The device generates audio of GPS data fed into it in real time, and it can also decode that audio. I have the decoded text version of the audio for reference.
I have set up a flow graph in GNU Radio see belowand it runs without error, but with all the variations I've tried, I still can't get the data. So I have a few questions: 1 The output of the flow graph should be binary 1s and 0s that I can later convert to normal text, right?
FSK Demodulation in GNU Radio
This is the result of the scope sink after demodulation maybe looks promising? The result is a promising-looking string of 1's and 0's, but nothing intelligible.
Here is one version of an updated flow graph based on Marcus's answer also trying other versions with polyphase clock recovery :. However, I'm still unable to recover data that makes any sense. The result is a long string of 1's and 0's, but not the right ones.
I've tried tweaking nearly all the settings in all the blocks. I thought maybe the clock recovery was off, but I've tried a wide range of values with no improvement.
Is there anything else I'm missing or should change? I'll share the configuration of the Xlating FIR here:. At this point, the actual bandwidth that's still present in the signal is much lower than the sample rate, so you might also just downsample without losses set decimation to something higher, e.
The time sink should now show better values.
Have a look at the edges; they are probably not extremely steep. For fun and giggles, I clicked together a quick demo demod GRC here :. Learn more. Asked 3 years, 11 months ago. Active 3 years, 8 months ago. Viewed 18k times. This is a FFT plot of the wav audio file before demodulation: This is the result of the scope sink after demodulation maybe looks promising?
Here is one version of an updated flow graph based on Marcus's answer also trying other versions with polyphase clock recovery : However, I'm still unable to recover data that makes any sense. Bird Bird 1, 3 3 gold badges 16 16 silver badges 38 38 bronze badges. The scope plot of the quadrature demod output, however, would be much more interesting. Oh yeah, I was just experimenting with that to see what the result of demodulation looked like. The scope plot after demodulation actually looked interesting, I will edit my post to add it.
Yes, I'd say, that's pretty promising.One of the most useful modulation techniques in applications requiring low receiver complexity is Frequency Shift Keying FSK. In an FSK scheme, digital information is transmitted by changing the frequency of a carrier signal.
Note that we are not distinguishing between a bit period and a symbol period because both are the same for a binary modulation technique. A block diagram of such a detector is reproduced below from GNU Radio wiki where the block Quadrature Demod is encircled in red. The input to the block is the complex baseband waveform.
Within the block, a product of the one-sample delayed input and the conjugate original signal is computed, the output of which is a complex number. This results in two carrier waves, one at 1 kHz representing a 0 and the other at 2 kHz representing a 1.
This is implemented in the following manner. At the Rx side, a frequency translating FIR filter with a center frequency of 1. According to its documentation, this block performs a frequency translation on the signal, as well as downsamples the signal by running a decimating FIR filter on it. The command firdes. A decimation operation can also be used at this stage as an argument of Frequency Xlating FIR Filter to operate only at a minimum number of samples dictated by the sampling theorem.
However I am not decimating the signal here since my objective is to display the proper waveforms for which a higher the number of samples produces better results. Now the Quadrature Demod block computes the product of this signal with a unit delayed and conjugated version of itself. This is the important point. The binary frequency modulated waveform has been sort of converted into a pulse amplitude waveform due to this operation.
This stream of -1s and 1s can be detected in the Quadrature Demod Output shown in the figure above. This stream can be passed through a binary slicer to produce the final bit stream. Any of the well known timing recovery algorithms can be applied for synchornization purpose. At first sight, it does not make sense that algorithms originally devised for a linear modulation scheme are applicable to an FSK waveform.
Indeed, this is a great cause of confusion in SDR beginners. However, after the above explanation of demodulation process, we can see that a binary FSK waveform is indeed a square wave signal similar to a linearly modulated sequence. A word of caution: GNU Radio is a tool to implement signal processing algorithms while leaving the underlying algorithms choice and development for custom blocks to the user. For a lab demo or a small project, there is no harm in performing the timing synchronization through any of the above mentioned techniques.
On the other hand, a professional solution working under several different operating conditions should be more suited to the exact problem itself. This becomes difficult as noise does not translate nicely from arguments to a linear representation and severely limits the performance at moderate to low SNRs.
Your email address will not be published. Multiply the bits, e. Multiply one minus the bits, e. Add the two waves together thus generating a BFSK waveform. Operation of Quadrature Demod Block Now the Quadrature Demod block computes the product of this signal with a unit delayed and conjugated version of itself.
Timing Synchronization Any of the well known timing recovery algorithms can be applied for synchornization purpose. Learn a little more each week. Get Updates. Leave a Comment Cancel reply Your email address will not be published. There are 26 letters in English language and countless rules. The language of signal processing is simpler. From there, we can build any discrete-time signal on which our 1s and 0s can be mapped.GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together.
If nothing happens, download GitHub Desktop and try again. If nothing happens, download Xcode and try again. If nothing happens, download the GitHub extension for Visual Studio and try again. This blocks takes a frequency modulated signal, filters out other frequencies, demodulates it, recovers the clock and outputs the result as bit stream.
Frequency Shift Keying is a way to transmit information over radio waves.
Frequency Shift Keying
By sending radio waves a bit faster and slower, two states can be encoded that are used of zeros and ones. Skip to content. Dismiss Join GitHub today GitHub is home to over 40 million developers working together to host and review code, manage projects, and build software together. Sign up. Branch: master. Find file. Sign in Sign up. Go back. Launching Xcode If nothing happens, download Xcode and try again. Latest commit. Latest commit a53f Feb 25, This blocks takes a frequency modulated signal, filters out other frequencies, demodulates it, recovers the clock and outputs the result as bit stream What is this about?
Install Open fsk-demod. You signed in with another tab or window. Reload to refresh your session. You signed out in another tab or window. Feb 25, Initial commit. Nov 15, Frequency Shift Keying FSK is the digital modulation technique in which the frequency of the carrier signal varies according to the digital signal changes.
FSK is a scheme of frequency modulation. The output of a FSK modulated wave is high in frequency for a binary High input and is low in frequency for a binary Low input. The binary 1s and 0s are called Mark and Space frequencies. The following image is the diagrammatic representation of FSK modulated waveform along with its input.
The FSK modulator block diagram comprises of two oscillators with a clock and the input binary sequence. Following is its block diagram. The two oscillators, producing a higher and a lower frequency signals, are connected to a switch along with an internal clock. To avoid the abrupt phase discontinuities of the output waveform during the transmission of the message, a clock is applied to both the oscillators, internally.
The binary input sequence is applied to the transmitter so as to choose the frequencies according to the binary input. There are different methods for demodulating a FSK wave. The main methods of FSK detection are asynchronous detector and synchronous detector.
The synchronous detector is a coherent one, while asynchronous detector is a non-coherent one. The block diagram of Asynchronous FSK detector consists of two band pass filters, two envelope detectors, and a decision circuit. Following is the diagrammatic representation.
The signal in each envelope detector is modulated asynchronously. The decision circuit chooses which output is more likely and selects it from any one of the envelope detectors. It also re-shapes the waveform to a rectangular one. The block diagram of Synchronous FSK detector consists of two mixers with local oscillator circuits, two band pass filters and a decision circuit.
The FSK signal input is given to the two mixers with local oscillator circuits. These two are connected to two band pass filters. These combinations act as demodulators and the decision circuit chooses which output is more likely and selects it from any one of the detectors.
The two signals have a minimum frequency separation.New subscribers can take advantage of this fantastic deal with a money-back guarantee if you decide Money Observer isn't for you. Interactive Investor Services Limited is authorised and regulated by the Financial Conduct Authority.
Recent Features The week ahead: Central banks, Ashtead, Carpetright 15 stocks in the 'buy zone' 10 most popular investment trusts - November 2017 Difficult first month for Winter Portfolios Five UK stocks in line for US tax windfall Most-read this week Best dividend yields and 10 'buy' ideas Saga shares plummet, but is anyone buying. Search by Manager GroupAllianz Global Investors Baillie Gifford BlackRock ETF Securities Fidelity GAM Janus Henderson Investors Invesco Perpetual iShares by BlackRock J.
Morgan Asset Management Witan Investment Trust Unicorn All Manager Groups. Stockwatch: Should fresh money move into Saga. Subscribe now Need help. Fall To 15-year Lows Find us on: Tsvetana is a writer for the U. Both forecasts missed by miles. Related: Oil Rises On Weaker Dollar, Stronger U. Six months later, with oil trading 20-ish-dollars below the Raymond James forecast, Molchanov continues to be bullish on oil after the OPEC deal to curtail output.
On the opposing side is Shawn Driscoll, portfolio manager at the T. Rowe Price New Era fund, who told Barrons. The market is likely to move into deficit in the first half next year by an estimated 600,000 bpd, said the International Energy Agency (IEA), as long as OPEC and non-OPEC producers manage to (and are willing to) stick to promised cuts.
In its latest Short-Term Energy Outlook from December 6, the U. BofA Merrill Lynch also factors in a rebound of the U. As always, the game of predicting oil prices will have its winners and losers next year, too.
But 2017 has some major wildcards for oil prices in store, including, but not limited to: Would OPEC stick to promised cuts. Would those cuts rebalance the market at some point next year. Even if they start the year with sticking to cuts, would some OPEC and non-OPEC producers start cheating and renege on pledges once they see more revenues at higher oil prices and be tempted to get more revenue.
How would this affect global supply and oil prices. How would OPEC react to the U. Next PostOilfield Services To See Spending Surge In 2017 Tsvetana is a writer for the U. How many would be needed to be added back to increase production commensurate with OPEC cuts. How much capex would it take reactivate over 1000 rigs. Can the shale producers really increase production to an extent to obviate the OPEC cut when LESS capex is being spent.
How long will it take to gets those new rigs up and running and producing. Phil Currie on December 23 2016 said: Craig Ferrell is correct. One more thing to add to his comments. Where will all the people come from to run these rigs to bring back this oil production. Many have left the industry, some will flock back, but not all. I do not see the rig count in the US going over 1000 for a very long time, if ever again.A weak but statistically significant correlation was demonstrated between caries incidence and caries prevalence.
No other significant correlations were shown. It was concluded that caries activity could not be predicted in this population. Low disease prevalence was a major reason for the weak correlations. Create File See comment in PubMed Commons belowCommunity Dent Oral Epidemiol. Klock B1, Emilson CG, Lind SO, Gustavsdotter M, Olhede-Westerlund AM. Author information1Bohuslandstinget, Partille, Sweden. AbstractOne hundred 14-yr-old children were observed over 1 yr to find out if caries incidence and caries progression could be predicted in a low prevalence child population by means of well-known caries related factors.
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The new study focused on patients with mild cognitive impairment (MCI), a condition in which seniors typically over the age of 65 develop minor but noticeable memory and cognitive problems. Although memory-related difficulties in patients with MCI are not as serious as those in people with Alzheimer's disease, most people with MCI do go on to develop this form of dementia.
In fact, the National Institute on Aging estimate that 8 in 10 people with MCI are diagnosed with Alzheimer's disease within 7 years of their MCI diagnosis. But what goes on in the brain between being diagnosed with MCI and being diagnosed with Alzheimer's. Researchers from the University of Birmingham, the University of Kent both in the United Kingdom and the University of California, Davis set out to investigate this in their new study. Lead study author Dr.GNURadio Frequency Modulation
Ali Mazaheri, of the University of Birmingham, explains the rationale for the investigation. Mazaheri continues, "if there were anomalies in brain activity during language processing in MCI patients which could provide insight into their likelihood of developing Alzheimer's.
Previous studies have shown that it takes the brain of an average person 250 milliseconds to process a written word. The brain activity associated with word processing can be seen on an electroencephalogram (EEG), which is a procedure that measures the electrical activity of one's brain by placing tiny electrodes on the scalp.
For the current research, Dr. Mazaheri and his colleagues used an EEG to study the brain activity of 25 participants while they were shown words on a computer screen. Participants comprised healthy seniors and elders diagnosed with MCI, as well as MCI patients who had received an Alzheimer's diagnosis within 3 years of being diagnosed with MCI. There are days when she can make a sentence then others when it is nothing more than gibberish. I feel that dementia is a hard disease to actually diagnose as there are so many others that can cause the same symptoms.
So I am wondering how can you really use this as a tester. Am so lucky I found this link that provides knowledge about good health. MNT is the registered trade mark of Healthline Media. Any medical information published on this website is not intended as a substitute for informed medical advice and you should not take any action before consulting with a healthcare professional.
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Register take the tour googleAdSlotInfo. Seniors whose brains take longer to process written words may go on to develop Alzheimer's disease.
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