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Article: Communications EW, part 6--RF modulations for digital signals.(EW101)
- Article from:
- Journal of Electronic Defense
- Article date:
- November 1, 2003
CopyrightCOPYRIGHT 2003 Horizon House Publications, Inc. This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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In order to be transmitted, digital data must be modulated onto an radio-frequency (RF) or laser carrier signal. We will focus on RF modulation, although the same discussion applies to the transmission at infrared or optical wavelengths.
Digital Modulations
Figure 1 shows a example of a simple digital modulation. This is an amplitude-shift-keyed (ASK) modulation. The RF carrier is amplitude modulated (AM) to carry the digital data. In this case, during transmission of a "one," the amplitude is higher than it is during a "zero." When this signal is AM detected in a receiver, the video output is evaluated against a threshold to regenerate the original ...