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# Modern Communications Receiver Design and TechnologyRF Cafe Quiz #32

All RF Cafe Quizzes make great fodder for employment interviews for technicians or engineers - particularly those who are fresh out of school or are relatively new to the work world. Come to think of it, they would make equally excellent study material for the same persons who are going to be interviewed for a job. Bonne chance, Viel Glück, がんばろう, buena suerte, удачи, in bocca al lupo, 행운을 빕니다, ádh mór, בהצלחה, lykke til, 祝你好運. Well, you know what I mean: Good luck!

Note: Some material based on books have quoted passages.

This quiz is based on the information presented in Modern Communications Receiver Design and Technology, by Cornell Drentea. Published by Artech House.

Note: Some of these books are available as prizes in the monthly RF Cafe Giveaway.

1.  What is the modern version of a "coherer?"

a)  Phase locked loop

d)  Coherent oscillator

2.  What is the difference between a heterodyne (1) and a superheterodyne (2) receiver?

a)  (1) uses tubes while (2) uses transistors

b)  (1) is direct conversion to 0 Hz while (2) uses an IF frequency prior to conversion to 0 Hz

c)  (1) is low power while (2) is high power

d)  (1) uses a DC supply while (2) uses an AC supply

3.  What is an image frequency?

a)  The reflection of a signal

b)  The anti-reflection of a signal

c)  The frequency generated in the mixer that duplicates the intended signal

d)  The signal on the other side of the LO that will also convert to the same IF as the intended signal

4.  What is a High Probability of Intercept receiver?

a)  One that surveys broad frequency ranges in narrow bandwidth samples at high sensitivity

b)  A statistical model of an ideal receiver type

c)  The mathematical duel of a Low Probability of Intercept receiver

d)  One that uses probability algorithms to extract signals form noise

5.  Why would a double conversion be used instead of a single conversion?

a)  Twice the efficiency

b)  Half the efficiency

c)  Avoiding high level intermodulation spurs from the mixer

d)  PCB space savings due to two mixers in one package

6.  What is the 1 dB compression point of an electronic device?

a)  The power level at which the device gain is reduced by 1 dB from the linear value

b)  The power level at which the device gain is increased by 1 dB from the linear value

c)  The 1 dB gain level

d)  The pressure where silicon or GaAs breaks from compressive forces

7.  What is one of the main reasons for using a fractional-N phase-locked loop (PLL) synthesizer?

a)  Higher power levels can be tolerated

b)  Small frequency steps can be obtained without using multiple PLL loops

d)  None of the above

8.  What type of diode usually makes the best RF signal switch?

a)  Schottky

b)  Zener

c)  Varactor

d)  PIN

9.  Why would you use a logarithmic amplifier (log amp)

a)  If you need to convert from linear units to decibels

b)  If you are only amplifying very small signals

c)  If you are only amplifying very large signals

d)  If you must accommodate a large dynamic range at the input while producing a smaller dynamic range at the output

10.  What is(are) the main difference(s) between an infinite impulse response (IIR) filter and a finite response response (FIR ) filter?

a)  An IIR represents "real" analog filters whereas an FIR does not

b)  An IIR can be unstable while an FIR is always stable

c)  An IIR filter uses feedback while a FIR filter does not

d)  All the above