Please help for system level design

[kobesitu]

Hi everyone, currently i am doing a system level design for a direct-convertion receiver by using simulink, including create the AGC block diagram,etc. it is my first time to do the system level design, i have spent more than a month on reading papers and searching online for the detail of the block design using simulink, but all of them just tell you the overveiw concepts you need to care about, i have no clue and my progress is stop now. i know the first time to do or to learn something is very very hard, especially for the system level design. please someone have experience about using simulink to do the system level design help me, please help me to modify my attach simulink model, if possible. i have used the random number generator and QAM modulator to generate the source signal, and used the physical mixer and analog filters to make the I and Q path, but i have no idea about how to make the AGC and the gain control, please help me. i have no too much time left, please help me to modify the model able to start simulation. i will do the simulation myself, if it can work. but i have no idea how to do it now. Thank you very much to all the people concern about this topic.

 

[kobesitu]

please somebody help

 

[RFDave]

System level design is a pretty big topic. I don't have Simulink at home so I can't take a look at it, but what are you trying to accomplish? Does your receiver work without AGC? I like to start modeling things at the lowest possible level, so I'd start with a QAM modulator and QAM demodulator, and make sure I get the right bits out of that combination. Then I'd start adding an starting point for a receiver, which would probably be a IQ mixer and filters.

Dave

 

[kobesitu]

thanks, i am trying to accomplish a system level design to achieve specification for a DVB-S2 standart satellite tunner( i can say a 16QAM receiver). yup , my receiver will work with a AGC, somebody gonna design the AGC, but i have better to design myself also. and what will you use to start with the QAM modulator and QAM demodulator.i look through the matlab demos but they are in very high level design, what i mean is just a very basic stuff about the receiver. that's why i have no idea, and now i am doing some calculation to make up the initial theoretical concepts about the filter, including the gain, SNR, sensitivity,etc.

 

[RFDave]

Well, I'd start with a block diagram that is functional, and make sure that you get a signal in and out, and ignore all of the gain/signal bw, etc. Direct conversion receivers are pretty straigtforward, so I wouldn't worry about signal levels etc. Just get a block diagram that works, and then you have a starting point.

I believe that the Simulink Communications toolbox has a QAM modulator/demodulator block available.

You also should look at Matlab Central for examples. They may be basic, but it sounds to me that is what you need.

Dave

 

[kobesitu]

how i can find the examples in that website? sorry, what i mean is what example is good?

 

[RFDave]

www.mathworks.com/matlabcentral/fileexchange/loadCategory.do is a starting point.

Dave

 

[kobesitu]

thanks a lot man, i found lots of useful information in the website