Tuesday, September 24, 2013

Cable models for USB3

A set of measured data were evaluated to establish some design targets for a USB3 front end circuit. This type of cable data is difficult to come by on the web so a TDR was used to measure two different length USB3 cables for only the loss characteristics. The measured data was bolstered by measured data from a USB3 cable manufacturer. The results are: 1 Meter long USB3 cable has a -3dB point at 5 Ghz. A 3 meter cable has its -3 dB point at 2.0 Ghz. A 2 meter USb3 cable has its -3 dB point at 1.6 Ghz.

Small loop antenna design

PCB small loop antenna design is required when designing with RF transmitter and receiver chips available as standard parts from a number of semiconductor manufacturers. A web survey turned up a small number of interesting and instructive articles on this topic. Of these articles only a very few met our purpose. Among these latter we found the most useful to be the one presented by Microchip Technology, Chandler, Arizona. ( Jan Van Niekirk, AN831). We generated an EXCEL spreadsheet using this article as a template for designing these types of antennas. It must be mentioned that this spreadsheet ( as well as the information in the article was found to be a starting point for the design. Some tweaking is still required using measurements.)This spreadsheet is available for download by interested parties from the SPG website located at http://www.signalpro.biz under Free Stuff.