FSK - sample rate and bit depth

Started by Scott Miller in comp.dsp15 years ago 1 reply

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 ...


FM Demodulation Woes

Started by Paul Solomon in comp.dsp15 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...


Coherent MFSK

Started by Vladimir Vassilevsky in comp.dsp8 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...


Data stream demodulation -- Tutorial and Books

Started by Tim Wescott in comp.dsp7 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...


OFDM-coherent

Started by Zeph80 in comp.dsp15 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?


DSP of Wideband Signals

Started by Randy Yates in comp.dsp12 years ago 11 replies

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


Digital FM demodulation

Started by Anonymous in comp.dsp14 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.


FM Demod Questions

Started by George W in comp.dsp16 years ago 1 reply

Hi Folks, I have a telecom application coming up and would appreciate advice on the best choice of DSP for the job. The DSP would be...

Hi Folks, I have a telecom application coming up and would appreciate advice on the best choice of DSP for the job. The DSP would be required to perform bandpass filtering and demodulation of an FM carrier containing voice modulation. The BPF must have good adjacent channel rejection at +/- 20 kHz from wanted channel center frequency, and good in-band group delay. It also must detect...


Seeking explanation of FSK demodulator algorithm

Started by Robert Krten in comp.dsp15 years ago 6 replies

Hi folks, I'm wondering if someone has a clear, simple explanation of the "classical" FSK demodulation algorithm below? I'm writing an...

Hi folks, I'm wondering if someone has a clear, simple explanation of the "classical" FSK demodulation algorithm below? I'm writing an article for the C Users Journal that makes use of the algorithm, and I'd really like to be able to include a description of the algorithm (more than just, "it does a bunch of DSP stuff that seems to work" :-)) Basically, what I'm doing is a Bell-202 Call...


Re: Beamforming and MRC basics

Started by Zeph80 in comp.dsp13 years ago 6 replies

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,...

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 + ...


FSK demodulation

Started by Tomeu in comp.dsp12 years ago 17 replies

Hello all, I am involved in the development of an underwater modem. Right now I am dealing with the simulation stage with simulink. The...

Hello all, I am involved in the development of an underwater modem. Right now I am dealing with the simulation stage with simulink. The modulation scheme I am using is a non-coherent FSK. The carrier frequencies are 20kHz and 22kHz. At the demodulator part, I have designed a matched filters scheme, with both bandpass FIR filters at 20 and 22kHz respectively. The question is, which should ...


Demodulation possible using PC !

Started by Nitin in comp.dsp15 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...


FM demodulation problem

Started by Anonymous in comp.dsp14 years ago 1 reply

Hi, I've designed a complete FM demodulator under Simulink, but I've got a problem. My FM IF is 70 MHz, 250 kHz deviation, 250 kHz message,...

Hi, I've designed a complete FM demodulator under Simulink, but I've got a problem. My FM IF is 70 MHz, 250 kHz deviation, 250 kHz message, so my bandpass signal is 1 MHz large (Carson BW =3D 2* (Delta F + Fmax message) =3D 1 MHz I first undersample the IF at 13.75 MHz so my FM signal is translated to 1.25 MHz, then I multiply with cosinus and sinus (1.25 MHz) to obtain I and Q signal...


FM Demodulation

Started by Randy Yates in comp.dsp14 years ago 61 replies

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...


Demodulation of SSB LSB

Started by benzini1985 in comp.dsp13 years ago 3 replies

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...


How to begin with DSPs

Started by lanbaba in comp.dsp14 years ago 7 replies

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...


Optimal digital FSK demodulator

Started by mf in comp.dsp11 years ago

Hi There, I was wondering if someone could help to define a good choice for digital FSK demodulation method? I need to demodulate a coherent...

Hi There, I was wondering if someone could help to define a good choice for digital FSK demodulation method? I need to demodulate a coherent FSK signal where fc=135kHz and mark and space separation is 10kHz. The detector must be able to work in a somewhat noisy environment but operate at (near) real-time. So a good trade-off between speed and accuracy as well as complexity since i'm only a und...


Optimal digital FSK demodulator

Started by mf in comp.dsp11 years ago 9 replies

Hi There, I was wondering if someone could help to define a good choice for digital FSK demodulation method? I need to demodulate a coherent...

Hi There, I was wondering if someone could help to define a good choice for digital FSK demodulation method? I need to demodulate a coherent FSK signal where fc=135kHz and mark and space separation is 10kHz. The detector must be able to work in a somewhat noisy environment but operate at (near) real-time. So a good trade-off between speed and accuracy as well as complexity since i'm only a und...


I/Q demodulation of bpsk signal

Started by ls00722 in comp.dsp8 years ago 7 replies

Hi all: Assuming x(t) is a BPSK modulated signal centered at f0, I split it into two parts, one is multiplied with cos(2*pi*fc*t), pass through...

Hi all: Assuming x(t) is a BPSK modulated signal centered at f0, I split it into two parts, one is multiplied with cos(2*pi*fc*t), pass through LPF and A/D, that became digitized In-phase, I(n). Another one is multiplied with -sin(2*pi*fc*t), LPF then A/D , it became Quadrature component Q(n). My question is, if we don't consider phase offset, noise, etc. Can I just use either I or Q for dec...


FMDemod, Phase noise and Polyphase

Started by Yip in comp.dsp14 years ago 10 replies

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...