implementing blind scanning in receivers

hello everyone..
I am a student working on this project...to design dvb-s cards..I am new
to DSP and MATLAB..have spend so much time to find a way to implement,but
unsuccessful.. and finally came to this forum for help..
i am using a particular demodulator chip ..If I input the centre
frequency, the chip start the demodulation process without any problem.
But i need to perform the blind scanning approach..wherein i specify the
frequency range and the target signal is checked at each frequency..when
there is an avialability of target signal, the demodulator start the
demodulation and the whole process repeats as normal..but scanning each
frequency..say for this range eg..950-1200 MHz.. has to start the scanning
from 950.001..950.002..and goes on till the end..but it takes lot of
time..to start at 950 and end up at 1200..
I am not sure if i can implement in FPGA or some controller..watever is
faster...
If anyone has any idea of a solution to the above problem..pls share with
me..your help will be appreciated..thanks for ur time..

karan

On Nov 20, 8:59 am, "prabu_cc" <prabu...@yahoo.com> wrote:
> hello everyone..
> I am a student working on this project...to design dvb-s cards..I am new
> to DSP and MATLAB..have spend so much time to find a way to implement,but
> unsuccessful.. and finally came to this forum for help..
> i am using a particular demodulator chip ..If I input the centre
> frequency, the chip start the demodulation process without any problem.
> But i need to perform the blind scanning approach..wherein i specify the
> frequency range and the target signal is checked at each frequency..when
> there is an avialability of target signal, the demodulator start the
> demodulation and the whole process repeats as normal..but scanning each
> frequency..say for this range eg..950-1200 MHz.. has to start the scanning
> from 950.001..950.002..and goes on till the end..but it takes lot of
> time..to start at 950 and end up at 1200..
> I am not sure if i can implement in FPGA or some controller..watever is
> faster...
> If anyone has any idea of a solution to the above problem..pls share with
> me..your help will be appreciated..thanks for ur time..
>
> karan

Is it really possible that the signal can be anywhere in 950-1200 MHz?
Or is there a defined channel plan with specific center frequencies in
that range? If so, you just need to check ranges around the nominal
center frequencies, to account for any frequency offset.

John

On Nov 20, 8:59 am, "prabu_cc" <prabu...@yahoo.com> wrote:
> hello everyone..
> I am a student working on this project...to design dvb-s cards..I am new
> to DSP and MATLAB..have spend so much time to find a way to implement,but
> unsuccessful.. and finally came to this forum for help..
> i am using a particular demodulator chip ..If I input the centre
> frequency, the chip start the demodulation process without any problem.
> But i need to perform the blind scanning approach..wherein i specify the
> frequency range and the target signal is checked at each frequency..when
> there is an avialability of target signal, the demodulator start the
> demodulation and the whole process repeats as normal..but scanning each
> frequency..say for this range eg..950-1200 MHz.. has to start the scanning
> from 950.001..950.002..and goes on till the end..but it takes lot of
> time..to start at 950 and end up at 1200..
> I am not sure if i can implement in FPGA or some controller..watever is
> faster...
> If anyone has any idea of a solution to the above problem..pls share with
> me..your help will be appreciated..thanks for ur time..
>
> karan

If you truly do need to be able to find signals across that entire
range instead of a predefined set of carrier frequencies, you might be
able to do something to shrink your search space a bit first. I'm not
sure how long it takes your demodulator to "lock" or determine that a
valid signal is at a specific frequency, but you might be able to do a
simpler search across the band first. Move in larger steps and just do
a quick RSSI check for each frequency, then only do further
investigations on frequencies whose received signal strength exceeded
a threshold. Whether or not you can implement something like this,
either in a speedy manner or at all, will depend on your hardware's
capabilities, but it might be a strategy worth thinking about.

Jason

>On Nov 20, 8:59 am, "prabu_cc" <prabu...@yahoo.com> wrote:
>> hello everyone..
>> I am a student working on this project...to design dvb-s cards..I am
new
>> to DSP and MATLAB..have spend so much time to find a way to
implement,but
>> unsuccessful.. and finally came to this forum for help..
>> i am using a particular demodulator chip ..If I input the centre
>> frequency, the chip start the demodulation process without any
problem.
>> But i need to perform the blind scanning approach..wherein i specify
the
>> frequency range and the target signal is checked at each
frequency..when
>> there is an avialability of target signal, the demodulator start the
>> demodulation and the whole process repeats as normal..but scanning
each
>> frequency..say for this range eg..950-1200 MHz.. has to start the
scanning
>> from 950.001..950.002..and goes on till the end..but it takes lot of
>> time..to start at 950 and end up at 1200..
>> I am not sure if i can implement in FPGA or some controller..watever
is
>> faster...
>> If anyone has any idea of a solution to the above problem..pls share
with
>> me..your help will be appreciated..thanks for ur time..
>>
>> karan
>
>Is it really possible that the signal can be anywhere in 950-1200 MHz?
>Or is there a defined channel plan with specific center frequencies in
>that range? If so, you just need to check ranges around the nominal
>center frequencies, to account for any frequency offset.
>
>John
>

john

thanks for ur information..
but ya..we do have signals in the entire frequency range..and i have to
find the center frequency in the entire range..that has the valid
signal..
To do so..i am actually planning to shrink the size of the range first and
look for the valid signal...since the entire range takes lot of time..
Looking at what you have said..i dont understand why i should worry about
the frequency offset..and what does it has to do with the scanning and
demodulation..?

regards
karan

>On Nov 20, 8:59 am, "prabu_cc" <prabu...@yahoo.com> wrote:
>> hello everyone..
>> I am a student working on this project...to design dvb-s cards..I am
new
>> to DSP and MATLAB..have spend so much time to find a way to
implement,but
>> unsuccessful.. and finally came to this forum for help..
>> i am using a particular demodulator chip ..If I input the centre
>> frequency, the chip start the demodulation process without any
problem.
>> But i need to perform the blind scanning approach..wherein i specify
the
>> frequency range and the target signal is checked at each
frequency..when
>> there is an avialability of target signal, the demodulator start the
>> demodulation and the whole process repeats as normal..but scanning
each
>> frequency..say for this range eg..950-1200 MHz.. has to start the
scanning
>> from 950.001..950.002..and goes on till the end..but it takes lot of
>> time..to start at 950 and end up at 1200..
>> I am not sure if i can implement in FPGA or some controller..watever
is
>> faster...
>> If anyone has any idea of a solution to the above problem..pls share
with
>> me..your help will be appreciated..thanks for ur time..
>>
>> karan
>
>If you truly do need to be able to find signals across that entire
>range instead of a predefined set of carrier frequencies, you might be
>able to do something to shrink your search space a bit first. I'm not
>sure how long it takes your demodulator to "lock" or determine that a
>valid signal is at a specific frequency, but you might be able to do a
>simpler search across the band first. Move in larger steps and just do
>a quick RSSI check for each frequency, then only do further
>investigations on frequencies whose received signal strength exceeded
>a threshold. Whether or not you can implement something like this,
>either in a speedy manner or at all, will depend on your hardware's
>capabilities, but it might be a strategy worth thinking about.
>
>Jason
>

Jason,

Yes..i have thought about that option as well..
start up with a coarse scanning first and do fine scanning..once i find
something smaller range..
btw..can u tell me what is RSSI..haven't heard of it before..?

On Nov 22, 2:05 am, "prabu_cc" <prabu...@yahoo.com> wrote:
> >On Nov 20, 8:59 am, "prabu_cc" <prabu...@yahoo.com> wrote:
> >> hello everyone..
> >> I am a student working on this project...to design dvb-s cards..I am
> new
> >> to DSP and MATLAB..have spend so much time to find a way to
> implement,but
> >> unsuccessful.. and finally came to this forum for help..
> >> i am using a particular demodulator chip ..If I input the centre
> >> frequency, the chip start the demodulation process without any
> problem.
> >> But i need to perform the blind scanning approach..wherein i specify
> the
> >> frequency range and the target signal is checked at each
> frequency..when
> >> there is an avialability of target signal, the demodulator start the
> >> demodulation and the whole process repeats as normal..but scanning
> each
> >> frequency..say for this range eg..950-1200 MHz.. has to start the
> scanning
> >> from 950.001..950.002..and goes on till the end..but it takes lot of
> >> time..to start at 950 and end up at 1200..
> >> I am not sure if i can implement in FPGA or some controller..watever
> is
> >> faster...
> >> If anyone has any idea of a solution to the above problem..pls share
> with
> >> me..your help will be appreciated..thanks for ur time..
>
> >> karan
>
> >If you truly do need to be able to find signals across that entire
> >range instead of a predefined set of carrier frequencies, you might be
> >able to do something to shrink your search space a bit first. I'm not
> >sure how long it takes your demodulator to "lock" or determine that a
> >valid signal is at a specific frequency, but you might be able to do a
> >simpler search across the band first. Move in larger steps and just do
> >a quick RSSI check for each frequency, then only do further
> >investigations on frequencies whose received signal strength exceeded
> >a threshold. Whether or not you can implement something like this,
> >either in a speedy manner or at all, will depend on your hardware's
> >capabilities, but it might be a strategy worth thinking about.
>
> >Jason
>
> Jason,
>
> Yes..i have thought about that option as well..
> start up with a coarse scanning first and do fine scanning..once i find
> something smaller range..
> btw..can u tell me what is RSSI..haven't heard of it before..?

http://en.wikipedia.org/wiki/RSSI