(a) Time Division Multiplexing (TDM) can be used to transmit several Pulse Code Modulation (PCM) channels along a single communications link. A system uses a PCM sampling frequency of 25 kHz to convert audio signals in the range 20 Hz to 10 kHz into digital form. A 10-bit code is used to define the sample levels with an input voltage range of 0 to 5V. Several signals are sent along one carrier using TDM. The TDM's clock rate of each PCM channel is 2MHz. Several PCM channels are transmitted down a single TDM link. (i) Calculate the time needed to transmit a single 10-bit PCM sample at a clock rate of 2MHz. [2 marks] (ii) How many sampling levels are available using a 10-bit code? (iii) Calculate the resolution. Table 1: QPSK Modulator (b) For the QPSK modulator with reference carrier oscillator of cos coct and phase shift of -90, determine the absent information as shown in Table 1. [4 Marks] QIQ+I+ BMQ 0 0 -1 -1-sin(wet) -cos(w.t) 0 1 -1 1 0 +1 -1 1 1 +1 +1 BMI Summer [2 marks] -sin (wet) -cos(wet) +1-sin(wet) cos(wet) -sin (wet)+cos(wet) [2 marks] QPSK Output Phase +135 +45