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How FSK modulation and demodulation is done?
The FSK signal is passed through the two Band Pass Filters BPFs, tuned to Space and Mark frequencies. The output from these two BPFs look like ASK signal, which is given to the envelope detector. The signal in each envelope detector is modulated asynchronously.
What are the main disadvantage of ASK and FSK?
Disadvantages of ASK modulation ➨It offers lower power efficiency. ➨ASK modulation is very susceptible to noise interference. This is due to the fact that noise affects the amplitude. Hence another alternative modulation technique such as BPSK which is less susceptible to error than ASK is used.
How to demodulate AFSK using FM demodulation?
FM demodulation of AFSK ¶ We can also demodulate AFSK using FM demodulation. Recall that the bandwidth of AFSK is approximately 2 Δ f + B where B is the bitrate (1200Hz for AFSK1200). The afsk signal is s (t) = c o s (2 π f c t + 2 π Δ f ∫ ∞ t m (τ) d τ).
What do you call a non return to zero AFSK signal?
For this reason, AFSK1200 has to be generated in the following way: where m ( t) has the value =1 for a duration of a mark bit, and a value =-1 for a duration of a space bit. Such m ( t) signal is called an Non-Return-to-Zero (NRZ) signal in the digital communication jargon.
What is the bandwidth of a FSK signal?
The exact frequency spectrum of a general FSK signal is difficult to obtain. But, when the mark and space frequency difference Δ f is much larger than the bit-rate, B, then the bandwidth of FSK is approximately 2 Δ f + B. This is not exactly the case for AFSK1200 where the spacing between the frequencies is 1000Hz and the bit-rate is 1200 baud.
How is the carrier frequency used in demodulation?
With both mixing and envelope detection, the carrier frequency must be much greater than the modulation (information) frequency. With mixing, demodulation is performed by mixing the measured signal with a signal with a frequency identical to the carrier frequency through a lock-in amplifier.