Frequency-shift keying FSK is a frequency modulation scheme in which digital information is transmitted through discrete frequency changes of a carrier signal. The simplest FSK is binary FSK BFSK. BFSK uses a pair of discrete frequencies to transmit binary 0s and 1s information. The time domain of an FSK modulated carrier is illustrated in the figures to the right. Reference implementations of FSK modems exist and are documented in detail. In general, independent oscillators will not be at the same phase and therefore the same amplitude at the switch-over instant, causing sudden discontinuities in the transmitted signal. In practice, many FSK transmitters use only a single oscillator, and the process of switching to a different frequency at the beginning of each symbol fsk preserves the phase. The elimination of discontinuities in the phase and therefore elimination of sudden changes in amplitude reduces sideband power, reducing interference with neighboring channels. Rather than directly modulating the frequency with the digital data symbols, "instantaneously" changing the frequency at the beginning of each symbol period, Gaussian frequency-shift keying GFSK filters the data pulses with a Gaussian filter to make the transitions smoother. This filter fsk the advantage of reducing sideband power, reducing interference with neighboring channels, at the cost of increasing intersymbol interference. For basic data rate Bluetooth the minimum deviation is kHz. Gaussian filtering is a standard way for reducing spectral width; it is called " pulse shaping " fsk this application. In MSK, the difference between the higher and lower frequency is identical to half the bit rate. Consequently, the waveforms that represent a 0 and a 1 bit differ by exactly half a carrier period. As a result, the modulation index m is This is the smallest FSK modulation index that can be chosen such that binary waveforms for 0 and 1 are orthogonal. A variant of MSK called Gaussian minimum shift keying GMSK is used in the GSM mobile phone standard. Audio frequency-shift keying AFSK is a modulation technique by which digital data is represented by changes in the frequency signal of an audio tone, yielding an encoded signal suitable for transmission via radio or telephone. Normally, the transmitted audio alternates between two tones: one, the "mark", represents a binary one; the other, the "space", represents a binary zero. AFSK differs from regular frequency-shift keying in performing the modulation at baseband frequencies. In radio applications, the AFSK-modulated signal normally is binary used to modulate an RF signal using a conventional technique, such as AM or FM for transmission. In addition to its simplicity, however, AFSK has the advantage that encoded signals will pass through AC - coupled links, including most equipment originally designed to carry music or speech. AFSK is used in the U. Phase 1 radios in the Project system use continuous 4 level FM C4FM modulation. Dots and dashes were replaced binary different tones of equal length. Some early CW transmitters employed an arc converter that could not be conveniently keyed. Instead of turning the arc on and off, the key slightly changed the transmitter frequency in a technique known as the compensation-wave method. The Bell and Bell modems used this technique. AFSK is still widely used in amateur radioas it allows data transmission through unmodified voiceband equipment. It is used at higher bitrates for Weathercopy used on Weatheradio by NOAA in the U. The CHU shortwave radio station in OttawaSignal broadcasts an exclusive digital time signal encoded using AFSK modulation. By using this site, you agree to the Terms of Use and Privacy Policy.
This is an interesting cultural clash among investigators, apparently reflecting personal commitments as much as anything else since many have similar professional training.
 circuit diagram.png "binary fsk signal")
This is an interesting cultural clash among investigators, apparently reflecting personal commitments as much as anything else since many have similar professional training.
In 2007 venture capitalist John Doerr gave a TED talk about climate change and alternative energy investment.
Now imagine that someone in the opposite corner of the room is getting ready for a big date, and he or she is spraying some cologne or perfume.