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Questions tagged [demodulation]

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4 answers
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Why do we need a diode in an AM demodulation circuit?

The incoming signal is a modulated carrier wave, right? If we only apply a low-pass filter to it, we will get an AC signal that can be passed to a speaker directly, right? Using a diode, we end up ...
Coykto's user avatar
  • 101
3 votes
3 answers
255 views

Synchronous demodulation

In the analog switch-based synchronous demodulation of a signal, say 1 MHz, how does the turn-on and turn-off time of the switch impact the demodulated and filtered DC output (demodulation here is ...
dhuwarkesh's user avatar
-1 votes
1 answer
119 views

Frequency demodulation circuit

This is how I designed the frequency modulation circuit, but I cannot perform the demodulation process. It can be done with a PLL but I couldn't install it. How can I demodulate?
Orhunemre's user avatar
0 votes
0 answers
74 views

AM Demodulation code error MatLAB

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MattCG's user avatar
  • 1
0 votes
1 answer
25 views

Reading a spectrum analyser in MATLAB

When demodulating an AM waveform why is there a frequency spike on the spectrum analyser of exactly two times the carrier frequency with an upper and lower sideband. It is past the cut off frequency ...
Lost student's user avatar
2 votes
0 answers
115 views

What Exactly Is Meant by a 2nd Order Phase Locked Loop?

I'm teaching myself about polyphase clock sync for demodulation of OQPSK. An article from gnuradio.org entitled "Polyphase Clock Sync" makes references to a 2nd order loop. The context seems ...
James Strieter's user avatar
0 votes
1 answer
42 views

How can I design a beta modulator block

I am simulating a block beta modulator, but the problem is to switch uses in that block. What component do I have to use in place of U3? I did not find this type of any component in LTspice library ...
Usha Kumari's user avatar
2 votes
1 answer
60 views

Simple detection of a transient FM frequency shift

I have an application with a 2D array of inductive sensors for position detection of an object on a plane. I have experimented with inductance to digital converters (https://www.ti.com/product/LDC1314)...
learnvst's user avatar
  • 1,341
0 votes
0 answers
188 views

Reverse engineering key fob RF signals

I have been trying to decode the signal of a keyfob with a cheap 315MHz RF receiver (XY-MK-5V) and a ...
chubakueno's user avatar
1 vote
2 answers
682 views

Simple envelope detector

I demodulated a signal using this simple envelope detector. When I checked the output, the amplitude was decreased - it was not the same as the original signal that was modulated (from the forward ...
jbean's user avatar
  • 35
0 votes
2 answers
307 views

FM demodulation circuit

I'm doing an FM demodulator circuit. I am copying the circuit from LTspice in the first image) to Multsim (the second image.) Is what I did in Multisim correct? How can I get a graph from Multisim ...
janna urb's user avatar
0 votes
1 answer
86 views

Name of RF demodulation technique using a demultiplexer

I can't remember the name of a demodulation technique I read the whitepaper on. My memory is not exact but I remember the following vaugely: Core to it is a 1:4 demultiplexer run at 4x the desired ...
foreverska's user avatar
1 vote
0 answers
96 views

What is the motivation behind ADA2200-style half-wave synchronous demodulator?

I came across an interesting IC that contains most components of a little lock-in amplifier (except output LPF) - ADA2200. I am curious however why they opted for such a design where instead of ...
Michał B.'s user avatar
-1 votes
1 answer
129 views

BPSK demodulation on scilab

I have a csv file which contains the time and magnitude of the BPSK modulated waveform. I now want to demodulate this. Its bitrate is fc/128 (~106 kbit/s) and the carrier frequency is fc/16 (~847 kHz)....
tan45's user avatar
  • 11
6 votes
1 answer
352 views

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 ...
Matthew Millman's user avatar
-2 votes
2 answers
140 views

What is the relation between a signal and its generated audio?

Assume we have a simple AM signal, which is a mix of the carrier wave and upper/lower bands. If I were to plot its time domain graph, I would get a graph with Y being its amplitude and X as time, ...
Dan's user avatar
  • 557
3 votes
3 answers
1k views

Cost-efficient mixers and/or demodulators for low frequencies

I am working on a circuit project where I need an in-phase/quadrature mixer for acoustic signals in the range of 200 kHz. I have seen that there are a lot of ICs for radio frequencies that implement a ...
PeterO's user avatar
  • 195
1 vote
1 answer
459 views

Choose optocoupler diode current limiting resistor

I've designed following circuit: But let's completely forget the MOSFET and only focus on the optocoupler. The signal provided to the input of the optocoupler (yellow) has following characteristics: ...
Fox's user avatar
  • 139
2 votes
2 answers
984 views

Removing DC offset in MATLAB

My teacher has a demodulated signal and he removed the DC offset with this one line of code in MATLAB: y_dc = y - mean(y) Can someone please explain how this line ...
user avatar
1 vote
1 answer
339 views

How does a phase shift keying receiver detect when a new incoming modulated signal is at the input?

This is not a math question. What I want to know is the physical implementation of the receiver where phase modulated signal is coming to the receiver. How does the receiver decide when the phase ...
onurkirmizi's user avatar
5 votes
5 answers
1k views

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 ...
john wickç's user avatar
0 votes
0 answers
38 views

How decreasing the effective load impedance in the secondary of a transformer heavily dampens it?

I am reading the operation of the ratio detector for FM demodulation. It works on the principle of diode variable damping (please see the figure here). The capacitor C9 restricts the changes in the ...
Userhanu's user avatar
  • 133
-1 votes
1 answer
266 views

Differences between phase locked loop on PCB and on breadboard

I have a question with regard to the differences between a PLL on a PCB and on a breadboard. In this test, I have connected the output of the amplifier (LMH6503) to both the PLL on the PCB and the PLL ...
Kwok's user avatar
  • 113
1 vote
2 answers
373 views

Hearing the radio by touching a jack plug

Here is what happened to me a few days ago: I own an amplified speaker with a jack plug. Usually, when I touch the jack plug with my finger I hear a "hum" sound. On this specific day, on a ...
J.Mayol's user avatar
  • 113
0 votes
0 answers
71 views

What is the value of voltage controlled switch to demodulate the PAM circuit

What is the possible value of V3 (voltage controlled switch) and the command to demodulate PAM signal?
Pro Ject's user avatar
1 vote
0 answers
138 views

Minimum value of A to be able to use envelope detector in amplitude demodulation when m(t) includes an exponential

This is one of the exam questions I have come across with. My approach was, To be able to get detected by the envelope detector, $$A\geq |\max(m(t))|$$ Max value of m(t) is 1 right? When t = 0 we get,...
leahnanno's user avatar
0 votes
0 answers
51 views

LPF based Differential demodulator design

I am designing LPF based differential demodulator(LPF_DDM) to retrieve differentially modulated signals, which are on-chip capacitive isolated [shown]. LPF_DDM includes a differential amplifier, LPF, ...
Bam_Khel's user avatar
1 vote
0 answers
120 views

MUX Pulldown resistor Questions

I have a precision application where I am demodulating two sine waves using an analog mux (ADG613) and then Low pass filter to measure it's amplitude. The ADG613 is a 1:4 MUX made into a DPDT (chosen ...
Josh Girgis's user avatar
0 votes
0 answers
95 views

why do i have to add a capacitor to observe AM output

so our TA asked us to simulate this modulator in lTspice but told us to add a capacitor that has a value of 0.1 uF at the output and record the result and confirm the envelope shape from message ...
lolls222's user avatar
0 votes
0 answers
201 views

Charge injection Compensation for Demodulation

I have a precision application where I am trying to limit the charge injection on an analog mux that is demodulating a sine wave from 0deg and 180deg components (with a trigger signal from a ...
Josh Girgis's user avatar
0 votes
2 answers
64 views

Frequency de-modulation question [closed]

Why is in some cases that the messaged received from the demodulation process has slightly more amplitude then the original message?
user avatar
0 votes
1 answer
307 views

How to calculate C for an AM demodulator?

I have read this equation from Savant's book that is used to calculate the capacitor for a demodulator: I've tried to calculate my circuit with this equation, but it didn't work. Then I tried to ...
Aethox's user avatar
  • 1
0 votes
0 answers
144 views

Problem with demodulation system, LTspice

First of all, I'm sorry if my English isn't perfect, that's not my natural language. I'm trying to simulate an electronic system for my project and I want to demodulate a sinusoidal signal. To do that,...
Benjamin M's user avatar
0 votes
1 answer
78 views

op amp random pulsing to ground

I have simple circuit with ada4891 op amp. I am using it to demodulate ASK modulated signal. But sometimes op amp is pulsing to ground for no reason. These pulses are short (about 1 us). I have ...
andz's user avatar
  • 254
0 votes
0 answers
532 views

Why does a phase shift happen in the demodulated AM signal using envelope detection?

I was studying AM signal demodulation using envelope detection with the circuit shown below. In the book it says the low pass filter part is called a post-detection filter and that this filter causes ...
korbey's user avatar
  • 1
1 vote
1 answer
319 views

433 MHz Transceiver - understanding OOK demodulator parameter 'OokFixedThreshold'

I would appreciate some help to understand a parameter for this device https://www.semtech.com/products/wireless-rf/fsk-transceivers/sx1231h. I'm far from an expert at RF matters and this question has ...
Smarties's user avatar
0 votes
1 answer
116 views

Is this a demodulated signal?

1st attempt I have a problem. I built the FM demodulator circuit, but i am not sure if this signal is demodulated. This was my first attempt which following an answer, resulted in a 2nd attempt ...
Chuckyy's user avatar
  • 33
0 votes
1 answer
116 views

How do you find the phase lag of the current in this FM demodulation "discriminator" circuit?

I need some help understanding this discriminator circuit for FM demodulation. (L1, C1) is the primary LC tank which resonates with the carrier frequency, whose FM signal is applied at V12. As the FM ...
Adriaan Berger's user avatar
2 votes
2 answers
705 views

Envelope detector and distortions

I am attempting to design an envelope detector, however, I'm having problems with regards to diagonal clipping and negative peak clipping of a certain input. While trying to follow this video's ...
charizo's user avatar
  • 21
0 votes
1 answer
159 views

Is it true that FPGAs and DSPs are widely used for modulation and demodulation of signals? [closed]

I have to write a thesis about digital communications, and I don't want to write something stupid in it. I also wrote that "most of the digital modulations and signal processing nowadays are done ...
Bálint Csejtei's user avatar
1 vote
0 answers
31 views

General approach of signal detection after demodulation of BPSK

I'm very new to electrical engineering. I'm trying to understand the basic approaches/options to detect symbols after demodulation of BPSK. I found some articles mentioning Maximum Likelihood ...
6cfc1's user avatar
  • 11
1 vote
1 answer
1k views

Envelope detector RC values [closed]

I have understood how the envelope detector works, but I am unable to find the formula for R and C appropriate values. The closest I have found is this link: Explain The Square Law Demodulation and ...
The Force Awakens's user avatar
-1 votes
2 answers
366 views

Why can FM be demodulated non-coherently while PM cannot be demodulated non-coherently?

I have read that frequency modulation has the advantage that it can be demodulated non-coherently while phase modulation can only be demodulated coherently. I don't find any reason to support this ...
SUNITA GUPTA's user avatar
2 votes
1 answer
203 views

Why is transformer coupling used in a simple slope detector? Can't the FM signal be applied directly in parallel to a tuned circuit?

This is what I mean by simple slope detector: Why can't it be like:
SUNITA GUPTA's user avatar
0 votes
1 answer
90 views

communication via ultrasound

I want to communicate simple requests and ids over ultrasound. To do this I need to modulate a message onto a 40kHz carrier to drive a ultrasound transducer. Here you can find a simulation of what I ...
le_lemon's user avatar
1 vote
1 answer
343 views

How to avoid false detection when using IR object detection circuit?

I have a circuit to demodulate 2KHz Infrared pulsed light which is generated by 555 timer IC and its output drives an IR transmitter circuit, which is received by IR receiver located 10 cm apart which ...
Nitin Kumar's user avatar
0 votes
0 answers
133 views

Can I debug this simple circuit without VNA and proper RF equipment?

I am debugging a very simple circuit (existing PCB, not designed by me) that downconverts an AM modulated signal at 900 MHz: The problem: What I measure at "Vo" does not match my LTspice ...
divB's user avatar
  • 1,326
1 vote
2 answers
179 views

N-stage rectifier as AM demodulator?

I want to downconvert a simple 100kbit/s NRZ OOK/ASK signal from 900 MHz. In a previous design I found two options: Option 1: simulate this circuit – Schematic created using CircuitLab Option 2:...
divB's user avatar
  • 1,326
0 votes
1 answer
2k views

FM demodulator LTspice

I am now designing an FM demodulator circuit. And the first step is turning FM into AM, so I could use envelope detector afterwards. Modulator circuit is designed using Colpitts topology. So frequency ...
Kral's user avatar
  • 7
1 vote
2 answers
200 views

How can picked up FM noise be demodulated?

I have a set of cheap computer speakers, which happens to use a TDA2822M. Its circuit is almost identical to the example circuit from TDA2822M's datasheet. It's USB powered and has no shielding. I ...
comiy's user avatar
  • 13