Amplitude-shift keying (ASK) is a form of amplitude modulation that represents digital data as variations in the amplitude of a carrier wave.In an ASK system, a symbol, representing one or more bits, is sent by transmitting a fixed-amplitude carrier wave at a fixed frequency for a specific time duration. For example, if each symbol represents a single bit, then the carrier signal could be transmitted at nominal amplitude when the input value is 1, but transmitted at reduced amplitude or not at all when the input value is 0.
Amplitude Shift Keying Pdf Free
More sophisticated encoding schemes have been developed which represent data in groups using additional amplitude levels. For instance, a four-level encoding scheme can represent two bits with each shift in amplitude; an eight-level scheme can represent three bits; and so on. These forms of amplitude-shift keying require a high signal-to-noise ratio for their recovery, as by their nature much of the signal is transmitted at reduced power.
Abstract:We propose an amplitude shift keying-type asymmetric quantum communication (AQC) system that uses an entangled state. As a first step toward development of this system, we evaluated and considered the communication performance of the proposed receiver when applied to the AQC system using a two-mode squeezed vacuum state (TSVS), the maximum quasi-Bell state, and the non-maximum quasi-Bell state, along with an asymmetric classical communication (ACC) system using the coherent state. Specifically, we derived an analytical expression for the error probability of the AQC system using the quasi-Bell state. Comparison of the error probabilities of the ACC system and the AQC systems when using the TSVS and the quasi-Bell state shows that the AQC system using the quasi-Bell state offers a clear performance advantage under specific conditions. Additionally, it was clarified that there are cases where the universal lower bound on the error probability for the AQC system was almost achieved when using the quasi-Bell state, unlike the case in which the TSVS was used.Keywords: entanglement; quasi-Bell state; asymmetric communication system; error performance
The output of a frequency shift keying modulated wave is high in frequency for a binary high input and is low in frequency for a binary low input. The amplitude and phase of the carrier signal remain constant.
The current 5.6 Gbps record for an optical data link between LEO to ground was demonstrated using coherent binary phase shift keying (BPSK) between two ESA TESAT laser communication terminals, one on board the NFIRE spacecraft and one on the ground at Tenerife, Spain11. These terminals were engineered for inter-satellite links, where atmospheric turbulence is not an issue and as such do not employ any active turbulence mitigation; only a reduction of the ground terminal aperture to reduce the effect of scintillation. The \(\sim \,5\) m beam size would ensure that the occurrence of deep fades due to beam wander at the ground terminal are negligible, but given turbulence in a ground-to-space link is concentrated at the ground, beam wander is significantly greater for the uplink than the downlink. This is reflected in the disparity in link quality, with the downlink remaining error free while the uplink showed a bit-error rate (BER) of \(\sim \,10^-5\), despite the identical hardware at each end. To push the data rates into the 100+ Gbps regime requires, at a minimum, tip/tilt adaptive optics (AO) stabilisation to improve downlink fiber coupling efficiency and pre-compensate uplink beam wander. Such ground stations are currently in development12,13 and have demonstrated AO-corrected SMF coupling from GEO14, but to our knowledge tip/tilt AO stabilised coupling has not been demonstrated at the more challenging tracking rates of LEO.
EVM measurements are normally used with multi-symbol modulation methods like multi-level phase-shift keying (M-PSK), quadrature phase-shift keying (QPSK), and multi-level quadrature amplitude modulation (M-QAM). These methods are widely used in wireless local-area networks (WLANs), broadband wireless, and 4G cellular radio systems like Long-Term Evolution (LTE) where M-QAM is combined with orthogonal frequency division multiplexing (OFDM) modulation.
Digital modulation methods convert bit voltage level transitions and patterns into sine wave carrier variations. The most basic forms of digital modulation are amplitude shift keying (ASK), frequency shift keying (FSK), and phase shift keying (PSK). ASK represents bit variations as different carrier amplitude levels. FSK represents bit variations as two different carrier frequencies. PSK translates the bit variations into two different carrier phases, usually 180 apart.
3. The 16QAM modulator uses digital-to-analog converters (DACs) to translate 2 bits of the four input bits into four amplitude levels. The four amplitude levels produce multiple amplitude and phase shifts in the balanced modulators that are summed to produce the output.
The main problem with such multi-phase, multi-level systems is that circuit imbalances, unintended phase shifts, amplitude differences, and noise distort the signal and therefore introduce errors. A phase shift and/or amplitude error means that the signal is interpreted incorrectly leading to bit errors and an increase in the BER. The greater the number of phase shifts or phase-amplitude symbols used, the more likely there will be errors due to signal impairments. For instance, 8-PSK is less susceptible to errors and thus more reliable than 16-PSK. QPSK is less susceptible to errors than 64-QAM under the same conditions. 2ff7e9595c
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