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WHAT IS PPM Encoder ? - slowlydance2me

 2 years ago
source link: https://www.cnblogs.com/slowlydance2me/p/17159911.html
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About PPM Encoder

The PPM encoder allows to encode up to 8 PWM (pulse width modulated) signals into one PPM (pulse position modulation) signal.

The function of the PPM encoder is to encode the multi-channel PWM signal output by the receiver into a PPM composite signal output (up to 8 channels of PWM input) to connect the supported flight controllers in a single line.

PWM and PPM Introduction

PWM stands for Pulse Width Modulation and PPM stands for Pulse Position Modulation. PWM is a technique used to relay data in the form of a varying pulse width. In PPM (Pulse Position Modulation) the analogue sample values determine the position of a narrow pulse relative to the clocking time.

Advantages

The advantages of pulse position modulation include the following.

  • PPM has the most power efficiency as compared to other modulations.

  • This modulation has less stable amplitude noise interference.

  • This modulation separates the signal easily from a noisy signal.

  • It needs less power as compared to PAM.

  • Separation of signal & noise is extremely simple

  • It has constant transmitted power output.

  • It needs extremely less power as compared to PAM & PDM because of amplitude & short duration pulse.

  • Easy noise removal in this type of modulation.

  • Power utilization is also extremely low as compared to other modulations because of stable pulse amplitude & width.

  • PPM communicates only simple commands from a Tx to an Rx, so it is frequently used in lightweight applications because of its low system necessities.

Disadvantages

The disadvantages of pulse position modulation include the following.

  • PPM is very complex.

  • It needs more bandwidth for transmission as compared to PAM.

  • It is extremely sensitive to multi-pathway interference like echoing that can disturb a transmission by changing the difference in arrival times of every signal.

  • Synchronization is necessary between transmitter & receiver which is not feasible each time & we require a dedicated channel for it.

  • Special devices are required for this kind of modulation.

Applications

The applications of pulse position modulation include the following.

  • The PPM is mainly used in telecommunication systems & air traffic control systems.

  • This modulation is used in radio control, an optical communication system & military applications.

  • This technique is used in planes, remote-controlled cars, trains, etc.

  • PPM is used in noncoherent detection wherever a receiver does not require any Phase lock loop or PLL to track the carrier’s phase.

  • It is used in RF (radio frequency) communication.

  • It is also utilized in high-frequency, contactless smart cards, radio frequency ID tags, etc.

关于PPM编码器

PPM编码器允许将多达8个PWM(脉冲宽度调制)信号编码为一个PPM(脉冲位置调制)信号。

PPM编码器的功能是将接收机输出的多路PWM信号编码为PPM复合信号输出(最多8路PWM输入)，以单线连接所支持的飞行控制器。

PWM和PPM简介

PWM代表脉冲宽度调制，PPM代表脉冲位置调制。PWM是一种用于以变化脉冲宽度的形式传递数据的技术。在PPM(脉冲位置调制)中，模拟采样值确定相对于时钟时间的窄脉冲的位置。

脉冲位置调制的优点包括以下方面。

与其他调制相比，PPM具有最高的电源效率。

这种调制具有较小的稳定振幅噪声干扰。

这种调制方式可以很容易地将信号从噪声信号中分离出来。

与PAM相比，它需要更少的能量。

信号和噪声的分离非常简单

它具有恒定的传输功率输出。

与PAM和PDM相比，它需要的功率非常少，因为它的振幅和脉冲持续时间短。

在这种类型的调制中容易去除噪声。

与其他调制相比，功率利用率也非常低，因为稳定的脉冲振幅和宽度。

PPM仅从Tx向Rx通信简单的命令，因此由于它对系统的需求较低，因此经常用于轻量级应用程序。

脉冲位置调制的缺点包括以下几个方面。

PPM非常复杂。

与PAM相比，它需要更多的带宽来传输。

它对回声等多路径干扰极其敏感，回声可以通过改变每个信号到达时间的差异来干扰传输。

发射机和接收机之间的同步是必要的，但不是每次都可行，我们需要一个专用的通道。

这种调制需要特殊的设备。

脉冲位置调制的应用包括以下几个方面。

PPM主要用于电信系统和空中交通管制系统。

这种调制被用于无线电控制，光通信系统和军事应用。

这项技术用于飞机、遥控汽车、火车等。

PPM用于非相干检测，接收机不需要任何锁相环或锁相环来跟踪载波的相位。

它用于RF(射频)通信。

它还用于高频，非接触式智能卡，射频ID标签等。

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