Communications Homework Help

9. Consider an 1800 MHz mobile radio system for cellular communication. The base station is at a height of 3 m above the ground and the mobile at 1 m. The gain of the base station antenna is 6 dBi and for the mobile antenna, the gain is 2 dBi. It is required to determine the minimum transmitted power in order for the BS to serve a mobile at a distance of 1000 m in a Line-of-sight communication link. The received power is -104 dBm.

11. What is a universal gate? Please justify your reasoning and give an example. 12. Implement the following Product-of-Sums function using logic gates. F = (X+Y)(Y+Z) 13. For the given function in question 12, implement F as a Sum-of-Products using logic gates. 14. Implement a 4-bit parallel adder using full adders. Clearly label the bits ofthe inputs. 15. Consider the question 14. If the carry propagation delay for a full adder is 2ns, how fast can the inputs to the 4-bit parallel adder be updated? 16. You are given a task of designing a circuit to produce a repetitive sequence of 1,2,3,1,2,3,... Represent this problem in a state diagram. 17. Consider the question 16. Derive the state table. 18. Consider the question 16 and 17. Draw the circuit diagram for the circuit. 19. Assume that you have access to a clock signal at a frequency of f. Propose a circuit that generates another clock signal with a frequency of f/4. 20. What is the difference between combinational and sequential logic circuits.

The output of an AM modulator is given by x(t)=A_{c} \cos (2000 \pi t)+50 \cos (2100 \pi t)+50 \cos (1900 \pi t) The carrier power is 5 kW. a. Determine the modulation index ma. b. Write an expression for the normalized modulating signal. c. Calculate the power efficiency. d. Calculate the PEP supplied by the AM transmitter and compareit with the normalized average power and the carrier power.

FM broadcasts are usually at a higher frequency than AM broadcasts because:

An audio signal of BW that is equal to 4 KHz is sampled 25% above the Nyquist rate and is quantized. The maximum Q error is not to exceed 0.1% of the peak signal amplitude. The resulting quantized samples are coded and transmitted using 4-array signaling. a. Determine the minimum number of 4-ary pulses need to encode each samples b. Determine the essential transmission bandwidth for this signal such that there is no ISI at key samples of the pulses (at the values corresponding to half/center of pulse duration) 1. if NRZ rect() pulses are employed 2. if sinc() pulses are employed 3. if raised cosines with α =0.25 are put to use.

Question 1. What is the output voltage Vout when PA2 is high, PA1 is high, and PAO is low? Assume VOH is3.3V and VoL = 0V.

6. Draw the constellation diagram of 16-QAM. How many bits are sent in one symbol in 16-QAM. How much the increase in data rate if 16 QAM is replaced by 64QAM (in 96age).

For a lowpass signal with a bandwidth of 6000 Hz, what is the minimum samplin frequency for perfect reconstruction of the signal? What is the minimum require sampling frequency if a guard band of 2000 Hz is required? If the reconstructic filter has the frequency response

Consider the message signal m(t) = sinc(20000t) which is frequency modulated with frequency deviation constant kf = 60 KHz. Find the effective bandwidth of the frequency modulated signal.

Part A [20 Marks] Consider an ASK (Amplitude Shift Keying) modulation system. The modulating signal is digital bit stream with a bitrate of 2kbps. The modulating signal amplitude is 0 to 5 Volts. The carrier signal is 12 Vpp signal and has a frequency of 800kHz. ● ● ● Sketch the ASK signal indicating signal levels. Calculate the modulation index. Sketch the frequency spectrum. Determine the bandwidth of the ASK signal.