BPSK demodulation

Hi all!! I have implemented BPSK modulation with DSK 6713.I'm writting a
program to implement BPSK modulation and demodulation on the same Kit DSK
6713, but it doesn't run. Can we implement BPSK modulation and demodulatio
on the same Kit DSP?. I wil post my source code later!
By the way! I also have a project about QPSK demodulation, but when I
recover carrier wave, I only recover sin wave(in_phase). How can I get cos
wave(Q-Phase) from sin wave?
Please help me! Thank you!
BRs!

On Tue, 29 Dec 2009 09:23:12 -0600, trung86 wrote:

> Hi all!! I have implemented BPSK modulation with DSK 6713.I'm writting a
> program to implement BPSK modulation and demodulation on the same Kit
> DSK 6713, but it doesn't run. Can we implement BPSK modulation and
> demodulatio on the same Kit DSP?. 

Yes, you most likely have a software error.

> I wil post my source code later! 

You will have better luck if you outline what you're doing -- source code 
takes ages to plow through, and only implementation bugs are obvious.  If 
yours is a bug at the architectural or design level (which is likely if 
you're a beginner) then posting code will just get in the way.

Be sure to include things like your data rate, your sample rate, your 
carrier frequency, your general approach, etc.

> By
> the way! I also have a project about QPSK demodulation, but when I
> recover carrier wave, I only recover sin wave(in_phase). How can I get
> cos wave(Q-Phase) from sin wave?
> Please help me! Thank you!
> BRs!

If you're recovering the carrier wave with some sort of a PLL where 
you're generating a carrier and comparing its phase to the (suppressed) 
carrier of the incoming signal, then you should be able to generate your 
quadrature carrier at the same time as your inphase, and solve all your 
problems.

If not, and if your sine wave is at a known frequency, ponder the effects 
of the filter

H(z) = (z + a) / (z - b)

on your sine wave if a and b are chosen to be close to 1.

-- 
www.wescottdesign.com

On Dec 29, 10:23&#4294967295;am, "trung86" <kiemkhachhop...@yahoo.com.vn> wrote:
> Hi all!! I have implemented BPSK modulation with DSK 6713.I'm writting a
> program to implement BPSK modulation and demodulation on the same Kit DSK
> 6713, but it doesn't run. Can we implement BPSK modulation and demodulatio
> on the same Kit DSP?. I wil post my source code later!
> By the way! I also have a project about QPSK demodulation, but when I
> recover carrier wave, I only recover sin wave(in_phase). How can I get cos
> wave(Q-Phase) from sin wave?
> Please help me! Thank you!
> BRs!

There are multiple ways to create the quadrature component of your
received signal. Here is a simple way:

http://www.claysturner.com/dsp/ASG.pdf

Since you are doing both sides (Tx and Rx), see if you can find a
source of signal (from other than your box) so you can "break the tie"
when your overall system doesn't work. I.e., is the problem in your Tx
or your Rx?

IHTH,
Clay