描述
在无线通讯的实际应用中,为有效提高通讯效果,减少天线输入功率,天线会做成各种带有辐射方向性的结构以集中辐射功率,由此就引申出“天线增益”的概念。简单说,天线增益就是指一个天线把输入的射频功率集中辐射的程度,显然,天线的增益与其方向图的关系很大,主瓣越窄、副瓣越小的天线其增益就越高,而不同结构的天线,其方向图的差别是很大的。
在通讯技术领域,与其它考量功率、电平等参数的量值同样,天线增益也采用相对比较并取对数的简化法来表示,具体计算方法为:在某一方向向某一位置产生相同辐射场强的时,对无损耗理想基准天线的输入功率与待考量天线的输入功率的比值取对数后乘以10(G=10lg(基准Pin/考量Pin)),即称为该天线在该点方向的增益。常用衡量天线增益的单位是dBi和dBd。对于dBi,其基准为理想的点源天线,即一个真正意义上的“点”来作天线增益的对比基准。理想点源天线的辐射是全向的,其方向图是个理想的球,同一球面上所有点的电磁波辐射强度均相同;对于dBd,其基准则为理想的偶极子天线。因偶极子天线是带有方向性的,故二者有个固定的恒差2.15即0dBd=”2″.15dBi。
我们这里有您急需的停产备件,
优势现货,询不到的,买不到的,请联系我们!
绝 对优势,绝 对低价!绝 对正品,优质的产品,一流的服务,充足的库存,
欢迎来电询价,我们将会给您最优惠的价格!
主营:世界知名品牌的PLC、DCS系统备件模块
①Allen-Bradley(美国AB)系列产品》
②Schneider(施耐德电气)系列产品》
③General electric(通用电气)系列产品》
④Westinghouse(美国西屋)系列产品》
⑤SIEMENS(西门子系列产品)》
⑥销售ABB Robots.FANUC Robots、YASKAWA Robots、KUKA Robots、Mitsubishi Robots、OTC Robots、PanasonicRobots、MOTOMAN Robots。
⑦estinghouse(西屋):OVATION系统、WDPF系统、MAX1000系统备件。
⑧Invensys Foxboro(福克斯波罗):I/A Series系统,FBM(现场输入/输出模块)
顺序控制、梯形逻辑控制、事故追忆处理、数模转换、输入/输出信号处理、数
据通信及处理等。Invensys Triconex:冗余容错控制系统、基于三重模件冗余(TMR)
结构的zui现代化的容错控制器。
⑨Siemens(西门子):Siemens MOORE,Siemens Simatic C1,Siemens数控系统等。
⑩Bosch Rexroth(博世力士乐):Indramat,I/O模块,PLC控制器,驱动模块等。
◆Motorola(摩托罗拉):MVME 162、MVME 167、MVME1772、MVME177等系列。
Reliance variable frequency ac drive 20 hp GV3000/SE
Reliance Electric Motor 150 HP RPM3575 Frame 445HPZ New
Reliance Electric AC Servo Controller HR2000 3RA2008U
Reliance 1326AB-B730E-21-K7 Series C Servo Motor
RELIANCE ELECTRIC DM-20 USPP DM20
RELIANCE ELECTRIC 9101-1132 USPP 91011132
Reliance 3RA2004
RELIANCE ELECTRIC 61C-605 USPP 61C605
RELIANCE ELECTRIC 45C-360 USPP 45C360
RELIANCE ELECTRIC – 14.5HP – 400V – VARIABLE SPEED MTR
RELIANCE ELECTRIC 0-51801 NSFP 051801
NEW RELIANCE 8014291SD 30 HP DC Drive
RELIANCE ELECTRIC VF-1-26-AT VARICYCLE A-C GENERATOR
RELIANCE ELECTRIC 690-520-00 USPP 69052000
RELIANCE ELECTRIC 0-52819 USPP 052819
RELIANCE ELECTRIC 608896-31X USPP 60889631X
RELIANCE ELECTRIC 0-48673 USPP 048673
1L841668T1 RELIANCE
Reliance 0-51848-1 PC Board
Reliance Electric AC Variable Speed Spindle Drive
1 NIB RELIANCE ELECTRIC 0-60028-2 MODUE DRIVER 0600282
1 NIB RELIANCE ELECTRIC 3RA2004 SERVO CONTROLLER
RELIANCE SS4000 DC SYNCHRONOUS RECTIFIER
Reliance Maxpak Plus Spindle Drive 2GA690746 103781-54A
Reliance Electric Thermocouple Input 61C605
Expedited shipping available
BONITRON RELIANCE BRAKING MODULE M3452-H9C00 NIB
Reliance Electric AC Variable Speed Spindle Drive
RELIANCE ELECTRIC 418227G 74VDC COIL
RELIANCE 20V4160 GV3000 AC DRIVE 20HP 27AMP ***XLNT***
1326AB-B515G-21-K5 RELIANCE SERVO MOTOR
One-day shipping available
RELIANCE ELECTRIC 61C-346 USPP 61C346
RELIANCE ELECTRIC 2GU41020 NSFP 2GU41020
RELIANCE ELECTRIC 0-54346 NSFP 054346
RELIANCE ELECTRIC 45C-201B USPP 45C201B
RELIANCE ELECTRIC 0-51851-4 NSPP 0518514
RELIANCE ELECTRIC 5FN4032 USPP 5FN4032
RELIANCE ELECTRIC 0-51890-3 USPP 0518903
RELIANCE ELECTRIC 73EV102004 USPP 73EV102004
RELIANCE ELECTRIC 86466-91SC USPP 8646691SC
RELIANCE ELECTRIC 86466-47T NSFP 8646647T
RELIANCE ELECTRIC 69000-3W NSPP 690003W
RELIANCE ELECTRIC 2SR41800 USED SNUBBER RESISTOR
Reliance Electric Tach 603515-5A
Used Reliance Electric DC Motor HP100 RPM 1750 #9168LR
ELECTRO-CRAFT RELIANCE DRIVE MODULE BRU-500 BRU500
Reliance Electric RPM III 7.5HP DC Motor T18R1301U
RELIANCE Servo Motor # P21M0304K-ZX P21M0304
NEW Reliance 78094-31R Starter Contactor 7809431R NIB
One-day shipping available
Reliance Electric 1AC2103U GP1000 AC Drive
!00 HP Reliance Enclosed Motor 460 Volts Item #8228
RELIANCE, DC,BO368ATZ, 60HP, FB56
RELIANCE ELECTRIC 86466-60W USPP 8646660W
RELIANCE ELECTRIC 0-51381-10 NSPP 05138110
RELIANCE 67700-1R/RE210 TACHOMETER 100V/1000RPM **NNB**
RELIANCE GV3000 15V4160 15HP 460V AC DRIVE ***RFB***
RELIANCE 6SP401-027CTAN SP600 AC DRIVE ****XLNT***
RELIANCE 0-51831-1 CVTB MODULE ***NNB***
RELIANCE ELECTRIC 2SR41800 USPP 2SR41800
RELIANCE ELECTRIC 0-52837 ACCA PC BOARD
RELIANCE ELECTRIC AUTOMATE 15 45C17C “NEW” 45C-17C
Reliance Electric HR2000 Brushless AC Servo Drive NEW
RELIANCE ELECTRIC 0-51893-1 CONTROLLER 0518931 NIB
Expedited shipping available
NEW RELIANCE DCS POWER MODULE S6-DIG HP 200-300 460V
RELIANCE ELECTRIC 61C-540 USPP 61C540
RELIANCE ELECTRIC 61C-540-A USPP 61C540A
RELIANCE ELECTRIC 422029-2A NSFP 4220292A