SIST EN 2591-221:2008

Overview

SIST EN 2591-221:2008 is a European aerospace standard developed by CEN, specifying the test method for assessing the Voltage Standing Wave Ratio (VSWR) of coaxial contacts and connectors used in electrical and optical aerospace connections. This standard defines a precise measurement methodology relying on vectorial methods using S-parameters, which are crucial for characterizing the performance of coaxial interconnections within their required frequency bandwidth. SIST EN 2591-221:2008 is intended to be used alongside EN 2591-100 for comprehensive testing procedures.

This standard is essential for ensuring that aerospace electrical connectors and contacts meet performance criteria related to impedance matching, signal integrity, and minimized signal reflection, which are vital in high-frequency aerospace applications.

Key Topics

• Scope and Application
  Specifies the measurement methods for VSWR on coaxial contacts or connectors with characteristic impedance within the required frequency range.

• Measurement Methodology
  Utilizes the vector network analyzer and "S" parameters (S11, S12, S21, S22) as defined in Annex A, providing a detailed approach to measure incident and reflected RF waves, essential for calculating VSWR.

• Sample Preparation
  Defines two methods (Method A and Method B) for preparing coaxial cable sections and connectors during testing, ensuring consistency:

  • Method A uses a test section with the device under test at both ends.
  • Method B places the device under test in the middle of the coaxial cable section flanked by standard connectors.

• Test Apparatus
  Requires a vector network analyzer, calibration kit, precision standard adapters, and possibly a 75 Ω transformation kit for adapting 50 Ω measurement instruments.

• Procedure and Calibration
  Details the calibration process of the measuring equipment before VSWR measurements, emphasizing the relevance of frequency range selection and sampling points.

• Measurement Requirements
  Stipulates that VSWR values must not exceed limits specified in related product standards to guarantee performance.

• Specification Details
  Mandates clear documentation of parts and devices used during testing, such as:

  • Coaxial device part numbers
  • Cable type and connectors
  • Measurement frequency range and impedance
  • Calibration tools and equipment details
  • Connector coupling torque and wiring tools

• S-Parameters Definition
  Annex A gives an in-depth explanation of S parameters, their physical significance, and how they define reflection and transmission characteristics in RF components.

Applications

• Aerospace Electrical and Optical Connections
  SIST EN 2591-221:2008 applies to aerospace industry components requiring rigorous electrical testing to ensure optimal signal transmission with minimal reflection, such as military and commercial aircraft wiring harnesses and interconnects.

• Connector Quality Assurance
  Used by manufacturers and testing labs to validate coaxial connectors ensuring low VSWR and compatibility with system impedance, crucial for maintaining system reliability and minimizing RF losses.

• Component Design and Development
  Enables engineers to verify design compliance with stringent aerospace standards, facilitating reliable high-frequency performance in critical systems.

• Maintenance and Troubleshooting
  Provides methodology for post-installation testing in aerospace facilities, assisting in fault detection related to signal integrity issues in connectors and cables.

Related Standards

• EN 2591-100: Aerospace Series Test Methods – General
  The foundational document providing general requirements and methods upon which EN 2591-221 relies.

• Other Aerospace Connector Test Standards in EN 2591 Series
  Cover additional electrical, mechanical, and environmental test methods for aerospace connector elements.

• CENELEC and IEC RF Test Standards
  Complementary standards for RF and microwave measurements, calibration techniques, and impedance testing relevant to aerospace connectors.

Summary

SIST EN 2591-221:2008 provides a comprehensive, standardized procedure for measuring the Voltage Standing Wave Ratio (VSWR) in aerospace coaxial connectors and contacts. Utilizing vector network analysis and S-parameter characterization, it ensures that connectors deliver optimal electrical performance by minimizing reflection and impedance mismatch across the relevant frequency bandwidth. This standard supports aerospace manufacturers, engineers, and testing laboratories in maintaining high-quality electrical and optical connection interfaces critical to the performance and safety of aerospace systems.

Keywords: EN 2591-221, Voltage Standing Wave Ratio, VSWR test method, aerospace electrical connectors, coaxial connector testing, S parameters measurement, vector network analyzer, aerospace standards, impedance matching, RF connector testing.