Good note Hans. I stand corrected. Brent
From: hansm [mailto:[email protected]] Sent: Friday, February 13, 2004 3:02 PM To: Brent DeWitt; [email protected] Subject: Re: High Frequency Measurements A bore sight antenna is implied in the rules and hence, the referenced measurement procedure C63-4 (section 4.1.5.4) by requiring the "beam width" and "coverage of the EUT" to be fully covered. Hans Mellberg Engineering Manager BACL, a TCB and an EU CAB 230 Commercial Street Sunnyvale CA 94085 USA 408-732-9162 x38 408-732-9164 fax From: "Brent DeWitt" <[email protected]> To: <[email protected]> Sent: Friday, February 13, 2004 8:37 AM Subject: RE: High Frequency Measurements > > Height scanning at frequencies above 1 GHz is a serious mixed bag of > effects. Most folks use horns for the measurement antenna which increased > the directivity, especially when compared to a LPDA. This has been the > argument for "bore-sighting" antenna masts which keep the major lobe of the > antenna aligned with the EUT. Since bore-sighting isn't required, the > manufacturer puts themselves at something of a disadvantage when trying to > meet the spirit of the law rather than the letter of it. > > The second effect is the directivity of the EUT source. If the EUT were > isotropic in radiation pattern, then height scanning would be largely > unnecessary, but this is not the case. Apertures and aperture arrays can be > highly directive as frequencies go up. For this reason alone, I believe > height scanning is necessary to provide a complete picture of the EUT > emissions. > > Brent DeWitt > Loveland, CO > > -----Original Message----- > From: [email protected] > [mailto:[email protected]]On Behalf Of [email protected] > Sent: Friday, February 13, 2004 3:33 AM > To: [email protected] > Subject: Re: High Frequency Measurements > > > > > > > > > Also above 1 GHz directivity comes more and more into play (another reason > for hieght-scanning). > > Bob Heller > 3M EMC Laboratory, 76-1-01 > St. Paul, MN 55107-1208 > Tel: 651- 778-6336 > Fax: 651-778-6252 > ======================================================= > > > > "Luke Turnbull" > <[email protected] To: > <[email protected]> > > <[email protected]> > Sent by: cc: > owner-emc-pstc@majordo Subject: Re: High > Frequency Measurements > mo.ieee.org > > > 02/13/2004 03:34 AM > Please respond to > "Luke Turnbull" > > > > > > > > The reason for height-scanning is that there are unavoidable reflections > from the groundplane, and the only way to ensure that your measurement > geometry is not causing a deep null is to scan the height. The reason that > reflections are unavoidable is that at 30MHz, absorber would have to be 2.5 > m deep which is not practical or economic.k > > At frequencies above 1 GHz, absorber is practical and economic, and I is > easy to put absorber on the ground to minimise the small effect that there > might be on your measurement due to ground reflections, and not bother with > height scanning. > > Luke Turnbull > > >>> "Wiz" <[email protected]> 12/02/2004 15:36:41 >>> > Hello, > > I have a need to make radiated measurements up to 40 GHz. I uses a low > loss cable that gives me enough dynamic range up to 18GHz. The cable is > very short and I have to move my measurements equipment out to the > antenna. I know I need to get a pre-amp and mixer, but what do I do > about the cable loss? I have called many places and I cannot find good > enough cable to measure to 40 GHz. The other alternative is waveguides > as I understand. Those would, I assume, be coupled directly to the > input of the mixer. This does not allow for antenna height adjustments > form 1 to 4m as required. I have seen other test reports where high > frequency data was taken where the antenna was held at about 1meter. I > can understand this since emissions will likely be very directional at > those frequencies. Is it acceptable to make measurements with the > receive antenna at 1 meter only? > > > > Thanks for any information you can provide. > > > > Wiz > > > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ieee-pses.org/ > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: [email protected] > Dave Heald: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc > > > > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ieee-pses.org/ > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: [email protected] > Dave Heald: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ieee-pses.org/ > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Ron Pickard: [email protected] > Dave Heald: [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > http://www.ieeecommunities.org/emc-pstc > This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ieee-pses.org/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: [email protected] Dave Heald: [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
