Review Questions

1.	A customer calls you up and tells you that their RFID portal has stopped reading tags completely. What is the first thing you should do when you get on-site? Call the reader manufacturer for help. Install the newest firmware. Set up a signal generator with a frequency equal to the center frequency of the interrogator and attach the reader's antenna to the signal generator. Reboot the reader.
2.	What is the best kind of cable to use for a dock door that is 15˝ to the center of the door from one side, if you are installing a reader on one side and antennas on both sides? LMR-240 LMR-400 PJS007 It does not matter; the cable is irrelevant.
3.	What type of software is required to change if you are going from reading one protocol to another, such as ISO to EPC, or Gen 1 to Gen 2? Firmware Middleware Shareware Edgeware
4.	A UHF tag was applied to a corrugated cardboard box and was read successfully when shipped. The box was transported by sea. The tag was well protected from any damage. On receiving the box, the tag did not read. What can be a probable cause for the failure? Tag was damaged Humidity Product inside the box Wrong tag for destination country frequency
5.	What accessory used with the spectrum analyzer helps determine the performance of an antenna? Reader Tag VSWR bridge Tuning fork
6.	A particular read zone did not have optimal performance. You tested the cable and noticed one of the following. Please indicate the reason that can lead to the poor reads. The cable was kinked. The cable was red in color. There was dust on cable. The cable used was LMR-400.
7.	You are attempting to write to tags with a newly installed reader; however, the process is constantly failing. What is the most likely problem? The tags are all damaged. The network connection is damaged. The reader is improperly configured. The reader antenna is improperly installed.
8.	You are reading tags on pallets of oatmeal in an interrogation zone but some of the tags do not get read. You find out that you are usually missing tags in a similar spot. What can be the problem? Oatmeal is RF-unfriendly material. Tags were not read in one spot because of a hole or null in antenna coverage. Oatmeal causes multi-path reflections. Your reader is improperly configured.
9.	You found out that in a particular interrogation zone, the UHF tags were not read at random times during the day, in periods varying from 1 to 10 minutes. What could have been the problem? Damaged tags were applied to products. The reading was triggered at incorrect times. A nearby airport was broadcasting communication signals at 1000 MHz with power many times what an RFID reader broadcasts. Warehouse workers were using microwave ovens in the reader proximity.
10.	How do you prevent reader interference from adjacent dock door interrogation zones? (Select two options.) Using time synchronization Using shielding Using anticollision By proper antenna tuning
11.	When you are trying to connect the reader to your laptop via a serial port, which of the following will be required? Serial cable Knowing the COM port number on the laptop Baud rate setting All of the above
12.	You are on a client site, trying to troubleshoot poor read rates. After some analysis, you come to a conclusion that tags may be the reason for the poor reads. You are equipped with only a reader, an antenna, a measuring tape, and a laptop. How can you evaluate the performance of 100 tags? (Select two options.) Perform distance testing on the 100 tags. Call the tag manufacturer. Vary reader power and obtain minimum effective power (MEP). Order new tags.
13.	Which of the following can result in power loss? (Select two options.) Long cable lengths Connectors A vacuum Nitrogen
14.	An HF RFID system is deployed in a conveyor system in a manufacturing plant. The system is surrounded by a lot of metal. The read performance is poor. How can you improve the performance? Use a VSWR bridge to tune the antenna back to 13.56 MHz. Provide shielding. Use a UHF system. Nothing can be done.
15.	From the following list, select the options that can introduce noise in a UHF RFID system. Adjacent readers Antenna cables having damaged insulation Wireless handheld system operating at 915 MHz All of the above
16.	You need to buy cables for deploying a UHF RFID system. What type of coax cable and RF connector connection (joint) method should you opt for? The core of the coax cable should be soldered to the connector. The core of the coax cable should be crimped to the connector. The core of the coax cable should be wrapped around the connector. The core of the coax cable automatically connects to the RF connectors.
17.	What is the best method for troubleshooting an RFID handheld device? Take the cover off and investigate the connections from the antenna to the CPU. Replace the battery and fully charge. Hold a tag in front of the reader and measure the distance away it will read. Call the manufacturer.
18.	You are receiving shipping containers in the European Union, where ETSI is the governing body. What is the first thing to check if you are not reading the active 433 MHz tag that is attached to each container? (Select two options.) Use a VSWR bridge to test the reader's antenna for a resonant frequency of 433 MHz. Check the battery of the active tag. Make sure your reader is also 433 MHz. Nothing can be done.
19.	A UHF RFID system is deployed in a data center to track servers coming and going through the door. The software attached to the portal and four antennas (two on each side) have stopped giving information on whether the server is coming into or out of the data center. What could be wrong? The antennas on one side of the door have stopped functioning. A firmware upgrade may have changed the configuration. Installing new middleware may have changed the reader's configuration. All of the above.
20.	An HF RFID system is deployed on a shelf in a hospital pharmacy. Recently the shelves were replaced and the system stopped working. What can you do to remedy the problem? Use a VSWR bridge to tune the antenna back to 13.56 MHz. Increase the power output in effective radiated power (ERP). Check the data being written to each tag. Switch out the reader.

Answers

1.	D. The first thing you should do is to reboot the reader. Readers are small computers, without the keyboard, video, and mouse, so occasionally they will lock up when things go wrong. The simplest first step after you've checked to see whether the power is on is to reboot the reader and see whether that fixes the problem.
2.	B. Because the dock door has to be 30" wide (15" to the center from one side, times two), that run is likely to cause excessive loss over LMR-240. Therefore, the correct choice is to use LMR-400, which will have less loss because of increased insulation.
3.	A. Firmware is the software that sits on the reader and controls what it can or can't do. Allowing it to read one type of tag and not another is part of its functionality. Middleware accepts read data from an interrogator and creates business logic or actionable items from the RFID data. The only time middleware can affect an interrogation zone is when the middleware is programmed to change the reader settings.
4.	B or D. Corrugated cardboard boxes have a high affinity to store humidity. The box was transported by sea, so the box must have absorbed humidity, which can detune the tag. (Moisture is RF unfriendly at UHF.) The tag could also be read by a different protocol reader, for instance a proprietary system might be trying to read an ISO tag.
5.	C. The VSWR bridge along with the spectrum analyzer helps determine the performance of an antenna. The larger the dip in the VSWR graph, the less loss exhibited by the antenna, and hence the better performance it will have.
6.	A. A kinked cable can introduce high losses resulting in less power for the tag to operate. This can lead to poor read rates.
7.	C. In this case, the reader is improperly configured, and most likely the air interface protocol and data protocol of the reader and the tag do not match.
8.	B. Multi-path interference or imperfections in antennas can cause holes in RF coverage in the interrogation zones. The unread tags in the same spot were most likely falling into the hole in the antenna field. This could be solved by overlapping fields as well as by moving the tagged objects.
9.	C. Completing the full Faraday cycle analysis will show things on the periphery of the frequency, and also show the power level. Having something close to one of the end frequencies (either 902 or 928 in the USA) can bleed over into the range used.
10.	B, D. To prevent interference from adjacent interrogation zones, you may need to use proper shielding and adjust the power going to the antenna. This will prevent interference by containing the RF fields within their own interrogation zones.
11.	D. To achieve serial connectivity between the reader and the laptop, it is essential that you have a serial cable with DB9 connectors and know the COM port number on the laptop, so you can configure the COM port. It is very important that you know what baud rate settings are required to connect with the reader. This information can be obtained from the reader manual.
12.	A, C. By determining a set distance where some tags for the batch respond and some don't, you can find superior, average, and under-performing tags. You can also find the superior, average, and under-performing tags by varying the reader power and keeping each tag from the batch at a set distance. By reducing the power below a certain value, tags will stop responding, allowing you to determine the MEP value for each tag and sort them as superior, average, and under-performing.
13.	A, B. In an RFID system setup, longer cable lengths and connectors add to power loss. In cables, the loss is due to impurities in conductors and leakage. In connectors, losses are due to contact resistance and leakage.
14.	A. The high amount of metal surrounding the conveyor system detunes the antenna. By using a VSWR bridge and tuning screwdriver, you can tune (change the inductance and capacitance) the system to operate at 13.56 MHz.
15.	D. Adjacent readers can be the biggest source of interference or noise; a reader that is noisy can easily kill a tag response, resulting in poor read rates. Cables that have a damaged insulation can directly add noise to the center conductor carrying the signal of interest. Just like the adjacent readers, the wireless handheld systems can also act as noise sources.
16.	A. The soldering approach provides the best connectivity in terms of both electrical and mechanical connectivity. Crimped connections result in mechanically weak joints. Wrapped connectors are difficult to use as RF connectors; also, wrapping the thick coax core conductor can result in higher resistance at the point of contacts, resulting in heat, which results in oxidation.
17.	D. RFID handhelds usually work out of the box, and you know the performance you are getting. If there is a problem, it's usually due to the handheld being dropped or damaged, and is best dealt with by the manufacturer.
18.	B, C. The battery tag is the first thing to check; it could have failed for a number of reasons, but an active tag without a battery will not read. The other issue is that the reader may be for a passive RFID tag for 968 MHz, and you are trying to read an active tag. Although this last point may seem obvious, you'd be surprised at the number of times it happens.
19.	D. The combination of middleware, firmware, and reader settings can create a number of issues. If something is working well and there is any change to the system, then it will be highly likely that one of the "soft" components of the RFID network has caused the problem.
20.	A. The shelves that were swapped out were likely metal shelves instead of wood, or perhaps the reader was tuned for metal shelves but wood shelves were installed. A simple check is to see whether the antenna has been detuned because of the change in material.