Varying the voltage of a carrier or a direct current in order to transmit analog or digital data. Amplitude modulation (AM) is the oldest method of transmitting human voice electronically. In an analog telephone conversation, the voice waves on both sides are modulating the voltage of the direct current loop connected to them by the telephone company.
Modulate a Carrier
Amplitude modulation (AM) is also widely used to alter a carrier wave to transmit data. For example, in AM radio, the voltage (amplitude) of a carrier with a fixed center frequency (the station's channel) is varied (modulated) by the analog audio signal.
AM is also used for digital data. In quadrature amplitude modulation (QAM), both amplitude and phase modulation are used to create different binary states for transmission (see QAM). AM is also used to modulate light waves in optical fibers. See modulation and carrier.
Vary the Amplitude
In AM modulation, the voltage (amplitude) of the carrier is varied by the incoming signal. In this example, the modulating wave implies an analog signal.
Digital Amplitude Shift Keying (ASK)
For digital signals, amplitude shift keying (ASK) uses two voltage levels for 0 and 1 as in this example.
Modulate a Carrier
Amplitude modulation (AM) is also widely used to alter a carrier wave to transmit data. For example, in AM radio, the voltage (amplitude) of a carrier with a fixed center frequency (the station's channel) is varied (modulated) by the analog audio signal.
AM is also used for digital data. In quadrature amplitude modulation (QAM), both amplitude and phase modulation are used to create different binary states for transmission (see QAM). AM is also used to modulate light waves in optical fibers. See modulation and carrier.
Vary the Amplitude
In AM modulation, the voltage (amplitude) of the carrier is varied by the incoming signal. In this example, the modulating wave implies an analog signal.
Digital Amplitude Shift Keying (ASK)
For digital signals, amplitude shift keying (ASK) uses two voltage levels for 0 and 1 as in this example.
 | Reproduced with permission from Computer Desktop Encyclopedia. Copyright (c) 1981-2009 The Computer Language Company Inc. All rights reserved. |
Additional Resources
- Filtered Noise Generator 1 (Windows)
- The Filtered Noise Generator TTG can generate noise signals and apply different frequency filters on them in real time. Applications are loudpspeaker or general audio testing, tinnitus masking, audio cross-over development, etc. Features include: White and pink noise signals with adjustable crest factor; Extensive scripting capabilities Macros, dedicated Script Editor...
- Software downloads 2008-03-07
- Collective 8 Audio Unit Bundle 2.1 (Mac)
- F8-V2 is an audio unit effect with 8 LFOs and 8 time-varying amplitude modulators. F8-V2 works by copying the audio input into 8 independent streams. Each LFO and sequence pattern can be set independently. The filters can be set as highpass, bandpass or lowpass. Each stream may have an amplitude...
- Software downloads 2007-12-10
- Electronics and Circuit Analysis Quick Study Guide. FREE first chapter in the trial (Mobile)
- Boost Your grades with this illustrated quick-study guide. You will use it from an undergraduate school all the way to graduate school and beyond. FREE first chapter in the trial version.Features Clear and concise explanations Difficult concepts are explained in simple terms Illustrated with graphs and diagrams Search for the...
- Software downloads 2007-07-24
- Test Tone Generator 4.2 (Windows)
- The Test Tone Generator TTG turns the PC into a function generator for testing or demonstration, sound tuning, education and many other purposes.Features include: Constant and swept tones log or lin; Many wave forms (Sine/square/triangle/sawtooth/white and pink noise with adjustable crest factor etc); Extensive scripting capabilities Macros, dedicated Script Editor...
- Software downloads 2007-04-12
- SynthMaster Free 1.0.1.43 (Windows)
- SynthMaster is a semi-modular software synthesizer and multi-FX plug-in for Windows, available in VST, VSTi, RTAS and Standalone (ASIO/MME) formats. As a software synthesizer, SynthMaster combines many different synthesis methods such as additive synthesis, subtractive synthesis, ring modulation, amplitude modulation, frequency / phase modulation, pulse width modulation, osc sync and...
- Software downloads 2006-12-05
- Voxynth 2.0.3 (Windows)
- Voxynth is a synthesizer VSTi, which can be used to create vocal sounds or synthetic choirs. In addition, the MIDI synth has a stereo delay and comes with 64 factory patches and a manual Adobe Acrobat. Voxynth has 3 oscillators per voice, pitch modulation, an amplitude envelope and a multimode...
- Software downloads 2006-07-11
- Troubleshooting Digitally Modulated Signals With a QAM Analyzer
- Quadrature Amplitude Modulation QAM is a modulation scheme which conveys data by changing modulating the amplitude of two carrier waves. This paper gives an overview of the features available in many QAM analyzers, and more importantly, how to use those features to troubleshoot problems with digitally modulated signals. This understanding...
- White papers 2006-06-13
- Performance Degradation of OFDM Systems Due to Doppler Spreading
- The focus of this paper is on the performance of Orthogonal Frequency Division Multiplexing OFDM signals in mobile radio applications, such as 802.11a and Digital Video Broadcasting DVB systems, e.g., DVB-CS2. The paper considers the evaluation of the error probability of an OFDM system transmitting over channels characterized by frequency...
- White papers 2006-06-01
- Ocean Waves 1.2 (Mac)
- Ocean Waves generates a simulated sound of ocean waves. Unlike the recorded sound of ocean waves on CD's, the simulated sound of ocean waves does not repeat for hours. You can save the simulated sound of ocean waves as an AIFF file (up to 400 minutes), and burn a CD...
- Software downloads 2006-05-19
- Using Constellation Shaping to Reduce the Peak and Average Power of OFDM Signals
- This paper suggests applying constellation shaping to reduce the peak and average power of Orthogonal Frequency Division Multiplexing OFDM signals using Quadrature Amplitude Modulation QAM in all subcarriers without clipping or reducing the data rate. Adopting the successful shell mapping algorithm for high data rate transmission over telephone channels, as...
- White papers 2006-05-01
- Adaptive Modulation (QPSK, QAM)
- This paper introduces the concepts of digital modulation used in many communication systems today. Techniques described include quadrature phase shift keying QPSK and quadrature amplitude modulation QAM and how these techniques can be used to increase the capacity and speed of a wireless network. These modulation techniques are the basis...
- White papers 2004-08-30
- OFDM or Single-Carrier Block Transmissions?
- This paper compares two block transmission systems over frequency-selective fading channels: orthogonal frequency-division multiplexing OFDM versus single-carrier modulated blocks with zero padding ZP. It first compares their peak-to-average power ratio PAR and the corresponding power amplifier backoff for phase-shift keying or quadrature amplitude modulation. Then it studies the effects of...
- White papers 2004-03-01
- MavenXP 1.2 (Windows)
- User-friendly, highly visual, fast and powerful audio editor. Even beginners can be productive in minutes. Record, edit, and mix sound across 8 tracks and save WAV or MP3 files in up to 16 bit 48 KHz audio, all in real time. 7 built-in real time editable effects include:...
- Software downloads 2004-01-08
- Sound Builder 3.0.1 (Mac)
- You can create dynamic, weird, wiggly, or natural sound, etc., with an easy operation. And you can use the sounds that you make as alert sound for Macintosh, sound effects for multimedia works and music projects, or can edit with other sound editor, because you can save the sounds as...
- Software downloads 2003-04-28
- Understanding Upstream Modulation Profiles
- Modulation profiles define how information will be transmitted upstream, from a cable modem to the cable modem termination system CMTS. Many upstream modulation profile variables can be changed, such as guard time of the burst, preamble, modulation (quadrature phase shift keying [QPSK] or 16-quadrature amplitude modulation [QAM]), and forward error...
- White papers 2003-01-01
- Orthogonal Frequency Division Multiplexing Based on Offset QAM
- One of the factors determining the performance of wireless Orthogonal Frequency Division Multiplexing OFDM systems is time-frequency localization of the transmitter and receiver pulse shaping filters. OFDM based on offset quadrature amplitude modulation (OFDM/OQAM) bypasses a major disadvantage of OFDM based on ordinary QAM, namely the fact that time-frequency well-localized...
- White papers
Neighboring Terms
Premier Vendor Content Whitepapers, webcasts & resources from our Power Center Sponsors
- Microsoft Dynamics CRM Online - Free Six-Month Trial for Eligible Organizations
-
Microsoft Dynamics CRM Online provides fast online access, simple contact management and better sales performance for a low monthly cost - the best value on the market today.
- Learn more about the free, six-month trial offer>>
- Keep Up With The Latest In Document Management with The DocuMentor.
-
Doc delivers the scoop on today's enterprise content management, printer maintenance, and all other issues related to document management. It's the DocuMentor Blog.
- Learn more >>
- Save time with automated shipping solutions
-
The Business Essentials Guide provides you useful tools and templates to help grow your business and save you time with automated shipping solutions.
- Visit the UPS Business Essentials Guide
SmartPlanet
- Thought-provoking progressive ideas on diverse topics that intersect with technology, business, and life, and matter to the world at large. Visit SmartPlanet
- More from IBM
-
- Can your business work smarter? Learn more about Lotus Symphony
- Learn how to work smarter and optimize cost using the IBM Smart SOA approach Download the eBook
- Smarter ways to make smarter products Read the brief from IBM
