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Amplitude modulation (AM) is a modulation technique used in electronic communication, most commonly for transmitting messages with a radio wave. In amplitude modulation, the amplitude of the wave is varied in proportion to that of the message signal, such as an audio signal. This technique contrasts with angle modulation, in which either the frequency of the carrier wave is varied, as in frequency modulation, or its phase, as in phase modulation.
Frequency modulation (FM) is the encoding of information in a carrier wave by varying the instantaneous frequency of the wave. The technology is used in telecommunications, radio broadcasting, signal processing, and computing.
In electronics and telecommunications, modulation is the process of varying one or more properties of a periodic waveform, called the carrier signal, with a separate signal called the modulation signal that typically contains information to be transmitted. For example, the modulation signal might be an audio signal representing sound from a microphone, a video signal representing moving images from a video camera, or a digital signal representing a sequence of binary digits, a bitstream from a computer. The carrier is higher in frequency than the modulation signal. The purpose of modulation is to impress the information on the carrier wave, which is used to carry the information to another location. In radio communication the modulated carrier is transmitted through space as a radio wave to a radio receiver. Another purpose is to transmit multiple channels of information through a single 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 demodulated to extract the information bearing modulation signal.
Phase modulation (PM) is a modulation pattern for conditioning communication signals for transmission. It encodes a message signal as variations in the instantaneous phase of a carrier wave. Phase modulation is one of the two principal forms of angle modulation, together with frequency modulation.
In radio communications, single-sideband modulation (SSB) or single-sideband suppressed-carrier modulation (SSB-SC) is a type of modulation used to transmit information, such as an audio signal, by radio waves. A refinement of amplitude modulation, it uses transmitter power and bandwidth more efficiently. Amplitude modulation produces an output signal the bandwidth of which is twice the maximum frequency of the original baseband signal. Single-sideband modulation avoids this bandwidth increase, and the power wasted on a carrier, at the cost of increased device complexity and more difficult tuning at the receiver.
In telecommunications, baseband is the range of frequencies occupied by a signal that has not been modulated to higher frequencies. Baseband signals typically originate from transducers, converting some other variable into an electrical signal. For example, the output of a microphone is a baseband signal that is an analog of the received audio. In conventional analog radio broadcasting the baseband audio signal is used, after processing, to modulate a separate RF carrier signal at a much higher frequency.
The cicadas are a superfamily, the Cicadoidea, of insects in the order Hemiptera. They are in the suborder Auchenorrhyncha, along with smaller jumping bugs such as leafhoppers and froghoppers. The superfamily is divided into two families, the Tettigarctidae, with two species in Australia, and the Cicadidae, with more than 3,000 species described from around the world; many species remain undescribed.
Receiver or receive may refer to:
In telecommunications, a carrier wave, carrier signal, or just carrier, is a waveform that is modulated (modified) with an information-bearing signal for the purpose of conveying information. This carrier wave usually has a much higher frequency than the input signal does. The purpose of the carrier is usually either to transmit the information through space as an electromagnetic wave, or to allow several carriers at different frequencies to share a common physical transmission medium by frequency division multiplexing. The term originated in radio communication, where the carrier wave creates the waves which carry the information (modulation) through the air from the transmitter to the receiver. The term is also used for an unmodulated emission in the absence of any modulating signal.
In electronics, ring modulation is a signal processing function, an implementation of frequency mixing, in which two signals are combined to yield an output signal. One signal, called the carrier, is typically a sine wave or another simple waveform; the other signal is typically more complicated and is called the input or the modulator signal. A ring modulator is an electronic device for ring modulation. A ring modulator may be used in music synthesizers and as an effects unit.
Ultrasound can be modulated to carry an audio signal. This is often used to carry messages underwater, in underwater diving communicators, and short-range communication with submarines; the received ultrasound signal is decoded into audible sound by a modulated-ultrasound receiver. A modulated ultrasound receiver is a device that receives a modulated ultrasound signal and decodes it for use as sound, navigational-position information, etc. Its function is somewhat like that of a radio receiver.
The Cicadinae are a subfamily of cicadas, containing the translucent cicadas. They are robust cicadas and many have gaudy colors, but they generally lack the butterfly-like opaque wing markings found in many species of the related Tibiceninae.
Thopha saccata, commonly known as the double drummer, is the largest Australian species of cicada and reputedly the loudest insect in the world. Documented by the Danish zoologist Johan Christian Fabricius in 1803, it was the first described and named cicada native to Australia. Its common name comes from the large dark red-brown sac-like pockets that the adult male has on each side of its abdomen—the "double drums"—that are used to amplify the sound it produces.
The tymbal is the corrugated exoskeletal structure used to produce sounds in insects. In male cicadas, the tymbals are membranes in the abdomen, responsible for the characteristic sound produced by the insect. In tiger moths, the tymbals are modified regions of the thorax, and produce high-frequency clicks. In lesser wax moths the left and right tymbals emit high frequency pulses that are used as mating calls.
Aleeta curvicosta is a species of cicada, one of Australia's most familiar insects. Native to the continent's eastern coastline, it was described in 1834 by Ernst Friedrich Germar. The floury baker is the only described species in the genus Aleeta.
Purana nebulilinea is a cicada species distributed in peninsular Malaysia, Sumatra, Borneo and nearby smaller islands. Its song consists of a long sequence of high pitched sounds with a characteristic frequency modulation pattern which can be repeated many times without interruption.
Magicicada neotredecim is the most recently discovered species of periodical cicada. Like all Magicicada species, M. neotredecim has reddish eyes and wing veins and a black dorsal thorax. It has a 13-year life cycle but seems to be most closely related to the 17-year species Magicicada septendecim. Both species are distinguished by broad orange stripes on the abdomen and a unique high-pitched song said to resemble someone calling "weeeee-whoa" or "Pharaoh." They differ only in life cycle length.
Decim periodical cicadas is a term used to group three closely related species of periodical cicadas: Magicicada septendecim, Magicicada tredecim, and Magicicada neotredecim. M. septendecim, first described by Carl Linnaeus, has a 17-year life cycle; the name septendecim is Latin for 17. M. tredecim, first described in 1868, has a similar call and appearance but a 13-year life cycle; tredecim is Latin for 13. M. neotredecim, first described in 2000 by Marshall and Cooley in an article in the journal Evolution, is a 13-year species but otherwise much more similar to M. septendecim than to M. tredecim as shown by studies of DNA and abdominal color variation by Chris Simon and colleagues in a companion article in the same journal issue.
Maua is a genus of cicadas from Southeast Asia. The males possess two pairs of dark ventral abdominal tubercles on third and fourth sternites.
Maua may refer to:
References
- ↑ Gogala M., Trilar T., Kozina U. and Duffels H., 2004: Frequency modulated song of the cicada Maua albigutta (Walker 1856) (Hemiptera: Cicadoidea) from South East Asia.- Scopolia 54: 1-15
