Talk:Modulation

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Spelling[edit]

Please be consistent about "Analogue" vs "Analog". As wikipedia redirects all "Analogue" articles to "analog" I changed the spelling here to be consistent. - Xeo 14:43, 12 October 2005 (UTC)

Diagrams[edit]

Would one or more simple diagrams of some of these concepts help? I am able to make some new (high quality) graphics, or 'refactor' existing ones. Any ideas or requests? At the very least, I think a few graphs illustrating the carrier and signal like the one over at Amplitude modulation ? --Aidan 10:52, 20 February 2006 (UTC)

I don't think we need to replicate the content of other articles here, no. That's why we have the other articles! We could use a system diagram or something generic and high-level like that. One that doesn't deal with a particular modulation scheme but has, you know "data source"->"modulator" -> etc (with a little bit more detail, perhaps). But then that might live better in a general communications article. -Splashtalk 19:18, 12 February 2006 (UTC)
Mmm, I totally agree about replicating graphics. The main reason I suggest this is I think 'Modulation' is a relatively broad/high-level topic. Including image(s) in this article could help demonstrate this idea. Also, from a usability perspective, it can instantly make it clear that this article is definately not about musical modulation (some people don't read). But yeah, now that I think about it, just because an article's 'child' articles have images, doesn't mean it should. (Also, useless images are just that...) Thoughts? --Aidan 10:52, 20 February 2006 (UTC)


Error(s)?[edit]

Kindly justify the points u think are errors. That touched my heart. --Electron Kid 16:27, 18 December 2005 (UTC)

Several things
  1. There was no reason to drop the whole section on "why modulation", since it contains perfectly correct, standard reasons for modulation.
  2. The section it was replaced with focuses entirely on antenna length; well yes, modulation has an effect on that by allowing us to shift up in frequency, but it's not the principal reason. It should be mentioned, but an approximate calculation of antenna length doesn't really have a lot to do with modulation: that info belongs elsewhere, and the text already mentioned "smaller...antennas". Plus, the example was a bit peculiar: why would we ever try to transmit at 20kHz?
  3. I didn't understand "Logical Reason" at all. We don't transmit signals at that frequency, but I'm not sure with what they would get superimposed, apart from human speech. It's an odd point to make, and again not directly related to the topic of modulation. (And why is this 'reason' logical?)
  4. "Redundancy" has nothing to do with modulation. Modulation doesn't introduce or require redundancy. I think you must be thinking of coding, where redundancy is key. Then the text in that section seemed to have nothing to do with redundancy, but did seem to be an unusual statement of the means of modulation — which is already present in clearer, cleaner language right at the top of the article.
  5. The musical use of modulation belongs at the top of the article, because that's how we do things like that in lots of other pages.
  6. Modulation seems odd in Category:Electronics and Category:Encodings, since the article doesn't talk, or need to talk about electronics (it would belong in the individual schemes' articles) and modulation isn't an encoding.
  7. The other categories you added were sensible but we usually only put articles in their most specific subcategories, otherwise the categorization scheme overlaps a lot. So I will put it in Category:Radio modulation modes and Category:Communication theory. overlapping nature of those category names does reveal the mess that the various parts of the comms categorisation scheme is in. -Splashtalk 05:45, 19 December 2005 (UTC)
  8. As u stated in ur point no. 1, all the reasons are perfectly sound. It must be explained why modulation theory was developed. This also removes the disambiguation. --Electron Kid 18:22, 23 December 2005 (UTC)
  9. I am new, and I took out this part: "There are several reasons to modulate a signal before transmission in a medium. These include the ability of different users sharing a medium (multiple access), and making the signal properties physically compatible with the propagation medium." It didn't make sense. That is because without modulation, it would be impossible to use a signal to carry information. So modulation to allow multiple users to share the medium, or to match the physical properties of the medium, only apply to specific modulation techniques designed to do so, and do not relate to the general property that is modulation.
  10. Again, I took out the following part for the same reason as number 9: "Modulation is generally performed to overcome signal transmission issues such as to allow Easy (low loss, low dispersion) propagation as electromagnetic waves Multiplexing — the transmission of multiple data signals in one frequency band, on different carrier frequencies. Smaller, more directional antennas Carrier signals are usually high frequency electromagnetic waves."
  11. This is regarding #9 and #10. I understand these changes have been made before, and been undone. I suggest review by a professional before putting the lines back in. I am the second person who thinks it didn't make sense for them to be there.
  12. Frequency modulation (FM) (here the frequency of the carrier signal is varied in accordance to the instantaneous frequency of the modulating signal) and Phase modulation (PM) (here the phase shift of the carrier signal is varied in accordance to the instantaneous phase of the modulating signal)

should read Frequency modulation (FM) (here the frequency of the carrier signal is varied in accordance to the instantaneous amplitude of the modulating signal) and Phase modulation (PM) (here the phase shift of the carrier signal is varied in accordance to the instantaneous amplitude of the modulating signal)

what are the modulation techniques used in mobile networks ????[edit]

In mobile communication systems, usually a combination of modulation techniques are used. The most common being NB-FM (for GSM), TDMA (now obsolete), FDMA, CDMA, etc.. Elaborate ur quesy/suggestion in the body with only the main theme in the title region. --Electron Kid 04:03, 22 January 2006 (UTC)

I have no idea what you are asking, sorry. -Splashtalk 04:23, 22 January 2006 (UTC)
GSM uses GMSK, I've no idea what "NB-FM" is. TDMA, FDMA and CDMA are multiple access schemes, not modulation schemes. TDMA is not obsolete - it's used in GSM, for instance (GSM also uses FDMA). Oli Filth 11:33, 23 August 2006 (UTC)

Too much jargon[edit]

A quick look around this bundle of articles is not very enlightening for an outsider. It's all incredibly difficult to penetrate. Is there a suitable entry point? Omphaloscope talk 18:42, 1 September 2006 (UTC)

I have added some metaphores from music and numerical examples, in an attempt to give the article a popular scientific touch. But we need lots of illustrations! Mange01 01:45, 27 November 2006 (UTC)
It still sucks. I'm going to make the entry strike home more. Something about modulation as being a variant of the more generally understood modification.

Polarization Modulation[edit]

Somebody can explain modulation formats in a wireless/wireline agnostic way. --பராசக்தி 21:35, 23 November 2006 (UTC)

Why?[edit]

The article doesn't explain why waves would be modulated. It doesn't explain why you would want to have a modulated wave, why an information wave is not suitable for long-range transmissions, etc. Titoxd(?!? - cool stuff) 07:36, 6 April 2007 (UTC)

digital modulation techniques[edit]

There is two list of the digital modulation techniques. I think this section should be revised. —Preceding unsigned comment added by 189.27.3.193 (talk) 17:20, 12 December 2007 (UTC)

Survey: bit/s/Hz, (bit/s)/Hz, bps/Hz or bit·s−1·Hz−1 as Spectral efficiency unit?[edit]

Please vote at Talk:Eb/N0#Survey on which unit that should be used at Wikipedia for measuring Spectral efficiency. For background, see the discussion at Talk:Spectral_efficiency#Bit/s/Hz and at Talk:Eb/N0#Bit/s/Hz. Mange01 (talk) 07:21, 16 April 2008 (UTC)

Suggestion: Format[edit]

The article shows Analog, Digital, and Spread Spectrum as three types of modulation. Analog and Digital are summarized in the article, but Spread Spectrum is not. The article for Spread Spectrum should be summarized here to highlight the important details of that type of modulation. Also modulation in music is mentioned in the opening paragraph, but modulation in telecommunications is the subject of the article. A link or a brief explanation of how it is used in music should be shown. (RobPSL (talk) 02:50, 5 June 2008 (UTC))

There is a link to Modulation (music) in the sentence you are referring to. Oli Filth(talk) 08:03, 5 June 2008 (UTC)

Merge?[edit]

It seems to me this article is very similar or identical in purpose and scope to the Amplitude modulation article. Could/should they be merged? --166.70.188.26 (talk) 17:45, 30 June 2008 (UTC)

Too many animations[edit]

See discussion at Talk:Frequency modulation#Too many animations

Needed - History of Modulation[edit]

The main article could be improved with a couple paragraphs on the history of modulation. Did it really start with telegraph wires that were turned into telephones? How did it differ in the later years, when radio broadcasting came to be the norm?

The main article contains the following sentence:

"Often a high-frequency sinusoid waveform is used as carrier signal to convey a lower frequency signal."

but doesn't explain the history or mathematics behind it. Why does the waveform have to be sinusoidal? Was that the easiest waveform to generate? What happens when some other waveform is used? Was there a spectacular failure or difficulty encountered by some early pioneer who tried a different waveform? Dexter Nextnumber (talk) 03:08, 17 December 2009 (UTC)

The first radio transmitters were spark-gap transmitter because an impulse sequence is the easiest waveform to generate. However, it is hard to detect. Transmitters generating sinusoid waveforms made it possible to build tuned receiver side filters. The tuner improves the signal-to-noise ratio and makes multiplexing possible (dividing the radio spectrum into channels). A sinusoid signal is easy to detect if the reception conditions are poor. Just like you can hear someone blowing a tone in a wistle allthough the weather may be windy, while a noisy and wide bandwidth signal is hard to detect.Mange01 (talk) 14:40, 17 December 2009 (UTC)
Do you mean gaps like in automobile spark plugs, or distributor point gaps? A spark of that nature would be a momentary all bands broadcast, wouldn't it? Dexter Nextnumber (talk) 23:24, 17 December 2009 (UTC)
See Spark-gap transmitter. I don't know how much it resembled these. And yes, it wold momentary affect large portions of the spectrum. The idea of sending impulse sequences over large portions of the spectrum is kind of reinvented in some of today's UWB proposals. Mange01 (talk) 12:06, 18 December 2009 (UTC)

Power requirements in the 1920s and 1930s[edit]

Were there significant differences in the consumption of power between AM and FM in the 1920s and 1930s? I am curious about the expenses an early station director would have had to consider, to decide which kind of modulation he would have to authorize in order to run his business. Dexter Nextnumber (talk) 03:16, 17 December 2009 (UTC)

Why the DSB-SC illustration?[edit]

Simple example of amplitude modulation.

I tried to remove the above illustration, but the removal was reverted. I don't see any motivatation of the illustration. It is hard to understand and shows DSB-SC AM, something not used in any application today. The carrier frequency should be much higher to make the illustration comprehensible, but anyway, DSB-SC is too academic and theoretical for this article. DSB-UC is the most common form of AM, and is already clearly illustrated in this article. Other common forms are QAM and SSB, but let's leave those for the AM article.

However, we need simple illustrations of the most common digital modulation schemes. Mange01 (talk) 21:28, 21 March 2011 (UTC)

First, a moan: per WP:BRD you should not make your edit a second time until after the discussion (and please don't mark an edit as minor when removing an image).
I had hoped that my edit summary ("while problematic, it is ok and needed for preceding para") would provide an alert that the paragraph preceding the image belongs to that image. To resolve the issue (I agree the image is problematic), I have removed the paragraph.
While doing that, I was tempted to change "in accordance to the instantaneous amplitude of the modulating signal" because "amplitude" is not really the right word. Perhaps "value"? Johnuniq (talk) 03:27, 22 March 2011 (UTC)
I'm sorry that I did not wait longer for your reply before I removed the illustration, and that I did not check the preceeding paragraph. That para was also incorrect. The modulated DSB-SC AM signal is the product of the carrier and the message signal, not the sum! In case of ordinary DSB-UC AM, you could say that you add the carrier wave once again after the multiplication, (or that you multiply the carrier signal by 1+the message signal.). Thanks for handling this is in a good way.
"Instantaneous amplitude" is okay, but I think "instantaenous value", "instantaneous level" or "instantaneous signal level" would be better. (My edits are default marked as minor, and I forgot to remove that. Sorry.) Mange01 (talk) 12:24, 22 March 2011 (UTC)

What is "multiplication"?[edit]

What does it mean to multiply two waves?

188.58.66.46 (talk) 09:39, 5 March 2012 (UTC)

Two definitions in introduction[edit]

The two leading paragraphs in the introduction give the impression that there are two different definitions of modulation in telecommunications and electronics. Are there? If true, it should be sourced. If not, maybe the two paragraphs should be edited to emphasize that these are just different ways of viewing the modulation process. --ChetvornoTALK 15:05, 8 February 2014 (UTC)

Tiny problem[edit]

There is a tiny problem in the following sentence (shown in bold):

"In telecommunications, modulation is the process of conveying a message signal, for example a digital bit stream or an analog audio signal, inside another signal that can be physically transmitted."

The sentence implies that "analog audio signal" can not be transmitted physically, and therefore needs to be carried in the carrier signal. However, analog audio signal is already a continuous-time signal (i.e. analog) which can be readily transmitted.

If what is meant by "analog audio signal" is sampled and quantized analog audio signal, then it isn't analog anymore, it is digital, i.e. the same as the first example; a digital bit stream.

A more clearer sentence would be:

Modulation is the process of conveying a message signal inside another signal that will be transmitted. The modulating signal (i.e. the message signal) can be a digital bit stream or an analog signal (e.g. analog audio signal), and depending on whether it is analog or digital, analog modulation or digital modulation is applied for transmission.

78.162.13.181 (talk) 13:00, 17 April 2014 (UTC)

Is that change really needed? Two people can shout to each across a street, so an analog audio signal can be transmitted physically, but they could also flash lights to communicate digitally. The point is that if you want, for example, to send an audio signal from a radio transmitter to a receiver a considerable distance away, the plain audio signal (even in electrical form) cannot be physically transmitted between the two points, while the carrier can. Johnuniq (talk) 23:54, 17 April 2014 (UTC)


well I think it is necessary, because plain audio signals can be, and indeed is everyday, transmitted via a microphone cable or a coaxial cable between two points without modulation (and therefore without a carrier signal). The analog audio signal is actually a modulated pressure wave when its outside, and a modulated electron wave when its inside. The points is, if you have an analog signal, it is already being transmitted physically regardless of whether a modulation will be done or not. An analog signal is a real-world signal in this sense.
There is nothing majorly wrong really, that's why I just dropped a line here. It's just that when you say that audio signals needed a carrier signal to be transmitted physically to a solid state physicist (I am not one), I think s/he would be bothered.


Also for the section "Digital Modulation Methods":
Digital modulation methods can be considered as digital-to-analog conversion (DAC), and the corresponding demodulation or detection as analog-to-digital conversion (ADC). However, there are two opposing definitions that classify the transmission (or the signal transmitted with digital modulation process) as either analog transmission (or analog signal) or digital transmission (or digital signal). According to one definition, the modulated signal is a digital signal, and according to another definition,the modulation is a form of digital-to-analog conversion (DAC). Most textbooks would consider digital modulation schemes as a form of digital transmission, very few would consider it as analog transmission: Data transmission, digital transmission, or digital communications is the physical transfer of data (a digital bit stream) over a point-to-point or point-to-multipoint communication channel. But it should be noted that apart from the nature of the message signal (analog or digital), the transmitted signal itself is always analog (i.e. continuous-time signal); every real signal, wired or wireless, is analog.
78.162.13.181 (talk) 02:00, 18 April 2014 (UTC)

I don't see the problem; that can be physically transmitted does not imply that the original signal cannot also be physically transmitted. Dicklyon (talk) 03:11, 18 April 2014 (UTC)