RF Physics

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These questions are derived from the Self Test Software Practice Test for CompTIA’s RFID+ exam.

Objective: RF Physics
SubObjective: Identify RF propagation/communication techniques

Single Answer, Multiple Choice

Which mechanism enables a tag’s circuit and an interrogator to communicate with each other to transmit power and information?

  1. encoding
  2. coupling
  3. operating frequency
  4. sequential (SEQ)

Answer:

B. coupling

Tutorial:

Coupling enables a tag’s circuit and an interrogator to communicate with each other to transmit power and information. Coupling occurs when the magnetic fields produced by one circuit overlap those produced by another circuit. The different coupling methods used for RFID applications are inductive coupling, capacitive coupling, and backscatter coupling.

Encoding assists in securing the tag data that is wirelessly communicated to the interrogators. Encoding encrypts the tag data to ensure that the data is read only by authorized interrogators. Several encoding schemes, such as biphase Manchester encoding, pulse interval encoding, or biphase space encoding, are used in RFID systems.

Operating frequency is an electromagnetic frequency that enables tags to power up and communicate with interrogators. The frequency ranges used in RFID systems are low frequency (LF), high frequency (HF), ultra high frequency (UHF), and microwave. LF has the lowest and microwave frequency has the longest read range. Depending on the system requirements and multiple factors, you can choose the appropriate frequency to be used in an RFID system.

SEQ is a procedure used in RFID systems to share the RF energy and transfer information between tags and interrogators by using pulse operation. In SEQ, the communication between tags and interrogators takes place for a limited period of time.

Reference:

RFID Essentials, Chapter 3: Tags, Coupling, pp. 63-67.

RFID+: The Complete Review of Radio Frequency Identification, Chapter 1: Primer, Coupling, pp. 36-38.

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