## Forums Search for: Modulation

## Modulation Diversity

inHi list, I understand the meaning of spatial diversity and frequency diversity. I'm in search of a proper definition for "Modulation...

Hi list, I understand the meaning of spatial diversity and frequency diversity. I'm in search of a proper definition for "Modulation Diversity". I know that such a thing exists (Google told me), but I'm not able to find the definition or at least understand from some of the papers which mention this term. Any directions? Best Regards, Nagaraj

## why fourier transform in AM and FM why not LT

inHello friends, I am little confused that why do we always apply fourier transform for amplitude modulation, frequency modulation why not laplace...

Hello friends, I am little confused that why do we always apply fourier transform for amplitude modulation, frequency modulation why not laplace transform. Second question is that when I studied control system then everywhere Laplace Transform is used. So please tell me why we use LT in controls and why FT in communication.

## Software modulation timing issue

inHello, I am developing a software modulator and am currently working on the qpsk portion of it. This problem will apply to pretty much...

Hello, I am developing a software modulator and am currently working on the qpsk portion of it. This problem will apply to pretty much all modulation schemes however. Let me first explain my algorithm: This program needs to be very fast (capable 100 mhz sampling rates) so I am pregenerating all of my samples. The user inputs the center frequency and the sampling rate and I fill a seri...

## Tin can modulation, OFDM, PAPR

inAs was kindly suggested to me, I've been experimenting with OFDM for my TCP/IP over tin cans project. Since the modulation on the "wire" is...

As was kindly suggested to me, I've been experimenting with OFDM for my TCP/IP over tin cans project. Since the modulation on the "wire" is at baseband, and I'm using a sound card as a DAC, this means my signals are audible. When modulating a random bitstream, the resulting audio is full of popping noises. I have taken steps to ensure that no clipping is occurring, so these pops are really...

## urgent: modulation normalisation factor

Hi friends, I have a big question in my head. The solution of this problem is very important for me as my supervisor waiting for my response....

Hi friends, I have a big question in my head. The solution of this problem is very important for me as my supervisor waiting for my response. Please help me!!! Here is my question. I read in HIPERLAN/2 physical layer ETSI/BRAN in part: signal constellation and mapping. They mention about this sentence: The normalization factor KMOD depends on the modulation. The purpose of the normal...

## Modulation methods

inSirs, Let me first say that probably this is a very basic question. In case of modulating carrier signals with data and doing de-modulation...

Sirs, Let me first say that probably this is a very basic question. In case of modulating carrier signals with data and doing de-modulation at the receiver, what would be the disadvantage if data is simply added to the carrier frequency and then performing filtering at the receiver to remove the carrier signal and recover the data. Thanks, manish

## Other Modulation Problem

inA baseband signal m(t) that has a Gaussian (amplitude) distribution frequency modulates a transmitter. Assume that the modulation has...

A baseband signal m(t) that has a Gaussian (amplitude) distribution frequency modulates a transmitter. Assume that the modulation has a zero-mean value and a peak value of Vp = 4*(sigma). The FM signal is transmitted over an additive white Gaussian noise channel. Let Beta = 3 and B = 15KHz. Find (S/N)out/(S/N)baseband when: A. No deemphasis is used. B. 75-u sec deemphasis is used. Again...

## Speech signals modulation entropy

Hi, I got a question regarding to modulation entropy of audio signal. There is some literature I found about this...

Hi, I got a question regarding to modulation entropy of audio signal. There is some literature I found about this topic, http://www.irit.fr/recherches/SAMOVA/FeaturesExtraction.html#me. I've already read sample .wav file. But now, how do I calculate entropy of this sampled signal with the lenght of N samples? How should I understand, in this case (in paper equation from above), propability of...

## IQ modulator &upconvertor(AD9857)

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...

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 form of analog signals . I would like some help on simulation of the quad modlr block with MATLAB code...

## Decoding FSK

inA Bell 202T modem uses FSK modulation (1200HZ, 2200HZ) and send data at up to 1800 bits per second. I need to replace an "analog" version of...

A Bell 202T modem uses FSK modulation (1200HZ, 2200HZ) and send data at up to 1800 bits per second. I need to replace an "analog" version of this with a digital version, sampling the phone line with an A/D and "decoding" the 1's and 0's in firmware (ARM C). My question is how.. The modulation index is too narrow to count zero crossings, so I believe I need a "phase coherent decoder"...

## Equalizers for FSK systems

inHi All, I'm looking at FSK modulation in practical multi-path channels. What type of equalizers are suitable for FSK ? What type of equalizers...

Hi All, I'm looking at FSK modulation in practical multi-path channels. What type of equalizers are suitable for FSK ? What type of equalizers are appropriate for other non-coherent modulation schemes ? Highly appreciate if you could provide any relevant paper or a book. Thanks in advance. Dan _____________________________ Posted through www.DSPRelated.com

## OFDM-coherent

What is coherent OFDM? Does this refer to the type of modulation I use(coherent modulation - QPSk, BPSK)?

What is coherent OFDM? Does this refer to the type of modulation I use(coherent modulation - QPSk, BPSK)?

## Recovery of IQ modulation frequency (DVB-T)

inHello, I am a bit unsure how the demodulator recovers the original IQ modulation frequency of a DVB-T baseband signal. In the standard the...

Hello, I am a bit unsure how the demodulator recovers the original IQ modulation frequency of a DVB-T baseband signal. In the standard the frequency "fc" is (IMHO) not specified, however there could be read (ETSI EN 300 744 V1.5.1 (2004-06), Page 45) "A subsequent up-conversion process then gives the real signal s(t) centred on the frequency fc". So it should be correct to look for the "ce...

## bt and wlan modulation and pulse shaping?

inHi all, I am working on the coexistence study between BT and WLAN. Anyone knows where are the spec on modulation and pulse shaping for BT and...

Hi all, I am working on the coexistence study between BT and WLAN. Anyone knows where are the spec on modulation and pulse shaping for BT and 802.11 a, b, g WLAN? cfy30

## GMSK Question

inHi, I am trying to simulate the GSM physical layer and have a simple question regarding GMSK modulation: I am trying to implement the GMSK...

Hi, I am trying to simulate the GSM physical layer and have a simple question regarding GMSK modulation: I am trying to implement the GMSK modulator using the quadrature baseband method outlined in: http://www.emc.york.ac.uk/reports/linkpcp/appD.pdf which states : NRZ sequence -> Gaussian filter convolution -> Integration -> I/Q decomposition -> Modulation. However, i have checked severa

## PSK Modulation and demodulation

inHello, I'm studying and maintaining an existing tele-communication system. I guess it's a BPSK modulation but not quite sure. The...

Hello, I'm studying and maintaining an existing tele-communication system. I guess it's a BPSK modulation but not quite sure. The transmitted data is a Chirp(up sweeping frequency)header followed by modulated data body. On the receiver side, the incoming data is auto-correlated with a locally stored up-chirp waveform and then defive 2 parameters, one is the sign the other is a delay inf...

## modulation scheme

inHello All, The classical modulation scheme is defined as, x(n)*cos(w_0*n) 0.5*[X(w+w_0) + X(w-w_0)] - eq(1) Similarly, text books...

Hello All, The classical modulation scheme is defined as, x(n)*cos(w_0*n) 0.5*[X(w+w_0) + X(w-w_0)] - eq(1) Similarly, text books also define frequency shifting as, x(n)*exp(j*w_0*n) X(w-w_0) - eq(2) It appears to me that scheme in eq(2) is much cleaner way of modulating a signal than scheme in eq(1). Second scheme requires complex multiplication in time while first sche

## Pulse shaping and modulation.

inHi all. I am starting out on signal processing. Conceptionally I think I understand the advantages of pulse shaping and raised cosine. But I am...

Hi all. I am starting out on signal processing. Conceptionally I think I understand the advantages of pulse shaping and raised cosine. But I am not clear where this is used in practice. Is pulse shaping just used on purely digital transmission i.e. A pulse train. Or is it combined with digital to analog modulation. E.g. QPSK. Any help would be much appreciated. Thanks in advance Steve. ...

## resolving two frequencies less than an fft bin apart?

inHumans resolve 2 nearly equal musical tones by listening for the "beat" notes (given that trigonometry formulas indicate that adding 2 sinusoids...

Humans resolve 2 nearly equal musical tones by listening for the "beat" notes (given that trigonometry formulas indicate that adding 2 sinusoids is equivalent to modulating one sinusoid). So why can't one resolve two very close sinusoids by examining the envelope of the mixed waveform for some sort of modulation artifact? If the envelope fits some fraction of one full cycle of modulation, t...

## FSK modulation and clean FFT

inHi, I'm looking at FSK modulation in matlab, using my own modulator as I don't have the matlab comms toolbox. In the time domain, the...

Hi, I'm looking at FSK modulation in matlab, using my own modulator as I don't have the matlab comms toolbox. In the time domain, the signal looks fine, but in the frequency domain, it just doesn't seem to work, I get lots of other garbage in the spectrum. I'm hoping someone can see an error in my ways... First, the time axis is 10 seconds sampled at 20Hz ie: t = 0:1/20:((200/20)-(1/2...