Answer Happy

(b) (i) A data source uses four symbols. X1,X2X3, and X4 with probabilities of occurrence 0.1, 0.1, 0.1 and 0.7 respectively. Calculate the entropy of this source. (ii) An amplitude shift keying (ASK) method uses rectangular pulses for the data, where the pulse width is 4 us and the amplitude 1. Write down an expression that describes the frequency content of a single pulse and determine the frequency where the amplitude first equals zero. Briefly explain how this expression can be utilised in communications.
(iii) The pulse shape in part (b) (ii) is used for the modulating data using the following three methods. Binary Amplitude shift keying. Carrier frequency - 10 MHz Binary Amplitude shift keying. Carrier frequency – 15 MHz Binary Frequency shift keying. Carrier frequencies – 16 MHz and 18 MHz For each of the three methods state all relevant frequencies in the modulated signal, such as centre frequencies and frequency ranges (bandwidth).