Yes, you may (at your choice) add or subtract 180 degrees for the reflected vertically polarised wave only!
I think Brent meant to say the same, but with another viewpoint.... Gert From: Pawson, James [mailto:james.paw...@echostar.com] Sent: Thursday 6 August 2015 11:13 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Re: [PSES] Calculating Reflection Angles on OATS/SAC Many thanks for all of the replies on this topic. The conceptual key I lacked was the "image" of the receiver below the ground plane which made the calculations a lot simpler and I've now got an up and running spreadsheet. I've also been introduced to things like cotangents and arctangents which are new to me. The only thing I still remain confused about is the phase of the reflection from the ground plane. Gert wrote: "Note that vertical waves invert in polarity on reflection with the ground plane, where horizontal polarized waves do not." Brent wrote: "...and take the difference for phase, remembering that the horizontally polarized image is 180 degrees out of phase to start with while the vertical image is in phase." I might be misunderstanding but these statements seem to contradict each other. I can kind of see how a vertically polarised wave would be reflected inverted. If this was the case, could this be compensated for by subtracting 180° from the reflected ground ray to ensure the phases added/subtracted correctly at the RX antenna? Thanks again James _____________________________________________ From: Pawson, James Sent: 31 July 2015 15:59 To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: Calculating Reflection Angles on OATS/SAC Hi, I'm trying to calculate the distances/angles at which a maximum (in phase) or minimum (anti-phase) signal would occur on an OATS/SAC. I can do this simply when the TX and RX antennae are the same height above the reflecting surface as the point of reflection lies halfway between the two antennae, Distance_tx = Distance_rx. The direct and reflected paths can be calculated using simple geometry and the wavelength is given by lambda = c / f. However when the height of the RX antenna is different to the height of the TX antenna then the horizontal distance to the reflection point is no longer equidistant. I can see that the ratio Height_tx / Distance_tx = Height_rx / Distance_rx remains the same because the angle of reflection is the same. But I'm left with two unknown Distance terms in the equation. Is there a standard equation for calculating the reflection angle on an OATS/SAC with a varying height antenna? Or can someone give me some pointers to help me figure it out myself? I was so distracted thinking about this that I missed my turnoff whilst cycling home the other day. I've tried Googling but maybe I'm not putting in the right search term. Any assistance gratefully received. Thanks and regards, James - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) <http://www.ieee-pses.org/list.html> List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.com> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <emc-p...@ieee.org> All emc-pstc postings are archived and searchable on the web at: http://www.ieee-pses.org/emc-pstc.html Attachments are not permitted but the IEEE PSES Online Communities site at http://product-compliance.oc.ieee.org/ can be used for graphics (in well-used formats), large files, etc. Website: http://www.ieee-pses.org/ Instructions: http://www.ieee-pses.org/list.html (including how to unsubscribe) List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <sdoug...@ieee.org> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
