The CG-515 Comb Generator is a conducted and radiated signal reference source. This Comb Generator can produce harmonics at 1 MHZ and 5 MHz. The step size can be selected by a toggle switch. These reference signals are used for validating EMC test sites; therefore the reference signal source must have a stable and precise output. Com-Power’s Comb Generators line is designed to meet this requirement.

Due to the broad frequency range, two antennas are supplied with the CG-515, a 12” antenna for low frequency up to 580 MHz, and 3” antenna for 580 MHz and above. The radiated signals are generated by connecting one of the two antennas to the BNC connector located at the centre of the CG-515. The circular chassis of Comb Generator helps radiate the signal more uniformly in all directions within the same plane. The conducted reference signals can be obtained by connecting a Coaxial Cable between the BNC connector mentioned above and a Spectrum Analyser.

The CG-515 is powered by an enclosed rechargeable battery pack to minimise disturbances of external cables that might interfere with the radiated signal. When the battery voltage reaches below the operating level, the output signal will shut off automatically to prevent further use and misleading data. When fully charged, the battery allows continuous use of the Comb Generator for up to 18 hours.

Application

EMI measurements are usually collected in an Open Area Test site (OATS) or inside an Anechoic Chamber. OATS and chambers must be calibrated before put into service using published calibration procedures at regular intervals. These calibration methods are very elaborate and time consuming to be performed before each test to ensure that the data taken is consistent and accurate. The CG-515 is a quick Site Verification tool that the test engineer can use to detect potential problems with site. Maintaining a log of the Comb Generator radiated readings, prior to taking measurement from a product in the same setup, and comparing them will help in detecting possible faults. The same process can be utilised when emissions measurements that are taken from the same products varies on a repeated test. It is difficult to determine if it is the test site or the product causing the variation. Using the same test setup, measurements can be taken with a Comb Generator in place of the product. This data can be compared with previous Comb Generator measurements to determine the problem. Other uses of the Comb Generator include testing cables and filters.