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Answers to Exam Prep Questions
- Answer C is correct. RFID interrogators are commonly called RFID readers. This name prevails from the past when the function of this device was limited to purely reading the tag's ID. An RFID interrogator is not called an RFID radiator or RFID transistor because these names are not established in RFID but in different technologies. Therefore, answers A and D are incorrect. An RFID interrogator is not called an RFID tag because that is another part of the whole RFID system. Therefore, answer B is also incorrect.
- Answer C is correct. The anticollision protocols are not used for collisions between vehicle-mounted interrogators. These must be avoided by proper operation of the vehicles on which these devices are mounted. Therefore, answer A is incorrect. The problems created by multiple readers operating in the same environment are solved by a dense interrogation mode or synchronization methods. And data moving through an RFID system is a network management issue. Therefore, answers B and D are incorrect.
- Answer C is correct. An inlay is not a part of an RFID interrogator but is part of an RFID tag. The power amplifier, controller/processor, and oscillator are parts of the RFID interrogator; therefore, answers A, B, and D are incorrect.
- Answers A, B, and D are correct. No antenna polarities are classified as vertical circular because the circular polarization is not orientation sensitive and is not referenced to a plane. Therefore, answer C is incorrect.
- Answer B is correct. The mono-static antenna is based on a principle by which a single antenna works as a transmitter as well as a receiver, and these functions are switched in fractions of seconds. A bi-static antenna includes two antennas that can be within one case or separated. One antenna is dedicated to transmitting, and the other antenna is dedicated to receiving. This implies that answer D is incorrect.Answer A is incorrect because the names of antennas in this case have nothing to do with the radiation direction. Answer C is also incorrect because the antenna gets the power from the reader, and the AC or DC power has nothing to do with the antenna design.
- Answer A is correct. Reading the data on a tag takes less time than writing the data to a tag; therefore, answers B and C are incorrect. The ratio of the reading and writing time does not depend on the frequency at which the readers operate; therefore, answer D is also incorrect.
- Answer C is correct. An antenna does not create power to radiate a stronger signal. Therefore, answer A is incorrect. Antenna gain is calculated as 10 times the logarithm of the power output to power input ratio; therefore, answer B is incorrect. Antenna gain is not achieved by focusing the radiated RF signal into wider patterns but narrower patterns; therefore, answer D is incorrect.
- Answer B is correct. The probability of communication with the tag is in the sweet spot, which is usually not immediately at the antenna. Some interrogators/antennas require a certain distance between the antenna and the tag when reading and writing the tag, to achieve a better communication, or because the tag could be damaged when too close to the antenna. Therefore, answer A is incorrect. It is always better if the tag in the antenna's field moves because this would prevent the possibility of the tag staying in a hole of antenna coverage, where it could not be interrogated. Therefore, answer C is incorrect. Because it is always better for the tag to be moving through the field, this option could be the right answer; however, for successful reading and mainly writing tags, the tag needs to be in the field for a certain time. If it moves too fast and stays in the field for too short a time, the communication could be unsuccessful; therefore, answer D is incorrect.
- Answer C is correct. The amount of switching required using a multiplexer would render a mechanical switch useless not only because of the wear the switch would undergo, but by the sheer volume of switching required to ascertain accurate reads. Answers A, B, and D are all true but not the correct answers. It is the capability of the solid state circuitry to switch rapidly each time with no moving parts that makes it a better option. Therefore, A, B, and D are not correct answers.
- Answer C is correct. Although A could be viewed as the correct answer, mesh metal would not give the required advantage of reading the tagged materials on a conveyor system because it would not reflect or focus the radiated signal on the projected area. Answer B is not correct. Answer D also is not correct; if a device was to hold the package until a successful read was achieved, it would not work well with a high-speed conveyor system.