Digital wireless systems

[Rich Webb]

Hi,

So, I need customized hardware to do this. Are you guys sure that
there are no chips available to do what I want to do? Any suggestions
or pointers that how should I proceed. I have FPGA generated clock and
data stream . Data is 48 bits wide and I am serially outing the data
at 1.5MHz.

What's the actual required throughput? Could you bring the 48 bits
into a FIFO and send them out at a slower (cheaper, easier to find)
rate?

 

[john]

Hi,

Okay , What is the slower , achievable rate? I can try to slow the
data rate down to that value

John

 

[linnix]

Hi,

Okay , What is the slower , achievable rate? I can try to slow the
data rate down to that value

John

100Kbps Bluetooth
250Kbps ZigBee

 

[Frank Raffaeli]

Hi,

So, I need customized hardware to do this. Are you guys sure that
there are no chips available to do what I want to do? Any suggestions
or pointers that how should I proceed. I have FPGA generated clock and
data stream . Data is 48 bits wide and I am serially outing the data
at 1.5MHz.

Regards,
John

6 feet? if you can use line of sight, consider optical. You can
serialize your 48 bits (I guess that would be 72 Mbps) and modulate
your optical transmitter with that, de-serialize at the other side.
Why can't you use a wire again?

Frank

 

[linnix]

6 feet? if you can use line of sight, consider optical. You can
serialize your 48 bits (I guess that would be 72 Mbps) and modulate
your optical transmitter with that, de-serialize at the other side.

My understanding is that the internal data path is 48 bits, but the
serial clock rate is 1.5MHz or 1.5Mbps. Either way, he need a custom
solution. If I am right, it would be a cheap custom solution. If you
are right, it would be an expensive custom solution.

 

[Frank Raffaeli]

My understanding is that the internal data path is 48 bits, but the
serial clock rate is 1.5MHz or 1.5Mbps. Either way, he need a custom
solution. If I am right, it would be a cheap custom solution. If you
are right, it would be an expensive custom solution.

Yep, it looks like 1.5 Mbps as you said. I wonder why no wires? 6 feet
looks like such a short range for wireless, especially RF wireless.
Since it's apparently only 1.5 Mbps, I'd consider something simple,
like FM carrier at 2.4 or 5.8 GHz, Manchester coded. That would double
the BW, but improve the SNR. It's still cheap and simple. I'd publish
a 1.5 Msps demodulator in Verilog for the right kind of beer ;-). The
up/downconverter is up to the OP.

Frank

 

[RFI-EMI-GUY]

My understanding is that the internal data path is 48 bits, but the
serial clock rate is 1.5MHz or 1.5Mbps. Either way, he need a custom
solution. If I am right, it would be a cheap custom solution. If you
are right, it would be an expensive custom solution.

He says he is "serial outing the data ay 1.5 MHz" . He needs to explain
better what he is doing or intends to do. Otherwise this thread is a
"waste of bandwidth".

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P

 

[linnix]

Yep, it looks like 1.5 Mbps as you said. I wonder why no wires? 6 feet

We need the OP back for sure. If he is really from Wayne State
University Medical Center, perhaps isolation issues from the operating
room?

 

[john]

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

 

[linnix]

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.

 

[Rich Grise]

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?

Haven't you bothered to read any of the dozens of answers you've already
gotten?

This is why people don't like googlies. Do you expect the answers to
just show up on your desk or something? If you ask on USENET, you get
answers on USENET.

Thanks,
Rich

 

[JosephKK]

6 feet? if you can use line of sight, consider optical. You can
serialize your 48 bits (I guess that would be 72 Mbps) and modulate
your optical transmitter with that, de-serialize at the other side.
Why can't you use a wire again?

Frank

As i come at this reading the whole thread OP is looking for about 1
mile range and three data sources.

 

[john]

Hi,

Each bit of the 48 bit data gets out of the FPGA at the rising edge of
the 1.5MHz of the Clock. I found following two transciever chips


http://www.nordicsemi.com/files/Pro...tware_Examples_Using_ShockBurst_Modesv1.0.pdf


http://www.chipcatalog.com/Datasheet/A1621136395209573B4A7AEFE50273A1.htm


What do guys think? Has anybody worked with these chips before?

John

 

[JosephKK]

Hi,

Each bit of the 48 bit data gets out of the FPGA at the rising edge of
the 1.5MHz of the Clock. I found following two transciever chips

http://www.nordicsemi.com/files/Pro...tware_Examples_Using_ShockBurst_Modesv1.0.pdf


http://www.chipcatalog.com/Datasheet/A1621136395209573B4A7AEFE50273A1.htm


What do guys think? Has anybody worked with these chips before?

John

Get a (better) news client. Even Outhouse Express (Outlook Express) is
ok by comparison. You need to have proper quoting.

Now that is off my chest, I suspect that neither of these chips will
do what you need directly.

The Nordic Semi device seems to be designed around a 100 ms sample
rate.

The fastest data transfer rate of the Micrel is 128 kb/s. Far less
than the speed it comes out of the FPGA.

What is the timing between 48-bit packets from your source again?

 

[Frank Raffaeli]

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


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.


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

 

[john]

Hi,
Its continous transmission no breaks, just unidirectional
communications. So, if I lowered the clock to lets say 500kHz then
nordic and Micrel chips would be ok to work with.

John

 

[linnix]

Hi,
Its continous transmission no breaks, just unidirectional
communications. So, if I lowered the clock to lets say 500kHz then
nordic and Micrel chips would be ok to work with.

John

Not enough details (especially the data rate) on your first link.
Can't access your second link.
If you email them to me, I will take a look.

contact me at www dot linnix dot com

 

[john]

Hello,

What inofmation do you require? Please let me know.

Regards,
John

 

[linnix]

Hello,

What inofmation do you require? Please let me know.

Regards,
John

For the first link. I don't think you need the 8051, if you already
have an FPGA.
I can't read the second link, so I can't tell if it's the right chip
or not. If you have the datasheet somewhere, just email me.

 

[JosephKK]

Hi,
Its continous transmission no breaks, just unidirectional
communications. So, if I lowered the clock to lets say 500kHz then
nordic and Micrel chips would be ok to work with.

John

I believe your original problem statement was 48bits per word,
transmitting continuously at 1.5 Mb/s. Neither chip will help you.
Your data rate is beyond what can handle. For the Micrel transmitter
you would have to cut the data rate down to 100kb/s. It may be
possible to use the WiMAX Chip but you will now eat batteries.

You should look for 1.5 to 2Mb/s chips for ISM bands, and narrow beam
antennas.