1. Amplitude Shift Keying (ASK):
- Definition: ASK is a digital modulation technique where the amplitude of the carrier signal is varied in accordance with the digital data. A binary "1" is represented by a high amplitude, and a binary "0" by a lower or zero amplitude.
- Characteristics:
- Simple to implement.
- Highly susceptible to noise, since amplitude variations are easily affected by interference.
- Used in optical fiber communications and some RFID systems.
- Applications: Low-speed communication systems like early radio transmissions and optical devices.
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2. Frequency Shift Keying (FSK):
- Definition: FSK is a digital modulation technique where the frequency of the carrier signal is varied according to the digital data. A binary "1" is transmitted with one frequency, and a binary "0" is transmitted with another frequency.
- Characteristics:
- More robust against noise than ASK, since changes in frequency are less affected by signal degradation.
- Easy to implement with simple frequency detectors.
- Widely used in low-speed radio communication, such as Bluetooth and modems.
- Applications: Radio transmission systems, wireless LANs, and pager systems.
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3. Phase Shift Keying (PSK):
- Definition: PSK is a digital modulation technique where the phase of the carrier signal is altered to represent binary data. A binary "1" might be represented by a phase shift of 0 degrees, and a binary "0" by a phase shift of 180 degrees (in BPSK – Binary PSK).
- Characteristics:
- More resistant to noise and interference compared to ASK and FSK.
- Variants include QPSK (Quadrature PSK), which encodes two bits per phase change, improving data rates.
- Requires more complex receivers compared to ASK and FSK.
- Applications: Satellite communication, Wi-Fi, and mobile phone networks (4G, 5G).
Each modulation technique balances complexity, noise resistance, and data rate, making them suitable for different communication environments.
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