Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [modulation]

Generic term for coding information onto another carrier signal

1
vote
1answer
225 views

In the logarithmic compressor in PCM, which law is used in countries other than the US, Canada and European countries?

US and Canada use A-law and Europe use µ-law. I can't seem to find what India and other countries use?
3
votes
2answers
376 views

Why is RZ-DPSK more nonlinear tolerant than NRZ-DPSK?

In fiber optics, why would RZ-DPSK be more suited for long-haul transmissions over NRZ-DPSK? Is the tolerance to non-linearity due to the power intensity or something else?
5
votes
1answer
4k views

FM Transmitter Modulation

I am designing an FM transmitter as a learning experience and for fun, but I am having some difficulty with FM modulation. I am using a VCO with a Colpitts topology and common emitter configuration. ...
5
votes
1answer
2k views

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 ...
36
votes
9answers
57k views

What is the basic difference between AM and FM radio?

I want to know the basic/fundamental difference between AM and FM radio. Why nowadays FM radio has replaced AM and has become more popular?
6
votes
3answers
5k views

Any ideas to make IR LEDs identifiable during position-tracking?

Background Johnny Lee demonstrated various interesting ideas (detailed, e.g., in this video as well as this page) that take advantage of the Infrared camera from a Wii-Remote. The IR camera has ...
3
votes
3answers
231 views

Network protocol over audio

I'm looking for open source, simple (simple enough for arduino, for example) protocol for transfer of some messages over audio (eg. in the apartment environment, not by analog line, but between ...
2
votes
1answer
202 views

frequency modulation

I hope this is a pretty easy question for you guys. I know for frequency modulation (FM) for fundamental frequency you have the expansion $$output = J_0(\beta)V\cos(\omega t)\pm J_1(\beta)\cos((\...
4
votes
2answers
1k views

How to Shift Carrier Frequency in QAM Signal?

If I wanted to apply a 100MHz frequency shift to a QAM signal with a 400MHz carrier frequency, I would Demodulate it at the carrier frequency Apply a frequency shift to the original signal Modulate ...
0
votes
1answer
147 views

Do comercial spectrum analyzers show a single-sided spectrum?

If I use a Bessell function to compute sidelobe power - do I need to double this power to get the power I will read on the specan?
2
votes
2answers
192 views

BPSK bandwidth for symbols not integer wavelengths

Most of the BPSK waveform examples in text books/online are for carrier frequencies that are integer multiples of the bit rate. This means that when the symbol polarity changes there is a ...
1
vote
2answers
477 views

How can I do a frequency sweep when the frequency modulation index is dependent on the amplitude?

I have a question regarding frequency modulation and the modulation index. I know that the modulation index can be given by $$\beta = \frac{\Delta \omega}{\omega_m}$$ So the value of the ...
3
votes
2answers
5k views

QAM modulation - how data in different frequencies are laid out?

I know that QAM modulation uses a change in phase and amplitude to send data. But We use a series of frequency spaces as bandwidth to send data. However, we know that different frequencies oscillate ...
1
vote
2answers
1k views

Generating various emission modes via DDS

I know it is common to generate sine waves via Direct Digital Synthesis (DDS). What I would like to know is if it is possible to generate a modulated signal via DDS and if so what would be a practical ...
3
votes
4answers
1k views

How Does FM Get Around the Gabor Limit?

The Gabor Limit states that it's impossible to simultaneously localize a signal in both frequency and time. FM communication modulates the instantaneous frequency of the carrier in step with changes ...
1
vote
2answers
6k views

Current modulator for laser driver?

For a project, I like to feed a sine wave to laser, this sine wave must have a DC value of 2V and it should oscillate between 2.5 and 1.5V at 100KHz. The current required is <50mA. What is the ...
1
vote
1answer
130 views

What are the main power draws within a mobile phone radio?

It is often quoted that "3g uses more power than 2g on voice calls" or other similar things, but it seems from a theory perspective that transmitting low bandwidth voice data with a high bandwidth ...
1
vote
2answers
11k views

Constellation diagram of FSK

I am learning digital modulation basics and I have question about frequency shift keying — how the constellation diagram of M-ary FSK looks like? I can somehow figure how binary FSK diagram looks (it ...
2
votes
2answers
14k views

I want to build a Frequency Modulation circuit

Does anyone have a simple circuit design that can implement Frequency Modulation or even Amplitude Modulation?
3
votes
1answer
923 views

Data modulation over Bluetooth headset profile?

What kind of data modulation schemes might be suitable for sending data to/from a Bluetooth audio headset? e.g. What kind of data modulation would likely survive the audio compression schemes and ...
2
votes
5answers
3k views

Simple power line communication circuit PLC design? [closed]

I need simple PLC power line communication design which I could transmit /receive a packet of data through two points ? Any block diagram with little details will be great for me . Update : Data ...
7
votes
3answers
782 views

Information content of amplitude modulation versus single-sideband transmission

An amplitude-modulated radio signal with carrier frequency C, which includes frequencies from 0 to F, will use output frequencies in the range C-F to C+F, or a total bandwidth of 2F. A modulation ...
2
votes
4answers
797 views

What solutions, if any, are there for visible light transmission (VLC)?

I want to know what ways are there to transmit data using LED's that are available to us today. I currently can find only one reasonable resource for this topic, which is this: http://www.siemens.com/...
21
votes
8answers
12k views

fastest way of doing on/off-modulation of a LED?

I need to modulate a LED quickly (multi-megahertz range) on/off. It's a high-power LED. I have had some trouble locating any well-known methods to do this. Simply switching the voltage with a FET ...
4
votes
1answer
189 views

Modulation And Other Communication Terms

Could somebody explain the concept of modulating a signal? It's such a broad term I never really understood what it meant. Are phase shift, frequency modulation, and amplitude modulation all ...
7
votes
3answers
6k views

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,...
5
votes
5answers
450 views

modem free high base AM data transfer possible?

not a very experienced EE, but I was thinking about a system for high speed data transfer, and it is fairly simple conceptually, so I imagine that there must be serious flaws with the method, because ...
6
votes
3answers
3k views

modulation in phase and frequency

what is the difference between frequency modulation and phase modulation?
2
votes
1answer
804 views

Complementary Code Keying

Asked the question here : I would like to understand Complementary Code Keying. How modulation and demodulation is done ? How higher data rate is achieved using CCK modulation in IEEE 802.11b ? ...
2
votes
3answers
1k views

Do chips which do analog modulation/demodulation of QAM exist?

I have this crazy idea of mixing Cb and Cr signals (from a YCbCr device outputting 720p video) into a chroma (C) signal, for a side project. Is there a simple drop-in chip solution for each side - ...
1
vote
1answer
295 views

Modulation of 36 MHz wireless microphones

I've been given a handful of wireless microphones that transmit in the 36 MHz band, but unfortunately no receiver was included and proper receivers for that wireless mikes seem to be crazy-expensive. ...
4
votes
2answers
613 views

How does frequency modulation takes place?

It is said that in frequency modulation the normal wave represents a '0' (False) and a more frequent wave represents a '1' (True). Is there any particular rule that the normal wave's frequency should ...