Prev: Diodes for boost converter SPICE parameters
Next: Transfer Circuit for Generator
From: andy baxter on 1 Jul 2010 12:19
Hello,

I am working for a small company who are working on a system which needs
to send digital signals over a noisy medium. We have something working
which uses a pair of frequencies (in the 100kHz-1Mhz range) to represent
0s and 1s, but would like something that gives better noise rejection.

We are looking at spread spectrum signalling for this, but don't have the
specific skills in house to develop this technique, so want to research
it a bit further to see if it is something that might be useful.

Can anyone recommend any good books on this subject which would cover a
range of techniques and give us some idea of which might be useful for
what we want to do?

Thanks for any help with this,

andy baxter.

--
(remove 'null' to email me)
From: Vladimir Vassilevsky on 1 Jul 2010 12:39

I am Vladimir Vassilevsky, and I am at your service.

http://www.abvolt.com


andy baxter wrote:

> Hello,
>
> I am working for a small company who are working on a system which needs
> to send digital signals over a noisy medium. We have something working
> which uses a pair of frequencies (in the 100kHz-1Mhz range) to represent
> 0s and 1s, but would like something that gives better noise rejection.
>
> We are looking at spread spectrum signalling for this, but don't have the
> specific skills in house to develop this technique, so want to research
> it a bit further to see if it is something that might be useful.
>
> Can anyone recommend any good books on this subject which would cover a
> range of techniques and give us some idea of which might be useful for
> what we want to do?
>
> Thanks for any help with this,
>
> andy baxter.
>

From: John Larkin on 1 Jul 2010 12:49
On Thu, 01 Jul 2010 11:39:11 -0500, Vladimir Vassilevsky
<nospam(a)nowhere.com> wrote:

>
>I am Vladimir Vassilevsky, and I am at your service.
>
>http://www.abvolt.com
>
>
>andy baxter wrote:
>
>> Hello,
>>
>> I am working for a small company who are working on a system which needs
>> to send digital signals over a noisy medium. We have something working
>> which uses a pair of frequencies (in the 100kHz-1Mhz range) to represent
>> 0s and 1s, but would like something that gives better noise rejection.
>>
>> We are looking at spread spectrum signalling for this, but don't have the
>> specific skills in house to develop this technique, so want to research
>> it a bit further to see if it is something that might be useful.
>>
>> Can anyone recommend any good books on this subject which would cover a
>> range of techniques and give us some idea of which might be useful for
>> what we want to do?
>>
>> Thanks for any help with this,
>>
>> andy baxter.
>>

What's your data rate? What's the data like? How are uou applying the
modulation? How are you detecting it?

Spread-spectrum won't necessarily give better performance, unless you
have some special-case interferance problems.

John

From: andy baxter on 1 Jul 2010 13:16
On Thu, 01 Jul 2010 09:49:04 -0700, John Larkin wrote:

> What's your data rate? What's the data like? How are uou applying the
> modulation? How are you detecting it?
>
> Spread-spectrum won't necessarily give better performance, unless you
> have some special-case interferance problems.

The data rate is pretty low - the situation is that we have a large
number of transmitters (which have to use as little power as possible),
and a smaller number of receivers. The problem is for each receiver to
continuously detect which transmitters are connected on the same physical
channel as it is operating on. We can send analog electronic signals over
this channel, but it is very lossy and subject to noise. (Sorry not to be
more specific but my boss has asked me not to talk about the actual
application in too much detail).

The data is just a unique id of each transmitter, sent around 10 times a
second.

The modulation technique we are using at the moment is to generate pulses
of one of two given frequencies using a programmable oscillator connected
to a microcontroller, and then decode them by putting them through a pair
of tuned filters.



--
(remove 'null' to email me)
From: Uwe Hercksen on 1 Jul 2010 13:53


andy baxter schrieb:

> The data rate is pretty low - the situation is that we have a large
> number of transmitters (which have to use as little power as possible),
> and a smaller number of receivers. The problem is for each receiver to
> continuously detect which transmitters are connected on the same physical
> channel as it is operating on. We can send analog electronic signals over
> this channel, but it is very lossy and subject to noise. (Sorry not to be
> more specific but my boss has asked me not to talk about the actual
> application in too much detail).

Hello,

you should look for the modulation used for the GPS system to transmit
the almanac data with low data rate. Each satellite uses the same
frequency and the signal at receivers is below the noise level, but due
to the clever digital modulation it is possible to detect and to
separate the signals from different satellites. A lot of computing power
is needed using a signal processor.

Bye

 |  Next  |  Last
Pages: 1 2 3 4
Prev: Diodes for boost converter SPICE parameters
Next: Transfer Circuit for Generator