I am using a PC to aquire data, this data will be QPSK modulated. Can anyone tell me if there is anywhere I can find information on how...

I am using a PC to aquire data, this data will be QPSK modulated. Can anyone tell me if there is anywhere I can find information on how to demodulate a QPSK modulated signal in software, any language will do. I have searched the internet for this but all I can find is implementations using electronics methods. Thanks, joseph

A common way of demodulating a 2-FSK signal involves shifting the complex baseband up and down by the deviation, convolving each shifted result...

A common way of demodulating a 2-FSK signal involves shifting the complex baseband up and down by the deviation, convolving each shifted result with a rectangular filter, and differencing the magnitudes at the filter outputs. This essentially places a sinx/x response at each tone frequency, and works well considering its low complexity. Now, suppose the signal is GMSK. The deviation is one ...

Hi all, Ive come to another promblem with the project I'm doing on DSL. I can't seem to figure out if a 180 degree phase reversal (hardware...

Hi all, Ive come to another promblem with the project I'm doing on DSL. I can't seem to figure out if a 180 degree phase reversal (hardware inversion) will make the demodulation of the DMT signal impossible. As I see it there will be a problem with phaseshifts that holds the carrier waveform "positive" for more than a half period, like the QAM modulation on the picture. http://www...

Hi everyone, I have a question. Assuming we have a band-limited signal from 10-20 MHz with a sampling frequency of 100 MHz. Let's say I want...

Hi everyone, I have a question. Assuming we have a band-limited signal from 10-20 MHz with a sampling frequency of 100 MHz. Let's say I want to obtain the envelope of this signal. One method would be to use a Hilbert filter, to obtain the quadrature signal and then do the whole envelope = sqrt(I^2 + Q^2). However, let's assume that I need to use the absolute value instead. What would happe...

Hello. As stated in the subject line, I am very interested in obtaining a copy of Mr. Shima's Master's Thesis, "FM Demodulation Using A...

Hello. As stated in the subject line, I am very interested in obtaining a copy of Mr. Shima's Master's Thesis, "FM Demodulation Using A Digital Radio and Digital Signal Processing", which i have seen mentioned in the past. I have done a search for it and follow all links i have found, but they all seem to be dead. Could someone point me to a working link where i can get it? Or if som...

Hi, I've designed a FM demodulator with (IdQ-QdI)/(I=B2+Q=B2). My FM modulator is center on 70 MHz with 250 kHz deviation. The demodultor...

Hi, I've designed a FM demodulator with (IdQ-QdI)/(I=B2+Q=B2). My FM modulator is center on 70 MHz with 250 kHz deviation. The demodultor works fine from 10 kHz to 250 kHz (message)... but under 10 kHz I lost a lot of amplitude in my IdQ-QdI signal... Is it because i made the derivative by x[n]-x[n-1] ? Is it working better with a FIR filter with 3 taps (-1,+1,0) ? If yes what are...

Hello, 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...

I am working on a project to demodulate SSB signals using software defined radio on a blackfin DSP. We are required to design and build a...

I am working on a project to demodulate SSB signals using software defined radio on a blackfin DSP. We are required to design and build a lower sideband SSB communications-quality speech receiver which will tune the band 7.040MHz?7.100MHz. We are using a softrock 40 board which multiplies the signals by a sin and cosine wave at 7.055MHz to generate the I and Q branches. I was just wondering if any...

I am trying to find the mathmatical magnitude response of the following FM demodulation...

I am trying to find the mathmatical magnitude response of the following FM demodulation equation: I[n-1]*(Q[n]-Q[n-2])-Q[n-1]*(I[n]-I[n-2]) ----------------------------------------- I[n-1]^2+Q[n-1]^2 How do I represent I and Q in terms of some x[n] to find the z transform of the equation? I know I[n]=x[n]*cos(phi) and Q[n]=x[n]*-sin(phi). But phi is also a function of 'n'. No...

In wideband systems such as CDMA (DSSS) and IR-UWB, the analog signal at the receiver is very wide even though the datarate may be...

In wideband systems such as CDMA (DSSS) and IR-UWB, the analog signal at the receiver is very wide even though the datarate may be relatively small. Therefore in order for demodulation and detection to be performed in the digital domain, very fast ADCs and front-end DSP must be utilized. In some modern IR-UWB systems, this may not be feasible due to the extreme bandwidth (> 1 GHz) of the signa

Hello all, Please, I wanna know more about maximal ratio combining post DFT techniques. I'm studing this receving method, also i found a...

Hello all, Please, I wanna know more about maximal ratio combining post DFT techniques. I'm studing this receving method, also i found a chipset improving this technique: http://www.teamcast.com/en/maj-e/c2a2i15040/products/dibcom-products/dvb-t-diversity-demodulatio n-chipset.htm but i do not understand the theory. The combining is frequency domain ? Someone can help me ? Best regar

Hi, If I have a 16-QAM demodulator I know I can use the I and Q values to access a lookup table and output soft codes for a Viterbi uisng...

Hi, If I have a 16-QAM demodulator I know I can use the I and Q values to access a lookup table and output soft codes for a Viterbi uisng LLR What do I do if I'm using 16-PAM? If my information is right its just amplitude modulation. So out of the demodulator I will get 1 of 16 values. How do I then create the soft codes indicating how strong, or weak the '1's and '0's are? Thanks Mike ...

I could use some help, since I am very new to DSP. Here is my situation: I am recieving I/Q data at 250kHz rate, demodulating it with...

I could use some help, since I am very new to DSP. Here is my situation: I am recieving I/Q data at 250kHz rate, demodulating it with demodulation algorithm: IdQ+QdI/I^2+Q^2. Then storing 800 samples and using the Goertzel algorithm to detect 4 different tones. Currently the DSP cannot calculate all of this and I am getting data overrun, I have a flag which tells me that the Goertzel is not...

I was wondering how to do carrier synchronization for CPFSK signals? I want to decode the CPFSK signal by computing the phase difference....

I was wondering how to do carrier synchronization for CPFSK signals? I want to decode the CPFSK signal by computing the phase difference. The shape of the phase difference is similar to the following plot |---| |---| fc+fd/2 - - -|- -| - | - | - - - fc ---| |---| |--- fc-fd/2 where fc is the carrier, fd is the peak frequency deviation. Before send this demodul...

I was wondering how to do carrier synchronization for CPFSK signals? I want to decode the CPFSK signal by computing the phase difference....

I was wondering how to do carrier synchronization for CPFSK signals? I want to decode the CPFSK signal by computing the phase difference. The shape of the phase difference is similar to the following plot |---| |---| fc+fd/2 - - -|- -| - | - | - - - fc ---| |---| |--- fc-fd/2 where fc is the carrier, fd is the peak frequency deviation. Before send this demodul...

Hi all, I am new to demodulation and FEC. How can I get each bit's soft-probability from the constellation? For example, the modulation...

Hi all, I am new to demodulation and FEC. How can I get each bit's soft-probability from the constellation? For example, the modulation method is 16QAM, How can I get P(bit1=0),P(bit2=0),P(bit3=0),P(bit4=0) from a symbol? Is it belong to the subject of detection and need viterbi algorithm? Or can you recommend some key words of this subject? Best regards, Davy

I want to make a digital FM demodulation and already found the block diagram but i really confused about Direct Phase Digitizer. The explanation...

I want to make a digital FM demodulation and already found the block diagram but i really confused about Direct Phase Digitizer. The explanation say that it's a phase detector by using zero-crossing method. Can some tell me the theory please coz i don't know about zero-crossing. Thx before! I put the explanation from my source in case u need it: DPD circuit uses a high-frequency reference cloc...

Sirs, Some questions related to decoding process. 1. When the data enters the first time for decoding, where does the a priori probability...

Sirs, Some questions related to decoding process. 1. When the data enters the first time for decoding, where does the a priori probability come from? Is it based on initial accessment after demodulation? 2. If block codes are used during transmission, how does the receiver know the size of the block code since the size of the block can vary on the fly. If this is based on fields i...

Hi I have written Matlab script for BPSK modulation. The way my code works is as follow: series of 0 and 1----> NRZ data (continuous...

Hi I have written Matlab script for BPSK modulation. The way my code works is as follow: series of 0 and 1----> NRZ data (continuous rectangular pulses with amplitude -1 and 1)---> multiply by carrier----> add noise--> multiply by carrier---> integration---> detection---> Bit Error collection? I would like to know can anyone tell me where I should apply DAC and ADC ? I am wondering shoul

Hi There, How does the demodulator of a non-coherent M-FSK system correctly time the "reading" of the symbols? In the book on Digital Comms...

Hi There, How does the demodulator of a non-coherent M-FSK system correctly time the "reading" of the symbols? In the book on Digital Comms by Proakis, it is mentioned that a bank of 2M correlators can be used. In the book there is also a model for non-coherent M-FSK in an AWGN environment. I have used the model to create a matrix of metrics and done the decoding/demodulation from there....