Compliance with European Directives for products that are to be used in the European Community is a legal requirement and should be taken into account in the design phase of a product.
The Electromagnetic Directive (EMC) is of particular importance in the design of electronic based products.
Signal Integrity is a key issue in the design of high speed electronic based products and in particular for printed circuit boards (PCBs).
As digital circuits operate at higher and higher clock speeds signal integrity becomes increasingly important.
The PCB can dramatically alter the performance of circuits and it should be considered as a major component that impacts on the design activity at an early stage. Signal integrity and EMC are interrelated.
For any product to be successful it must work and it must also comply with any regulatory requirements of the marketplace it is to be used in.
Electronic products use electrical signals to transmit and process information.
Products are expected to work in ever increasingly polluted electromagnetic environments.
For a product to work signals must meet specified levels of integrity
For a product to be saleable into the European Market it must comply with relevant regulatory requirements which includes the EMC directive
Of course the product must comply with a raft of regulatory requirements, such as health and safety, disposal of dangerous substances, etc.
However compliance with the EMC directive and standards is the most technically challenging.
Signal integrity and EMC compliance are intimately linked- the higher the levels of signal integrity the more immune is the product to electromagnetic interference.
Products that are to be used in the European Community must comply with a number of relevant directives and standards that are intended to ensure they are safe to use and perform satisfactorily in their intended operating environment.
The Low Voltage Directive (LVD) must also be complied with for any electrical product that is to be sold in the European community.
The EMC directive relates to a set of harmonised standards, that is standards that apply to all member states of the European Union (EU). The directive itself is relatively short and is mainly concerned with legal issues.
A list of the current harmonised standards that fall under the EMC directive may be obtained from:
The harmonised standards define requirements and test conditions for all aspects of EMC.
They are available from the British Standards on Line web site.
The low voltage directive is a safety related standard and applies to equipment and products that use voltages of 2000 volts and less.
The EMC directive is concerned with:
Emissions from products- a product must not interfere or adversely affect the operation of equipment and other products in the local environment
Immunity of products to emissions- products should be capable of working when subjected to interference, that is emissions, from equipment and products operating in the local environment.
For the EMC directive, electromagnetic environments are classified as:
This environment is reserved for heavy industrial locations that do not connect to any public voltage supplies.
This environment includes locations that are directly connected to the main public voltage supply network. In the European Union, Offices, and most companies, including SMEs, fall into this category.
A product should not cause other products operating nearby to malfunction.
Emission categories are broadly classified as:
A product should be capable of operating as intended in its electromagnetic environment, that is it should be immune to emissions from products and equipment operating in the local environment.
There are six different categories of Immunity:
Radio Frequency Electromagnetic Fields
Electrical Fast Transients
Conducted Surge Voltages
Radio Frequency Fields
The performance of a product, when tested to determine its immunity, is described by the following performance criteria:
During testing, normal performance of the product, within the specification limits, are maintained. There can be no degradation of performance at all during the test.
During testing, temporary degradation, or loss of function or performance of the product is allowed, provided it recovers without any human intervention, that is the product recovers and performs normally of its own accord.
During testing, temporary degradation, loss of function or performance that requires operator intervention or system resetting for the product to recover normal operation, is allowed.
Degradation or loss of function which is not recoverable due to damage to the product, equipment, components, or software (failing criteria).