有空再翻译

Abstract  
The helix antenna, invented in the late fourties by John Kraus (W8JK), can  be considered as the genious ultimate simplicity as far as antenna design is  concerned. Especially for frequencies in the range 2 - 5 GHz this design is very  easy, practical, and, non critical. This contribution describes how to produce a  helix antenna for frequencies around 2.4 GHz which can be used for e.g. high  speed packet radio (S5-PSK, 1.288 Mbit/s), 2.4 GHz wavelans, and, amateur  satellite (AO40). Developments in wavelan equipment result in easy possibilities  for high speed wireless internet access using the 802.11b (aka WiFi) standard.  
  

Theory in a birds eye  view
The helix antenna can be considered as a spring with  N turns with a reflector. The circumference (C) of a  turn is approximately one wavelength (l), and, the distance  (d) between the turns is approx. 0.25C. The size of the  reflector (R) is equal to C or l, and can be a  circle or a square. The design yields circular polarization (CP), which can be  either 'right hand' or 'left hand' (RHCP or LHCP respectively), depending upon  how the helix is wound. To have maximum transfer of energy, both ends of the  link must use the same polarization, unless you use a (passive) reflector in the  radio path.
The gain (G) of the antenna, relative to an  isotrope (dBi), can be estimated by:  

G = 11.8 + 10 * log {(C/l)^2 * N *  d}  dBi                (1)  

............

Tags - 天线 ]]> https://www.gclz.cn/post//#blogcomment <user@domain.com> Thu, 01 Jan 1970 00:00:00 +0000 https://www.gclz.cn/post//#blogcomment