| f = 100 MHz | ||
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| f = 200 MHz | ||
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| f = 400 MHz | ||
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| f = 800 MHz | ||
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T. Sato, 2016-10-16
In CISPR 25 ALSE method, a long test harness will be used, and receiving antenna will be placed at a fixed point at distance of 1 m. The test distance is very close compared to the harness length, even if general far-field considition of λ/2π (> 1 m below 47 MHz) and 2D2/λ (> 1 m above 67 MHz) are not considered.
It is expected that difference in test harness length may cause variations in field pattern at 1 m distance, which may then cause variations in test results.
Here, I used xnec2c and estimated electric field patterns at 1 m distance in CISPR 25 ALSE setup.
I think these results rather inacculate, but I think the results at least suggest that different harness length may cause significant variation in resulting field patterns.
f = 100 MHz f = 200 MHz f = 400 MHz f = 800 MHz
In the above examples, load simulator side of the test harness is assumed to connected to the ground plane.
Here are comparison of the above results for 1.5 m harness, and those estimated for load simulator side open.
I think these results rather inacculate, too, but I think the results at least suggest that different load simulator impedance may cause significant variation in resulting field patterns.
f = 100 MHz, load simulator side grounded f = 100 MHz, load simulator side open 
f = 200 MHz, load simulator side grounded f = 200 MHz, load simulator side open 
f = 400 MHz, load simulator side grounded f = 400 MHz, load simulator side open 