Digital wireless systems

[Frank Raffaeli]

Hi,

I am looking for a digital design or technique that I can use to
transmit the 48bit of data at 1.5MHz frequncy wirelessly. So, what I
gathered so far is that a digital frequncy modulator can be made using
a FPGA and the demodulator can also be made using FPGA. Am I right ,
if yes then i need more guidance , some literature to understand
exaclty how can I do this? The thing that I do not still understand
that If I am right about the FPGA based frequency modulator and
domodulator then how would I design the wireless part of the system?

John

After re-reading some of your posts, it seems clear that your data
rate is 72 Mbps. It would help to know if this is a one-off
(feasibility) or a design project ... Since you already have a Spartan
on the transmit side, you can use it as a modulator (e.g QAM),
followed by an up-converter, and use another FPGA after down-
conversion on the receive side. I think questions about what "chips"
to use for the RF (or optical) section might be more productive after
we know more about the cost / size and power constraints.

Frank Raffaeli

 

[john]

Hi,

1.5MHz is the serial clock rate. So, the time period of this clock
will be approx. 66 ns. Now, at each rising edge of the clock, FPGA
puts a bit out and keep it at its output for one clock cycle. So, FPGA
uses 48 clock cycles to output 48 bits. So, according to my guess the
data rate to transmit one 48 bit frame is (66ns x 48 = 32usec)....The
time interval between two consective 48 bit frames can be anything...
I can transmit one after another or can have some delay between them.

Now , I need a wireless system that can transmit and recieve this
data, clock and a synch. I heard that I can use FSK technique to do
this by programming FPGA as modulator and demodulator. or I can
interface FPGA with the some RF chips that can handle this data rate.
So, I am looking into chips. I can lower the data clock to 600kHz.

The chips links that I found are as follows

http://www.nordicsemi.com/files/Product/applications/nAN24-12Software...

http://www.micrel.com/_PDF/micrf501.pdf

John

 

[linnix]

Hi,

1.5MHz is the serial clock rate.

This is your internal data clock. You have to buffer the data and
shift out at a lower rate.

Now , I need a wireless system that can transmit and recieve this
data, clock and a synch. I heard that I can use FSK technique to do
this by programming FPGA as modulator and demodulator. or I can
interface FPGA with the some RF chips that can handle this data rate.
So, I am looking into chips. I can lower the data clock to 600kHz.

You have to lower it to 128khz for the Micrel chip

 

[john]

Hi,

By 128khz, you meant the Data clock frequency. Am I right?

John

 

[Frank Raffaeli]

Hi,

By 128khz, you meant the Data clock frequency. Am I right?

John

First you say 1.5M clock, 48 bits at 1.5 MHz, then 66nS, It's
difficult to know what you mean.... If you want to call me, I'll help
you sort it out. I can help you if you want (I have the day off), but
I think it will go 100x faster by phone.

http://www.aomwireless.com/

 

[JosephKK]

John wrote on 5/12/2008

Clear as mud.

Sorry if you are unable or unwilling to read the whole thread. It
might make better sense to you then. Not that it is all that clear in
the first place. OP has been given several offers of professional
advice (probably paid for). I have no idea if OP has pursued them.

 

[JosephKK]

John wrote on 5/12/2008

Clear as mud.

You got it. OP does not seem to understand what the actual
requirements are.

 

[David L. Jones]

Hi,

I programmed Spartan chip to produce serial data ( main_Clock, Data
Clock, Data and Tag ) stream for a DAC. I need to make this system
work with out wires. The main clock is 3MHz, Data clock is 1.5MHz. Can
anybody advice me how to make it digital wireless ( Transmitter plus
receiver). I have not done anything like this before. The DAC will be
at 6 feet away from the Spartan chip.

Thanks
John

Looking at this differently...

Is there perhaps a *smarter* system level way for you to achieve the
same end result?
i.e. do you have to actually output that amount of data continuously
to the DAC via the wireless interface?
Does the DAC output anything repetitive that you can automate on the
receiver side? e.g. if it's say for example a sine wave bust, can you
send a short "generate sine wave burst" "command" instead of the huge
amount of actual DAC data itself?

Dave.