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Another purpose of modulation is to transmit multiple [[Communication channel|channels]] of information through a single [[transmission medium|communication medium]], using [[frequency-division multiplexing]] (FDM). For example, in [[cable television]] (which uses FDM), many carrier signals, each modulated with a different [[television channel]], are transported through a single cable to customers. Since each carrier occupies a different frequency, the channels do not interfere with each other. At the destination end, the carrier signal is [[demodulation|demodulated]] to extract the information bearing modulation signal.
A '''modulator''' is a device or [[electric circuit|circuit]] that performs modulation. A '''demodulator''' (sometimes ''[[detector (radio)|detector]]'') is a circuit that performs [[demodulation]], the inverse of modulation. A [[modem]] (from '''mod'''ulator–'''dem'''odulator), used in bidirectional communication, can perform both operations. The lower frequency band occupied by the modulation signal is called the ''[[baseband]]'', while the higher frequency band occupied by the modulated carrier is called the ''[[passband]]''.<ref>{{
Signal modulation techniques are fundamental methods used in wireless communication to encode information onto a carrier wave by varying its amplitude, frequency, or phase. Key techniques and their typical applications include:<ref name=":0">{{Cite web |title=Modulation Methods {{!}} Electronics Basics {{!}} ROHM |url=https://www.rohm.com/electronics-basics/wireless/wireless_what3 |access-date=2025-07-20 |website=www.rohm.com}}</ref><ref>{{Cite web |date=2024-07-18 |title=Understanding the Role of Modulation in WiFi Radio Transmission. |url=https://avsystem.com/blog/role-of-modulation-wifi-radio-transmission |access-date=2025-07-20 |website=avsystem.com |language=en}}</ref><ref>{{Cite web |last=Frenzel |first=Lou |date=2021-07-14 |title=Understanding Modern Digital Modulation Techniques |url=https://www.electronicdesign.com/technologies/communications/article/21798737/electronic-design-understanding-modern-digital-modulation-techniques |access-date=2025-07-20 |website=Electronic Design |language=en}}</ref>
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