RADIATED AND CONDUCTED SIGNAL SOURCES FOR QUICK EMC SITE MEASUREMENT
EMC labs calibrate their radiated emissions test sites, instrumentation and accessories at least once a year. The calibration procedures are elaborate and time consuming and may require other specialized test equipment and in some cases use of outside services. However, calibration does not prevent equipment malfunction in between calibration period such as damaged receivers,, broken cables, poor connections, bad antenna, etc. To improve the measurement accuracy or reliability, you have to check these items at closer intervals. It could be a daily procedure. Performing a full calibration each time is expensive and daily is not practical. The problems with equipment may not be noticed during EMC testing and faulty data may result. A quick test using a Comb Generator can avoid this situation. Monitoring a few frequencies regularly on the Comb Generator's broadband radiated output can verify the entire setup quickly and efficiently. Any potential problems with the test setup can be detected before it causes erroneous results. In addition, Comb Generator data gathered over a period of time will provide information about the measurement consistency of the site. This will turn increases overall measurement confidence of the test site.
The Comb Generator can also be utilized to compare sites. Sometime, questions arise when EUT emissions test data is not consistent between two test sites. Comb Generator can be used to compare the sites. Gathering the comparison data is valuable for mitigate these issues and to identify the problem. EMC labs with multiple sites can utilize the Comb Generator as a standard to compare all the sites, increasing overall confidence in the measurement capability of the entire test facility.
The Comb Generator is self contained, small and portable. Unlike other signal sources it has no interconnecting cables that might interfere with the radiated output. The Comb Generator is powered by internal rechargeable batteries. When the unit is turned on all the frequency harmonics of specified step size is available up to maximum range of operation. The Comb Generator uses extremely stable components to minimize output variations. The output is uniformly radiated in all directions using monopole antennas.
Although Comb Generators were designed for EMC site testing, it can be a signal source for applications such as testing cables, filters and shielding effectiveness.
CGC SERIES COMB GENERATORS TO VERIFY CONDUCTED EMISSIONS SETUP
The CGC series Comb Generator was specifically designed to test installed Line Impedance Stabilization Networks (LISNs). LISNs are used for EMC conducted emissions testing according to FCC Part 15, CISPR, and EN requirements. The Comb Generator output is connected to the LISN EUT power port and measurements are taken similar to an EUT. For convenience, the CGC series Comb Generators have 3 prong standard US plug for LISNs with matching EUT power socket. By using the Comb Generator the test engineer can quickly identify any problems with the conducted setup before making any measurements with an EUT.
the Application Note AN-104 provides more details on the Comb Generator.