prEN 3475-812

Overview

The prEN 3475-812:2025 is a European standard within the aerospace series that defines test methods for measuring return loss and voltage standing wave ratio (VSWR) of coaxial cables used in aircraft electrical systems. Developed by CEN through ASD-STAN, this standard focuses on quantifying signal reflections caused by impedance mismatches along cable runs. It updates and supersedes the earlier EN 3475-812:2009, incorporating significant technical improvements such as standardized sample length (10 meters) and a defined formula for calculating VSWR.

Return loss measurement is critical to ensure the integrity and performance of electrical cables in aerospace applications, as it directly indicates the quality of impedance matching and cable uniformity. This standard complements related documents EN 3475-100 and EN 50289-1-11, reinforcing best practices to achieve reliable, high-frequency cable testing.

Key Topics

• Scope and Purpose
  Specifies test procedures for return loss and VSWR to assess reflection levels in coaxial cables across required frequency ranges pertinent to aerospace applications.

• Sample Preparation
  Test specimens are standardized to a 10-meter cable length with connectors fitted at each end to interface with measuring instruments. Ensuring proper cable connection quality is advised through time domain reflectometry per EN 3475-805.

• Measurement Methodology
  Return loss is measured following EN 50289-1-11’s electrical test methods, specifically Method C with the cable's far end terminated by a load matching the system’s nominal impedance.

• VSWR Calculation
  VSWR is derived using the standard formula:
  VSWR = (1 + |Γ|) / (1 - |Γ|)
  where |Γ| is the reflection coefficient measured under defined termination conditions. This calculation enables clear quantification of standing wave phenomena in the cable.

• Compliance Requirements
  Measured return loss and VSWR values must not surpass limits set by the applicable product standard to guarantee cable performance and system compatibility.

• Correction Procedures
  Emphasizes the use of correction methods outlined in EN 50289-1-11:2016 Annex B to reduce measurement errors caused by cable preparation, particularly at high frequencies.

Applications

prEN 3475-812:2025 is essential for aerospace manufacturers, cable designers, test engineers, and quality assurance professionals who:

• Develop and validate coaxial cables for aircraft electrical systems to ensure minimal signal reflection and loss.
• Perform routine testing during production and maintenance cycles to verify cable integrity and adherence to stringent aerospace requirements.
• Optimize impedance matching within cable assemblies to enhance signal transmission quality and reduce electromagnetic interference risks.
• Support certification and regulatory compliance processes for electrical cables used in modern aircraft designs.

This standard provides a consistent and reliable framework for assessing cable performance, directly contributing to safer and more efficient aerospace electrical installations.

Related Standards

• EN 3475-100: General test methods for aerospace electrical cables, establishing foundational testing protocols.
• EN 3475-805: Methods focused on measuring characteristic impedance, complementing return loss assessments and ensuring cable uniformity.
• EN 50289-1-11:2016: Detailed electrical test methods including those for characteristic impedance, input impedance, and return loss, along with essential correction procedures for accurate high-frequency measurements.

Incorporating prEN 3475-812 alongside these standards creates a comprehensive testing suite enabling aerospace industries to uphold international quality and safety benchmarks for aircraft electrical cables.

Keywords: prEN 3475-812, aerospace cable standards, return loss testing, VSWR measurement, coaxial cable testing, aircraft electrical cable, impedance mismatch, cable signal reflection, EN 3475-100, EN 50289-1-11, ASD-STAN, aerospace electrical systems, cable quality assurance.