Advanced Microwave Engg - May 2013
Electronics & Telecomm. (Semester 8)
TOTAL MARKS: 100
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks. 1 (a) Explain Large Signal characterization with reference to load pull contours. How is it measured? (5 marks) 1 (b) What are the causes of low frequency noise and high frequency noise associated with the mixer? (5 marks) 1 (c) Define and explain with neat diagram noise correlation matrix for general noisy two port network. (5 marks) 1 (d) What is unilateral figure of merit of an amplifier?(5 marks) 2 (a) If the transistor has following S-parameters at 5Ghz with 50Ω impedance.
Determine the stability criteria and plot the stability circles. (10 marks) 2 (b) Derive the parameters of an Amplifier:
(i) Power gain (G)
(ii) Available gain (GA)
(iii) Transducer gain (GT)(10 marks) 3 (a) Explain using suitable diagrams two methods of designing broadband amplifier.(10 marks) 3 (b) A BJT with IC = 30 mA and VCE = 10V is operated at a frequency of 1 GHz in a 50Ω system. Its S-parameters are -
Determine whether the transistor is unconditionally stable. If yes, calculate optimum terminations, GSmax, GLmax, GTUmax. (10 marks) 4 (a) A certain GaAs MESFET has following noise figure parameters measured at Vds = 50, Ids = 20 mA with 50Ω resistor once for frequency of 9 GHz,
Fmin = 4dB, Γopt=0.55∠175, R0= 4Ω.
Plot noise figure circles for given values of f1 at 2, 2.5, 3.5, and 4.5 dB. (15 marks) 4 (b) Define stability. List the various criteria for stability.(5 marks) 5 (a) If a one port microwave diode has Γin=1.5∠60° with respect to Z0=50Ω. Design an oscillator for desired frequency of 10GHz.(12 marks) 5 (b) For a two port oscillator at steady state oscillations prove that if τLτin=1 then τinτout=1(8 marks) 6 A certain MESFET is biased for large signal class A operation with following small signal S-parameters at 5GHz:
The large signal forward transmission coefficient S21 is measured to be S21=2.1∠180°. Design a large-signal class A amplifier with maximum transducer gain in a 50Ω system. Assume (±)0.5dB error in gain. What is the high-power amplifier gain? (20 marks) 7 (a) Write a note on optimal loading used in 1+PA design.(10 marks) 7 (b) A wideband amplifier (2-4 GHz) has gain of 10dB, an O/P power gain of 10dBm and a noise figure of 4dB at room temperature. Find the output noise power in dBm.(10 marks)