Com-Power CGO-520 사용 설명서 - 페이지 10

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Comb Generators model CGO‐520

Compare these levels with all subsequent measurements to make sure that the pattern does not have abrupt

change from the established daily log at any frequency. The more higher the number of frequency points the

higher the accuracy of the reference measurements.

This log is used to detect any test equipment or test site related problem as described below.

Problems Related to Test Equipment

Variation on the log of the Comb Generator output data is dependent on the test equipment as well as site. The

Comb Generator replaces the EUT. The Comb Generator not only generates the output simultaneously at all the

harmonics, but it minimizes any variation of its output. This is achieved by utilizing a stabilized signal circuit as well

as geometry of the radiator. The circuit stability is maximized by design, whereas the geometry of the radiated

source is optimized by eliminating all cables during the Radiated Emission Mode. The typical variation of Comb

Generator output at any frequency is less than ± 1 dB.

With the variations due to the EUT practically eliminated, only variations remaining are due to other factors,

mainly the test instrumentation and the site. The variation due to test instrumentation is limited to the sum total

of the tolerance on all test equipment used (spectrum analyzer, antenna, preamplifier, cables). A few days of data

will establish the range of variation to be expected at a site. This is generally less than ± 3 dB. Any variation in the

readings above normal variation indicates a potential problem.

After the daily log is established for a few days, any problem is easily detected as a larger variation. This procedure

allows immediate detection of a major problem with the test equipment.

Problems Related to site

The above procedure cannot distinguish the problems related to the test site. The Comb Generator can be used in

two ways to detect any problem with a test site. One method is to start the daily log immediately after the test site

is calibrated. This way, one is certain about the validity of the data taken on the test site. The second method is to

calibrate the Comb Generator radiated output as absolute emission level. Such calibration is provided as an option

with the Comb Generators.

In addition, when difficulty arises with any EUT data taken at two different sites, the Comb Generator can be used

to determine if both sites give reliable results, just by comparing the data at the two sites with the Comb

Generator. In this case, if the two sites do not produce comparable results, a Comb Generator with calibrated data

is certainly required to determine the faulty site.

Problems Related to Test Personnel

The Comb Generator cannot directly help to eliminate the test personnel related problems. However, by

increasing the confidence level and establishing definite procedures for eliminating site and equipment related

problems it helps tremendously to reduce the problems related to EMI measurements.

(949) 459‐9600

www.com‐power.com

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