波長天線 3G 2G WIFI Antenna

手機, 無線網路的頻率

GPRS/GSM 800 / 1800 / 1900 MHz

3G UTMS 2100 MHz = 2.1x10⁹Hz

WIFI 2.425 GHz =2.425x10⁹Hz

天線到底要多長?

Frequency (f) = number of cycle per second, unit is Hz

Wave speed (Vw) = speed of light or electromagnetic radiation in vacuum = 299,792,458 m/s or about 3x10⁸ m/s

lambda (λ) = Vw / f, unit is meter

here is when f = 800 MHz = 8x10⁸Hz

λ = (3x10⁸⁾ / (8x10⁸) = 3/8 = 0.375m

		波長 λ
		λ(m)	λ(mm)
	f (MHz) 頻率	λ(m)	λ	1/2λ	1/4λ	1/8λ	1/16λ
Cable TV	5	59.958	59958	29979	14990	7495	3747
Cable TV	890	0.337	337	168	84	42	21
DVB-T	550	0.545	545	273	136	68	34
GSM	800	0.375	375	187	94	47	23
GSM	1800	0.167	167	83	42	21	10
GSM	1900	0.158	158	79	39	20	10
3G UTMS	2100	0.143	143	71	36	18	9
WIFI	2425	0.124	124	62	31	15	8

天線名詞
yagi antenna	八木天線
pi antenna	偶極天線
vertical antenna	直立天線
rhombic antenna	菱形天線
slope antenna	斜天線
half wave dipole antenna	半波振子天線, 魚骨
quad antenna	方框天線
cage antenna	籠形天線

This is a reference for Helical arial antenna, some basic calculation
http://www.wireless.org.au/~jhecker/helix/

A typical implementation for the above calculation
http://www.instructables.com/id/10--WIFI-16dBi-Super-Antenna-Pictorial/

Another style of (rhombic antenna) 菱形天線, or someone call [double square antenna], different calculation of reception & theory, it is smaller and not so buclky.
http://rushoun.myweb.hinet.net/WANLAN/QUAD/4ant.htm

see the wiki for some more reference about rhombic antenna
http://en.wikipedia.org/wiki/Rhombic_antenna
http://www.wiki.cn/wiki/%E8%8F%B1%E5%BD%A2%E5%A4%A9%E7%BA%BF

Free material avaialble on-line about the antenna handbook
http://www.scribd.com/doc/299766/USMC-Field-Antenna-Handbook