#DIFFERENCE BETWEEN ASK FSK PSK SERIAL#

The maximum theoretical data rate or channel capacity (C) in bits/s is a function of the channel bandwidth (B) channel in Hz and the signal-to-noise ratio (SNR): C = B log2 (1 + SNR) The spectral efficiency is 2 bits/Hz, meaning twice the data rate can be achieved in the same bandwidth as BPSK. QPSK is very spectrally efficient since each carrier phase represents two bits of data. A constellation diagram in Figure 3b shows the same information. Each unique pair of bits generates a carrier with a different phase (Table 1).Р В РІР‚СњР В РІР‚РЋigure 3a illustrates QPSK with a phasor diagram where the phasor represents the carrier sine amplitude peak and its position indicates the phase. The two phases are added together to produce the final signal. The binary data modulates each phase, producing four unique sine signals shifted by 45Р В РІР‚в„ўР вЂ™Р’В° from one another. In a popular variation of BPSK, quadrature PSK (QPSK), the modulator produces two sine carriers 90Р В РІР‚в„ўР вЂ™Р’В° apart. BPSK is very spectrally efficient in that you can transmit at a data rate equal to the bandwidth or 1 bit/Hz. This involves carrier recovery and other complex circuitry.Р В РІР‚СњР В РІР‚С› simpler version is differential BPSK or DPSK, where the received bit phase is compared to the phase of the previous bit signal. The proper demodulation of BPSK requires the signal to be compared to a sine carrier of the same phase. BPSK is coherent as the phase transitions occur at the zero crossing points. GSM cell phones widely use a popular combination, Gaussian filtered MSK (GMSK), which allows a data rate of 270 kbits/s in a 200-kHz channel.Р В РІР‚СњР вЂ™Р’В«inary Phase Shift Keying (BPSK) And Quadrature Phase Shift Keying (QPSK) A very popular digital modulation scheme, binary phase shift keying (BPSK), shifts the carrier sine wave 180Р В РІР‚в„ўР вЂ™Р’В° for each change in binary state ( Fig. Special Gaussian and raised cosine low pass filters are used for this purpose. This rounds the signal off, lengthening the rise and fall times and reducing the harmonic content. Both coherent ASK/OOK and coherent FSK have fewer harmonics and a narrower bandwidth than non-coherent signals.Р В РІР‚СњР В РІР‚С› second technique is to filter the binary data prior to modulation. This is called continuous phase or coherent operation. The idea is to synchronize the stop and start times of the binary data with when the sine carrier is transitioning in amplitude or frequency at the zero crossing points. These discontinuities produce glitches that increase the harmonic content and the bandwidth.

First, select data rates, carrier frequencies, and shift frequencies so there are no discontinuities in the sine carrier when changing from one binary state to another. Here are two ways to further improve the spectral efficiency for both ASK and FSK. Smaller values are also used such as m = 0.3. A popular version of FSK called minimum shift keying (MSK) specifies m = 0.5. Smaller values of m produce fewer sidebands. T is the bit time interval of the data or the reciprocal of the data rate (1/bit/s). Р В РЎвЂєР Р†Р вЂљРЎСљf is the frequency deviation or shift between the mark and space frequencies, or: The bandwidth produced is a function of the highest modulating frequency including harmonics and the modulation index, which is: m = Р В РЎвЂєР Р†Р вЂљРЎСљf(T) FM produces multiple sideband frequencies above and below the carrier frequency.

The bandwidth required is two times the highest frequency content including any harmonics for binary pulse modulating signals.Р В РІР‚СњР В РІР‚РЋrequency shift keying (FSK) shifts the carrier between two different frequencies called the mark and space frequencies, or f m and f s (Fig. In Figure 1b, the binary signal turns the carrier off and on to create OOK.Р В РІР‚СњР В РІР‚С›M produces sidebands above and below the carrier equal to the highest frequency content of the modulating signal.

In Figure 1a, the carrier amplitude is shifted between two amplitude levels to produce ASK. There are two types of AM signals: on-off keying (OOK) and amplitude shift keying (ASK).

#DIFFERENCE BETWEEN ASK FSK PSK SERIAL#

These basic modulation forms are still used today with digital signals.Р В РІР‚СњР В РІР‚РЋigure 1 shows a basic serial digital signal of binary zeros and ones to be transmitted and the corresponding AM and FM signals resulting from modulation. More sophisticated methods combine two or more of these variations to improve spectral efficiency. There are three basic ways to modulate a sine wave radio carrier: modifying the amplitude, frequency, or phase. Amplitude Shift Keying (ASK) and Frequency Shift Keying (FSK)

Difference between ask fsk psk