The Growth of RF Spectrum Usage, EMI and Device Coexistance
Increased reliance on radio frequency communication has created issues for Electromagnetic Interference (EMI) and Device Coexistence. Cellular devices and equipment using the Internet of Things (IoT) are major causes of this increase. This has effected product development strategies for both commercial and defense applications, particularly for safety critical devices where unexpected operation or complete failure is not an option.
Product Design Considerations
Understanding the possible RF environments a product will operate in is essential during the specification phases. Often conducting a thorough Susceptibility Analysis is required to develop an understanding of the variety of sources that could compromise a products performance and their probable signal strengths. Equipment that can be expected to operate in radio rich environments such as airports can be expected to encounter high internet usage as well as radar and radio communications.
For communication devices the crowded electromagnetic spectrum is it making more difficult to ensure reliable connections. As an example the Department of Defense (DoD) is working to design a communication system known as the Wideband Adaptive RF Protection Program to develop adaptive filters to prevent signal cancelling. For other such devices establishing minimum desired levels of reliability and developing protocols for re-transmission can be a solution.
Techniques for Evaluation
For EMI/EMC susceptibility a number of standards are in place that can prove sufficient in assessing equipment’s abilities to operate as specified in a busy RF spectrum. Often these tests are not requirements for categories of equipment compliance, so a product developer must be proactive in seeking these methods out. Once an appropriate method has been found signal strengths and dwell times can be modified to achieve the desired level of product verification that replicates the anticipated environment of operation.
For wireless coexistence there are fewer options. One possibility is ANSI C63.27-2017 “American National Standard for Evaluation of Wireless Coexistence”. Although its primary application is medical equipment it can be used for any wireless application. This testing can be used to:
- Develop user guidance necessary to achieve a desired level of reliable operation. In this case the deliverables can be guidance to the user on the maximum recommended operational distance between communicating devices and the minimum recommended separation distances to equipment that has the potential to cause loss of FWP due to interference.
- Determine the potential for successful operation of the Functional Wireless Performance (FWP) with regard to coexistence. The deliverables for this purpose can be a risk assessment, written with the intention that it be a part of a larger and more extensive total risk assessment for the product.
- Estimate the user experience. When the purpose is to predict the user experience, the test results are applied to the understanding of the intended operating environment to estimate the user experience in the intended operating environments. In estimating user experience, additional factors, beyond those included in testing, are involved. The resulting estimation has an evaluation uncertainty, which includes the Measurement Uncertainty (MU) of the test results, the estimation of the variability in the operating environment, and the certainty of the operating environment data used in preparing the estimate.
- Diagnose complaints and failure reports, reproduce those field environments, and qualify modifications that remediate the product performance. With this objective, the deliverables will include evidence that the problematic field environment has been reproduced and that test modifications can be expected to achieve desired levels of performance.
- Identify the intended environment parameters at which the EUT fails to coexist.
CVG Strategy Can Help With EMI and Device Coexistance
CVG Strategy EMI/EMC consultants can provide susceptibility analysis and recommend appropriate test methodologies for verification a product’s ability to perform as specified in today’s congested spectrum. Contact us today to see how we can help.