Digital telecommunication systems are becoming more prevalent as new types of products appear and companies develop digital devices to replace analog designs in existing systems. Much of this equipment operates wirelessly and requires antennas for transmitting and receiving their signals. The antennas used for digital devices are generally no different from those found on similar analog devices.
Digital television offers high-definition broadcasts, many new cars have navigation systems with global positioning capability and satellite radios, and most telephones are either cellular or use wireless links to their handsets. Hand-held mobile devices seem to be everywhere and computers increasingly use Wi-Fi to connect to the Internet. All of these digital devices require transmitting and receiving antennas to transfer their content.
Antennas are transducers that either convert electrical signals into electromagnetic waves for transmitting, or turn incident electromagnetic energy into electric currents for the receiver to process. The alternating electric current applied to a transmitting antenna requires its electrons to move in response. The movement of the charged particles creates a magnetic field that in turn interacts with the moving electrons to form a companion electric field. The resulting electromagnetic field creates a radio wave that radiates outward from the antenna. Conversely, the incoming electromagnetic wave causes electron motion in the receiving antenna creating very small electric currents that the radio receiver can amplify and process.
Digital Vs. Analog Signals
The difference between digital and analog signals is in the modulation applied to the carrier waves to represent the transmitted information. In analog radio or television broadcasts, the information signal directly represents the voice or picture, and it usually changes the amplitude or frequency of the carrier wave. In digital systems, the information signal is a series of numeric codes representing some data that continually change the amplitude, frequency or phase of the carrier.
Antennas for Digital and Analog Systems
There is no real difference in the way antennas work in digital systems as compared to their analog counterparts. The characteristics of the radio frequency carrier is the primary factor in how a specific antenna operates, not the specific type of modulation it uses. A good example of antennas used on similar digital and analog systems is television. Television broadcasts in the U.S. were analog until 2009 when they all went digital. The power, directivity and frequency of the carrier waves for digital television are about the same as in the older analog system. Not surprisingly, most analog television antennas work just as well with a high-definition digital television.
- Digital Communications; Ian Glover, Peter Grant
- Boston University: Physics Lecture Demonstrations: Oscillations and Waves
- Illustrated Dictionary of Electronics; Stan Gibilisco
- Digital Communications; Bernard Sklar
- Federal Communications Commission: Consumer Facts: Antennas and Digital Television
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