Signal Processing

Hi FvM,

But which information do you want to help me.

thanks

--- Quote Start ---

I think Filipe gave enough info.

..

If this is student project then it is unfair to ask for any full spec.

--- Quote End ---

I don't agree. He has been asking e.g. for the required ADC resolution. The question can rarely be anwered from the given information. I would also guess, that a spectral analysis of the input signal is intended, unfortunately it hasn't been said clearly. Just copying the project title would most likely clarify a lot.

At the present state, the appropriate general suggestion is: Start with a digital signal processing text book, e.g. Stearns/Hush.

Thank you Kaz,

That is my problem. I will do a downconverter frequency before ADC .

thank you so much

I think Filipe gave enough info. He wants to sample some specific signals for spectrum display. The signal will be downconverted to baseband before ADC by someone.

If this is student project then it is unfair to ask for any full spec. All what is needed is a general purpose ADC that can cover speed well above twice highest frequency expected then do fft inside fpga then display the fft output vectors(Re/Im) on pc.

Hi people,

I have all details, but which details you want to know.

thanks

If the ADC output represents a bandlimited signal, calculating the variance will give the total signal power. It's a rather simple algorithm.

The overall problem is however missing many specification details. The questions you are asking can't be answered without a full specification, Furthermore, the way you are asking suggests that you are far from understanding the problem complexity.

Hi Dave,

Thanks for your tip.

You asked me what I will do with the signal, detect and demodulate or just detect the power.

In my case I want just detect the power, not demodulate.

thanks for all

--- Quote Start ---

Hi Dave, thanks for all.

My problem is: I have a frequency range 100 KHz to 3 GHz and I have to detect all signals between that frequency range, for example (AM, FM, GSM, Bluetooh...etc). I need to choice a ADC and implement the signal processing in FPGA. I don't know which ADC I can use. The maximum bandwith that I have to try to sample is 20 MHz, But I don't know how many bits my ADC must have.

--- Quote End ---

You still have not specified what you want to do with the signals.

By 'detect' do you mean demodulate, or just 'detect' power?

The number of bits required from your ADC will depend on what type of signal processing you want to perform. However, a 16-bit 100MHz ADC will likely do anything you want. There are Altera HSMC cards with that feature (Terasic), and some of the Altera DSP kits have 100MHz ADCs.

Are you planning on buying a commercial demodulator? Building a demodulator that takes 3GHz down to DC is a non-trivial task. You will likely need different types of analog front-ends, and switch between them, eg. op-amp based designs from DC to ~100MHz, and RF amplifiers above that.

Of course, you could sample the signal directly, but you would need an ADC with an analog input bandwidth of over 3GHz. National Semiconductor and e2v have GHz clock rate parts, eg.

http://www.e2v.com/products-and-services/hi-rel-semiconductor-solutions/broadband-data-converters/datasheets/

You might be able to find a manufacturer with one of these ADCs on an Altera board, eg. Bittware

http://www.bittware.com/products/hardware/prod_desc.cfm?prodshrtname=3fad-s43x

Depends whether you're looking to build or buy really.

Cheers,

Dave