## Forums Search for: Demodulation

## FSK demodulation

inHello 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 ...

## 4FSK blind Demodulation

inDear all, I am working on a four-FSK blind demodulator, and there are some problems, I can't resolve very well. The first one pertains to...

Dear all, I am working on a four-FSK blind demodulator, and there are some problems, I can't resolve very well. The first one pertains to the Frequency Offset Of the received Signal. The algorithm which is implemented uses energy per tone to decide which symbol is transmitted. Timing offset is calculated the same way, by finding the sample offset (within the symbol) that yields maximum...

## Digital FM Demodulation - Filtering

inHi, I have no experience of 'software radio', however I am now trying to model a digital FM radio. I am using a simple arctan of the I and Q...

Hi, I have no experience of 'software radio', however I am now trying to model a digital FM radio. I am using a simple arctan of the I and Q to generate the instantaneous phase and then differentiating by subtracting successive phases and dividing by the sample interval to give the FM output. My questions are: What if any low pass filtering should I put on the output of my FM demodula...

## Seeking explanation of FSK demodulator algorithm

inHi 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...

## O-QPSK Demodulation

inHi all, I have to demodulate an O-QPSK signal. As usual in this kind of modulation, symbols (chips) have an half-sine shape, and the Q...

Hi all, I have to demodulate an O-QPSK signal. As usual in this kind of modulation, symbols (chips) have an half-sine shape, and the Q channel has a 90 degree (half simbol) offset with respect to the I channel. The first thing I have to do (and perhaps the most difficult) is removing the frequency offset from the received I and Q signals. I cannot use a simple Costas loop since it doesn't wo...

## Converting I and Q to real signal

inHello, I am a Mech Eng, so I'm not exactly a ninja at quadrature demodulation, and I have a problem that i've been trying to figure out for a...

Hello, I am a Mech Eng, so I'm not exactly a ninja at quadrature demodulation, and I have a problem that i've been trying to figure out for a while. Some background on the system: I am measuring vibrations using doppler ultrasound, vibrations induced by an actuator at around 200 Hz. The Doppler ultrasound setup I have spits out pulses of 5MHz at a frequency of 1563 pulses per sec. The mac...

## FM Demod Questions

inHi 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...

## Re: PM demodulation

Allan Herriman wrote: > On Fri, 05 Nov 2004 10:11:08 +0800, Steve Underwood > wrote: > > > > > Allan Herriman wrote: > > > > ...

Allan Herriman wrote: > 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. > > > > > > Regar

## Matlab simulation of beamforming

inHi all, I would like to know how I could model the effect of beamforming in a monte carlo simulation (running Matlab). A simple simulator...

Hi all, I would like to know how I could model the effect of beamforming in a monte carlo simulation (running Matlab). A simple simulator structure for the beginning could be something like: 1.random bit input 2.modulation (M-PSK or M-QAM) 3.beamformer 4.channel 5.demodulation 6.error counter, calculate BER as a function of SNR So, how to implement the beamforming part? Can I do the si...

## I/Q demodulation of bpsk signal

inHi 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...

## Tracking a moving FM carrier

inHello, I'm looking into a demodulation application for an FM signal. The message signal is fixed bandwidth (~30kHz), but due to the measurement...

Hello, I'm looking into a demodulation application for an FM signal. The message signal is fixed bandwidth (~30kHz), but due to the measurement environment, the carrier (nominally around 500kHz) moves above and below the nominal frequency within about a 100kHz range. To demodulate, I'd like to mix to baseband, so I need to find the carrier of the incoming FM signal. The carrier moves about t...

## Optimal digital FSK demodulator

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

inHi 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...

## DSP Algorithm for LVDT Synchronous AM Demodulation

inHello, I am wondering if anyone can provide some insight into how one may go about doing the following: To obtain magnitude and phase of a...

Hello, I am wondering if anyone can provide some insight into how one may go about doing the following: To obtain magnitude and phase of a sinusoidal output of an LVDT transducer that can be implemented on a TI C2000 series of DSPs. The magnitude of the sinusoid varies linearly with the distance of the plunger from the center and the phase changes depending on which side of the LVDT's center...

## DPSK's relation with OFDM and Demodulation

inHi, I understand that simplified equalization is one of the good reasons for going with OFDM. But, how do they manage it ? That is, The OFDM...

Hi, I understand that simplified equalization is one of the good reasons for going with OFDM. But, how do they manage it ? That is, The OFDM may be viewed as using many slowly-modulated narrowband signals rather than one rapidly-modulated wideband signal. So, The Differential modulation such as DPSK / DQPSK if applied to each sub-carrier, equalization can be completely omitted. ( Reason - ...

## coherent sampling and I/Q demod

in(how) does coherent sampling (used primarily in A/D testing?) differ from I/Q demodulation? Say for instance I'm using I/Q to close a PLL. In...

(how) does coherent sampling (used primarily in A/D testing?) differ from I/Q demodulation? Say for instance I'm using I/Q to close a PLL. In this case the 'sine wave' I'm locked to is being sampled at x4 the sine frequency. This would seem to satisfy the coherent sampling requirement that regarding the digitizer clock. next question - coherent sampling removes the need for windowing in FFT ap...

## GSM channel filter

inHi, Suppose I have to extract a single 200kHz channel from the GSM band and I'd do it using a non-linear phase response filter. Could someone...

Hi, Suppose I have to extract a single 200kHz channel from the GSM band and I'd do it using a non-linear phase response filter. Could someone give me an idea or a reference on how to evaluate the impact of the phase distortion? I mean how the GMSK demodulation process will be affected. Any advice or reference regarding this would be appreciated. thank you, friedman

## fm-demodulation on an FPGA

Hi all, I have created an FM-receiver which is implemented on an FPGA (Virtex-II)= =2E After the FM-demodulator (currently I'm subtracting...

Hi all, I have created an FM-receiver which is implemented on an FPGA (Virtex-II)= =2E After the FM-demodulator (currently I'm subtracting the phase of the=20 previous sample from the phase of the current sample) I have to put a=20 highpass filter removing the lower 300 Hz of the output signal,=20 otherwise I have a tone on approx. 250 Hz. The funny thing is that the=20 250 Hz tone only s...

## Can a binary signal be cyclostationary?

inI was reading this post and found your comment on cyclostationary. My understanding of cyclostationary are signals that there...

I was reading this post and found your comment on cyclostationary. My understanding of cyclostationary are signals that there statistical measurements are periodic in time. From my understanding also, this cyclostationary feature appears on "modulated" signals due to the built in periodicity in the carrier. However, I am not sure if a pure binary signaly after demodulation is considered as cyclost...

## Re: AM digital demodulation using the absolute value

I don't think you are grasping the idea of the low pass filter. It is to r= eject the carrier, not just the aliasing. You want the modulated...

I don't think you are grasping the idea of the low pass filter. It is to r= eject the carrier, not just the aliasing. You want the modulated signal wi= thout the carrier. So the cutoff frequency of the filter would be above yo= ur modulating signal frequency and below the carrier frequency. Everything= else you decide will depend on the details of your problem. =20 BTW, you can do bett...