Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [demodulation]

167 questions
43
votes
4 answers

Can somebody explain what IQ (quadrature) means in terms of SDR?

This is a bit of a basic question, but I am having trouble understanding why a signal needs to be broken up into I and Q components to be useful for software-defined radio (SDR). I understand that the I and Q components are the same signal, just 90…
Malvineous
  • 1,649
  • 1
  • 15
  • 27
23
votes
2 answers

Understanding the relationship between LoRa chips, chirps, symbols and bits

I'm trying to understand the actual relationship between LoRa chips, "chirps", symbols and bits. I don't mean just the equations that relate the various rates, but actually how these things relate quantitatively. The Semtech document AN1200.22 LoRa™…
uhoh
  • 3,399
  • 2
  • 23
  • 63
7
votes
4 answers

Transfering data using ultrasound

Yamaha InfoSound and ShopKick application use technologies that allow to transfer data using ultrasound. That is playing an inaudible signal (>18kHz) that can be picked up by modern mobile phones (iOS, Android). What is the approach used in such…
alexey
  • 171
  • 1
  • 2
6
votes
3 answers

Phase locked Loop in Demodulation

Can someone please clarify how a PLL works and how it can the result is used to deduce phase? My understanding is that a PLL is used to demodulate in situations when the demodulator knows the carrier frequency but does not know the phase. The…
KillaKem
  • 1,740
  • 2
  • 13
  • 26
6
votes
1 answer

Analog television: What is the difference between the first IF and second (demodulated) IF?

I am trying to understand what kind of changes occur to a signal in the chips which sit between the tuner and, for example the FM audio demodulator. Take the attached example - the TDA2546A. It takes 38.9 MHz IF from the tuner, which'll be…
Matthew Millman
  • 349
  • 2
  • 7
6
votes
2 answers

Techniques for digitally copying video laserdiscs

I’m attempting to design a system that can back-up the information stored on a video laserdisc by interpreting the RF signal generated by the photodiodes within the optical deck of the player. The RF signal is a frequency modulated analogue output…
Simon Inns
  • 61
  • 3
6
votes
3 answers

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 have found and done: In my country Caller ID data…
Ebubekir Çağrı Şen
  • 63
  • 5
5
votes
3 answers

FM Quadrature detector - is it the best choice

My input is an FM carrier of 80.00MHz. It is FM modulated with 625kbpsec data. The deviation from carrier is about +/-700kHz. The data never spends more than about 38us in a low state or high state i.e. it is scrambled. Carrier is frequency locked…
Andy aka
  • 434,556
  • 28
  • 351
  • 777
5
votes
5 answers

Half wave rectifier query

This is an ASK asynchronous demodulator In the circuit, we can see 3 differentiated parts: One half-wave rectifier, one envelop detector and a comparator. The circuit receives SIG which is a ASK modulated signal and demodulates it. I'm having…
john wickç
  • 51
  • 2
5
votes
1 answer

Questions about heterodyne receivers

All radio receivers seem to use the heterodyne principle. I can see that it will be easier to work with a fixed frequency than demodulating from a wide range. Questions: what's the difference between heterodyne and superheterodyne what does a…
Federico Russo
  • 9,658
  • 17
  • 68
  • 117
5
votes
2 answers

IR Demodulator - How Does It Work?

I have a circuit here which was designed by others. It takes a 32.768 kHz IR input and outputs a logic low when the input is present. I see 3 distinct stages... everything up to U1A, everything between U1A and Q3 and everything to the right of Q3. I…
Jason
  • 1,923
  • 1
  • 20
  • 31
5
votes
3 answers

What is the voltage source and ground on an antenna?

I've seen a few diagrams relating to AM demodulation, and I can't for the life of me figure out where the voltage source and ground come from in an antenna. From what I understand, an antenna can just be a piece of wire. How can it have a voltage…
USER_RESU
  • 257
  • 1
  • 2
  • 7
5
votes
3 answers

Separating the AM and QAM components in PAL signal demodulation

I'm attempting to emulate the modulation and demodulation of a PAL video frame in software, but I'm having trouble understanding how the AM (luma) and QAM (UV) components of the signal are separated during the demodulation process. Background: The…
Polynomial
  • 10,562
  • 5
  • 47
  • 88
5
votes
3 answers

RC time constant and diode detector

For a better detection of the modulated signal with the diode detector below, one requirement is that the time constant of the RC filter conforms to: $$ \frac{1}{\omega_{c}} \leq RC \leq \frac{ \sqrt{1-\mu^{2}}}{\omega_{m}\mu} …
MicroGame
  • 77
  • 1
  • 1
  • 5
4
votes
2 answers

How is digital information encoded/decoded in light or radio waves?

I know exactly how DAC and ADC works; that's not my concern. What I am asking is how the constituent state of matter (and the "states" represented by them) in a circuit can be transferred to a set of photons (with no mass) and hold varying "states"…
Vasiliy
  • 7,323
  • 2
  • 21
  • 38
1
2 3
…
11 12