Antenna basics

Antenna basics ( 天线基础知识 )

http://www.marinesatellitesystems.com/index.php?page_id=99

AZ Azimuth ( AZ方位角 )

The azimuth is the horizontal angle from true north in a clockwise direction , or bearing of the satellite from the antenna .
( 方位角是从真北沿顺时针方向的水平角，或者是卫星与天线之间的方位角。 )
Obviously, the azimuth of the antenna must match the azimuth of the satellite, or it will not acquire the satellite. This  satellite azimuth depends only on the satellite longitude and the position of vessel.
( 显然，天线的方位角必须与卫星的方位角匹配，否则它将无法获取卫星。 该卫星方位角仅取决于卫星经度和船只的位置。 )
The most common reasons for an antenna not finding the satellite is that it is pointing to the wrong place in the sky. This could be due to compass error, antenna alignment errors, the wrong ship position from the GPS, or the wrong satellite longitude selected.

( 天线找不到卫星的最常见原因是，它指向天空中的错误位置。 这可能是由于指南针错误，天线对准错误，GPS的错误船舶位置或错误的卫星经度造成的。 )

 

REL: Relative Azimuth ( REL：相对方位角 )

Relative azimuth is the bearing of the satellte referenced from the bow of the vessel, in a clockwise direction. This is computed considering the ship's heading and the Azimuth.
( 相对方位角是从船首沿顺时针方向引用的卫星的方位。 计算时要考虑船的航向和方位角。 )
The Azimuth is counted clockwise from North through 360 degrees. The Azimuth does not change unless the ship moves to a different location. The azimuth stays the same as the ship turns.
( 方位角是从北向360度顺时针方向计数的。 除非船移到其他位置，否则方位角不会改变。 方位角与船转弯相同。 )
The Relative is counted clockwise from the bow through 360 degrees. The Relative changes with heading, as the ship turns.
( 相对是从船首顺时针旋转360度。 相对方向随着船的转向而变化。 )
(See limited azimuth TV antenna Relative description)
( （请参阅有限方位角电视天线的相对描述） )

 

Elevation ( 俯仰角 )

Elevation is the pointing angle from the horizon to the satellite. The elevation and azimuth are calculated by the antenna based on the GPS position of the vessel and the Satellite longitude, nothing else.
( 仰角是从地平线到卫星的指向角。 天线根据船只的GPS位置和卫星经度计算俯仰角和方位角，仅此而已。 )
Zero degrees is looking at the horizon and 90 degrees is looking at the zenith (or directly overhead).

( 零度注视地平线，而90度注视天顶（或正上方）。 )

 

Parabolic dish ( 抛物面碟形 )

The parabolic dish focuses the weak signals from the satellite to the center of the feed.

( 抛物面碟形天线将卫星发出的微弱信号聚焦到馈源中心。 )

With any reflective surface, the angle of incidence is equal to the angle of reflection. Whatever angle the signal hits the dish it will bounce back off at the same angle.
( 对于任何反射表面，入射角均等于反射角。 无论信号碰到碟子的角度如何，它都会以相同的角度弹回。 )
The shape of the parabola is such that the signals coming in from the satellite are reflected off the surface toward a common focal point.
( 抛物线的形状使得从卫星进入的信号从表面反射到一个公共焦点。 )
In the same way, the transmit signal from the feed toward the dish is reflected back in a parallel beam toward the satellite.

( 同样，从馈送到碟形天线的发射信号也会以平行光束的形式反射回卫星。 )

 

AGC ( 自动增益控制 )

Automatic Gain Control. The signal strength of the received signal.
( 自动增益控制。 接收信号的信号强度。 )
The term originates from a reference voltage in radio receivers that would automatically turn down the gain of the receiver as the signal increased. Today in satellite terms it refers  to the strength of the signal.
( 该术语源自无线电接收器中的参考电压，该参考电压会随着信号的增加而自动降低接收器的增益。 今天，在卫星方面，它指的是信号的强度。 )
On a SeaTel antenna, for example, you may have an AGC of 1400 when you are  off the satellite, and 1800 when you are on the satellite. The importance is the difference between these two levels and not necessarly the actual level.

( 例如，在SeaTel天线上，当您离开卫星时，AGC可能为1400，而在卫星上时，AGC可能为1800。重要的是这两个层次之间的区别，而不一定是实际水平。 )

 

BUC ( 上变频功率放大器 习惯性的称呼为 块变频器 )

Block Up Converter is the transmitter of the antenna system. It converts the IF frequencies up to RF frequencies and amplifies the signal for transmission by the antenna.
( Block Up Converter是天线系统的发射器。 它将IF频率转换为RF频率，并放大信号以通过天线传输。 )
It contains an upconverter that changes the frequency from the IF frequency (usually L-Band) up to the RF frequency (C-Band, Ku-Band or Ka-Band). It also has the final power amplify that boosts the signal to the transmit power level. It is called a BLOCK up converter as it converts the entire block of signals from the IF to RF frequencies. (A regular up converter would only convert a narrow band of the required signal to RF frequencies).
( 它包含一个上变频器，可将频率从IF频率（通常为L波段）更改为RF频率（C波段，Ku波段或Ka波段）。 它还具有最终的功率放大功能，可将信号提升到发射功率电平。 它被称为BLOCK UP转换器，因为它将整个信号块从IF转换为RF频率。 （常规的上变频器只会将所需信号的窄带转换为RF频率）。 )
It is most often called a BUC (pronounced like buck) but some perfectionists refer to it as a B.U.C (like bee you see)

它通常被称为BUC（发音像buck），但一些完美主义者把它称为B.U.C（就像你看到的bee）

 

LNB Low Noise Block DownConverter ( 低噪声模块下变频器 )

The LNB is the radio receiver of a satellite antenna system. Depending on the type of feed, the LNB is installed either in front of, or behind the dish. It receives high frequency radio signals from the satellite and converts them to, more easily managed, intermediate frequencies.
( LNB是卫星天线系统的无线电接收器。 根据饲料的类型，LNB可以安装在培养皿的前面或后面。 它从卫星接收高频无线电信号，并将其转换为更容易管理的中频。 )
Super high radio frequencies, like Ku-band and C-band, are extremely sensitive to losses and noise, thus requiring sophisticated and expensive equipment and cables to process and transport the signals.
( Ku波段和C波段之类的超高射频对损耗和噪声极为敏感，因此需要复杂且昂贵的设备和电缆来处理和传输信号。 )
The LNB, converts the higher frequency radio signals, recieved by the dish, to lower, intermediate frequencies, that can be handled and transported using lower cost equipment and cables, down to the satellite receiver, or modem.
( LNB将碟形天线接收到的较高频率的无线电信号转换为较低的中频信号，可以使用成本更低的设备和电缆来处理和传输这些较低的中频信号，直至卫星接收器或调制解调器。 )
LNB stands for Low Noise Block converter, because it converts the entire block or range of Ku-Band or C-Band signals received from the satellite, down to a range of IF frequencies, usually L-band(1.5Ghz) in the case of Ku-band systems, and 70Mhz in the case of C-Band systems.

( LNB代表低噪声块转换器，因为它会将从卫星接收到的Ku波段或C波段信号的整个块或范围转换为IF频率范围，对于IF频率通常为L波段（1.5Ghz）。 Ku频段系统，对于C频段系统则为70Mhz。 )

 

VSAT - Very Small Aperture Terminal ( VSAT-小孔径终端 )

VSAT- ALWAYS ON - FIXED PRICE. Technically, all parabollic dish satellite terminals less than 3.8 m could be called Very Small Aperture Terminals, or VSATs, but the term VSAT generally refers to  transmit/receive (TX/RX) satellite terminals used for two way, data and voice traffic, like internet and telephone. A VSAT service is typically billed on a monthly contract, rather than by the minute, or by the megabyte like Inmarsat satcoms. 

( VSAT-始终在线-固定价格。 从技术上讲，所有小于3.8 m的抛物面碟形卫星终端都可以称为甚小孔径终端，或VSAT，但术语VSAT通常是指用于数据和语音通信等两种方式的发射/接收（TX / RX）卫星终端，例如 互联网和电话。 VSAT服务通常按月合同计费，而不是按分钟计费，也不像Inmarsat卫星通讯这样按兆字节计费。 )

 

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