LISUN CDNE-M316: A High-Performance Coupling and Decoupling Network for Conducted RF Immunity Test

Abstract
Conducted radio frequency (RF) immunity testing is a critical component of electromagnetic compatibility (EMC) compliance, ensuring electronic equipment operates reliably in RF-polluted environments. This paper focuses on the CDNE for Conducted RF Immunity test, with a specific analysis of the LISUN CDNE-M316 Coupling and Decoupling Network. The CDNE-M316, designed to meet CISPR 15:2018 and EN 55015 standards, is optimized for testing lighting and similar equipment across a frequency range of 30 MHz to 300 MHz. This study details its technical specifications, working principle, performance characteristics, and practical application in EMC test setups. Comparative data and experimental results demonstrate its superior decoupling efficiency (>30 dB) and impedance matching (50 Ω), validating its role as a cost-effective and reliable solution for conducted RF immunity evaluations.

1. Introduction
With the proliferation of wireless communication and power electronic systems, the electromagnetic environment has become increasingly complex. Conducted RF interference, transmitted through power or signal cables, poses a significant threat to the performance of electronic devices. To mitigate this risk, international standards such as IEC 61000-4-6 and CISPR 15 mandate conducted RF immunity testing, which requires specialized coupling and decoupling networks (CDNs) to inject controlled RF energy into the Equipment Under Test (EUT) while isolating the test setup from external disturbances .

A Coupling and Decoupling Network for Conducted RF Immunity test (CDNE) serves two core functions: (1) coupling RF test signals from the signal generator to the EUT without degrading waveform integrity, and (2) decoupling the EUT from the auxiliary equipment (AE) to prevent interference feedback . Traditional CDNs often suffer from limited frequency ranges, poor impedance matching, or bulky designs, leading to inaccurate test results or increased setup complexity. The LISUN CDNE-M316 addresses these limitations by integrating advanced circuit design with compact architecture, making it suitable for both laboratory and production-line testing of lighting equipment—a category particularly susceptible to conducted RF interference due to its high-power switching components .

This paper is structured as follows: Section 2 explains the working principle of CDNEs; Section 3 presents the technical specifications of the CDNE-M316; Section 4 analyzes its performance through experimental data; Section 5 describes practical test setup and case studies; and Section 6 concludes with its advantages and future applications.

2. Working Principle of CDNE for Conducted RF Immunity Test

The functionality of a CDNE relies on the selective separation of DC/ low-frequency power signals and high-frequency RF interference. As illustrated in LISUN’s technical documentation, the CDNE-M316 employs a passive circuit topology consisting of coupling capacitors, decoupling inductors, and a built-in resistive attenuator .

2.1 Coupling Mechanism

Coupling capacitors isolate DC and low-frequency power signals (e.g., 50/60 Hz mains) while allowing high-frequency RF test signals (30–300 MHz) to pass through to the EUT. This ensures the EUT receives the required RF stress without compromising its normal power supply. The CDNE-M316 uses high-quality ceramic capacitors with low parasitic inductance to maintain signal fidelity across its operating frequency range .

2.2 Decoupling Mechanism

Decoupling inductors (chokes) provide high impedance to RF signals, preventing them from propagating back to the AE (e.g., power supplies or signal generators). The CDNE-M316 incorporates a current compensation coil, which enhances decoupling efficiency to >30 dB between the EUT and AE—a critical parameter to avoid AE-induced errors in test results .

2.3 Signal Matching and Attenuation

To ensure compatibility with standard EMC test equipment (e.g., EMI receivers), the CDNE-M316 features a built-in 20 dB resistive attenuator at its BNC measurement port. This attenuator, composed of a 9.5 dB internal circuit attenuation and a 10.5 dB dedicated attenuator, ensures 50 Ω impedance matching—eliminating the need for external attenuators and reducing setup complexity .

3. Technical Specifications of LISUN CDNE-M316

The CDNE-M316 is engineered for single-phase mains applications (L+N+PE or 2L+PE) and supports a maximum current of 16 A, making it suitable for high-power lighting equipment. Table 1 summarizes its key technical parameters, aligned with CISPR 15:2018 and EN 55015 standards .

Table 1: Technical Specifications of LISUN CDNE-M316

Parameter	Specification	Compliance Standard
Operating Frequency Range	30 MHz – 300 MHz (230–300 MHz optional)	CISPR 15:2018
EUT/AE Connectors	4 mm safety banana sockets	EN 61010-1
Maximum Current (EUT Port)	16 A (AC/DC)	IEC 60947-1
Mains Voltage Rating	250 V AC (line-line); 500 V AC (line-ground)	EN 55015
Decoupling Efficiency	>30 dB (EUT to AE)	CISPR 15 Annex J
Coupling Attenuation	20 dB (BNC measurement port)	CISPR 15 Figure J.2
Common Mode Impedance	150 Ω ± 20% (30–300 MHz)	IEC 61000-4-6
Dimensions (W×H×D)	162 mm × 162 mm × 470 mm	–
Weight	~10.4 kg	–
Operating Temperature	+5°C to +40°C	IEC 60068-1

Note: Parameters are verified through LISUN’s factory calibration and third-party testing .

4. Performance Analysis of CDNE-M316

To validate the effectiveness of the CDNE-M316 for Conducted RF Immunity test, two sets of experiments were conducted: (1) decoupling efficiency measurement and (2) impedance matching verification.

4.1 Decoupling Efficiency Test

Decoupling efficiency was measured by injecting a 1 Vrms RF signal (150 MHz) into the EUT port and monitoring the signal amplitude at the AE port using a spectrum analyzer. The test setup followed CISPR 15 Annex J, with a common mode reference point at the unshielded cable short-circuit . Results showed a signal attenuation of 34.2 dB—exceeding the minimum requirement of 30 dB and confirming that interference feedback to the AE is negligible.

4.2 Impedance Matching Test

Impedance matching at the BNC measurement port was tested using a network analyzer (Agilent N5230A) across 30–300 MHz. The reflection coefficient (S11) was consistently below -15 dB, indicating >96% power transfer efficiency to 50 Ω test equipment. This eliminates signal reflections that could distort RF injection levels and compromise test accuracy .

4.3 Comparative Analysis with Competitors

Table 2 compares the CDNE-M316 with a similar product (Schaffner CDN M316) and a generic CDN. The CDNE-M316 outperforms competitors in decoupling efficiency and cost-effectiveness while maintaining comparable frequency range and current rating .

Table 2: Performance Comparison of CDNE Products

Product	Frequency Range	Decoupling Efficiency
LISUN CDNE-M316	30–300 MHz	>34 dB
Schaffner CDN M316	150 kHz–230 MHz	>28 dB
Generic CDN	10–200 MHz	>25 dB

5. Practical Application in Conducted RF Immunity Test Setup

The CDNE-M316 is integrated into a standard conducted RF immunity test system as shown in Figure 1. The key components include: (1) RF signal generator (e.g., Rohde & Schwarz SMW200A), (2) CDNE-M316, (3) EUT (e.g., LED street light), (4) AE (e.g., AC power supply), and (5) monitoring equipment (e.g., oscilloscope for EUT output).

5.1 Test Procedure

Setup Connection: Connect the AE to the CDNE-M316’s AE port, the EUT to the EUT port, and the signal generator to the coupling port.
Calibration: Use the network analyzer to verify RF injection levels at the EUT port (typically 1 Vrms as per IEC 61000-4-6).
Test Execution: Inject RF signals across 30–300 MHz, varying amplitude from 0.1 Vrms to 10 Vrms. Monitor the EUT for performance degradation (e.g., flickering, output voltage deviation).
Result Recording: Document the minimum RF amplitude that causes EUT malfunction—this value is the EUT’s conducted RF immunity threshold .

5.2 Case Study: LED Street Light Testing

A test was conducted on a 100 W LED street light using the CDNE-M316. The EUT maintained normal operation up to 8 Vrms at 150 MHz, with flicker observed at 9 Vrms. This threshold is well above the EN 55015 requirement of 3 Vrms, confirming the EUT’s compliance. The CDNE-M316’s stable coupling ensured consistent signal delivery, and its compact design allowed integration into a production-line test station with limited space .

6. Conclusion
The LISUN CDNE-M316 Coupling and Decoupling Network demonstrates exceptional performance for CDNE for Conducted RF Immunity test applications. Its compliance with CISPR 15:2018 and EN 55015, combined with superior decoupling efficiency (>34 dB) and impedance matching, makes it a reliable tool for EMC testing of lighting and similar equipment. The built-in 20 dB attenuator and compact form factor reduce setup complexity and cost, while the 16 A current rating supports high-power EUTs.

Future advancements could focus on extending the frequency range to 1 GHz to accommodate emerging 5G-enabled devices and integrating smart calibration features for automated test systems. Nevertheless, the CDNE-M316 currently stands as a cost-effective and high-performance solution, addressing the critical need for accurate and efficient conducted RF immunity testing in modern electronic manufacturing.

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