Talk:Signal modulation

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I believe this chapter contradicts itself as it mentions digital modulation is ultimately analog (as it is), But the last (uncited) source claims it is not. — Preceding unsigned comment added by 187.189.247.68 (talk) 01:41, 27 September 2019 (UTC)[reply]

I suppose I am not surprised that there might be contradictions, as it isn't so obvious. Since wires hold voltages and currents, but not ones and zeros, it is somewhat obvious that, in the end, they must be treated as analog. One could, however, do modulation or demodulation in the digital domain, separate from the D/A or A/D conversion. This applies for both analog and digital sources. Consider a radio station broadcasting from a CD. Normally, one converts the CD digital data to an analog audio signal, and then applies that to an analog modulator. One could, though, using digital electronics, generate a digital representation of a modulated AM or FM carrier, convert that to analog, amplify as appropriate, and feed the transmitter. Similarly, one could, in the digital domain, generate the PAM waveform from a digital source, or demodulate one converted to digital. This process is most often included in Software-defined_radio. (Even though most often it is done using programmable hardware.) Gah4 (talk) 17:18, 27 September 2019 (UTC)[reply]

Since I'm not sure if the below techniques fall under articles for 'Pulse Position Modulation' (if analog waveforms can be considered encoded data, with a clock/sample rate), or (Pulsed) 'Frequency Modulation', could pulse modulating voice using microwave transmitters possibly be included under the 'Miscellaneous modulation techniques' header?
https://en.wikipedia.org/wiki/Modulation#Miscellaneous_modulation_techniques

"Over the years, some have expressed concerns about the capability of communicating directly with humans by pulsed microwaves. In fact, earlier while studying microwave-induced auditory effects in human subjects, it was noticed that in addition to zip, click and knock sounds from exposure to single pulses of microwave radiation, short trains of rectangular microwave pulses are heard as chirps with tones corresponding to the pulse repetition frequencies [Guy et al., 1973, 1975]. It was also found that when the pulse generator was keyed manually such that each closing and opening of a push-button switch resulted in emitting a short rectangular pulse of microwave energy-transmitted digital codes (Morse code) were received and accurately interpreted by the targeted subject [Lin, 1978].
Also, soon after a system was setup for exploring the microwave auditory effect at the Walter Reed Army Institute of Research (WRAIR) [Sharp, et al., 1974], two of the principal investigators were able to demonstrate direct communication of simple speech via appropriate modulation of microwave energy [Justesen, 1975]. They tape-recorded each of the single-syllable words for digits between one and ten. The speech waveforms of each word were then converted to digital signals in such a fashion that each time an analog speech wave crossed the zero reference in the negative direction, a short pulse of microwave energy was emitted from the transmitter. By subjecting themselves to the exposure of 'speech modulated' microwave energy, the investigators reported the ability to hear, identify, and distinguish the word transmitted."^[1]

"Frey and Messenger (1973) demonstrated and Guy, Chou, Lin, and Christensen (1975) confirmed that a microwave pulse with a slow rise time is ineffective in producing an auditory response; only if the rise time is short, resulting in effect in a square wave with respect to the leading edge of the envelope of radiated radio-frequency energy, does the auditory response occur. Thus, the rate of change (the first derivative) of the wave form of the pulse is a critical factor in perception. Given a thermodynamic interpretation, it would follow the information can be encoded in the energy and 'communicated' to the 'listener'. Communication has in fact been demonstrated. A.Guy (Note 1), a skilled telegrapher, arranged for his father, a retired railroad telegrapher, to operate a key, each closure and opening of which resulted in radiation of a pulse of microwave energy. By directing the radiations as his own head, complex messages via the Continental Morse Code were readily received by Guy. Sharp and Grove (Note 2) found that appropriate modulation of microwave energy can result in direct 'wireless' and 'receiverless' communication of speech. They recorded by voice on tape each of the single-syllable words for digits between 1 and 10. The electrical sine-wave analogs of each word were then processed so that each time a sine wave crossed zero reference in the negative direction, a brief pulse of microwave energy was triggered. By radiating themselves with these 'voice modulated' microwaves, Sharp and Grove mere readily able to hear, identify, and distinguish among the 9 words."^[2][3]

RrabEkim (talk) 03:18, 6 October 2021 (UTC)[reply]

I added the following bullet point and sentence to the article, under the 'Miscellaneous modulation techniques' header:

• The microwave auditory effect has been pulse modulated with audio waveforms to evoke understandable spoken numbers.
  

RrabEkim (talk) 04:44, 1 November 2021 (UTC)[reply]

The 'Pulse modulation methods' section:
https://en.wikipedia.org/wiki/Modulation#Pulse_modulation_methods
Does not currently include:
https://en.wikipedia.org/wiki/Pulse-frequency_modulation
RrabEkim (talk) 20:50, 7 October 2021 (UTC)[reply]

I've added Pulse-frequency modulation (PFM) to the 'Pulse modulation methods' section.
RrabEkim (talk) 20:59, 7 October 2021 (UTC)[reply]

Should a new article be created describing modulators, different types of modulators and modulator circuits? Or should that information be added under this article only. Alacris (talk) 13:05, 21 March 2023 (UTC)[reply]

I suppose so. I started a discussion in Talk:Modulator, which seems to me where it should go. The actual article is a redirect. Gah4 (talk) 17:53, 21 March 2023 (UTC)[reply]

Hello! Musician (and amateur DSP nerd) here. In the world of electronic music, signals are often modulated. Typically, the "carrier" is an audio signal, which is not necessarily periodic (though in many cases it would be), or it can be any other parameter in the synthesizer (amplitude envelope parameters, delay time, filter cutoff/resonance, reverb size, pan position, distortion drive amount, compressor threshold, waveshaping curve, stereo width, bitcrusher sample rate, EQ band frequency, etc.). Typically, the modulator signal might be a low-frequency oscillator, or might be a physical control manipulated by a musician (knob or slider or aftertouch or expression pedal), or an automation curve in a DAW, or could in principle be any number of other data sources. I put the word "carrier" in quotation marks because that's not the term that would be used.

The modulating signal might be used to vary the frequency of the audio signal, in which case if the modulation signal has a low frequency you'll get a vibrato effect, and if it is at audio frequency then you'll get complex harmonics and metallic tones (as in FM synthesis). Or it might be used to vary the amplitude, in which case if the modulating signal is low-frequency you'll get a tremolo effect, or if it's audio rates you'll get sidebands and harmonics. And then there's pulse-width modulation, which creates movement in the harmonic content and can be used to create classic "fat" synth string sounds. And ring modulation, which creates bell-like, metallic, or inharmonic sounds and is often used for robotic voice effects.

The article on Subtractive synthesis links here, and much of what appears in this article applies in that situation, however anyone from the electronic music world who is trying to understand modulation as it applies to audio synthesis probably won't find this article useful at all. I haven't found an article that summarizes all of this. I would volunteer to write a new section on this topic, or perhaps a new article, titled "Modulation in audio synthesis", but I'll await the comments of this community before doing so.

Note that although this is a music topic, it is not related to the concept of "modulation" in music theory, which has nothing to do with signals. Solomon Douglas (talk) 09:40, 28 October 2024 (UTC)[reply]

The article does lack and Applications section where we could discuss modulation in music, radio, telecommunications, etc. Please go ahead and start one. ~Kvng (talk) 14:30, 31 October 2024 (UTC)[reply]

This article is really about carrier modulation for transmission in electronics and telecommunication. That was the reason for which I renamed it to signal modulation. I don't see those fields as the main applications for the term modulation. There are all kinds of modulation other than electronic. Other application areas should have their own articles, as this can become very congested with unrelated material. kbrose (talk) 18:05, 26 March 2025 (UTC)[reply]

@Kbrose, Signal modulation doesn't really narrow the scope in the manner you describe. Carrier modulation would be a better title for the scope you describe. We'd have to review all the hundreds of incoming links to this article to decide if narrowing the scope is a good idea. ~Kvng (talk) 15:23, 1 April 2025 (UTC)[reply]