Adaptive Filter | ADPCM | ADSP | ADSP-2181 | Aliasing | AMR | Anti-Aliasing | ARMA | Autocorrelation | AutoCovariance | Beamforming | Bessel | Blackfin | Butterworth | C6713 | CCS | Chebyshev | CIC Filter | Circular Convolution | Code Composer Studio | Comb Filter | Compression | Convolution | Cross Correlation | DCT | Decimation | Deconvolution | Demodulation | DM642 | DSP Boards | DSP/BIOS | DTMF | Echo Cancellation | Equalization | Equalizer | ETSI | EZLITE (Ez-kit Lite) | FFT | FFTW | FIR Filter | Fixed Point | FSK | G.711 | G.723 | G.729 | Gaussian Noise | Goertzel | GPIO | Hilbert Transform | IFFT | IIR Filter | Interpolation | Invariance | JTAG | Kalman | Laplace Transform | Levinson | LPC | McBSP | MIPS | Modulation | MPEG | Multirate | Notch Filter | Nyquist | OFDM | Oversampling | Pink Noise | Pitch | PLL | Polyphase | QAM | QDMA | Quantization | Quantizer | Radar | Random Noise | Reed Solomon | Remez | Resampling | RTDX | Sampling | Sharc | TI C6711 | Undersampling | Viterbi | Wavelets | White Noise | Wiener Filter | Windowing | XDS510PP | Z Transform

I am working on a tutorial about IQ modulation and demodulation.  I
have been thinking about this topic for a long time and have begun
putting together some stuff.  Here is an interactive page (exclusively
for comp.dsp to look at :-)

This shows the difference between an FFT that is stuffed with real
data and an FFT that is stuffed with complex data.  This has been real
eye opening for me to see that the Nyquist sampling rate is blown away
with complex data :-)



http://www.fourier-series.com/fun/IQdemod.html

______________________________
New DSP Code Snippets Section now Live.   Learn more about the reward program for contributors here.

On Apr 29, 10:24=A0am, brent <buleg...@columbus.rr.com> wrote:
> I am working on a tutorial about IQ modulation and demodulation. =A0I
> have been thinking about this topic for a long time and have begun
> putting together some stuff. =A0Here is an interactive page (exclusively
> for comp.dsp to look at :-)
>
> This shows the difference between an FFT that is stuffed with real
> data and an FFT that is stuffed with complex data. =A0This has been real
> eye opening for me to see that the Nyquist sampling rate is blown away
> with complex data :-)
>
> http://www.fourier-series.com/fun/IQdemod.html

BTW, this is preliminary stuff with no audio.  It will be incorporated
into larger tutorial later.

______________________________
New DSP Code Snippets Section now Live.   Learn more about the reward program for contributors here.

On Apr 29, 10:24=A0am, brent <buleg...@columbus.rr.com> wrote:
> I am working on a tutorial about IQ modulation and demodulation. =A0I
> have been thinking about this topic for a long time and have begun
> putting together some stuff. =A0Here is an interactive page (exclusively
> for comp.dsp to look at :-)
>
> This shows the difference between an FFT that is stuffed with real
> data and an FFT that is stuffed with complex data. =A0This has been real
> eye opening for me to see that the Nyquist sampling rate is blown away
> with complex data :-)
>
> http://www.fourier-series.com/fun/IQdemod.html

The sampling requirement is unchanged. You need something more than
two samples per cycle of the highest frequency being sampled. It
doesn't matter if those samples are sequential, in-phase and
quadrature, function and derivative, or just about any other
mathematically related pair.

Jerry
--
Engineering is the art of making what you want from things you can get.

______________________________
New DSP Code Snippets Section now Live.   Learn more about the reward program for contributors here.

On Apr 29, 10:31=A0am, Jerry Avins <j...@ieee.org> wrote:
> On Apr 29, 10:24=A0am, brent <buleg...@columbus.rr.com> wrote:
>
> > I am working on a tutorial about IQ modulation and demodulation. =A0I
> > have been thinking about this topic for a long time and have begun
> > putting together some stuff. =A0Here is an interactive page (exclusivel=
y
> > for comp.dsp to look at :-)
>
> > This shows the difference between an FFT that is stuffed with real
> > data and an FFT that is stuffed with complex data. =A0This has been rea=
l
> > eye opening for me to see that the Nyquist sampling rate is blown away
> > with complex data :-)
>
> >http://www.fourier-series.com/fun/IQdemod.html
>
> The sampling requirement is unchanged. You need something more than
> two samples per cycle of the highest frequency being sampled. It
> doesn't matter if those samples are sequential, in-phase and
> quadrature, function and derivative, or just about any other
> mathematically related pair.
>
> Jerry
> --
> Engineering is the art of making what you want from things you can get.

Depends how you look at it.  Sampling rate is the same, but complex
samples are applied to the FFT

______________________________
New DSP Code Snippets Section now Live.   Learn more about the reward program for contributors here.

On Apr 29, 8:43=A0am, brent <buleg...@columbus.rr.com> wrote:
> On Apr 29, 10:31=A0am, Jerry Avins <j...@ieee.org> wrote:
>
>
>
> > On Apr 29, 10:24=A0am, brent <buleg...@columbus.rr.com> wrote:
>
> > > I am working on a tutorial about IQ modulation and demodulation. =A0I
> > > have been thinking about this topic for a long time and have begun
> > > putting together some stuff. =A0Here is an interactive page (exclusiv=
ely
> > > for comp.dsp to look at :-)
>
> > > This shows the difference between an FFT that is stuffed with real
> > > data and an FFT that is stuffed with complex data. =A0This has been r=
eal
> > > eye opening for me to see that the Nyquist sampling rate is blown awa=
y
> > > with complex data :-)
>
> > >http://www.fourier-series.com/fun/IQdemod.html
>
> > The sampling requirement is unchanged. You need something more than
> > two samples per cycle of the highest frequency being sampled. It
> > doesn't matter if those samples are sequential, in-phase and
> > quadrature, function and derivative, or just about any other
> > mathematically related pair.
>
> > Jerry
> > --
> > Engineering is the art of making what you want from things you can get.
>
> Depends how you look at it. =A0Sampling rate is the same, but complex
> samples are applied to the FFT

Sampling times are the same but two samples per time doubles the
rate.

Nyquist hasn't changed, you've just applied it to a two channel
system.

Dale B. Dalrymple

______________________________
New DSP Code Snippets Section now Live.   Learn more about the reward program for contributors here.

On 04/29/2011 08:43 AM, brent wrote:
> On Apr 29, 10:31 am, Jerry Avins<j...@ieee.org>  wrote:
>> On Apr 29, 10:24 am, brent<buleg...@columbus.rr.com>  wrote:
>>
>>> I am working on a tutorial about IQ modulation and demodulation.  I
>>> have been thinking about this topic for a long time and have begun
>>> putting together some stuff.  Here is an interactive page (exclusively
>>> for comp.dsp to look at :-)
>>
>>> This shows the difference between an FFT that is stuffed with real
>>> data and an FFT that is stuffed with complex data.  This has been real
>>> eye opening for me to see that the Nyquist sampling rate is blown away
>>> with complex data :-)
>>
>>> http://www.fourier-series.com/fun/IQdemod.html
>>
>> The sampling requirement is unchanged. You need something more than
>> two samples per cycle of the highest frequency being sampled. It
>> doesn't matter if those samples are sequential, in-phase and
>> quadrature, function and derivative, or just about any other
>> mathematically related pair.
>>
>> Jerry
>> --
>> Engineering is the art of making what you want from things you can get.
>
> Depends how you look at it.  Sampling rate is the same, but complex
> samples are applied to the FFT

Yes, it does depend on how you look at it -- but if you don't look at it 
the way the math demands, you'll get it wrong.

A complex number gives you twice as much information as a real number, 
so it counts as two samples.  Sampling the signal and it's derivative, 
ditto.  It's very simple, if you just hold your mouth right.

-- 

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

______________________________
New DSP Code Snippets Section now Live.   Learn more about the reward program for contributors here.

On Apr 29, 8:43 am, brent <buleg...@columbus.rr.com> wrote:
> On Apr 29, 10:31 am, Jerry Avins <j...@ieee.org> wrote:
>
>
>
> > On Apr 29, 10:24 am, brent <buleg...@columbus.rr.com> wrote:
>
> > > I am working on a tutorial about IQ modulation and demodulation.  I
> > > have been thinking about this topic for a long time and have begun
> > > putting together some stuff.  Here is an interactive page (exclusively
> > > for comp.dsp to look at :-)
>
> > > This shows the difference between an FFT that is stuffed with real
> > > data and an FFT that is stuffed with complex data.  This has been real
> > > eye opening for me to see that the Nyquist sampling rate is blown away
> > > with complex data :-)
>
> > >http://www.fourier-series.com/fun/IQdemod.html
>
> > The sampling requirement is unchanged. You need something more than
> > two samples per cycle of the highest frequency being sampled. It
> > doesn't matter if those samples are sequential, in-phase and
> > quadrature, function and derivative, or just about any other
> > mathematically related pair.
>
> > Jerry
> > --
> > Engineering is the art of making what you want from things you can get.
>
> Depends how you look at it.  Sampling rate is the same, but complex
> samples are applied to the FFT

the most general form of the sampling theorem is this, for a
bandlimited signal of B hz, over a length T seconds , you need 2BT
independent pieces of information to completely reconstruct the signal

______________________________
New DSP Code Snippets Section now Live.   Learn more about the reward program for contributors here.

steve <b...@yahoo.com> wrote:

(snip, someone wrote)
>> Depends how you look at it.  Sampling rate is the same, but complex
>> samples are applied to the FFT
 
> the most general form of the sampling theorem is this, for a
> bandlimited signal of B hz, over a length T seconds , you need 2BT
> independent pieces of information to completely reconstruct the signal

You have to be pretty careful when defining the sampling theorem
over a finite interval.  That is usually ignored, and for a sufficiently
long interval, usually close enough.

Otherwise, you need N >= 2BT in the limit as N and T go to infinity.

-- glen

______________________________
New DSP Code Snippets Section now Live.   Learn more about the reward program for contributors here.

On Apr 29, 11:43=A0am, brent <buleg...@columbus.rr.com> wrote:
> On Apr 29, 10:31=A0am, Jerry Avins <j...@ieee.org> wrote:

  ...

> Depends how you look at it. =A0Sampling rate is the same, but complex
> samples are applied to the FFT

How many sample-and-holds are needed to get a complex sample?

Jerry
--
Engineering is the art of making what you want from things you can get.

______________________________
New DSP Code Snippets Section now Live.   Learn more about the reward program for contributors here.

On Apr 29, 11:57 am, glen herrmannsfeldt <g...@ugcs.caltech.edu>
wrote:
> steve <bungalow_st...@yahoo.com> wrote:
>
> (snip, someone wrote)
>
> >> Depends how you look at it.  Sampling rate is the same, but complex
> >> samples are applied to the FFT
> > the most general form of the sampling theorem is this, for a
> > bandlimited signal of B hz, over a length T seconds , you need 2BT
> > independent pieces of information to completely reconstruct the signal
>
> You have to be pretty careful when defining the sampling theorem
> over a finite interval.  That is usually ignored, and for a sufficiently
> long interval, usually close enough.
>
> Otherwise, you need N >= 2BT in the limit as N and T go to infinity.
>
> -- glen

don't understand what you are getting at, it is >2BT for any size T,
large or small

practically speaking your correct because for real analog signals B is
always infinite

______________________________
New DSP Code Snippets Section now Live.   Learn more about the reward program for contributors here.