It seems that the training symbols have to use the same modulation as the data symbols. Is there any way that I can use different modulations? ...

It seems that the training symbols have to use the same modulation as the data symbols. Is there any way that I can use different modulations? say QPSK for training and 16QAM for data. I tried equalizing the two parts separately with a constellation change in between. The shape of the equalized constellation seems correct, but it is compressed. Of course the demodulation result is wrong. ...

On Fri, 05 Nov 2004 10:11:08 +0800, Steve Underwood wrote: > Allan Herriman wrote: > > > > > All "solid state" finals for broadcast FM...

On Fri, 05 Nov 2004 10:11:08 +0800, Steve Underwood wrote: > Allan Herriman wrote: > > > > > All "solid state" finals for broadcast FM have been around since the > > '80s. At the time, they were better in terms of reliability, but not > > initial purchase price. > > > > I don't know how the comparison stands today. > > > > Regards, > > Allan > > > > > I said big FM transmitters.

I have an application where I need to detect an unmodulated tone at a fixed baseband frequency on an FM carrier. The mod index of the tone is...

I have an application where I need to detect an unmodulated tone at a fixed baseband frequency on an FM carrier. The mod index of the tone is quite low, such that only the first Bessel pair of FM sidebands is significant. Can I demodulate the tone by directly detecting its Bessel components (the first two sidebands) at RF without first passing the composite FM signal through a discrimi...

Hello I guess it is one of the most basic topics, but I am not able to understand this topic, mainly because I have not found yet any...

Hello I guess it is one of the most basic topics, but I am not able to understand this topic, mainly because I have not found yet any reference explaining it: I am trying to understand the iterative turbo decoding, but I am still trying to understand the APP decoding part. The computation of gamma implies to find gamma(s',s)=P(yk|xk), being yk the received codeword and xk the transmitted code...

Hi! to expand on the subject briefly: I'm experimenting with mechanical television a la Baird televisor. I think it would be neat to...

Hi! to expand on the subject briefly: I'm experimenting with mechanical television a la Baird televisor. I think it would be neat to encode three channels of color (YIQ) into one audio channel. I would like to use a fairly cheap microcontroller for demodulation because I have lots of experience with it (Atmel Atmega32). Thus far, SSB AM has been the most straightforward approach. On...

Gentle and Wise Readers of comp.dsp, Two ways to demodulate FM are: 1. Find the instantaneous phase (e.g., by examining the phase of the ...

Gentle and Wise Readers of comp.dsp, Two ways to demodulate FM are: 1. Find the instantaneous phase (e.g., by examining the phase of the analytic signal) and compute the phase differences, i.e, f = dtheta/dt. 2. Lock a PLL to the FM signal and use the VCO control voltage as the demodulated signal. It seems to me that method 1 is much simpler. Why would anyone do FM demodulat...

Hey there I am the new one and I am from Germany. Currently I am in the USA writing my Bachelor Thesis. I have the following issue: I have...

Hey there I am the new one and I am from Germany. Currently I am in the USA writing my Bachelor Thesis. I have the following issue: I have an AM modulated signal with a carrier voltage about 100V to 500V and a message voltage of about 250mV. This signal is out of a coil which is part of an RFID reader (more MCID - magnetic coupling... that's why the voltage is so high). The carrier has a fr...

Hi all I have implemented a non-realtime DVB-T receiver in C++ and tested it successfully with signals off the air. Now I have to implement a...

Hi all I have implemented a non-realtime DVB-T receiver in C++ and tested it successfully with signals off the air. Now I have to implement a real-time receiver. The baseband signal processing includes time and frequendy synchronization, channel estimation, coherent demodulation and docoding. The corresponding caculations are - arithmatic calculation - correlation - FFT and IFFT - matrix in...

Hi! I am trying to write a demodulator for a 6MHZ-wide QAM256 signal. I have captured a sample file with the aid of a USRP, and I carry on...

Hi! I am trying to write a demodulator for a 6MHZ-wide QAM256 signal. I have captured a sample file with the aid of a USRP, and I carry on the rest in Matlab. [Question regarding sampling frequency]: I get max 8MS/s from the USRP (although the spec says it should support 16MS/s - I can't seem to get that for some reason). It seems like I should take > 12MS/s to avoid aliasing for a 6MHz si

Hello, I did some simulation to develop an FM demodulator. I used Simulink for modeling. I create a 40 MHZ carrier signal...

Hello, I did some simulation to develop an FM demodulator. I used Simulink for modeling. I create a 40 MHZ carrier signal modulated with 1K data signal and sampled at 102.4 M sample per cycle. The signal is then feed into a FIR filter to make IQ signal. I used Atan and unwrap and differentiator to demodulate the signal and I was able to successfully demodulate it. ...

Hi All, I am trying to debug a FM demodulation noise problem for a FPGA prototype. The output in general looks ok, but the THD+N of a clean...

Hi All, I am trying to debug a FM demodulation noise problem for a FPGA prototype. The output in general looks ok, but the THD+N of a clean 60% modulated signal is only in the mid-40's dB (noticable even by ear), and that is mainly due to a high noise floor. The FM architecture is using the differentiator approach dAtan(Q/I)/dt with [1 -1] as the differentiator. (Phase wrap-around at +/-p...

Hi all, After seaching the comp.dsp archive for FM demod I did not find anything on the case where there is a frequency offset between...

Hi all, After seaching the comp.dsp archive for FM demod I did not find anything on the case where there is a frequency offset between the transmitter and receiver. Is there a reference that explains how the frequency offset between the transmitter and reciever effects the performace of the demodulator? I assume that a digital PLL implementation would be required or would the method in t...

Hi guys, I'm newbie in those groups. I tried to make a CW demodulator (Telegraphy). I would like to make this because it's the simplest signal. I...

Hi guys, I'm newbie in those groups. I tried to make a CW demodulator (Telegraphy). I would like to make this because it's the simplest signal. I have somes algorithms about USB/LSB/AM/FM demodulators, with theis I/Q signals, but what do I have to use to try it? or are there any simple solution?. In tha analog world, it's only IF-LO= CW Audio, but in the digital world, is is simpler than analog?. ...

To all the guardians of signal processing, iam writing a matlab code for the pulse amplitude modulation and demodulation. i have done in the...

To all the guardians of signal processing, iam writing a matlab code for the pulse amplitude modulation and demodulation. i have done in the following way 1.a sine signal with 1000Hz frequency. 2.then a square wave(carrier) of 10000Hz frequency. 3.multiplied these 2 for sampling. 4.quantized the resultant signal. 5.i have added some noise by using rand() fn. 6.at the receiver side i corr...

Hi! I have to demodulate a signal (detect the envelope) for which the bandwidth is not known in advance. By filtering out the "noise" with a...

Hi! I have to demodulate a signal (detect the envelope) for which the bandwidth is not known in advance. By filtering out the "noise" with a bandpass filter, I can get a substantial improvement in signal to noise ratio of the demodulated signal. I was thinking about using an adaptive filter of some kind, but maybe somebody already has some expirience or ideas on this. I think that ju...

Hello everybody, I have a few questions, maybe you can help me. I have 2 signal I,Q @ 40khz and the task is to obtain the instantaneous...

Hello everybody, I have a few questions, maybe you can help me. I have 2 signal I,Q @ 40khz and the task is to obtain the instantaneous frequency. What i did in matlab is this: first of all i found the phase with atan2, i unwrapped the phase and I derivated in order to have the frequency (with command diff). A first issue is here: I had to average the phase to see somenthings in frequency 'c...

Hi fellows, since I appreciate very much your opinion and expertise, I'd launch some brainstorming around a future project we plan. This is...

Hi fellows, since I appreciate very much your opinion and expertise, I'd launch some brainstorming around a future project we plan. This is the idea: We have a sine wave signal @ 1MHz which carries analog modulation and - naturally lots of unwanted noise etc. Frequency of the unmodulated signal is known, the phase however isn't (might vary but can be assumed as stable, but unknown). We'...

I'm working on a couple of demodulators - one for 1200 baud AFSK (and possibly other bitrates) and one for 9600 baud baseband FSK - and I've got...

I'm working on a couple of demodulators - one for 1200 baud AFSK (and possibly other bitrates) and one for 9600 baud baseband FSK - and I've got some questions. I'm using an ARM7TDMI chip, so I'm rather CPU constrained. An issue I'm having trouble with is that the CODEC I'm considering offers sample rates in multiples of 8 khz. It seems to me that any of the demodulation techniques ...

hello everyone.. I am a student working on this project...to design dvb-s cards..I am new to DSP and MATLAB..have spend so much time to find a...

hello everyone.. I am a student working on this project...to design dvb-s cards..I am new to DSP and MATLAB..have spend so much time to find a way to implement,but unsuccessful.. and finally came to this forum for help.. i am using a particular demodulator chip ..If I input the centre frequency, the chip start the demodulation process without any problem. But i need to perform the blind scanning...

Hello , I despair on how to regain the initial information from the seperate I and Q bits after MSK modulation/demodulation. If d(t) is...

Hello , I despair on how to regain the initial information from the seperate I and Q bits after MSK modulation/demodulation. If d(t) is the data, a sum of delta pulses g(t) is the frequency response (MSK: REC) and c(t)=g(t)*d(t) (* convolution !) then phi(t) is the phase , which is calculated by cumsum(c(t)) (MSK:"linear ramps up and down according to the bit") an...