Amplitude Shift Keying (ASK) & Frequency Shift Keying (FSK). Digital Communication Systems. Some of the modulation techniques employed by digital communication systems are explained throughout this Lab. Today, Amplitude Shift Keying and Frequency Shift Keying are to be explained.
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Amplitude Shift Keying (ASK)&Frequency Shift Keying (FSK)
OFF by the binary sequence to be transmitted.
m(t)=0 for logic 0
0≤ t ≤ Tb
m(t)= 1 for logic 1
Note: the carrier frequency is chosen such that
fc=n*Rb ; where n is an integer
- S1(t)=0 for logic 0
- S2(t)=V cos (2*pi*fc*t) for logic 1
Illustration of ASK
1 0 1 1 0 0 1 0 1 0
ASK modulated signal
Amplitude varying-frequency constant
interference of other signals through selecting the BW
of each signal.
trigger. ( Threshold = V/2 ) . They are used to convert the
analog signal to a digital one.
amplitude is not constant.
from each others by transmitting one of the two sinusoidal
signals that differ in frequency by a fixed amount.
0≤ t ≤ Tb
Illustration of FSK
1 0 1 1 0 0 1
Carrier 1 (frequency #1)
Carrier 2 (frequency #2)
FSK modulated signal
Frequency varying-amplitude constant