# Questions tagged [fsk]

Frequency Shift Keying - A digital transmission technique in which a "1" is represented by one frequency and a ")" by another. It is the digital equivalent of FM.

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### How can find the bandwidth of the transmitted M-FSK signal?

I'm tried to find the solution, but I failed. my question in the figure below, and the correct answer it's shown at the end of Figure. I'm using this formula but the answer is not correct! Is there ...
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### N Fractional PLL spectrum

I'm studying the different types of N-fractional PLLs based on switching between two or more frequencies to get the desired frequency. However, I'm facing difficulties to understand how the output ...
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### PLC carrier frequency

I am trying to build a communication system over a power line using FSK. I want to stay within the frequency band A of the CENELEC protocol which goes from 3 to 95 kHz. I am trying to determine ...
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### distortion on transition of bits in FSK

I have a question regarding the distortion I see at the transition of bit '0' and '1' in an FSK, I have the receiver connected to a sensing circuit at two frequencies, because my input is current ...
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### Coherent and non-coherent detection

Let's say I am simulating something as simple as BFSK. It has two symbols, one entirely on the real plane, and one entirely on the complex plane for representing let's say zero. That is how the ...
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### Transimpedance Amplifier and Photodiode for BFSK

I am working on my first transimpedence amplifier circuit and am having some trouble. I have am looking to reconstruct a BFSK signal modulated on an LED. The BFSK signal uses a 50kHz sine wave at 80mA ...
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### Hacking ATM with its aux port [closed]

(I opened a topic about it a few minutes ago but I thought it would be better if I ask my question more properly.) I wonder if is it possible to hacking an ATM (through it's aux port) with connecting ...
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I have a complicated issue. I set my HM-TRP radio modules to use: 117Khz receive bandwidth, 39Khz deviation frequency and 38Kbps air and data rate. The attached picture is my basic room setup for ...
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### How high should I make an FSK modulation index value?

After consulting with the radio manufacturer about a setup for my FSK radio module (HM-TRP), they have suggested I program it with the following values when setting up the module for 115kbps: ...
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### ramp-up "guard" time (data receiver)

I have looked at multiple datasheets of multiple radio modules including one I'm using (HM-TRP) and none of them specify a ramp-up or a ramp-down time. According to research, this is known as the ...
1 vote
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### Trouble with FSK VCO modulation circuit

Circuit shown is a VCO that reliably creates a 200MHz sine wave at 3V pk-pk. I would like to use this VCO to create an FSK modulated signal. My bit 1 frequency = 200Mhz and my bit 0 frequency = 205Mhz ...
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### Distinguishing simple FSK and Manchester coding?

I'm examining the signal sent by my car's fob. Using an RTL-STR and GNU Radio Companion, I've been able to capture and demodulate the signal. Now I'm working on decoding the signal. What I'm not ...
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### understanding AFSK and FSK

I’d like to understand 1200Hz/2200Hz AFSK in commonly used APRS/Packet/AX.25 applications. When I look at the datasheets for some of the chips existing projects use (e.g the Si446x transceiver-on-a-...
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### Help decoding line code

I have collected a burst signal from a radio device using an RTL-SDR and gnuradio and demodulated the FSK, but am having trouble deciphering what the line code is. Signal is at 151.3MHz Here is the ...
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### In CPFSK, suppose we transmit a continuous bit stream of 1, then for how long will the frequency go on increasing?

I read something about phase memory but didn't get proper information. My specific doubt is, let's say phase memory is L, then after L '1s', will we have a phase discontinuity and will the frequency ...
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### Why do we need orthogonality for FSK carriers?

I keep on coming across a requirement for FSK carrier separation, $1/T$ for non-coherent detection and $1/2T$ for coherent detection, where $T$ is bit period. I understand where this comes from ...
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I'm in the pencil-and-paper stage of building a radio receiver that has the following characteristics: AM shortwave/HF three fixed frequencies - 3.33, 7.85 and 14.67 MHz single upper sideband with ...
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### Build an FSK modulator using the HB100's transmitting signal

I want to use the HB100 to make an FSK modulation on a microwave signal. The reason why I use HB100 is that in this way the RF circuit is ready. I thought about doing an FSK modulator like the scheme ...
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### Coherent FSK Modulation correlation coefficient derivation

FSK has a large bandwidth requirement and its minimum bandwidth is around $4 B_T$, where $B_T$ is the bit rate. In a coherent FSK system the signals $s_1(t)$ and $s_2(t)$ representing bit ...
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### Why radio exhibits better sensitivity with a wider deviation when Rx bandwidth remains constant

I used an RF generator transmitting FSK packets with a datarate of 50 kbps. The deviation was 12.5 kHz. With this combination of datarate and deviation the modulation index is 0.5. I found that my ...
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### Generating two signals with small difference in frequency using one oscillator

I am building a data transmitter for which I chose FSK modulation. The frequencies should be around 27 MHz. I have single crystal with 27 MHz frequency and I need to get two separate frequencies that ...
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### FSK demodulation using DSP

Especifically talking, I need to demodulate a low frequency FSK signal( betwen 120 and 140 kHz ). I already have a circuit of antenna that receive the signal and I already can sample it, but I still ...
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### Stability of crystal and crystal-less oscillator transmitters

I have stumbled upon this very cheap so called "crystal-less" RF transmitter: http://www.mouser.com/ds/2/368/Si4012-35123.pdf It says there on page 5 the Carrier Frequency Accuracy is 250 ppm while ...
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### FSK constellation and eye diagrams [closed]

why do constellation diagram and eye diagram not show any useful output for FSK? I have tried to find that on Simulink Mathwork, but the progress was negetive.
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### How to build a FSK modulator and demodulator?

I want to build a FSK modulator and demodulator, the center frequency is 4.234MHz +-175kHz, FL is 3.951MHz, FH is 4.516MHz, mean data rate will be 564.48kbit/s. After searching the web, I found that ...
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### Problem in FSK demodulation

I have a FSK modulated signal of binary data. This I am trying to recover using PLL. The mark and space frequencies are in the range of 1.5MHz to 7MHz. I am struggling because, the PLL output is not ...
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### FSK Bandpass Filters for 900 MHz

I'm attempting to design a basic FSK transceiver (architecture shown below) using only discrete components (transistors, diodes, resistors, etc). My idea was to separate the two binary frequency ...
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### Filtering and Delay Compensation in Matlab and Simulink

I have built a FSK modulator and demodulator in Simulink. Everything is working fine except the received signal after the channel has short spikes, which are introducing a short pulses in the ...
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### How to perform FSK modulation in VHDL

FSK Modulation in VHDL Hello, I have a VHDL block that performs FSK modulation. It looks like this The operation of the VHDL block goes like this. Fsk_data selects ...
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### Understanding this circuit for getting sensor data from an arduino to a phone via the headphone jack

I am trying to understand the circuit below which relates to getting sensor data from an arduino to a phone via the headphone jack. The instructions on this page aren't clear on what the function of ...
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### Transmitting data over inductive charging coils (or boosting RFID/NFC power supply)

I know that data can be sent over power lines through various different types of modulation - that is as far as my knowledge ends. I have a small D.I.Y. project (a board game) that requires some form ...
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### Has fsk over wired communication channels ever been done?

I have done multiple searches to figure out if fsk encoding of binary data has ever been used in a "wired" communication scheme but have come up with very little. It seems, at least to me, that ...
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### Software based Caller ID project- Problem with getting caller ID signal

Nowadays, I am trying to make a Caller ID project without using Caller ID ICs. Firstly, I have done a lot of research in Google to get information of phone lines and their electrical properties. I ...
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### Identifying 40Hz frequency shift

I have a signal that is at 4 kHz. This signal shifts by 40 Hz depending on some user input. I like to detect this change in software as fast as I can. What should be the ADC frequency I should use? ...
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I was wondering what energy efficient protocol should I use for a FSK modulation in a steel conductor. My limitation is on the number of continuous bits I can transmit due to the charging and ...
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### How to determine a Signal Generator's Marker (Event) output delay?

I am using an Agilent N5182B Signal Generator for modulating a 2-FSK waveform on a 160MHz RF carrier. For that, I am using a baseband waveform (I/Q mode), generated by a Matlab FSK modulator script. ...
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I have a small doubt in a one way wireless communication. If I am using a receiver chip to demodulate an FSK signal. How does the receiver understands, which frequency to listen to? For example, I ...
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### BFSK Modulation Output

I'm having trouble understanding outputs of a BFSK modulator. $$S_1(t) = cos(πt/T)$$ $$S_2(t) = cos(2πt/T)$$ If the input 0 or 1, how can I calculate the output? Edit: There is a formula to ...
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### How to generate 2-FSK signal from the bit stream(symbols)?

I’m trying to generate a 2-FSK Signal, Let’s just consider the following, Symbol Rate : 1 MS/s Sample Rate : 10 MHz, Frequency Deviation: 150 KHz & -150 KHz And assume I’ve 100 symbols : {1,0,0,...
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### Simple way to decoding FSK

I'm trying to build simple fsk transmitter and receiver, the transmitter is just an FPGA with a wire, the logic is quite simple, I mix (with a XOR) the transmission ...
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### Constellation diagram of FSK

I am learning digital modulation basics and I have question about frequency shift keying — how the constellation diagram of M-ary FSK looks like? I can somehow figure how binary FSK diagram looks (it ...
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### What is 2-FSK modulation?

In the documentation for a radio chip, I keep seeing the term 2-FSK, which seems to be a modulation scheme. My understanding is that in FSK, data is encoded by emitting a carrier wave on a number of ...
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