Brian This test is typically done in a fully anechoic chamber with antennas aligned and near centre axis of chamber. Separation distance of 3-4 metres would be typical.
Ideally the device under test is completely isolated on a non-conductive mount, but if you need to feed a signal to the EUT for test or calibration purposes then use a narrow co-ax cable that is loaded with ferrite sleeve. Equipment that needs to be in a radiated link to be exercised is typically configured so that its link is via one, or more, antennas that are on a plane perpendicular to the central axis. Regards Charlie From: Kunde, Brian [mailto:brian_ku...@lecotc.com] Sent: 24 February 2012 13:44 To: EMC-PSTC@LISTSERV.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<mailto: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<http://www.Aerohive.com> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. 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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>
