250e

If the Signal to Noise Ratio (SNR) of a wireless link is 20DB and the Radio Frequency(RF) bandwidth is 20kHz, using Shannon's capacity formula, determine the maximum theoretical data rate that can be transmitted.(5 marks) b)With the aid of block diagrams explain the principle operation of (DSSS) Direct Sequence Spread Spectrum and (FHSS) Frequency Hopping Spread Spectrum transmission techniques.(12 marks) With the aid of a diagram and a brief explanation, what is the purpose of the autocorrelation function, and how does it work in a DSSS WLAN.(8 marks)

(a) A 50 m long lossless transmission line with Zo = 50 ohms operating at 50 MHz is terminated with a load ZL = 90 + j 30 ohms. If the wave velocity is u =0.8 c,where cis the speed of light in vacuum, find: i. The reflection coefficient ii. The input impedance (b) The Direct Broadcast System (DBS) satellite (at a distance of 39000 km)transmits at 13 GHz in the Ku Band, with a transmit power of 200 W, with a transmit antenna gain of 35 dB and with an IF (Intermediate Frequency)bandwidth of 30 MHz. The ground receiving station dish has a gain of 32 d Band sees an average background brightness temperature of Tb = 50 K. The receiver LNB (Low Noise Block) has a noise figure of 1.8 dB. Find: i.The EIRP (Effective Isotropic Radiated Power) ii.The power received at the input of the LNB iii.The signal to Noise ratio at the LNB output iv.Comment on what would happen if both transmit and receive antennas are replaced by typical monopole antennas. (c) A certain two-port network is measured and the following scattering matrix is obtained: [S]=\left[\begin{array}{cc} 0.3 \angle 0^{\circ} & 0.7 \angle 90^{\circ} \\ 0.7 \angle 90^{\circ} & 0.3 \angle 0^{\circ} \end{array}\right] From the data determine: i.If the network is reciprocal ii.If the network is lossless (d) Briefly describe how the following RF systems operate: i.Wilkinson power divider ii.Circulator

Problem 2. (15 points) Design the lead compensator such that you can achieve the both requirements. D_{c}(s)=\frac{T_{d} s+1}{\alpha T_{d} s+1} where a < 1. Use K you designed in Prob. 1. Provide the Bode plot of the open-loop with the stability margins. You will need iterations to find the correct max and max

Consider the closed-loop control system shown below: \text { where } C(s)=K D_{c}(s) \text { and } G(s)=\frac{1}{(s+1)\left(\frac{s}{2}+1\right)\left(\frac{s}{5}+1\right)} The design requirements are given below: \text { 1. Stcady-state requircment: } K_{p} \geq 9 \text { ( } K_{p} \text { is a static position crror constant.) } 2. Transient requirement: phase margin > 45 deg Problem 1. (10 points) Assuming De(s) = 1, dctcrminc K such that you can achicve thesteady-state requirement. Then, provide the Bode plot of the open-loop with the stabilitymargins (use "margin" command in MATLAB).

Problem 3. (15 points) Design the lag compensator such that you achieve the both re-requirements. D_{c}(s)=\frac{T_{i} s+1}{\alpha T_{i} s+1} where a > 1. Use K you designed in Prob. 1. Provide the Bode plot of the open-loop with the stability margins. You will need iterations to find the correct T; and a.

At 50m you receive a -60 dBmW signal, at a frequency of 5GHZ. What was thetransmitted power in Watts if you ignore antenna gain and any losses.Please show all your working.(a)(10 marks) (b)A data transmission line has the following characteristics: Characteristic impedance: 50N Сараcitance: 100pF/m Attenuation (per 100m):1 1. The inductance per metre of the line 2. The attenuation coefficient at 10MHZ 3. The phase delay in degrees between two points over 5 metres at a frequency of10MHZ(6 marks)

3. Use the "Sommerfeld ground" option in FEKO and choose some specific values of the parameters for the lossy ground. You can use a value for the conductivity 10-03 ≤ ≤ 12 × 10-03 Siemens/meter, and, the relative permittivity as & = 15; the permeability is Mo = 4π X 10-07 Henries/meter. (These are the data one needs to enter when using the Sommerfeld ground option in FEKO.) Repeat the results of part 1 using the lossy ground option and compare your results in part 3 against the ones obtained in parts 1 and 2.

Electro Magnetic Interference (EMI) is normally considered as being either conductive or radiative. For each type of interference describe ways of reducing their effects. A carrier of frequency 800kHz is being Amplitude Modulated (AM) by a modulating signal that is a sine wave at a constant frequency of 8kHz and constant amplitude. The modulation index is less than 100%. Determine the frequency of the upper sideband and lower sideband and total bandwidth of the resultant Amplitude Modulated(3 marks)waveform. If the carrier in part (b) has a peak-to-peak voltage of 10V and the modulating signal has a peak-to-peak voltage of 5V, determine the modulation index, the maximum and minimum voltages of the resultant Amplitude Modulated waveform and the peak amplitude of the upper and lower side bands. Hence, determine the modulating signal voltage that would result in 100% modulation.(7 marks) Briefly describe the process by which the modulating signal would be extracted from the Amplitude Modulated waveform at a receiver. Using the signal described in part(b) and if the demodulator comprises a simple diode detector, determine a value for the demodulator's time constant and justify your choice. Hence, determine the value of capacitance required if the resistance = 2k.(9 marks)

1- When a cable carries multiple currents, all in the same direction, this would be associated with which coupling mode? Select one: A. Differential mode B. Common mode C. Antenna mode D. Common impedance E. None of the above 2- Interference at the source can be reduced by: Select one: A. Low noise design B. Shielding C. Decoupling D. Filtering E. All of the above 3- Shielding for magnetic fields at low frequency can be done with: Select one: A. Purely conductive material B. Aluminium C. Copper D. A high-permeability material such as mu-metal or its derivatives E. B & C 4- In hazardous areas, one would be more inclined to consider Select one: A. both the upper and lower explosive limit B. the lower explosive limit C. the upper explosive limit D the upper flammable limit 5- An instrument is to be mounted in a hazardous area. If it is marked T2" (maximum surface temperature of 300°C). Select one: A. it is safe to be used with gasses and vapours that have an ignition temperature greater than 300°C. B. it is safe to be used with gasses and vapours that have an ignition temperature lower that 300°C. C it can only be used with gasses and vapours whose ignition temperature is 300°C. D. it is unsafe as it gets too hot 6- ATEX 100a European Directive deals solely with Select one: A. the minimum requirements for improving the safety and health protection of workers potentially at risk from an explosive atmosphere B. the zone classification of a hazardous area C equipment and protective systems intended for use in potentially explosive atmospheres D. the IEC Standard to which equipment is certified 7- Who, generally speaking, is held responsible for the appropriate explosion protection safety of any given installation? Select one: A. The installer B. The equipment supplier C. The certifying authority D. The plant owner 8- HAZOPS work best if they are conducted Select one: A. when the P&IDs have been finalised, but before detailed design has commenced B. at any time. They are not influenced by P&IDs C. over beer and pretzels D. before the P&IDs have started 9- Which of the following listed certificate numbers would be for an equipment which has special conditions for installation of operation? Select one: A. BASOSATEX1234 U B. PTB07ATEX1784X C. SIRA09ATEX0645/1 D. CESI08ATEX1323

2. Model the geometry in FEKO. To do so, take the same frequency as in question 1, and select the dipole length to be ≤ and carrying a constant current. Repeat the case of question 1 but now the full-wave solver FEKO is used which is assumed to be more accurate than the analytical model. Now present your results for part 1 and 2 (analytical vs. full-wave FEKO) and comment on the accuracy of the analytical results.