In electronic product design, component selection often determines product performance. Radio Frequency Identification (RFID) technology, as a mature automatic identification solution, has seen increasingly widespread adoption. However, engineers frequently face selection challenges when confronted with the diverse array of RFID tag options available. This article provides an in-depth analysis of three primary RFID tag types—passive, semi-passive, and active—examining their working principles, advantages, disadvantages, and ideal applications to offer comprehensive technical guidance.

Radio Frequency Identification (RFID) is a non-contact automatic identification technology that uses radio frequency signals to identify target objects. A typical RFID system consists of two components:

• RFID Reader (Interrogator): Emits radio frequency signals, communicates with RFID tags, and reads or writes data.
• RFID Tag: Attached to target objects, containing a data-storage chip and an antenna for receiving/transmitting RF signals. Based on power supply methods, tags are categorized as passive, semi-passive, or active.

Passive RFID tags represent the simplest tag type, consisting of an integrated circuit (IC) chip and an antenna, typically encapsulated on substrate material to form an "inlay." Their defining characteristic is the absence of any internal power source.

Passive RFID tags operate using energy from the reader's RF signal. When entering the reader's RF field, the tag antenna converts received RF energy into electrical power to activate the IC chip. The chip then retrieves stored data and reflects it back to the reader through backscatter modulation.

• Low cost: Simple structure enables mass production with per-unit costs ranging from cents to under a dollar.
• Compact size and lightweight: Ideal for space-constrained applications.
• Extended lifespan: Potentially decades-long operation limited only by material aging.
• Maintenance-free: No battery replacement required.
• Strong interference resistance: Minimal electromagnetic radiation emission.

• Short read range: Typically centimeters to a few meters (UHF may reach several meters).
• Limited storage capacity: Suitable only for basic data like product IDs.
• High reader power requirements: Requires strong RF signals for activation.
• No active signaling capability: Purely reactive communication.
• Environmental sensitivity: Metal and liquids can impair performance.

• Supply chain management
• Retail (inventory control, anti-theft)
• Library systems
• Access control
• Animal identification

Semi-passive tags incorporate batteries but still rely on backscatter modulation for communication.

The internal battery powers the chip continuously, enabling extended read ranges and sensor support while maintaining backscatter communication with readers.

• Extended read range: Typically tens of meters.
• Sensor compatibility: Can monitor environmental conditions.
• Increased storage capacity: Battery enables larger memory.

• Higher cost than passive tags
• Larger form factor
• Limited battery lifespan (typically years)
• Reader dependency remains

• Cold chain logistics
• High-value asset tracking
• Environmental monitoring

Active tags represent the most capable (and expensive) option, featuring onboard batteries and active transmission capabilities.

The battery powers both the chip and transmitter, enabling autonomous signal broadcasting without reader interrogation. Some models support bidirectional communication.

• Maximum read range: Hundreds of meters or more.
• Active signaling: Enables real-time monitoring and location tracking.
• Advanced sensor support: Accommodates complex monitoring.
• Enhanced processing: Capable of sophisticated data analysis.

• High cost: Typically $5-$50 per unit.
• Bulky design: Larger than passive alternatives.
• Battery limitations: Requires eventual replacement.
• EM interference potential: Active transmission may affect nearby electronics.

• Vehicle management systems
• Personnel tracking
• Shipping container monitoring
• Intelligent transportation systems

When selecting RFID tags, consider these key factors:

• Read range: Match tag capability to operational distance requirements.
• Cost: Balance performance needs with budget constraints.
• Form factor: Ensure physical compatibility with application.
• Power longevity: Evaluate battery replacement feasibility.
• Environmental conditions: Account for potential interference sources.
• Data requirements: Align storage capacity with information needs.
• Sensing capabilities: Determine if environmental monitoring is required.

Each RFID tag type offers distinct advantages for specific applications. Successful implementation requires careful evaluation of technical requirements, environmental factors, and cost considerations. As RFID technology continues advancing, tag capabilities will expand, creating new opportunities across industries. For electronics engineers, mastering RFID selection criteria and pairing it with professional PCB design tools represents a critical competency for developing high-performance, reliable products.