Mid-term

Mid-term - modulator for the following input bit sequence...

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EE513 Mid-Term Examination Based on the Shannon limit, determine S/N required to operate DTV, i.e., 19.4 Mbps using 6 MHz bandwidth. (15 pts) Phase locked loop is an important circuit in communications. Describe signals in PLL. Describe several applications (more than one) of PLL in communications systems. (15 pts) For a 0.4 V input, what is the output voltage of a μ -law compander? Assume the full voltage is 4 V and μ equals 255. (15 pts) For AM DSBFC with a modulation index of 0.9, what is the percentage power of the carrier, i.e., power of carrier / total power? (15 pts) Two amplifiers with a gain of 10.0 dB and a noise figure of 3.0 dB each are placed in series. For the cascaded amplifier what is the noise figure? (15 pts) Determine the oscillation frequency of the following oscillator? (15 pts) Which is the output phase sequence of a differential phase shift keying (DPSK)

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Unformatted text preview: modulator for the following input bit sequence, 010100111? Assume the first reference bit is 0. (10 pts) 100 μ H 100 pF 100 pF I = B log2 (1 + S/N) 19.4x10^6=6x10^6 log2 (1+S/N) S/N=8 or 9.24dB PLL generates one signal after the loop filter and the other signal after VCO. PLL can be used in synchronizing the local oscillator to the carrier frequency. It can also be used to detect FM modulation. m-max=4V, m-s=0.4V m-c (output) = 2.364V Total power = Pc + P-lsb + P-usb m=0.9 Ratio = Pc/Total power = 0.7117 or -1.48dB NF=NF1+(NF2-1)/A1+(NF3-1)/A1A2+… A1=A2=10 3dB is equivalent to a factor of 2. NF=2+(2-1)/10=2.1 or 3.22 dB C = (100p in series with 100p) L = 100 u f = 1 / 2 pi sqrt(LC) = 2.25 MHz 010100111 XOR 1 1 1 1 1 1 1 4 2 c usb lsb P m P P = =...
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Mid-term - modulator for the following input bit sequence...

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