Brian:
I did some pattern testing in a 30’ x 24’ x 9’ semi-anechoic 461-style enclosure (right, with the big table-top ground plane still in the chamber). I did patterns at various times for 2.45 GHz Wi-Fi, 300 MHz and 225 MHz, usually at a separation distance of 5 meters. Both the EUT antenna and the measurement antenna used vertical polarization, and were centered 1 meter above the floor. All coax cables used a lot of clamp-on ferrite tubes, and all coax cables were taped in place. When we went inside the chamber, we were careful to not touch anything other than to position the EUT antenna, even operating the door very gently so as to not flex the chamber walls. If you took a reference level at the start of a 180-degree rotation, after stepping 180 degrees CW, then 360 degrees CCW and then 180 degrees CW, sometimes you could go back to the original point and get a new level that was less than 0.5 dB different. And sometimes the level had changed 2 dB, so you got to repeat the test. None of this was super precise, but it was good enough to allow us to evaluate matching networks, differing antennas and ground plane schemes. Also, using the Friis formula, we could calculate the gain of the EUT antennas. It was a long way from the old days of scale model airplanes on 3-axis positioner arms on a several hundred foot antenna range, but still it was good enough. Ed Price El Cajon, CA USA From: Kunde, Brian [mailto:brian_ku...@lecotc.com] Sent: Friday, February 24, 2012 5:44 AM To: edpr...@cox.net; emc-p...@ieee.org Subject: RE: [PSES] Antenna Pattern for 2.4 GHz and 5GHz Is this test done in an semi-anechoic or full-anechoic setup and typically what is the distance between antennas? Is the receive antenna at one height or is it similar to site attenuation or antenna calibration? If one height, what is typical? I’ve never none this test before but I’ve always wanted to play around with it. The Other Brian From: emc-p...@ieee.org [mailto:emc-p...@ieee.org] On Behalf Of Ed Price Sent: Friday, February 24, 2012 1:16 AM To: emc-p...@ieee.org Subject: RE: [PSES] Antenna Pattern for 2.4 GHz and 5GHz Chris: I would be very careful about the physical and electrical setup of the access point. Although you could feed the access point’s antennas with a low-level CW signal from a signal generator, I think that the coax cables (even if you use very small diameter and very flexible coax) will have nasty effects on the antenna patterns. I would try to not use any external devices, but rather use the real signal from the access point’s intentional radiators. Now, I’m imagining this “access point” to be like a conventional wireless router, so it will have perhaps an unshielded Ethernet cable and a 2-wire small DC power cable from a wall-wart power pack. Yep, these cables will also have effects on your antenna patterns, so you will have to define a cable positioning protocol and make sure the cables don’t move around when the access point is being rotated around its axes. I’m also imagining the access point will probably not have nice isolation of its antennas from the rest of the access point (that is, plastic cases and antenna stalks that may have multiple angles of deployment). Let’s at least hope that the case doesn’t flex or twist as the access point is rotated through your measurement arc. And I assume that you only want to measure with matched polarizations. If all goes well, an ordinary spectrum analyzer can be used to monitor the amplitude. You can start with the access point sitting on a plastic tripod, and do a measurement cut 360 degrees around the Z axis. Then, you tilt by maybe 18 degrees on the X axis, and then do another 360 degree cut around the Z axis. You can do this by walking into your test chamber and just manually moving the tripod, but be very careful to not move anything else. Obviously, an automated antenna range is best, but you can substitute time for facilities. BTW, sometimes you might get better amplitude readings by setting the spectrum analyzer to zero-span and using video triggering. Also, I would prefer using a very directional measurement antenna, like a horn, so that I didn’t have to worry about sidelobe responses from a typical Biconical or Yagi. You can also spend a lot of time playing with varying positions of cables connected to the access point. If you are conservative, you might want to use the position that gives you the worst gain. OTOH, if you intend to depend on that FCC style wording (move everything around until something finally works better), then maybe you will want to use the best performance positioning combination. If you have two or three intentional RF emitters running at the same time, so long as none overload your spectrum analyzer, then you can do multiple measurements at multiple frequencies each time you move the physical position by one increment. Be prepared with a nice matrix to keep you from getting confused about what angle of which cut and which frequency you are measuring. I have done one frequency with several cuts in a half-day, so if you have two frequencies and want relatively fine data increments, then a couple of days sounds reasonable. Ed Price El Cajon, CA USA From: Christopher [mailto:cksal...@yahoo.com] Sent: Thursday, February 23, 2012 1:23 PM To: EMC-PSTC@LISTSERV.IEEE.ORG Subject: [PSES] Antenna Pattern for 2.4 GHz and 5GHz Folks, I would like to get the antenna patterns for our 802.11 Access point Antenna's. I am looking for a Test lab in Bay Area (preferably) that has the facility to provide antenna patterns and schedule some days of test time (that is my estimate, but, we may need more/less depending on various factors). For each AP, a signal generator is connected to the antenna’s and the unit I rotated in one axis and then turned and rotated is the other axis to get the antenna pattern at the receiving antenna. I think in MIMO all the antenna’s may be energized simultaneously?. Any help in this regard is appreceiated. regards Christopher 408-470-4915 www.Aerohive.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://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <emcp...@radiusnorth.net> 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://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher <j.bac...@ieee.org> David Heald <dhe...@gmail.com> _____ LECO Corporation Notice: This communication may contain confidential information intended for the named recipient(s) only. If you received this by mistake, please destroy it and notify us of the error. Thank you. - ---------------------------------------------------------------- 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://listserv.ieee.org/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas <emcp...@radiusnorth.net> Mike Cantwell <mcantw...@ieee.org> For policy questions, send mail to: Jim Bacher: <j.bac...@ieee.org> David Heald: <dhe...@gmail.com>
