that system 200 operates within defined power limits. Resistor 310 is configured to limit DC power 116, thereby ensuring that system 200 does not draw excessive power that could lead to overheating or other hazards. By effectively managing the consumption of DC power 116, system 200 not only ensures operational efficiency but also significantly reduces the risks associated with energy-related anomalies such as overheating or sparking. This strategic power management translates to longer equipment life, reduced maintenance requirements, and, most critically, enhanced safety in explosive environments. On the other hand, capacitor 320 plays a role in establishing low-impedance paths for high-frequency signals, ensuring they are effectively grounded. Herein, capacitor 320 exhibits good behavior at high frequencies (no inductance) and provides safety to meet intrinsically safe specifications. Therefore, capacitor 320 ensures that any high-frequency noise, whether from internal components, external interference, or harmonics, is effectively grounded, thus preventing potential interference or hazards. The dual mechanism provided by the limiting unit 210 using resistor 310 and capacitor 320 ensures the simultaneous management of DC and high-frequency risks.

[0034] In an embodiment, such as Figure 4 As shown, system 200 is implemented with a first ground plane 410 associated with wireless communication module 110 and a second ground plane 420 associated with RF output circuitry 120 (including antenna 128). In this document, system 200 is designed to combine different grounding mechanisms to optimize both performance and safety. The first ground plane 410 ensures that any electrical noise or interference associated with the operation of wireless communication module 110 is effectively grounded, thereby maintaining the strength of the signal managed by wireless communication module 110. The second ground plane 420 provides a grounding path for the RF signals processed by RF output circuitry 120, ensuring that incoming and outgoing RF signals remain free from unwanted interference or distortion. This dedicated ground also helps protect RF output circuitry 120 from potential electrical anomalies or surges, thereby enhancing its lifespan and operational reliability.

[0035] Here, as Figure 4As shown, the first ground plane 410 and the second ground plane 420 are implemented as a first printed circuit board (PCB) layer (denoted by reference numeral 412) and a second PCB layer (denoted by reference numeral 422) that are separate from each other. That is, the ground planes 410 and 420 are implemented on separate PCB layers 412 and 422, ensuring that they are clearly separated from each other. Those skilled in the art will envision that the ground planes 410 and 420 can be located inside or outside the corresponding PCB layers 412 and 422 (i.e., the inner or outer surface of the corresponding board) without any limitation. By embodying the ground planes 410 and 420 within the PCB layers 412 and 422, system 200 allows the ground paths of the wireless communication module 110 and the RF output circuit 120 to remain isolated from each other. This configuration also provides a reliable and consistent ground path, taking into account the uniformity and accuracy associated with the PCB manufacturing process. Furthermore, with this configuration, system 200 ensures a compact and efficient layout, thereby creating most of the available space.

[0036] In this configuration, isolation is provided when the limiting unit 210 is connected (embodied) between the first ground plane 410 and the second ground plane 420, thereby ensuring effective grounding and safety. Hereinafter, the capacitor 320 of the limiting unit 210 is composed of a first PCB layer 412 and a second PCB layer 422, and an insulating material 430 between the first PCB layer 412 and the second PCB layer 422. In a non-limiting example, the insulating material 430 is a PCB substrate material known in the art. The creepage distance 'd' (also referred to as the "insulation distance") between the first PCB layer 412 and the second PCB layer 422 is set based on one or more intrinsically safe definition standards for wireless devices. For example, the creepage distance 'd' can be set to meet the requirements of intrinsically safe standards such as IEC60079-11 (for ATEX Europe) and IECEX. In this example, for voltages less than 10 V, the creepage distance 'd' is set to at least 0.5 mm. This configuration ensures optimal performance while maintaining a creepage distance 'd' between PCB layers based on defined standards, ensuring that any potential risks are mitigated and keeping the device within safe operating parameters.

[0037] Furthermore, in this embodiment, the resistor 310 of the limiting unit 210 is implemented as a surface-mount resistor connected to the first PCB layer 412 and the second PCB layer 422 via one or more vias 432. That is, instead of a conventional through-hole resistor or any other conventional resistor form factor, the resistor 310 is implemented as a surface-mount device (SMD) resistor. Here, SMD (also known as surface mount technology (SMT)) is utilized due to its compactness, efficiency, and accuracy. By employing the surface-mount resistor 310, the system 200 ensures a smaller footprint, resulting in a more compact design, while also benefiting from the high reliability and performance associated with SMD components. Furthermore, the integration of the resistor 310 within the system 200 is achieved in a manner that allows it to interact with both the first PCB layer 412 and the second PCB layer 422. This is achieved through the strategic use of one or more vias 432. Vias are conductive paths that facilitate electrical connections between different layers of a PCB. In this configuration, via 432 enables resistor 310 to connect to both PCB layers 412 and 422, thereby ensuring that it can effectively manage and regulate the DC power flow across these layers.

[0038] In this embodiment, the resistor 310 of the limiting unit 210 is divided into multiple resistors distributed along the first PCB layer 412 and the second PCB layer 422. By utilizing multiple resistors along the first PCB layer 412 and the second PCB layer 422 instead of a single monolithic resistor, this design achieves a more uniform resistance distribution. This can result in better heat dissipation, reduced localized heating, and overall more efficient and reliable operation. Given the destructive nature of the resistor 310, this distribution also helps minimize potential electromagnetic interference (EMI) or crosstalk between components and adds redundancy.

[0039] This embodiment, especially Figure 4The disclosed embodiments ensure optimal RF performance by integrating and utilizing resistor 310 to block DC power and capacitor 320, while adhering to the safety requirements of DC operation of the wireless device's circuitry 100, thus ensuring intrinsic safety. Grounding is a critical aspect of any electronic system, especially for devices operating in explosive environments. The proposed grounding mechanism, characterized by the unique placement of the limiting unit 210 and a dual grounding plane configuration with separation between the first grounding plane 410 and the second grounding plane 420, ensures that the system 200 remains stable and safe. The proposed invention ensures the intrinsic safety of wireless devices, particularly in explosive environments, thereby bridging the gap between the convenience of wireless technology and the stringent safety requirements of such industrial environments. The introduction of the limiting unit 210, including both resistor 310 and capacitor 210, ensures that the wireless device (embodied by circuitry 100) remains within safe operating parameters regardless of internal or external interference. Therefore, this system 200 not only mitigates risks but also ensures optimal RF performance, providing a balance that traditional systems might not be able to achieve. This ensures that the system 200 can be deployed in various sectors, from the petrochemical industry to mining operations, and even in sectors where intrinsic safety may not be a primary concern but reliable and efficient wireless communication is desired.

[0040] While the invention has been described in detail with reference to certain embodiments, it should be understood that the invention is not limited to those embodiments. In view of the invention, many modifications and variations can be presented to those skilled in the art without departing from the scope of the various embodiments of the invention as described herein. Therefore, the scope of the invention is indicated by the appended claims rather than the foregoing description. All changes, modifications, and variations within the meaning and scope of the equivalents of the claims are considered to be within its scope.

Claims

1. A system (200) for intrinsically safe wireless devices, the system (200) comprising: The wireless communication module (110) is powered by direct current (DC) power (116); A radio frequency (RF) output circuit (120), connected to the wireless communication module (110), the RF output circuit (120) including a series of filters (122, 124, 126) and an antenna (128); and The limiting unit (210), associated with the RF output circuit (120), includes a resistor (310) for limiting the DC power (116) and a capacitor (320) for establishing a low-impedance path for the high-frequency signal to ground.

2. The system (200) according to claim 1 further includes a first ground plane (410) associated with the wireless communication module (110) and a second ground plane (420) associated with the RF output circuit (120), wherein the first ground plane (410) and the second ground plane (420) are respectively implemented as a first printed circuit board (PCB) layer (410) and a second PCB layer (422) separated from each other.

3. The system (200) according to claim 2, wherein, The limiting unit (210) is connected between the first ground plane (410) and the second ground plane (420).

4. The system (200) according to claim 3, wherein, The capacitor (320) of the limiting unit (210) is composed of the first PCB layer (412) and the second PCB layer (422) and an insulating material (430) between the first PCB layer (412) and the second PCB layer (422).

5. The system (200) according to claim 3 or 4, wherein, The resistor (310) of the limiting unit (210) is implemented as a surface mount resistor connected to the first PCB layer (412) and the second PCB layer (422) through one or more vias (432).

6. The system (200) according to any one of claims 3 to 5, wherein, The resistors (310) of the limiting unit (210) are divided into a plurality of resistors (310) distributed along the first PCB layer (412) and the second PCB layer (422).

7. The system (200) according to claim 4, wherein, The creepage distance ('d') between the first PCB layer (412) and the second PCB layer (422) is based on the intrinsic safety definition standard of the wireless device.

8. The system (200) according to any one of the preceding claims, wherein, The wireless communication module (110) includes a system on chip (200) (SoC) (112) having a radio device with a transmitter and a receiver and connected to a decoupling capacitor (320) (114).

9. The system (200) according to any one of the preceding claims, wherein, The RF output circuit (120) includes a first PI filter (122) for impedance transformation, a suppression filter (124) for preventing spurious emissions, and a second PI filter (126) for further impedance matching with the antenna (128).

10. The system (200) according to any one of the preceding claims, wherein, The wireless communication module (110) together with the RF output circuit (120) having the associated limiting unit (210) is adapted for use in explosive environments.

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