Forums Search for: Demodulation
Robust FSK demodulator ?
inDear all, We are looking for a robust FSK demodulator and framer solution for an SDR application (decoding of simultaneous narrow channels at...
Dear all, We are looking for a robust FSK demodulator and framer solution for an SDR application (decoding of simultaneous narrow channels at some kbps each from a wider baseband stream) : channel filtering, center frequency tracking, demodulation, bit-level timing recovery, synchronisation frame detection, etc. Could be either DSP or FPGA based. Any "off the shelf" industrial-level I...
Re: Beamforming and MRC basics
inI have a very basic question with regards to beam-forming or MRC. When I apply complex weigths for example while doing co-phasing for MRC,...
I have a very basic question with regards to beam-forming or MRC. When I apply complex weigths for example while doing co-phasing for MRC, does this phase rotate my constellation. Everywhere I read , I never see a beamforming effect on the demodulation. Given Im using a PSK kind of modulation,don't these complex weights affect my constellations.After all isnt pSk modulation some form of Sin(wct + ...
How RA Code Output Extrinsic Probability....
Hi all.... I do simulate about jointly demodulation and decoding now. The channel encoder is a RA encoder, the iteration between...
Hi all.... I do simulate about jointly demodulation and decoding now. The channel encoder is a RA encoder, the iteration between demodutor and decoder. I see many papers, but i don't know how RA ouput a soft probability to modulator. (I use the Dr.Jilei Hou's RA decoding Schedule.) When first iteration, In demodulator : channel outputs and priori probabilities from decoder input to the...
Phase and sampling relationship in digital demodulation
inHi I tried to demodulate FSK (8 bit uart data caller id) according to the theory but was not successful unless i did bit processing at proper...
Hi I tried to demodulate FSK (8 bit uart data caller id) according to the theory but was not successful unless i did bit processing at proper phase by looking at already implemented FSK demodulator source code by some one. rxbit=demodulate(); // getting result by matched filters for 0 and 1 if ( (prevbit != 0) && (rxbit == 0) && (FSKstatus == 10) ) //not my code { status = 9;...
cosine generation from sine signal in DSP
inHello, I want to generate cosine signal from the sine signal avaiable. What all different techniques by which i can do it???? Hilbert...
Hello, I want to generate cosine signal from the sine signal avaiable. What all different techniques by which i can do it???? Hilbert transform????how to do this using hilbert transform. Any reference or suggestion will be great.... This sin and cos is for Iq demodulation I will be first testing it on matlab and then on DSP waiting for reply with regards praveen
Re: Demodulating QPSK
inJohn E. Hadstate wrote: > After extensive tests, I've hit upon one robust, sure-fire system for > demodulating long-duration QPSK. ...
John E. Hadstate wrote: > After extensive tests, I've hit upon one robust, sure-fire system for > demodulating long-duration QPSK. (This system is not especially useful > for signals that occur in short bursts.) Why reinventing a wheel? Demodulation of the long duration QPSK without noise, fading and frequency wander is a piece of cake task, and there is 10000 solutions for
AM demodulation with fast settling time
inHello all, I am seeking advice on possible DSP approaches on the following problem: I measure a AM modulated signal which has precise...
Hello all, I am seeking advice on possible DSP approaches on the following problem: I measure a AM modulated signal which has precise control of the modulating frequency. However, during the transmission process, the AM modulated signal are contaminated with noise (The types of noise include: higher harmonics of the modulating frequency, most noise has a lower frequency than the modulat...
Gardner Timing Error Detector - Loop Filter
inHi! I'm simulating a burst QPSK modulation and demodulation through a canal with distortion and additive white Gaussian noise. Thus far...
Hi! I'm simulating a burst QPSK modulation and demodulation through a canal with distortion and additive white Gaussian noise. Thus far everything is going as planned and I can retrieve the data. I've decided to implement a gardner timing error detector in order to compensate for some very small clock drift. So I've read some documentation and I now compute the Gardner TED error. But i...
BER vs SNR under BPSK bandlimited channel
inHi I have done some work with BPSK modulation such modulating and demodulating the waveform and plotting the BER vs SNR under BPSK for...
Hi I have done some work with BPSK modulation such modulating and demodulating the waveform and plotting the BER vs SNR under BPSK for AWGN channel. However I wonder how would I perform the simulation if the channel is bandlimited meaining that assume frequency response of channel is w/(w^3+w^2+w+1) then how to do demodulation and eventually finding the bit-error ? Thanks. ----------------...
MC-CDMA AND MC-DS-CDMA SIMULATION USING MATLAB
inHELLO EVERYBODY! I'M TRYING TO COMPARE MC-CDMA AND MC-DS-CDMA USING SINGLE USER AND MULTI-USER DETECTION TECHNIQUES IN TERMS OF BIT ERROR RATE...
HELLO EVERYBODY! I'M TRYING TO COMPARE MC-CDMA AND MC-DS-CDMA USING SINGLE USER AND MULTI-USER DETECTION TECHNIQUES IN TERMS OF BIT ERROR RATE AND SPECTRAL EFFICIENCY IN A MOBILE COMMUNICATION USING MATLAB.THAT IS USING DIRECT SEQUENCE SPREAD SPECTRUM(TRANSMITTING THE CHIPS OVER SEVERAL SUB-CARRIERS),PERFORMING THE MULTI-CARRIER MODULATION AND DEMODULATION USING IFFT AND FFT OPERATIONS, SEPA...
Alamouti MIMO simulation works with PSK but not QAM?
inDear All, I'm currently simulating a Alamouti MIMO system to find out the BER for the different number of antennas and different modulation...
Dear All, I'm currently simulating a Alamouti MIMO system to find out the BER for the different number of antennas and different modulation schemes over the Rayleigh fading channel with AWGN for the selected SNR range. I've been using the predefined "modem.pskmod" and "modem.qammod" in matlab for my modulation, demodulation and maximum likelihood decoding. All is working well for the PSK m...
BPSK demodulation and synchronization (square wave subcarrier)
inHi I have a squarewave subcarrier signal @ 2Mhz modulated with a 250Khz NRZI data signal (no pulse shaping). The data is send in bursts with a...
Hi I have a squarewave subcarrier signal @ 2Mhz modulated with a 250Khz NRZI data signal (no pulse shaping). The data is send in bursts with a 32 microsecond preeamble (subcarrier only). I sample this witha a free-running ADC @ 10Mhz. This will give me 40 samples/symbol so I decimate this with a rate of 4 and BP-filter the result. I would like to demodulate this signal with a digital Costas ...
Carrier recovery for FM demodulation
inHi All I need your help to understand a basic concepts while demodulating FM in digital domain. Do we need a digital PLL to lock the FM...
Hi All I need your help to understand a basic concepts while demodulating FM in digital domain. Do we need a digital PLL to lock the FM while demodulating complex baseband. I am more into DTV demodulator which needs carrier recovery to recover the signal band. Is this the case here or it can withstand carrier offsets? I am demodulating using phase differentiator in digital domain . Please...
Quadrature Modulation tutorial
inI have made a tutorial using flash programs that will help you understand how quadrature modulation and quadrature demodulation works. It is...
I have made a tutorial using flash programs that will help you understand how quadrature modulation and quadrature demodulation works. It is located here: http://www.fourier-series.com/IQMod/index.html I try to show you without getting bogged down in the math. The hope is that after going through the tutorial that the math will be easier to understand. (The math for this stuff can b...
Question about Timing recovery
I want to simulate a circuit of timing recovery in a QPSK digital demodulation system . In the receiver,the upsampled signals are...
I want to simulate a circuit of timing recovery in a QPSK digital demodulation system . In the receiver,the upsampled signals are match filtered and tranmitted to a interpolation filter ,then followed a TED and loop filter. In order to determine the parameters of the loop filter,the error detector sensitivity Kd should be known first,Kd is the slope of the detector around zero error.Kd i...
Box car filter
inHello, I've got after the FM demodulation (by derivative : (IdQ-QdI) / (I=B2+Q=B2)) a low pass filter. This filter is a IIR Butterwoth 4th...
Hello, I've got after the FM demodulation (by derivative : (IdQ-QdI) / (I=B2+Q=B2)) a low pass filter. This filter is a IIR Butterwoth 4th order. But I know that I can use a box car filter. But what is a box car filter ? Is it a FIR filter with rectangular window ? Or FIR filter with all the coefficients to value one ? I think that I just need to make an integration of my FM demo...
Image-reject IF downmixing
inWhen digitally mixing an IF down to baseband, one is left with a spectrum that consists of the baseband (Fif - Fmix = 0Hz) and an image (Fif +...
When digitally mixing an IF down to baseband, one is left with a spectrum that consists of the baseband (Fif - Fmix = 0Hz) and an image (Fif + Fmix). If the IF is greater than the Nyquist freq, the image will wrap back into the first Nyquist zone (0 to Fn). Normally the next step in demodulation is decimation, which consists of lowpass filtering out the image (often with CICs) and then drop...
ROC curves
inHi guys I am doing my phd related to sonar signal processing. I have implemented active sonar signal processing chain involving complex...
Hi guys I am doing my phd related to sonar signal processing. I have implemented active sonar signal processing chain involving complex demodulation, beamforming, match filter , normalization etc in MATLAB. I have tested sp chain with simulated data also. The problem i am facing now is how to set detection threshold for my active system?I have gone through some literature describing ROC curv...
FSK Versus OOK Demodulation
inWith the right filtering, an FSK signal can be viewed as two complementary OOK (on-off keyed) signals. Is the optimal FSK demodulator more...
With the right filtering, an FSK signal can be viewed as two complementary OOK (on-off keyed) signals. Is the optimal FSK demodulator more optimal, less optimal, or equivalent to two optimal OOK demodulators with their outputs combined? -- Randy Yates % "Watching all the days go by... Digital Signal Labs % Who are you and who am I?" mailto://yates@ieee.or...
SDR Captured Files samples scaling
inHi, All Please ignore my question if any one thinks it to be stupid as i am novice in DSP but learning and experimenting DSP techniques. I have...
Hi, All Please ignore my question if any one thinks it to be stupid as i am novice in DSP but learning and experimenting DSP techniques. I have been doing FM/AM demodulation in various captured files for RF signals that i have downloaded from internet including gnuradio, SDRSharp and RTL-SDR files. These all works fine as long as i read and multiply samples read from file with some constant for...