Consider a pulse s(t) = sinc(at) sinc(bt) where a ≥ b.
a. Sketch the spectrum S(f) of the pulse.
b. Suppose that the pulse is to be used over an ideal real baseband channel with one-sided bandwidth 400 Hz. Determine a and b such that the pulse is Nyquist for 4-PAM at 1200 b/s and exactly fills the channel bandwidth.
c. Now, suppose that the pulse is to be used over a passband channel spanning the frequency band 2.4–2.42 GHz. Assuming that we use 64-QAM at 60 Mb/s, determine a and b so that the pulse is Nyquist and exactly fills the channel bandwidth.
d. Sketch an argument showing that the magnitude of the transmitted waveform in the preceding settings is always finite.

Acommercial grade cubical freezer, 4 m on a side, has a composite wall consisting of an exterior sheet of 5.0-mm thick plain carbon steel (kst= 60.5 w/m k), an intermediate layer of 100-mm thick polyurethane insulation (kins 0.02 w/m k), and an inner sheet of 5.0- mm thick aluminium alloy (kal polyurethane insulation and both metallic sheets are each characterized by a thermal contact resistance of r 2.5 x 104 m2 k/w. (a) what is the steady-state cooling load that must be maintained by the refrigerator under conditions for which the outer and inner surface temperatures are 25°c and -5°c, respectively? (b) for power saving purpose, which wall material should be increased/reduced in. thickness in order to reduce 50% of the cooling load found in part (a)? redesign the thickness of the proposed material. 177 w/m-k). adhesive interfaces between the q=575.93 w