The first embodiment is a 4-wire fractional-winding helical antenna in which a spiral conductor pattern is formed easily and precisely on the surface of a supporting member in the form of a cylindrical tube or a stepped cylindrical tube form by the photoetching technology. This 4-wire fractional-winding...http://www.google.com.tw/patents/US5353040?utm_source=gb-gplus-share專利 US5353040 - 4-wire helical antenna
