# Questions tagged [modulation]

Generic term for coding information onto a carrier signal.

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26 views

### Cannot decode IR signals using IRRemote Library

I'm using RC5 encoding for my project. I'm sending signals using RC5 Protocol. The transmitter is sending the signals correctly. But on the receiver node, when I decode the signals, Library is unable ...
36 views

### Modifying modulation parameters in RC5 [closed]

I am a computer science student working on a research project that uses IRRemote library for IR communication. I'm using RC5 modulation and the system is working. However, for the next part of this ...
81 views

### Why is my oscilloscope math mode showing an RMS voltage in gigavolts (unexpectedly high value)

I'm experiencing an issue with my Rigol DS1202 oscilloscope. When using the math function to measure the RMS voltage of the difference between two channels (A - B), the RMS value is displayed in ...
1 vote
62 views

### Is the probability transition matrix of M-PSK signaling in AWGN channel invertible?

Consider an AWGN channel with MPSK modulation, and let $P=[p_{i,j}]$ denote the corresponding transition probability matrix, where $p_{i,j}$ denotes the probability that symbol $j$ is detected ...
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117 views

### How can an audio signal with varying frequency be modulated using FM? [closed]

An audio signal can have varying frequency and amplitude and both are the part of the information. As I understand it, frequency modulation is a technique where the frequency of the carrier wave is ...
82 views

### How to properly trigger and measure a modulated square wave signal with an oscilloscope

I'm having trouble getting a stable trigger on my Rigol DS-1202 oscilloscope for a complex waveform. The waveform is composed of a 25.5kHz carrier square wave modulated by a 200Hz square wave, both ...
72 views

### How to inject and extract a high frequency modulated signal onto and from the AC powerline?

I'm generating a square wave carrier signal of 125 kHz using 555 timer, I modulate it with a data signal generated from ATmega32 Tx pin (UART 9600 Baudrate) using OOK-Modulation, and now I'm trying to ...
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87 views

### How do we calculate the amplitude levels in QAM modulation technique

so I came across M-ary Modulation technique in my ADC subject. While I understood the basic principle behind it, I still cant get my head around the amplitude levels taken . Like lets say i am using ...
100 views

### Amplitude modulation problems

I am trying to do amplitude modulation using a diode, but my circuit will not work. This is the circuit I am using: simulate this circuit – Schematic created using CircuitLab I don't know why ...
55 views

### Why 8051 is not detecting logic from circuit's voltage?

I am working on a ASK modulator and demodulator circuit which I wish to interface with a 8051 microcontroller to read serial data from demodulator circuit. The mod/demod circuit is developed and ...
228 views

### Must LC resonant frequency be identical to oscillating frequency in RF circuit?

I am developing an RF circuit for 503.3 MHz. It will be an AM RF transmitter. The LC circuit I built into this circuit consists of L = 0.1 μH and C = 1 pF. The carrier frequency which carries the ...
66 views

### Switching circuit with logic 3.3V control on p-channel JFET

The task is to derive sinewave (of higher frequency) chopped by step-function (also periodic but of lower frequency, i.e. several periods of sine wave are placed in that pulse). So I have a sinewave ...
79 views

### Modulate a digital message using FSK/PSK combination

I am beginner and I want to modulate the digital signal: 101101 based on the combination: frequency/phase (2 frequencies/2 phases). For that, I set the 4 possible combinations: ...
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50 views

### Error probability of BPSK with intersymbol interference

Consider an AWGN channel with BPSK modulation. Assume that the information bits are i.i.d. Bernoulli with parameter 0<p<1, we have ISI due to a timing offset at the transmitter, and the decoder ...
• 11
180 views

### Why do we need to transmit in a cable with a digital modulation? Can't we just put high voltage for 1 and no voltage for 0? [closed]

We know that we can't transmit a square wave pulse via EM and we need to convert it to an analog signal via some modulation. But why can't we just put high voltage in the cable to represent bit 1 and ...
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393 views

### Phase modulation for binary data - higher frequency harmonics?

I've recently learned about PSK and QAM. I first came across it in this youtube video (timestamped), and my understanding for how it works has remained the same as what is shown in that video. (I also ...
• 355
59 views

### Delta Sigma Modulator for 2/3 Multi modulus divider used in FracN PLL

I have been trying to implement a Delta Sigma modulator for a 2/3 Multi Modulus divider. I am referring to Riley's paper: https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=229400 I have designed ...
17 views

### Equidistant PAM-n symbols

Why do we choose PAM-n symbols to be equidistant ? What will happen if it's not so? Any references are welcomed !
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166 views

### Difference between MC1496 / LM1496 balanced modulator

I am working on a project that uses an MC1496, but unfortunately it’s not available here. Luckily I have found an LM1496 which seems to be an alternative, but I have no clue how to bias it correctly ...
42 views

### Bit sharing in IQ channel

In 16 QAM, each channel $I$ and $Q$ carries bits of the information it wants to encode. For example: if the symbol is (0011) then $I$ and $Q$ channel carries two bits (00 and 11 respectively). ...
1 vote
61 views

### QAM Modulation - destructive addition?

Doesn't symbols in QAM modulation add destructively as they are symmetric about the origin (equal amplitude and opposite phase) about the I axis?
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?
812 views

### Are these low frequency FFT components due to insufficient op-amp slew rates?

In my circuit I have three op-amps in (direct) series connection: AD8422 acting as an input buffer (a large input impedance is needed) with a fixed gain (slew rate: 0.8 V/us) LTC6910 being used as a ...
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48 views

### Why do we get increase in BER with increase in Eb/N0 of the signal?

I'm working on a problem of MSK modulation scheme. I have passed my modulated signal through SUI channel Models and AWGN. But As I want to do analysis on the performance of SUI channels I'm getting ...
2k views

### How is power line communication (PLC) possible without screwing up the line as a viable power source?

[I am not an EE so bear with me with this] I've been learning about power line communication and see that it is mainly achieved by modulating the carrier signal (for this discussion let's say that's ...
125 views

### SRIX4K Emulator - ASK transceiver

I'm trying to build a simple SRIX4K emulator using an ATMEGA328p, I found this circuit on the internet, and it should work as a simple ASK transceiver, using the MCU to transfer data using the SRIX4K ...
125 views

### AM radio spectations - how does it work

I have captured a RF-AM transmitter circuit on internet. It is clear that the input signal will be pre-amplified and then it will begin to modulate the signal. The question is about how the circuit ...
125 views

### How to increase the carrier signal voltage of RF AM modulation?

The circuit below is an example for RF modulation: Question is about carrier signal voltage of RF AM modulation. What happens when the message signal is amplified and it would have more voltage and ...
21 views

### Effect of 2ASK Sampling Points on Bit Rate

“I reduced the only one sampling points while using 2ASK modulation, and the bit error rate increased by 20%. Can you help me with this?” Question happens in this line: ...
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 ...
417 views

### Understanding an op-amp modulator circuit

I'm trying to understand an op-amp modulator circuit I came across in a book. The circuit uses switches. According to the book, switches S1 and S4 are on during the positive half cycle of the carrier ...
• 353
37 views

### Delta Sigma modulation proof of average

It can easily be proven that an ideal analogue delta sigma modulator shapes the quantisation noise, as explained for example in this AD note under EQ 3: https://www.analog.com/media/en/training-...
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141 views

### QPSK Modulation towards DAC

Modern DACs are able to accept 2 digital values (representing I and Q), multiply them internally by a Sine and Cosine waveforms and combining the result to form the output signal. When dealing with ...
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1 vote
87 views

### How to convert low voltage digital signal (0-3.3V) to high power current signal 15-40W ranging from 1kHz to 1MHz?

I need to convert a digital signal generated from a microcontroller GPIO (0-3.3V) to a high-power (15-40W) current signal to drive an LED chip for illuminance, where the signal frequency can range ...
486 views

### Can Bandwidth be Traded Off with SNR in Analog Modulation?

With typical linear digital modulation schemes, we can, for a given bit rate, make a trade-off between modulation bandwidth and modulation order (effectively, how close the constellation points are). ...
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132 views

### Designing loop filter for frequency-modulated PLL

I'm designing a PLL circuit to stabilize a ~200MHz VCO against temperature-induced frequency drift. However, I need to be able to occasionally (~few times/sec) send a short pulse (~few μs) to modulate ...
1 vote
46 views

### Testing an IC : IO PAD experiences 2nd-order ramping effect

The IO is a regular PMOS-PULL-up and NMOS-PULL-dn IO with series resistors on pull-up and pull-dn branches. The IO is input an clock signal around 50MHz and it experiences an approximately 2nd-order ...
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157 views

### How to determine Phase Angle of 16-QAM

I am trying to figure out how the angles for the following input are obtained. For example, why is 0100 -105 degrees and not 45 degrees? Is there a specific method or do we estimate what the angle ...
48 views

### How phase is modulated according to our message signal?

My question: let message signal m(t) be sin(w1t).For frequency modulation (instantaneous phase deviation=phi(t)) d[phi(t)]/dt=kf m(t) so i get that at 90° or π/2 frequency will be max because the ...
77 views

### What is the transfer function of electroabsorption modulators?

Can anyone give me a reference that I may find a closed-form formula for the output electric field (not power) in terms of the input small-signal electrical waveform (not input power) of an ...
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219 views

### IQ data for analog FM modulation

I am trying to understand how I can produce analog FM modulation using IQ data. So far, I know to generate the FM modulation with an IQ modulator (like the LTC5599.) I have to apply IQ data in ...
• 1
584 views

### Why does the frequency deviation of a FM wave have different definitions?

Source 1 defines the modulation index in the expression for FM as follows: As per the expression for frequency modulated wave, isn't the frequency deviation same as Modulation index 'M'? "The ...
• 3,032
56 views

### CC1125 tramsmit data from the nanosatellite to ground station

does the chip cc1125 can transmit data between nanosatellites to ground stations the distance between them is up to 400km with band frequency UHF from uplink and vhf of the downlink. If yes can use ...
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874 views

### How to improve the sine wave coming in to reduce the power bill?

Can the sine wave from the electricity that comes from the electric company be modified to make your appliances run more efficiently in turn saving electricity cost? How? Related: How to make pure ...
1 vote
360 views

### LoRa - Frequency Shift Chirp Modulation - chips in a symbol

I am trying to create a form of FSCM (frequency shift chirp modulation) based on LoRa principle just to learn from it and to obtain a deeper understanding. What I do not get: why is (or must be?) the ...
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130 views

### VHDL: Testbench for ASK modulator

I've been trying to learn VHDL recently and came across the following tutorial for an ASK modulator: https://surf-vhdl.com/implement-digital-ask-modulator-vhdl/ I tried writing a testbench for this ...
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190 views

### Where and how are the carrier and message signal multiplied in this circuit?

I have this circuit diagram of an AM modulator and I am trying to understand what is going on. I know that the c(t) is taken from the collector of transistor Q1 and the multiplication of signals : m(t)...
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59 views

### Signal modulation with VNA

I want to apply a 1 V, 1 MHz signal to my DUT (coaxial waveguide) while sweeping the frequency from 300 kHz to 6 GHz by the VNA. Right now, I applied the signal by the signal generator to the bias tee ...