GPS理论与应用--伪随机码测距原理 ppt课件
合集下载
相关主题
- 1、下载文档前请自行甄别文档内容的完整性，平台不提供额外的编辑、内容补充、找答案等附加服务。
- 2、"仅部分预览"的文档,不可在线预览部分如存在完整性等问题,可反馈申请退款(可完整预览的文档不适用该条件!)。
- 3、如文档侵犯您的权益，请联系客服反馈,我们会尽快为您处理(人工客服工作时间：9:00-18:30)。
GPS理论与应用
（5.伪随机码测距原理）
GPS理论与应用 5.伪随机码测距原理
授课内容 1.GPS卫星的测距码信号 2.GPS测距原理 3.伪随机码基础 4.GPS中的伪码扩频 5.伪随机码测距原理
GPS理论与应用 5.伪随机码测距原理
1.GPS卫星的测距码信号
GPS卫星发送的信号采用L波段的两种
GPS理论与应用 5.伪随机码测距原理
This modulation of the signal, which is really just a series of “dots and dashes,” is very long and complicated. So complicated, in fact, that if you were just to look at it without knowing what it was, it would simply look like a bunch of random noise that made no sense at all. But it really does make sense to those in the know. Thus the term pseudo-random noise.
This simply means that the carrier signal is modulated (varied) by changing its phase (updown position of the waves) back and forth (biphase) at a regular and programmed rate and interval.
载频作载波，分别被称作L1的主频率和 L2的次频率。
这些载波频率由扩频码（每一颗卫星均 有专门的伪随机序列）和导航电文所调
制。所有卫星均在这两个相同的载波频 率上发射，但由于伪随机码调制不同， 因此无明显的相互干扰。
源自文库
GPS理论与应用 5.伪随机码测距原理
GPS理论与应用
5.伪随机码测距原理
Each satellite transmits its ranging signal on two different radio frequencies: 1575.42 Megahertz (part of the so-called “L-Band”) which is referred to as the L1 Carrier, and 1227.60 Megahertz (also of the L-Band) designated as the L2 Carrier.
(3)大气衰减小，有利于研制用户设备。GPS卫星采 用L波段，避开了大气的谐振吸收，衰减较小，且电 离层延迟的影响小，有利于用较经济的接收设备测 量GPS信号。而采用两个载频，目的在于测量出或 消除掉由于电离层效应而引起的延迟误差。
GPS理论与应用
5.伪随机码测距原理
When a radio transmits a signal, it is in the form of a simple sine wave that has a particular frequency (the number of “humps” on the sine wave that pass a fixed point per unit of time-usually given as Hertz, or times per second), wavelength (the distance between “humps” or any matching successive point on the sine wave), and amplitude (the “height” of the “humps”).
Radio wavelengths can range from tens of kilometers down to tiny fractions of micrometer. Frequencies, intrinsically linked to wave-lengths, also have wide ranges, from only a few per hour (low frequency) to billions per second (high frequency).
A basic carrier sine wave is illustrated at the top of the diagram.
There are two different pseudo-random code strings used by the GPS: the Coarse Acquisition Code (C/A-code), sometimes called the “Civilian Code” , and the Precise, or Protected Code (P-Code).
Superimposed on these radio carrier wave signals are pseudo-random, binary, bi-phase modulation codes called PRN (Pseudo Random Noise) codes that are unique to each individual satellite.
GPS理论与应用 5.伪随机码测距原理
选择L波段的优点是：
(1) 减少拥挤，避免“撞车”。目前L波段的频率占 用率低于其他波段，与其他工作频率不易发生“撞 车”现象，有利于全球性的导航定位测量。
(2) 适应扩频，传送宽带信号。GPS卫星采用扩频技 术发送卫星导航电文，其频带高达20 MHz左右，在 占用率较低的L波段上， 易于传送扩频后的宽带信号。
（5.伪随机码测距原理）
GPS理论与应用 5.伪随机码测距原理
授课内容 1.GPS卫星的测距码信号 2.GPS测距原理 3.伪随机码基础 4.GPS中的伪码扩频 5.伪随机码测距原理
GPS理论与应用 5.伪随机码测距原理
1.GPS卫星的测距码信号
GPS卫星发送的信号采用L波段的两种
GPS理论与应用 5.伪随机码测距原理
This modulation of the signal, which is really just a series of “dots and dashes,” is very long and complicated. So complicated, in fact, that if you were just to look at it without knowing what it was, it would simply look like a bunch of random noise that made no sense at all. But it really does make sense to those in the know. Thus the term pseudo-random noise.
This simply means that the carrier signal is modulated (varied) by changing its phase (updown position of the waves) back and forth (biphase) at a regular and programmed rate and interval.
载频作载波，分别被称作L1的主频率和 L2的次频率。
这些载波频率由扩频码（每一颗卫星均 有专门的伪随机序列）和导航电文所调
制。所有卫星均在这两个相同的载波频 率上发射，但由于伪随机码调制不同， 因此无明显的相互干扰。
源自文库
GPS理论与应用 5.伪随机码测距原理
GPS理论与应用
5.伪随机码测距原理
Each satellite transmits its ranging signal on two different radio frequencies: 1575.42 Megahertz (part of the so-called “L-Band”) which is referred to as the L1 Carrier, and 1227.60 Megahertz (also of the L-Band) designated as the L2 Carrier.
(3)大气衰减小，有利于研制用户设备。GPS卫星采 用L波段，避开了大气的谐振吸收，衰减较小，且电 离层延迟的影响小，有利于用较经济的接收设备测 量GPS信号。而采用两个载频，目的在于测量出或 消除掉由于电离层效应而引起的延迟误差。
GPS理论与应用
5.伪随机码测距原理
When a radio transmits a signal, it is in the form of a simple sine wave that has a particular frequency (the number of “humps” on the sine wave that pass a fixed point per unit of time-usually given as Hertz, or times per second), wavelength (the distance between “humps” or any matching successive point on the sine wave), and amplitude (the “height” of the “humps”).
Radio wavelengths can range from tens of kilometers down to tiny fractions of micrometer. Frequencies, intrinsically linked to wave-lengths, also have wide ranges, from only a few per hour (low frequency) to billions per second (high frequency).
A basic carrier sine wave is illustrated at the top of the diagram.
There are two different pseudo-random code strings used by the GPS: the Coarse Acquisition Code (C/A-code), sometimes called the “Civilian Code” , and the Precise, or Protected Code (P-Code).
Superimposed on these radio carrier wave signals are pseudo-random, binary, bi-phase modulation codes called PRN (Pseudo Random Noise) codes that are unique to each individual satellite.
GPS理论与应用 5.伪随机码测距原理
选择L波段的优点是：
(1) 减少拥挤，避免“撞车”。目前L波段的频率占 用率低于其他波段，与其他工作频率不易发生“撞 车”现象，有利于全球性的导航定位测量。
(2) 适应扩频，传送宽带信号。GPS卫星采用扩频技 术发送卫星导航电文，其频带高达20 MHz左右，在 占用率较低的L波段上， 易于传送扩频后的宽带信号。