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9 votes
Accepted

FSK demodulation using DSP

A very simple but elegant approach to demodulate FSK is a delay and multiply. (Followed by a simple low pass filter). This is a non-coherent FM detector using the principal that the output of a ...
Dan Boschen's user avatar
5 votes
Accepted

Generating two signals with small difference in frequency using one oscillator

I thought about amplifying the signal to generate harmonics, from which I will then filter out the frequencies I need. Harmonics are always multiples of the base frequency so you'd get 27 MHz, 54 MHz,...
Bimpelrekkie's user avatar
4 votes

FSK demodulation using DSP

There's a lot of approaches for decoding FSK. Zero-crossing detection will be pretty sensitive to noise. At these low rates, you don't have to worry. Every milkcan these days has enough compute power ...
Marcus Müller's user avatar
4 votes

Constellation diagram of FSK

In terms of an I/Q constellation diagram (i.e. a phasor or real/imaginary diagram), any frequency deviation from the center frequency would result in the IQ vector rotating around in a circle, with ...
MckennaCisler's user avatar
4 votes
Accepted

FSK Modulation using I/Q

Yes. Set your local oscillator halfway between f1 and f2 i.e. (f1+f2)/2. As your I/Q data, make a sine/cosine wave (i.e. a complex sine wave i.e. a point going around in a circle) with a frequency of ...
Quitting Due To Antisemitism's user avatar
3 votes

Transimpedance Amplifier and Photodiode for BFSK

The easiest modification you can make to your single rail photodiode amplifier is to reverse the photodiode position and have the anode grounded like this: - I've also marked on the direction of ...
Andy aka's user avatar
  • 460k
3 votes
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Software based Caller ID project- Problem with getting caller ID signal

It's an old thread but in case you are still working on this, or anyone else is interested, there are 2 examples of completed Software based PSTN Telephone Caller ID projects here: https://forum....
6v6gt's user avatar
  • 228
3 votes

Understanding this circuit for getting sensor data from an arduino to a phone via the headphone jack

R1 is needed for the android device to recognize that there is something connected to the earphone port. R3 and R2 are a voltage divider to reduce the signal level from the arduino to a level that the ...
JRE's user avatar
  • 71.9k
2 votes

FSK constellation and eye diagrams

An eye diagram shows amplitude against time but FSK has nominally constant amplitude and carries zero amplitude information. Apart from that, an eye diagram is used for the raw data and not a carrier ...
Andy aka's user avatar
  • 460k
2 votes
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How to build a FSK modulator and demodulator?

Some thoughts but certainly not a full design: - The modulator is a lot simpler than the demodulator. For each data bit, the number of oscillation cycles is as follows: - Bit = high, number of clock ...
Andy aka's user avatar
  • 460k
2 votes
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Problem in FSK demodulation

Well, if you can stabilize the PLL a bit more this is going to provide better pay-back when it comes to recovering the data but, in the absense of any improvement, you could try passing the signal ...
Andy aka's user avatar
  • 460k
2 votes

How to perform FSK modulation in VHDL

If I am not wrong, this is my idea. You want to change your data stream on base of fsk_data and use counter for selection purpose. Let say you provide the ...
ARK91's user avatar
  • 121
2 votes

Understanding this circuit for getting sensor data from an arduino to a phone via the headphone jack

To one way of quickly looking at it, R3 and R2 form a resistive divider which limits the amplitude of the output to something which will not excessively overdrive the microphone input. C1 is a DC-...
Chris Stratton's user avatar
2 votes

Build an FSK modulator using the HB100's transmitting signal

If you put a fixed carrier frequency (10.525 GHz) into a mixer/multiplier and feed the other input of the mixer with a baseband signal you will get double sideband suppressed carrier amplitude ...
Andy aka's user avatar
  • 460k
2 votes

In CPFSK, suppose we transmit a continuous bit stream of 1, then for how long will the frequency go on increasing?

You seem to misunderstand the mathematical formula given here. In a system with two symbols, there will only be two frequencies, one indicating a '1' has been sent, one indicating that a '0' has been ...
DonFusili's user avatar
  • 1,067
2 votes

Hacking ATM with its aux port

I don't think that's possible. Do you know what the aux port is there for? I assume it's there to give feedback to blind people using the ATM. If that's the case, the aux port probably is output only ...
Sim Son's user avatar
  • 2,793
2 votes

How high should I make an FSK modulation index value?

If the regulations allow you, as wide as your transceiver supports, as long as it doesn't harm the sensitivity. For example, under FCC regulations in the 915MHz band, a transceiver can use ~500KHz for ...
Lior Bilia's user avatar
  • 7,580
2 votes

ramp-up "guard" time (data receiver)

The main purpose of the "guard time" is to give the the receiver's AGC the time it needs to adapt to the new carrier level and allow the data demodulator to begin operating correctly. Many AGCs have ...
Dave Tweed's user avatar
  • 174k
2 votes

FSK Modulation using I/Q

Yes, you can use an I/Q system to do FSK. The quadrature receiver can be beneficial, especially in a setup like the one described by @user253751 where the LO frequency is halfway between the bit 1 ...
CMH12's user avatar
  • 181
2 votes
Accepted

SX126x IC: which is the correct frequency deviation formula?

They are the same equation. Without even looking at what the chip does, it looks like there is some phase accumulator implementing a DDS.
Justme's user avatar
  • 152k
1 vote

FSK Modulation in Python

f1-f2 is a 1 Hz sinusoid, and f1+f2 is 3 Hz sinusoid. Regardless of whether they are cosine or sine, ideal multiplication will only have the sum and difference frequencies in the mixer output: 2 ...
Eeyn's user avatar
  • 146
1 vote

FSK Modulation using I/Q

Sure, phase is the integral of the frequency, so to generate a FSK signal, you need to generate the I/Q signal from a constant amplitude and the numerical integration of the frequency.
Simon Richter's user avatar
1 vote

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

I think there's not much right here in the question, the slides, and your answer, so that's not your fault. The author confuses "\$M\$-tone Frequency Shift Keying" (M-FSK) with "Minimum ...
Marcus Müller's user avatar
1 vote
Accepted

distortion on transition of bits in FSK

greatly appreciate any pointer! It appears (and it isn't that obvious so I might be wrong) that you have an input filter circuit that is very highly tuned as per this in your question: - And if that ...
Andy aka's user avatar
  • 460k
1 vote
Accepted

understanding AFSK and FSK

"Ordinary" frequency shift keying is what happens if you make a transmitter toggle between two frequencies. It turns out that because a single sideband transmitter is basically an image-rejecting ...
Chris Stratton's user avatar
1 vote
Accepted

Trouble with FSK VCO modulation circuit

You need to have a much higher impedance between your modulation source and the tank circuit of your VCO at the VCO frequency. Otherwise, the source loads down your tank to the point where it no ...
Dave Tweed's user avatar
  • 174k
1 vote
Accepted

Multi-fixed-station AM receiver

Try a vertical whip. Have 3 high-Q PI matching networks; these frequencies are not harmonically related, thus high-Q networks will minimally interact even tho fed by the same (whip) antenna. Let the ...
analogsystemsrf's user avatar

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