I am not familiar with the details of the referenced specs. I can say that generally any ground surface will have some reflectivity, and that if you are doing a test whose results should be reproducible on another test site (or indeed the same test site at another time), the only way to achieve similar results is to have similar reflectivity, and that means for all practical purposes one of two choices: no reflections (absorber) or complete reflections (metallic surface). Since suitable absorber was not available when MP-4 and CISPR 22 and others of their ilk were invented, metallic ground planes are almost universally employed.
---------- From: [email protected] To: [email protected], [email protected] Subject: RE: CISPR 12 Testing List-Post: [email protected] Date: Mon, Nov 11, 2002, 11:41 AM Ken and all who replyed, I appreciate all of the responses I've received and at the same time realize that I should have given you all more information concerning my question and it also would have helped if I had worded the question properly. First thing, of course an OATS facility must have a ground plane but not necessarily a metallic ground plane. When we first looked into running tests per CISPR 12 we assumed, like most everyone else, that our OATS facility with the solid aluminum ground plane would be the proper test site. It was then brought to our attention that CISPR 12 does not specifically indicate the use of a metallic ground plane and CISPR 16.1, depending on the product, recommends the use of non-metallic ground planes. CISPR 16.1:1999, Section 5.6.5 calls out the construction of a ground plane using a wide range of material from earth to metal and depending on the product, a metallic ground plane may not be the preferrable ground plane. CISPR 12, AS/NZL 2557:1999 and CAN/CSA-C108.4-M92:1992 all reference CISPR 16.1 for OATS setup. Should a product, which falls into the scope of CISPR 12, AS/NZL 2557 and CAN/CSA-C108.4-M92, be tested on a non-metallic ground plane? Are these the products referred to in CISPR 16.1? Thanks in advance, Steve -----Original Message----- From: Ken Javor [mailto:[email protected]] Sent: Friday, November 08, 2002 12:44 PM To: [email protected]; [email protected] Subject: Re: CISPR 12 Testing That means reflecting surfaces above ground, not the ground plane itself. The old FCC MP-4 showed a clear area being an ellipse whose major axis was twice the EUT-antenna separation, and whose minor axis was the EUT-antenna separation, with the minor axis perpendicular to the vector separating the antenna and EUT. This ellipse had to be clear of all obstructions, trees, shrubs, etc. ---------- From: [email protected] To: [email protected] Subject: CISPR 12 Testing List-Post: [email protected] Date: Fri, Nov 8, 2002, 10:41 AM According to CISPR 12, Section 5.2.1, the OATS requirement calls out "a clear area free from electromagnetic reflecting surfaces". Does this imply that the OATS facility should not have a ground plane or were they referring to any other electromagnetic reflecting surfaces. I would appreciate all input on this topic. Best Regards, Steve O'Steen 919-554-0901x240
