Re: Digital wireless systems

On May 15, 12:45 pm, linnix <m...@xxxxxxxxxxxxxxxxxx> wrote:
On May 15, 7:33 am, john <conphil...@xxxxxxxxxxx> wrote:

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, is it 1.6Mbps or 48x1.5=72Mbps?

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.

The modulator/demodulator can be configurated/controlled by the FPGA,
but you need analog RF circuits. You need to be very careful with PCB
layouts. RF PCB layouts are very tricky.

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?

First thing is to pick your encoding scheme. Manchester FM sounds
good, as suggested by other posters.

I still don't know the OP's requirement for data rate, it's still
ambiguous; however, I meant to use the FPGA as the 2nd stage down-
conversion and the demodulator both. The whole receiver (all COTS):
1) 5.8 GHz BPF
2) Mini-circuits mixer
3) Fixed L.O. (with amp)
4) IF amp (assume a 1st I.F of about 1.2 GHz)
5) IF filter (e.g. EPCOS) - don't use SAW unless triple-transit ok.
6) ~500 MSPS converter (with at least 1200 MHz BW)
7) FPGA: Cyclone 3, Spartan, Virtex5, etc ...

The above is for 72Mbits/s. If it's only 1.5 Mbps, then it can be a
lot simpler. Step 4,5,6 could be adapted for direct conversion, which
would be cheaper, but lower performance.

Frank

.

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