Software Defined Radio Multiple Choice Questions & Answers (MCQs) on “”.
1. Which of the following is not present in the conversion stages of super heterodyne receiver?
a) Local oscillator
b) Additional filter
c) Step attenuator
d) Amplifier
Answer: c
Clarification: Each conversion stage of super heterodyne receiver has one LO, additional filters and amplifiers. Step attenuator is present after the pre-selector filters. It confines the total power at the input of first conversion stage within its linear range.
2. Which of the following is used in base station applications?
a) Super heterodyne receiver
b) Direct conversion receiver
c) Digital-RF receiver
d) Homodyne receiver
Answer: a
Clarification: Super heterodyne receiver is used in base station applications. Direct conversion receiver is used in handsets. Digital-RF receiver performs demodulation at RF.
3. Direct conversion receiver is a heterodyne receiver.
a) True
b) False
Answer: b
Clarification: The direct conversion receiver is a homodyne receiver which may use non-zero baseband center frequency.
4. Which of the following is a challenge for direct conversion receiver?
a) GaAs circuitry
b) CMOS circuitry
c) LO leakage and DC bias
d) Difference between CMOS and GaAs circuitry
Answer: c
Clarification: LO leakage and DC bias are a challenge for wide band digital signal processing using direct conversion receiver.
5. In which technique RF is amplified until it is hard-limited into a square wave?
a) Super heterodyne receiver
b) One-bit direct conversion digital receiver
c) Two-bit direct conversion digital receiver
d) Phase crossing counter receiver
Answer: b
Clarification: One-bit direct conversion digital receiver amplifies RF until it is hard limited into a square wave. An advantage of this architecture is that the channel states are stored in lookup tables.
6. When ____ of N zero crossings count becomes small, a signal is considered to be present.
a) mean
b) correlation
c) standard deviation
d) variance
Answer: d
Clarification: When zero crossings are simply counted, a small variance of N zero crossings indicate a signal to be present. A disadvantage of this technique is the presence of high speed logic and lack of equalization.
7. Which of the following is not used to control interference at RF?
a) Programmable digital notch filters
b) Active cancellation
c) Frequency separation
d) Antenna separation
Answer: a
Clarification: Physical antenna separation, frequency separation, programmable analog notch filters and active cancellation are the steps used to control interference at RF.
8. The ______ of out-of-band signal with bandpass characteristic of the receiver gives the interference in the receiver owing to out-of-band energy at the transmitter.
a) correlation
b) correlation and convolution
c) integral
d) convolution
Answer: d
Clarification: The convolution of out-of-band signal with bandpass characteristic of the receiver gives the interference in the receiver owing to out-of-band energy at the transmitter.This type of interference can affect the roll-offs. Frequency separation is employed to suppress this type of interference.
9. ____ separates uplink and downlink.
a) Frequency Division Duplexing
b) Time Division Duplexing
c) Frequency Division Multiplexing
d) Time Division Multiplexing