Start with logic 0s and 1s. Convert them to pulses that look
roughly like Gaussian bell curves each going from near-zero to
maximum to near-zero in one bit time, 0s going negative, 1s
going positive. Use said negative-and-positive-going pulses to
frequency-modulate a carrier.
What is th...
PCM stands for pulse code modulation. Can there be PCM without
modulation? Is it still PCM if the modulation carries more than one bit
per symbol? Radium is confused (or a clever troll), but his ravings
raise an interesting question.
Engineering is the art of making what you wan...
Considering DVBT modulation (which is also an OFDM signal), the
effect of groupdelay variation over the carriers used by the modulation
will result in varying rotations for each of the points in the QAM
=> without equalizer , the MER (modulation - error rati...
On Thu, 11 Dec 2008 09:26:41 -0600, Vladimir Vassilevsky
> Dennis wrote:
> > Does anyone know of a good page that describes that Pulse Position
> > Modulation PPM is? I am a newbie to modulation.
> Here is what commonly referred as the pulse position modulation:
> 1 i...
So you have a signal that has some form of modulation on it? Or do
you have multiple signals that you need to deinterleave? There are
lots of available algorithms for detecting modulation types etc, check
out your local IEEE Xplorer, heck even google should produce some. I
am not sure what y...
Shouldn't amplitude modulation really be called "Magnitude
After all, in FM, the amplitude is still being modulated, but
the magnitude is constant.
Or maybe I have too much time on my hands.
I have the following question:
1) For each modulation scheme, there is a corresponding bandwidth
efficiency (let's call it n). n = R/B where R is the data rate and B is
the bandwidth. My question is can I simple say R = n*B no matter how big B
is. i.e. can I reach higher data rate by...
i want to take FM modulation to a signal which is changing in its
amplitude and frequency. Give me a idea how to start.
This message was sent using the Comp.DSP web interface on
On 11 Sep, 13:37, arun wrote:
> =A0 =A0I am new to this group. I have very basic doubt about
> digital modulation.
> We modulate the carrier frequency based on the digital input values...
> So is the output of modulator block a digital signal with samples
> representing the ...
Randy Yates wrote:
> I'm guessing so. In almost 30 years, I've never heard of a
> PCM-demodulator, but I am getting old and senile. Where did you come
> across this term?
Well, the M is for modulation, but I agree using the term
"demodulator" in that case is unusual.
In the pa...
This sounds like modulation to me. Have you looked into calculation of the
modulation index? If the "wavyness" is modulation, then the proper way to
measure the "wavyness" is to pass the signal through a detector appropriate to
the type of modulation and measure the statistics of the output ...
Can anybody tell the key motivation of the inventor (who is the
genius behind it?) to use digital modulation instead of its analog
counterpart and how did it happen historically and experimentally?
What kind of modulation scheme that will suit high speed transmission
(at least to 1 Gbps)?
And obvious choice will be those highly spectral efficient modulation
scheme like OFDM. However, if the linearity requirement and the
sensitivity to phase noise are very high, then OFDM coul...
Is Quadrature Frequency Modulation used? What for?
AFAIK, Quadrature Amplitude Modulation uses a combo of AM and
So QFM would use a combination of FM and PSK. Would this decrease the
bandwidth required for broadcasting FM luminance video signals?
I did a Googl...
We have two digital modulations, both are the same, the only different is
the symbol rate.
Usually low symbol rate modulation have less BER than high symbol rate
modulation. But my question is if in the case of a bad carrier stability,
high symbol rate modulation could have less BER than low s...
I have a question about the bit rates offered by lasers and diode
A laser source and a diode source of the same central frequency are quite
different types of sources. The laser is more collimated, higher power
density, much smaller linewidth (bandwidth) which conveys...
I have a doubt regarding 1 other project. I have to get the modulation
transfer function of an image (and the same image defocused). The
defocus is either induced by constructing a bessel filter (similar to
airy functions, defocus created by unfocused thin lens). Even though I
Using Matlab, I need to send a message through a simulated AWGN channel.
I have defined the signal pulse to be a square pulse with different
amplitudes depending on the bit, a0 for a 0 and a1 for a 1.
I modulate the signal by tx = tx .* cos(2*pi*fmod) where tx is
> Don't forget to compare TCM and BICM.
That's Bit-Interleaved Coded Modulation, right? You mentioned in
another thread (august 2004) that "Bit Interleaved Coded Modulation
further decouples the system from the modulation and signal processing,
and is known to always be as good or b...
> You shouldn't need to "unwrap" your phase value, as it shouldn't ever
> break out of the [-pi, pi] interval. ...
Doesn't that depend on the amount of modulation? I know of nothing
inherent in FM (PM, actually) that limits the modulation to any
My current work involves estimation of modulation index for a PM signal
with or without subcarriers. I have found articles to do the same without
subcarriers, but I am yet to find something which might work when
subcarriers are included. An important method to estimate the modulation
I am working on AD9857 which copmrises an IQ modulator and in fact is a
quadrature up convertor Using 14 bits I Q input data , I want
to try out various modulation schemes like AM, FSK,FM,BPSK,GMSK, QPSK and
QAM. I`ve tried IQ modulation in different (analogue) shchemes with MATLAB
using IQ in for...
"Green Xenon [Radium]" wrote in message
> Aliasing is a digital entity. What is the analog equivalent of aliasing?
Aliasing isn't a digital entity it's a sampling entity. That you digitize
the samples has nothing to do wi...
The spectrum of a PWM signal is complicated, because PWM is kind of like a
frequency or phase modulation.
The spectrum depends on exactly how the width of the pulse is determined
from the modulation waveform.
A width exactly proportional to the amplitude of the samples of the
Thank you for your help!
A simple question:
Does 10*log10(rate) mean the code gain of BPSK modulation?
And is there code gain of QAM modulation?
Any suggestions will be appreciated!
does anyone know why differential encoding of data is done
in GSM before modulation ?
( As I understand , this is not to enable noncoherent detection, but
is related to the connection between gmsk and msk which is an offset-PAM
I read two very nice articles about Pulse-Shaping, and they both
individually makes a lot of sense, but when I want to draw a conclusion, I
Here is the fist article:
which in depth explains why pulse shaping is used.
So, in this...
> I am currently working on a project which involves determining the
> relationship between the the "bandwidth"(as my advisor puts it) and
> power consumption of an I/Q transmitter.
This might not be related to your question, but I have always
found the term "bandwidth"...
I would like to calculate the BER of an optical communications
The only known value is the total collected intensity as a function of
time (I thus can calculate mean intensity, variance,...). The
modulation format doesn't matter. The simplest is the best; so we can
take OOK mod...
Which modulation scheme is most suitable for transmitting information
(a bitstream) over an acoustic channel? i.e. a loudspeaker outputs the
modulated signal and a cell phone microphone picks up the acoustic
signal and extracts the information from the modulated signal. I'm
looking for a modula...
I have a pretty elementary question.
For an unshaped, 2-FSK signal, the modulation index h is defined
as the ratio of the difference between the two tone frequencies
to the symbol rate.
For shaped 2-FSK, how is h usually defined? I can think
of a few possibilities:
(1) Base it on the pe...
a short time ago, I posted I was doing computed modulation.
I now have 2 nice sidelobes.
The q is this:
Where mathematically, and more to the point, where should I
account for the necessity in code of doing an DC offset to audio
array samples in order to achieve the "Carrier" in AM mod...
Hi all!! I have implemented BPSK modulation with DSK 6713.I'm writting a
program to implement BPSK modulation and demodulation on the same Kit DSK
6713, but it doesn't run. Can we implement BPSK modulation and demodulatio
on the same Kit DSP?. I wil post my source code later!
By the way! I also hav...
Just found this great forum on DSP. This is my first post and hope someone
I am searching for the knowledge on GMSK demodulation and found that some
articles say that some carrier/timing recovery algorithms (like Gardner,
Early-Late etc) are only applicable to LINEAR modula...
Please can anyone give me a pointer to a material that does an in
depth comparison of the 16QAM and 16PSK modulation in terms of
different properties and their SNR vs BER comparison. Any comment
about this modulation comparison would be helpful couldn't turn up
anything using google and even IE...