OFDM Question

Started by Bob the Builder in comp.dsp13 years ago 4 replies

I was wondering about demodulation. We woudl need phase coherence of both the main carrier and the sub-carriers. I assume the main carrier can...

I was wondering about demodulation. We woudl need phase coherence of both the main carrier and the sub-carriers. I assume the main carrier can be locked onto with a PLL but what about the sub-carriers? Do they use a pilot sequency of some sort when multiply up to get the other frequencies? Thanks Tom


What kind of filter is this?

Started by Zerofall in comp.dsp15 years ago 7 replies

Hi, This is my first post to comp.dsp. I found the filter below but I haven't been able to identify the type of filter it is (so I can...

Hi, This is my first post to comp.dsp. I found the filter below but I haven't been able to identify the type of filter it is (so I can understand and modify its parameters, properties, look for the theory, etc). It is used to separate U and V color components of chroma prior to demodulation by rotation according to the phase of the carrier. Using a sine as input, the output of y is 23 ...


Need of Eqaulization ?

Started by mite_learner in comp.dsp5 years ago 31 replies

Dear Members, I am experimenting on digital 4-FSK (orthogonal) communication system. On the demodulation side, I am using AGC and then 4...

Dear Members, I am experimenting on digital 4-FSK (orthogonal) communication system. On the demodulation side, I am using AGC and then 4 filters to detect tones and then using symbol timing. My question is how can I know that I need equalization looking at the signal if I transmit and receive the signal over the air? How can I verify that my signal is being affected by multipaths ? ...


Re: OT: Tubes (was PM demodulation)

Started by Jerry Avins in comp.dsp14 years ago

Randy Yates wrote: > Steve Underwood writes: > > > [...] > > What's this about old tube technology? What do big FM transmitters use >...

Randy Yates wrote: > Steve Underwood writes: > > > [...] > > What's this about old tube technology? What do big FM transmitters use > > today? Only the exciter has changed since the time Jerry was talking > > about. > > > Do you doubt that a freshly-graduated BSEE of the day would > most likely know little-to-nothing about tubes? When I was > going to DeVry in 1976, I was


Digital FM demodulation

Started by benpeterson in comp.dsp11 years ago 1 reply

Hi all, I have a question, I have a wav.file, which is a FM modulated signal. It has 3 channels. I want to demodulate them, in Signal...

Hi all, I have a question, I have a wav.file, which is a FM modulated signal. It has 3 channels. I want to demodulate them, in Signal Processing Toolbox of Matlab. (but just the first and second channel (not the third one)) I used "demod" function, but it functions very bad and the problem is that, i need to demodulate both channels at the same time (mixed), in order to have both of the...


OFDM-coherent

Started by Zeph80 in comp.dsp13 years ago

Im a little confused about how you employ coherent demod in OFDM. After the FFT at the receiver, how do I perform a coherent demodulation-dont I...

Im a little confused about how you employ coherent demod in OFDM. After the FFT at the receiver, how do I perform a coherent demodulation-dont I need a carrier for phase estimation in case of BPSK, QPSK etc. Also this is what coherent OFDM is, right?


Data stream demodulation -- Tutorial and Books

Started by Tim Wescott in comp.dsp5 years ago 15 replies

I'm working with a customer to design a system. The preferred development model seems to have settled into one where I do all the heavy...

I'm working with a customer to design a system. The preferred development model seems to have settled into one where I do all the heavy lifting mathematically, and they implement the algorithms that I cook up. Their software guy is willing, but we both think he'd benefit from a tutorial or three, and perhaps a book on basic data communications. Does anyone have any recommendations? A...


Phase modulation and badnwidth

Started by Anonymous in comp.dsp3 years ago 6 replies

Hi everyone, say that we have a signal of this kind x(t) = A*cos(2*pi*f*t + B*y(t)); say that f is 1 kHz. If y(t) has a low frequency...

Hi everyone, say that we have a signal of this kind x(t) = A*cos(2*pi*f*t + B*y(t)); say that f is 1 kHz. If y(t) has a low frequency content compared to the carrier frequency, I find that it easy to extract the B*y(t) signal either using quadrature demodulation or the Hilbert transform. However, in the case where y(t) has a high bandwidth, for example a wideband signal with frequen...


PM demodulation

Started by kl31n in comp.dsp13 years ago 3 replies

For my final project at university I'm working on a special measurement hardware. I've a tone at a certain frequency. I want to analyze the...

For my final project at university I'm working on a special measurement hardware. I've a tone at a certain frequency. I want to analyze the phase noise which is present in a bandwidth of 1 MHz around the tone. For doing that, stated that I'm using an FPGA with an ADC and given that the frequency of the tone is known, I demodulate the tone, getting I and Q and then I take the atan of thei...


fsk demodulation

Started by harsh17 in comp.dsp14 years ago 7 replies

I am a novice in DSP.I am trying to demodulate a FSK signal wherein the mark and space frequencies are 16MHz and 24MHz respectively.I am...

I am a novice in DSP.I am trying to demodulate a FSK signal wherein the mark and space frequencies are 16MHz and 24MHz respectively.I am thinking of using delay and multiply method.Can this be implemented using an ADSP-2181?More specifically will the DSP be able to handle the high throughput involved?Please correct me if I am conceptually going wrong somewhere. This message was sent using the...


FM Demodulation Woes

Started by Paul Solomon in comp.dsp13 years ago 9 replies

Hi All, I have been working for some time now on making a multichannel FM demod / remod, and I have finally gotten my hands on some test...

Hi All, I have been working for some time now on making a multichannel FM demod / remod, and I have finally gotten my hands on some test equipment to put this design through its paces and have found that I have a strange problem. To start with I will outline the design that I am using.. I undersample the FM signal at 80MSPS using a 12bit ADC, this signal is then mixed down to baseba...


AM demodulation using DSP

Started by c1910 in comp.dsp12 years ago 41 replies

hi! i want to demodulate AM signal digitally... i want to use a digital filter to separate the carrier and the information signal. i've searched...

hi! i want to demodulate AM signal digitally... i want to use a digital filter to separate the carrier and the information signal. i've searched a lot...and i haven't found the answer. can anyone help?please... thx... -chris(c1910)- _____________________________________ Do you know a company who employs DSP engineers? Is it already listed at http://dsprelated.com/employers.php ?


FSK Demodulator

Started by biff in comp.dsp11 years ago 14 replies

Hi folks, I manage a hardware engineering group for a telcom company and I am beginning to look around for FPGA IP to implement both FSK...

Hi folks, I manage a hardware engineering group for a telcom company and I am beginning to look around for FPGA IP to implement both FSK modulation and demodulation. I am wondering if any of you have any experience with any of the IP around today. The demodulator is the most difficult part and I believe the following list of requirements is fairly close: * 300 KHz bandwidth * 5-21 MHz ...


Demodulation possible using PC !

Started by Nitin in comp.dsp13 years ago 10 replies

Hi Guys, I am doing a project on Software Defined Radio receiver.. I have generated a AM signal which is coming from a microphone and it goes...

Hi Guys, I am doing a project on Software Defined Radio receiver.. I have generated a AM signal which is coming from a microphone and it goes to a signal mixer. I have a local oscillator and the two signals are mixed (Superhet). The output from the mixer forms the IF(Intermediate Frequency).Now what I have to do is to demodulate the signal and feed it to the speaker using a AF Amplifier. So...


baseband tasks - newby question

Started by mike turner in comp.dsp14 years ago 1 reply

In a baseband processor, 802.11b 1Mb/s (bpsk) for example, what are the tasks done? For receive, I am guessing a) demodulation b)...

In a baseband processor, 802.11b 1Mb/s (bpsk) for example, what are the tasks done? For receive, I am guessing a) demodulation b) sync Is there source code somewhere for an audio bpsk modem somewhere to inspect? Something that might be compiled for a blackfin and used to play on a test bench... TIA.


IQ Demod Questions

Started by EfiimoFunk in comp.dsp14 years ago 17 replies

Hey guys, I have a few questions regarding digital I/Q demodulation that I can't seem to figure out on my own. I notice that if you sample at...

Hey guys, I have a few questions regarding digital I/Q demodulation that I can't seem to figure out on my own. I notice that if you sample at 4 times the carrier frequency you can essectially get the I/Q channels for free. This is due to the fact that the samples are 0,90,180,270 etc. (Note: of course this is only for the carrier frequency and other frequencies will not have the correct phase...


ADSL Demodulation

Started by DougB in comp.dsp7 years ago 8 replies

Hello, In every book and article aobut ADSL processing the A/D and D/A sample rates are given as 2.208 MHz. For a transmitter implementation...

Hello, In every book and article aobut ADSL processing the A/D and D/A sample rates are given as 2.208 MHz. For a transmitter implementation at this sample rate you would get the conjugate symmetric image spewing out of your D/A since one may use up to bin 255 and there is absolutely no oversampling, and no analog filter in the world can cut-off that fast. Likewise for the receiver, any si...


Coherent MFSK

Started by Vladimir Vassilevsky in comp.dsp6 years ago 11 replies

There are communication systems with orthogonal multitone physical layer. That is, one of N frequencies in the set is sent at a time. An example...

There are communication systems with orthogonal multitone physical layer. That is, one of N frequencies in the set is sent at a time. An example of such system is "Olivia": http://en.wikipedia.org/wiki/Olivia_MFSK . In the systems like that, they usually demodulate signal by incoherent detector. The loss due to incoherent demodulation is 1dB ballpark. There are, of course, technical reaso...


general fsk question

Started by frumious in comp.dsp10 years ago 3 replies

I am trying to understand fsk demodulation in general. Is there an industry standard set of specific demod schemes or just classes of particular...

I am trying to understand fsk demodulation in general. Is there an industry standard set of specific demod schemes or just classes of particular methods (i.e. matched filter, correlation, coherent vs non-coherent) that are invoked on a project by project basis?


Digital FM demodulation

Started by Anonymous in comp.dsp12 years ago 12 replies

Hi everybody, I demodulate a FM signal with this : IdQ - QdI But in a paper I see that after this, we have to add an Integrate and Dump !!...

Hi everybody, I demodulate a FM signal with this : IdQ - QdI But in a paper I see that after this, we have to add an Integrate and Dump !! But for this operation, we need and integrate clock time over the symbole to demodulate.... If I don't put this Integrate and Dump block I think that in presence of noise the demodulator works bad !!! Do you have suggestions ? Thanks.