Krishnan, Only your CAD RF engineer can do this job. He/she just has to know the dielectric properties of the laminate you use, the thickness of dielectric and copper, length and width of trace, and distance to other parts on the board plus RF power. With this information put into computer, you will get an answer, that you direct to the PWB manufacturer. 13 MHz, sounds like typical home electronics, like the one below. http://www.copytag.com/acatalog/actinic.html?http%3A//www.copytag.com/ac atalog/13_56_MHz_Antennae.html&CatalogBody Inge -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Balasubramanian Krishnan Sent: den 5 september 2006 16:41 To: [log in to unmask] Subject: [TN] Impedance coupon design for differentials signal without reference plane Dear All, For an 13.56 MHz antenna trace (25 mil wide & 400 mm long) running between 2 pins of a differential transceiver (Tx1 & Tx2) we want to maintain dimensional tolerance of + / - 10 % (trace width & trace thickness including masking)? What has to be specified in the fabrication notes for this? There is no reference plane below this trace. How to ensure the impedance tolerance is within 10 %? How should be the impedance coupon designed for this purpose to do TDR measurements? Sincerely K.Balasubramanian Project Leader - Hardware. --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------