General RF Electronics
RF Cafe Quiz #2

All RF Cafe quizzes would make perfect 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.

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Note: Many answers contain passages quoted in whole or in part from the text.

1. On a Smith chart, what does a point in the bottom half of the chart represent?
a) An inductive impedance
b) A capacitive impedance
c) Power saturation

2. While we're on the subject of Smith charts, what is the impedance of the point at the far left edge of the center horizontal line?

a) Infinite ohms (open circuit)
b) Zero ohms (short circuit)
c) 50 ohm match

3. A single-conversion downconverter uses a high-side local oscillator (LO) to translate the input radio frequency (RF) to an intermediate frequency (IF). Will spectral inversion occur at IF?

a) Yes, always
b) No, never
c) Sometimes

4. What happens to the noise floor of a spectrum analyzer when the input filter resolution bandwidth is decreased by two decades?

a) 20 dB increase
b) 20 dB decrease
c) 40 dB decrease

5. What is a primary advantage of a quadrature modulator?

a) Low LO power required
b) Four separate outputs
c) Single-sideband output

6. What is meant by dBi as applied to antennas?

a) Isolation in decibels
b) Physical size relative to intrinsic antennas
c) Gain relative to an isotropic radiator

7. What is the power dynamic range of an ideal 12-bit analog-to-digital converter (ADC)?

a) 36.12 dB
b) 120 dB
c) 72.25 dB

8. An ideal 10 dB attenuator is added in front of a load that has a 2.00:1 VSWR. What is the resulting VSWR of the load + attenuator?

a) 1.07:1
b) 2.10:1
c) 12.0:1

9. What is the thermal noise power in a 1 MHz bandwidth when the system temperature is 15 degrees Celsius (assume gain and noise figure are 0 dB)?

a) -114.0 dBm (in a 1 MHz bandwidth)
b) -114.0 dBm
c) -114.0 dBm/Hz

10. Two equal amplitude tones have a power of +10 dBm, and generate a pair of equal amplitude 3rd-order intermodulation products at -20 dBm. What is the 2-tone, 3rd-order intercept point (IP3) of the system?

a) +40 dBm
b) +25 dBm
c) +20 dBm

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