# Questions tagged [digital-modulation]

Digital modulation is encoding a data signal onto a carrier wave for transmission. There are several different methodologies for digital modultion.

103 questions
Filter by
Sorted by
Tagged with
53 views

### Distinguishing light sources with STM32 ADC and fast fourier transform

I want to identify if there are other light sources present at the same time as a 5 kHz 50% duty cycle PWM LED is on (this is arbitrary and it can be modulated at a different frequency). I have an ...
• 165
57 views

### How does this delta-sigma modulator work without a clock signal

I've been recently studying about delta-sigma modulators trying to understand a schematic of an amplifier, while I came across this simulation of 2nd order D-S modulator, by far this is what I was ...
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 ...
179 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 ...
• 53
392 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
79 views

### Frequency meter (counter)

I am currently working on designing a circuit that should be able to measure the frequency of an input signal by giving off a value directly proportional to the frequency at the input. The circuit ...
• 129
1 vote
62 views

### Measuring Doppler and Doppler rate at a receiver

I am simulating receiving a digital signal, QAM modulation, raised cosine pulses... from a satellite to a receiver on the ground. I wanted to honestly simulate measuring the Doppler and Doppler rate ...
1k views

### Regular DACs versus audio DACs

Context In trying to make modular linear power supply with digital control, I figured I'd need a DAC to output the correct voltages into the feedback circuitry (two - one for voltage and one for max ...
• 355
1 vote
86 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 ...
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 ...
• 147
88 views

### Amplitude shift keying using NMOS cascode transistor configuration

. I am using 50 MHz as a carrier signal and a pulse signal as the data signal. Unfortunately, I could not get my desired modulated ASK signal. I am using ADS software. Kindly guide me on how to do it. ...
58 views

### Isolators and Level shifters - default to logic 1

I've been making my first boards to do some testing in power electronics. I'm testing unpowered circuits, and there's something that baffles me. I'm testing if pulses appear correctly on gate drives ...
• 49
43 views

### Constellation diagram of an 8-PSK modulator with $\cos(\omega _ct)$ as reference oscillator [duplicate]

For the figure and problem below, is my 000 input plotted correctly and has the correct phase angle in my constellation diagram? The cos(ωct) is located on the positive x-axis since according to my ...
• 19
547 views

### Constellation diagram of an 8 PSK with a $\cos(\omega _ct)$ reference oscillator

Please help me with this problem in Tomasi's book for digital modulation. After getting the summer output, I got confused about what to draw in the constellation diagram. According to my prof, since ...
• 19
67 views

### Why does norm of the PAM bandpass signal give energy of the pulse over two?

I would like to understand why $\int_{-\infty}^{+\infty}g^2(t)cos^2(2\pi f_c t)dt = \mathcal{E}_g/2$ $g(t)$ is a pulse of duration T. the background is: reading the book "Digital ...
140 views

### Can you identify this digital signal? It looks like a UART signal and can't figure out the baud rate

I'm trying to read the signal between my quadcopter's camera board that is controlled by an android app, and the rotor control board in the drone. There are two boards in the drone: the camera board, ...
• 2,022
183 views

### Carrier Waves, modulation over RF vs on wire

I’m reading about carrier waves and signal modulation. It appears signaling has differences over RF vs wire. RF requires accelerating charges to induce a voltage change at the receiver. Straight wire ...
• 383
437 views

### Ultrasonic digital parametric speaker: What kind of modulation and how does it need to be modulated?

I searched for information on digital 40kHz ultrasonic parametric speakers. While most open sources do mention that you need some modulation, what type of modulation and how it does so is hardly ever ...
• 187
83 views

### The relation between data bandwidth (BW) and BW of the local oscillator of a transmitter

Say we have some sort of data we want to send by means of a transmitter having a local oscillator as its carrier. The local oscillator can simply be realized by a phase locked loop with a certain loop ...
• 1,804
36 views

I was solving a problem about digital modulations from my university exam that consider a QAM-8 system with adjacent signals coded by gray code, I know that the error of this system is: $$P_{QAM-8} =... 0 votes 1 answer 190 views ### What are the M and N values when modulation formats (QPSK,8QAM) are polarization multiplexed? I always get confused in the terminology of modulation level (M) and number of bits per symbol (N). Please correct me if I am wrong. Because with these values, my question extends to polarization ... 0 votes 1 answer 2k views ### How is PAM-3 used with binary digits? I've seen a post on Anandtech. Apparently Intel is planning to use PAM-3 for USB80. My question, how efficiently can we map binary digits into a PAM-3 modulation? For instance, 2 successive PAM-3 &... • 677 2 votes 0 answers 126 views ### How does BICM work? Can someone explain bit-interleaved coded modulation (BICM) in plain language, focusing on the practical mechanisms and properties rather than the deep analytical details? I found a few papers and ... • 10.8k 1 vote 1 answer 94 views ### Probabilistic Analog to Digital Convertion I was listening to a talk where the speaker mentioned a couple of ways to represent an analog signal with a digital signal. He mentioned the typical ones like: Encoding the analog value in terms of ... 2 votes 2 answers 139 views ### Does the bandwidth at the receiver really affects the noise in digital modulations? I know that, in a telecommunicacion system, the AWGN power after going through the receiver filter is$$ P_z = KTB $$where B is the bandwidth of the filter, T is the operating temperature of the ... • 21 -1 votes 2 answers 363 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 ... • 465 1 vote 1 answer 412 views ### Frequency Key Shift technique to superpose the digital communication on top of 4–20 mA signals I start working with HART devices and I really try to understand how digital data is transferred trough 4-20 mA current loop. I start read this article: https://instrumentationtools.com/hart-... • 253 2 votes 1 answer 559 views ### The SPH0645LM4H-B microphone seems to output all negative values via I2S Attached is an image from the analyzer. I am afraid that the I2S is shifted one bit, because as it stands, the MSB bit is always high, all samples come back 0x3nnnn (18-bits, so MSB bit is on the left)... • 558 -1 votes 1 answer 146 views ### What are the Electronic Components & Devices for Digital Modulation Formats? [closed] So I have been searching on google for hours but I found nothing, I want to know what are the Components and Devices for Digital Modulation Formats ? Our Professor asked us to write a report The ... • 15 0 votes 4 answers 273 views ### What's the benefits to using analog-to-digital conversion like PCM? I was reading a textbook, Data Communications And Networking, by Behrouz A. Forouzan, which says: A digital signal is superior to an analog signal. The tendency today is to change an analog signal to ... • 255 1 vote 2 answers 829 views ### How are the neat sinc function shaped carriers produced in OFDM? I am learning about OFDM and QAM. Every explanation I have read illustrates how the separate carriers are sinc functions that are arranged to overlap in a nice orthogonal way so as to cancel out ... • 421 0 votes 0 answers 33 views ### Does Carrier frequency offset (CFO) means difference of the message frequency and integrator? Can anyone here tell me what is CFO? Initially, I thought it might be when the message signal mi, that is$$r(t) = 2P cos(2\pi fc*fi+\delta f)$$doesn't match with integrator$$\int_0^T r(t) * cos((...
109 views

I was listening to a local FM station from my smartphone using a headset. While I was surfing over the available bands I saw that few FM stations can broadcast the name of the song/music details (...
378 views

### Help with a Closed loop and zero order hold function ZoH * 1/s(s+a) type

i would appreciate some help in solving this problem, i need to find the transient response for a unit step, i have a brief idea of how to solve, but my graphs in matlab doesnt seem to fit with the ...
1 vote
135 views

### What is the price of increasing the QAM number?

In a QAM modulation scheme, you have a certain number of possible states which have different amplitudes/phases (like 4-QAM, 16-QAM). If you increase the number, for example switch from 16-QAM to 64-...
• 302
97 views

### Can I transmit to several FM radio channels concurrently using one digital transmitter?

I have an Si4720 that can transmit at one FM radio frequency at a time, and if I use several of them on my board, I would be able to transmit at several FM radio frequencies at the same time. This ...
538 views

### How to generate custom digital signals without microprocessors?

I'm in IT but I'd like to try some EE without any programming... I'd like to make a circuit that outputs some custom digital signals. For example, an SOS signal: ...
56 views

### What is the meaning of "Demodulation in quadrature sense"? [closed]

With regard to stepped frequency radar, what does it mean when we say that the transmitted signal is "demodulated in a quadrature sense"? The property of interest in this kind of radar is the phase ...
• 25
46 views

### How to get a band-limited digital modulation of X type?

I am developing a program which should create modulated signals and combine them to get an RF signal with different modulations on different frequencies with non-interfering bandwidths. The problem ...
232 views

### creating IQ data for LMS6002D SDR

I have an FPGA connected to an LMS6002D SDR from Lime micro. I also have an BladeRF board which I am using to help me verify the functionality. I starting out with trying to create IQ data for BPSK ...
565 views

### What is the transmission bandwidth for a BASK (Binary Amplitude Shift Keying) signal?

What is the transmission bandwidth for a BASK (Binary Amplitude Shift Keying) signal? Shouldn't it be infinity as short periods of sinusoids are used to depict 1 and 0 to depict 0?
372 views

### Digital transmission of composite video [closed]

As the tittle suggests, I was thinking about making a wireless composite video transmission between a small camera (such as those sold for flying FPV) and a receiver. The two main specifications it ...
• 308
63 views

### What kind of Modulation? Who transmits on 850 MHz (LTE-Uplink or GPRS?)?

Hey, I found an interesting Signal on 850MHz (in Germany). It is not symmetric and very strong (relative to many others due to bad antennas). On the right side the bandwith is permanently used, on the ...
• 664
1k views

### How is companding different from pre-emphasis and de-emphasis?

What I know is that interference increases linearly with frequency and thus noise power is concentrated at higher frequency. So, to reduce noise, pre-emphasis and de-emphasis filters are used which ...
• 524
108 views

### Quadrature modulation Digital to Analog

I want to use an FPGA to generate quadrature modulated signals for use with an RF transceiver (something like MAX2828 ). I am confused specifically about how the digital to analog modulation should ...
• 175
192 views

### What device can convert (EEG) voltage data to real voltage? [closed]

I seek a device that can be programmed to output physical voltages based on a set of datapoints. For example: ...
5k views

### What's the name of signal encoding used by WS2812 LEDs? [duplicate]

The WS2812b color LED uses some kind of duty cycle encoding to encode three states: one zero reset This can be seen in the following figure: (Source: https://cpldcpu.files.wordpress.com/2014/01/...
• 3,957
1 vote
114 views

### Geometric representation of GMSK signal

Can anyone provide me the geometric representation of GMSK signal? Also, am I correct in saying that bit energy of GMSK is same as its symbol energy since MSK is a binary modulation scheme with only ...
1 vote
64 views

### Method to find Correlation for a random variable and thereby power spectral density of random signal

I'm trying really hard to understand the segment of text from a standard communication book ( Modern digital and analog communications by B P Lathi). We are trying to find the power spectral density ...
• 354
1 vote