Implementing QPSK modulation and Demodulation

2011 1 26
1 个回答
回答已采纳
5 次查看（30 天）

0 个投票

I have implemented QPSK modulation and demodulation system but does not give the 4 constellation points from the qpsk modulator block. The output is displayed on to discrete-time scatter plot scope and shows only 2 constellation points when I run the simulation. I have used Bernoulli binary generator for ease of analyzing and to generate a 2stage square wave.

请先登录，再回答此问题。

 采纳的回答

Rob Graessle
Rob Graessle 2011-1-26

0 个投票

The Bernoulli generator block is only going to generate a square wave with a value of 0 or 1. This explains why you are only seeing two constellation points at the output of the QPSK modulator. For QPSK, you want to have a message signal with possible values of 0, 1, 2 or 3 as an input to the QPSK modulator block. The Random Integer Generator block should do what you're looking for.
Or, you could still use the Bernoulli generator block with the output set to 2 samples per frame, and configure the QPSK modulator block to accept Bit input instead of Integer input.

2 个评论
显示 无 隐藏 无

Nauka Fernando
Nauka Fernando 2011-1-26
Thankx rob.. it solved my problem.i set the bernoulli generator to 2 samples per frame and configured the modulator and demodulator blocks as you said. but i can't get the display out to a scope to see how it modulated because it gives me errors as below,
"Invalid frame-based input with frame size 2 specified at port 1 of scope 'modulationwiterros/Scope'. For the case of frame-based inputs, the Scope requires that the frame size be 1. Alternatively, you may use the Vector Scope provided by the Signal Processing Blockset"
i need to take the display out at every output from each block for my analyzing..
need help please..
Rahool
Rahool 2011-11-15
how to implement qpsk modulator and demodulator using square root raised cosine function as shaping pulse

请先登录，再进行评论。

更多回答（0 个）

类别

在 帮助中心 和 File Exchange 中查找有关 QPSK 的更多信息

产品

标签

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by