Software Defined Radio Questions and Answers – Antenna Tradeoffs – 1

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This set of Software Defined Radio Multiple Choice Questions & Answers (MCQs) focuses on “Antenna Tradeoffs – 1”.

1. The parameters of the antenna considered for RF access are ______
a) RF band and bandwidth
b) RF band and resonant frequency
c) noise constraints and bandwidth
d) directivity and RF band
View Answer

Answer: a
Explanation: The parameters of the antenna considered for RF access are RF band and bandwidth. Antenna architecture determines the number and bandwidth of RF channels. This imposes constraint on number and bandwidth of ADCs.
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2. How is bandwidth expressed in a Software Defined Radio?
a) Ratio of highest RF to lowest RF
b) Ratio of median RF to lowest RF
c) Ratio of lowest RF to highest RF
d) Ratio of lowest RF to median RF
View Answer

Answer: c
Explanation: Bandwidth can be expressed as a percentage of carrier frequency. An alternate method is to take the ratio of lowest RF to highest RF over which the parameters such as VSWR are operable.

3. What type of antenna is the Yagi antenna?
a) Surface-wave
b) Resonant
c) Traveling wave
d) Aperture
View Answer

Answer: a
Explanation:The Yagi antenna is a surface-wave antenna operating at 1 – 6 GHz range. It is used as radar feed and array. The setup of a Yagi antenna consists of a driven element, a reflector, and one or more directors.
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4. What is the operating range of a pyramidal horn antenna?
a) 1 – 6 GHz
b) 1 – 5 GHz
c) 300 MHz – 70 GHz
d) 100 MHz – 35 GHz
View Answer

Answer: c
Explanation: The pyramidal horn antenna is an aperture type antenna operating in the range 300MHz – 70GHz. It is used in radar communication.

5. The increase in the bandwidth of the antenna causes the thermal noise power to ______
a) decrease linearly
b) increase linearly
c) increase exponentially
d) decrease exponentially
View Answer

Answer: b
Explanation: Wider bandwidth results in increase of noise which reduces the value of SNR, affecting the performance negatively. Filtering of antenna channels according to subscriber signals can give better performance.
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6. Which method is used to estimate time-difference of arrival and angle of arrival?
a) Optical interferometry
b) Interferometric dynamic measurement
c) Frequency scanning interferometry
d) Phase interferometry
View Answer

Answer: d
Explanation: Time-difference of arrival and angle of arrival are determined by phase interferometry. These parameters play an important role in network-based emitter location techniques.

7. Both TDOA and CDMA continuously compute ______
a) time difference of arrival
b) time of arrival
c) angle of arrival
d) time delay of arrival
View Answer

Answer: b
Explanation: Time Difference of Arrival (TDOA) and Code Division Multiple Access (CDMA) continuously compute time of arrival in order to recover the direct sequence and spread spectrum waveform.
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8. Antenna separation effectively controls _________
a) directivity
b) external noise
c) self-generated interference
d) external interference
View Answer

Answer: c
Explanation: Antennas in same enclosure or when closely spaced often lead to interference. This can be mitigated by antenna separation. The benefit of separation can be estimated by link-based spreadsheet.

9. Which of the following gives permissible levels of exposure to radiation in terms of whole body average SAR as per US FCC?
a) 0.02
b) 0.04
c) 0.06
d) 0.08
View Answer

Answer: d
Explanation:The radiation from antenna might have a harmful impact on the human body. The US FCC imposes a limit of 0.08 for whole body average SAR and 1.6 for spatial peak SAR.
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10. Human body interaction causes distortions in antenna pattern and health risk in human beings.
a) True
b) False
View Answer

Answer: a
Explanation: Human body interaction causes distortions in antenna pattern and health risk in human beings. Handheld device generally tilt the wire antenna away from the user for minimal absorption and better radiation efficiency.

11. Which of the following is not a concern for antenna tradeoff?
a) RF access
b) Calibration
c) Phase noise
d) RF MEMS
View Answer

Answer: d
Explanation: RF access, antenna calibration, phase noise are some parameters which influence antenna tradeoffs. The antenna establishes the available RF band and is responsible for the directional properties of the system.

12. SPEAK easy aimed to developed a full band antenna that operated over the range ______
a) 2 MHz to 2000 MHz
b) 2 Hz to 2 MHz
c) 20 Hz to 2 MHz
d) 20 MHz to 2000 MHz
View Answer

Answer: a
Explanation: The RF range of 2 MHz to 2000 MHz was aimed to be achieved by SPEAKeasy. This falls in the range of 1000:1, it spans over 3 decades.

13. What was the frequency range achieved by SPEAKeasy – 1?
a) 20 – 300 MHz
b) 5 – 300 MHz
c) 30 – 3000 MHz
d) 30 – 400 MHz
View Answer

Answer: d
Explanation: SPEAK easy split the operating range into three bands: a) 2 – 30 MHz; b) 30 – 400 MHz; and c) 400 – 2000 MHz. Band b was achieved by SPEAK easy – 1 and band a, b was achieved by SPEAKeasy – 2.

14. Which of the following are frequency independent antennas?
a) Dielectric rod and Yagi
b) Log-periodic and Equiangular Spiral
c) Half-wave dipole and Half-wave slot
d) Axial mode helix and Pyramidal horn
View Answer

Answer: b
Explanation: Log-periodic and Equiangular spiral antennas are frequency independent antennas. Log – periodic antenna operates over the range 10 MHz – 12 GHz. Equiangular spiral operates over the range 100 MHz – 35 GHz.

15. Lower gain antenna reduces link margin and decreases the outage probability proportionally.
a) True
b) False
View Answer

Answer: b
Explanation: Lower gain antenna reduces link margin and increases the outage probability proportionally. These antennas become optimal when aggregate cost and quality of information services across the combination of bands and modes is considered.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn | Youtube | Instagram | Facebook | Twitter