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sree_405
Posts: 79
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Hi help abt BPSK/QPSK signal waveform

Hi sir,
I am using modulation toolkit for generating bpsk/qpsk signals.Here i am attaching wavefrom image.what i seen the psk waveform like this(psk1.jpg and psk2.jpg).
But i am getting like this(bpsk_ouput.jpg).is it correct?it looks like only phase changes are appearing.
Please give me some clear information abt this signals.


Thanking you sir


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David L.
Posts: 383
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Re: Hi help abt BPSK/QPSK signal waveform

Hi Sree,

I would like to ask for any VI’s you are using, along with further information about your project. I believe you are using the 5640R (IF-RIO), correct? From the post, I believe the 5640R is being used for PSK acquisition, but what is being used to generate your signal? I would like to ask for as much detail as possible ( all rates, inputs, outputs, etc) when you post, so we can best help to determine why you are not seeing the correct signal.

David L.
Systems Engineering
National Instruments
Member
sree_405
Posts: 79
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Re: Hi help abt BPSK/QPSK signal waveform

Hi David L,
I need to generate some modulated signal(bpsk,qpsk,ook) modulated signal,with Fs=25MHz,Fc=8.6MHz and baudrates 4800,9600,19200 etc.
with some user bitstream.

i need just some psk signal VI.i have one doubt i seen psk signal in matlab is different then wat i get in labview modulation kit.

allready i posted two type output images.please tell me which one is correct,if  both correct tell me how?

Thanks
Sreenivasulu.
Active Participant
David L.
Posts: 383
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Re: Hi help abt BPSK/QPSK signal waveform

Hi Sree,

I do not know the formulas or methods used to create your images psk1.jpg or psk2.jpg, along with not knowing the bit pattern for your BPSK signal, so I cannot say if they are exactly correct, but the FFT looks reasonable. With the limited information from the post, I cannot determine if the LabVIEW VI is giving correct results, therefore I would like to again request information from my previous post – Can you please post the VI used for 5640R Acquisition? What is generating the signal (5640R or 3rd party device)? What is the bit pattern being used for the BPSK signal? It is good to know that you have Fc = 8.6M, and Fs=25M, but what is your IQ rate? With BPSK, we should not see amplitude changes, but only phase changes, so the LabVIEW image demonstrating only phase changes does not seem incorrect.

David L.
Systems Engineering
National Instruments
Member
niton
Posts: 7
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Re: Hi help abt BPSK/QPSK signal waveform

hello, David L.,

 

I am also trying to use 5640R to get a PSK modulation signal. But the result is not correct. The envelope should be constant in PSK modulation signal. what I get is shown in pic1.

My Host and FPGA .Vi is posted in pic 2 and pic3.

can you help me to resolve it?

 

Niton