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RFID Technology White Paper

1. Radio Frequency Identification (RFID) Overview

1.1. Introduction

This document describes the summary of the Radio Frequency Identification (RFID) technology, its applications, and the IBS HONGKONG’s RFID chip specification.

RFID is a technology that enables the electronic labeling and wireless identification of objects using radio frequency communications. An RFID transponder will identify itself when it detects a signal from a compatible device, known as a reader or interrogator. In a typical RFID system, transponders, or tags, are attached to objects. Each tag carries with it information: a serial number, model number, color, place of assembly or any other imaginable data. When these tags pass through a field generated by a compatible reader, they transmit this information back to the reader, thereby identifying the object.

1.2. Components of an RFID System

A basic RFID system consists of these components:

1.3. RFID Tag

The RFID tag consists of an integrated circuit (IC) embedded in a thin film medium. Information stored in the memory of the RFID chip is transmitted by the antenna circuit embedded in the RFID inlay via radio frequencies, to an RFID reader. The performance characteristics of the RFID tag will then be determined by factors such as the type of IC used, the read/write capability, the radio frequency, power settings, environment, etc.

RFID tags are categorized as either passive or active depending on whether they have an on-board power source or not.

The information stored in an RFID chip is defined by its read/write characteristics.

A barcode scanner cannot read more than one barcode at a time. RFID readers, however, may be driven by specific software applications that can handle the reading of multiple RFID tags. This feature is called anticollision as it permits a reader to avoid data collision from several tags that enter the reader’s coverage.

RFID systems are designed to operate at a number of designated frequencies, depending on the application requirements and local radio-frequency regulations:

  1. o Low Frequency (125 kHz);

     

  2. o High Frequency (13.56MHz);

     

  3. o Ultra High Frequency (860-960 MHz)

     

  4. o Microwave (2.45 GHz)

     

Low-frequency tags are typically used for access control & security, manufacturing processes, harsh environments, and animal identification applications in a variety of industries, which require short read ranges. Read ranges are inches to several feet. High-frequency tags were developed as a low cost, small profile alternative to low frequency RFID tags, with the ability to be printed or embedded in substrates such as paper. Popular applications include: library tracking and identification, healthcare patient identification, access control, etc. These tags have a read range of up to several feet. UHF tags boast greater read distances, superior anti-collision capabilities increasing the ability to identify a larger number of tags in the field at a given time. The primary application envisioned for UHF tags, is supply chain tracking. Microwave tags are mostly used in active RFID systems. Offering long range and high data transfer speeds, at significantly higher cost per tag, making them more suitable for railroad car tracking, container tracking, and automated toll collection. Table1 highlights the different characteristics of the four RFID operating frequency ranges.

Table 1: Transponder Performance at Various Transponder Frequencies

Frequency Range LF 125 KHz HF 13.56 MHz UHF 868 - 915 MHz Microwave 2.45 GHz & 5.8 GHz
Typical Max
Read Range < 0.5 m ~ 1 m ~ 3 m ~ 1 m
(Passive Tags)
General Characteristics Relatively expensive, even at high volumes. Low frequency requires a longer, more expensive copper antenna. Additionally, inductive tags are more expensive than a capacitive tag. Least susceptible to performance degradations from metal and liquids, though read range is very short. Less expensive than inductive LF tags. Relatively short read range and slower data rates when compared to higher frequencies. Best suited for applications that do not require long range reading of multiple tags. In large volumes, UHF tags have the potential for being cheaper than LF and HF tags due to recent advances in IC design. Offers good balance between range and performance especially for reading multiple tags. Similar characteristics to the UHF tag, but with faster read rates. A drawback to this band is that microwave transmissions are most susceptible to performance degradations due to metal and liquids, among other materials. Offers the most directional signal, ideal for certain applications.
Active tags with Active tags with
Tag Power Source Generally passive tags only, using inductive coupling Generally passive tags only, using inductive or capacitive coupling integral battery or passive tags using capacitive, E-field coupling integral battery or passive tags using capacitive, E-field coupling
Typical Applications Today Access control, animal tracking, vehicle immobilizers, POS applications including SpeedPass "Smart Cards", Item-level tracking including baggage handling (non-US), libraries Pallet tracking, electronic toll collection, baggage handling (US) SCM, electronic toll collection
Notes Largest install base due to the mature nature of low frequency, inductive transponders. Currently the most widely available high frequency worldwide, due mainly to the relatively wide adoption of smart cards. Japan does not allow transmissions in this band. Europe allows 868 MHz whereas the US permits operation at 915 MHz, but at higher power levels.  
Data Rate Slower     Faster
Ability to read
near metal or Better Worse
wet surfaces
Passive Tag Size Larger     Smaller

Source: Allied Business Intelligence Inc

 

Figure 1: Semi-passive backscatter RFID system

Figure 2: Comparing the range limitations for different types of RFID tag

1.5. RFID Applications

RFID has emerged as the leading solution for many applications. Electronic toll collection, access control systems and vehicle immobilizers are all systems that would not be nearly as efficient or effective without RFID technology. See Table 3 for a listing of key application segments, including representative applications and competing technologies.


Asset management /Inventory control: RFID tags can be permanently attached to capital equipment and fixed assets including pallets, RPCs, cylinders, lift trucks, tools, vehicles, trailers and equipment. Fixed position readers placed at strategic points within the facility can automatically track the movement and location of tagged assets with 100 percent accuracy. This information can be used to quickly locate expensive tools or equipment when workers need them, eliminating labor-wasting manual searches. Readers can be set to alert supervisors or sound alarms if there is an attempt to remove tagged items from an authorized area. By tracking pallets, totes and other containers with RFID, and building a record of what is stored in the container as items are loaded, users can have full visibility into inventory levels and locations. With visibility and control, manufacturers can easily locate items necessary to fill orders and fulfill rush orders without incurring undue managerial or labor time. Shipping & Receiving: The same tags used to identify work-in-process or finished goods inventory could also trigger automated shipment tracking applications. Items, cases or pallets with RFID tags could be read as they are assembled into a complete customer order or shipment. The individual readings could be used to automatically produce a shipment manifest. Manifest information encoded in an RFID tag could be read by the receiving organization to simplify the receiving process and to satisfy requirements like those for advance shipping notices. Having complete shipment data available in an RFID tag that can be read instantly without manual intervention is very valuable for cross dock and high-volume distribution environments. Incoming shipments can be automatically queried for specific containers.

 

Returns & Recall Management: Companies could supplement the basic shipment identification information by writing the specific customer and time of shipment to the tag immediately prior to distribution. Producing and recording this information would provide several benefits. In the event of a recall, companies could trace specific shipments to specific customers, which would enable a highly targeted notification and return operation and avoid a costly general recall. For general returns, companies could verify that the customer returning merchandise is actually the customer who received it, which would deter diversion, counterfeiting and other forms of return fraud.

Library Information Systems: Tracking a library’s assets and loan processing is a very time-consuming process. Traditional bar-coding systems help to improve the process. However, RFID technology offers additional enhanced features such as efficient processing (faster and more efficient tracking), security, and inventory management (a few hours instead of week or months for inventory checking).

Table 3: RFID Application Matrix

Application Segment Representative Applications Competitive Technologies Current Penetration Typical Tag Type
Access Control Doorway entry Other keyless entry technologies High Passive
Asset Tracking Locating tractors within a freight yard None Low Active
Asset Tagging Tracking corporate computing systems Bar Code Low Passive
Authentication Luxury goods counterfeit prevention Holograms Low Passive
Baggage Tracking Positive bag matching Bar Code, Optical Character Recognition Low Passive
POS Applications SpeedPass Credit Cards, Debit Cards, Smart Cards, Wireless Phones Medium Passive
SCM (Container Level) Tracking containers in shipping terminals GPS-based Systems Low Active
SCM (Pallet Level) Tracking palletized shipments Bar Code Minimal Active, Passive
SCM (Item Level) Identifying individual items Bar Code Minimal Passive
Vehicle Identification Electronic toll collection Bar Code, License plate, reader systems Medium Active, Passive
Vehicle Immobilizers Automotive ignition systems Other theft prevention technologies High Passive

Source: Allied Business Intelligence Inc.

2. IBS HONGKONG & RFID system

We are positioned to be one of the large suppliers in the RFID market either as a product or as an IP. We have fabricated and tested a couple of RFID ICs and planned to produce RFID readers and tags with sensor interface and eventually single chips consisting of a sensor and an EPC compliant RFID tags.

2.1. PEDM RFID chip (Cronos110)

PEDM has an innovative dual mode (passive and semi-passive) ISO-compliant RFID tag and plans to fabricate ISO and EPC compliant RFID tag with sensor capability. The configurable 64 byte EEPROM memory contained in the chip is organized in 32 words of 16 bits for ID and user applications. The CRONOS110 has a built-in anti-collision protocol which allows an unlimited number of transponders in the reader field to communicate simultaneously. The transmission antenna and battery (in semi-passive mode) are the only external elements required and all the other elements are integrated on chip. The specification of Cronos110 is shown in Table 3.

Table 3: Cronos110 General Specification

General Specification
Protocol ISO 18000-4 part 1 / ISO 18000-6 type B
User Memory 48 bytes (user area)
Memory type 64-byte EEPROM organized in 32 words of 16 bits
Communication frequency 2.45 GHz / UHF
Data retention 10 years
Number of overwrites 100,000 times for each address
Ambient temperature in operation -40°C to 85°C
Modes of operation Dual mode: passive and semi-passive (battery-assisted)
Die size < 2 mm2 (now), <1.5 mm2 (next si either passive or active)

Cronos110 is an ultra low power RFID tag which can operate either in passive mode or semi-passive mode. Figure 5 shows the supply connections.

In passive operating mode, the supply voltage is extracted from the RF field and applied to the common circuit blocks (shared circuits between passive and active modes such as bias circuit and clock generator) and digital part. In this mode, the supply node of semi-passive circuits is connected to ground to prevent undesired transitions.

In semi-passive operating mode the supply voltage comes from an external battery and applied to the exclusive semi-passive circuits, common circuits and digital part. The chip uses backscattering concept for both operating modes to reduce the power consumption.

Figure 5: Supply connections for the dual mode RFID tag chip

Figure 6 shows the block diagram of the RFID chip. The building blocks of the analog front-end will be discussed in the following sections.

The main blocks are envelope (peak) detector, demodulator (consists of an amplifier, a Schmitt trigger, an offset cancellation circuit, etc), bias circuits and clock generator (or oscillator). All of these circuits are designed for low power operation in order to achieve an ultra low power RFID tag chip. All blocks can operate with supply voltages ranging from 1.5V to 3.6V. Also some blocks can operate with lower supplies down to 1.2V. The description of some blocks are as follows:

2.1.1. DC and envelope extractor block

This block uses a new idea to provide larger DC supplies using extracted envelop. The rectified output voltage is 2-3 times larger than the amplitude of the input RF signal. Also a protection block is used to limit the rectified voltage level.

2.1.2. Power on Reset (POR)

The POR block detects the extracted voltage level and applies a reset signal to the digital part. Also it provides appropriate signals to the bias and oscillator blocks to turn them on or off.

Vdd

RF+ Ant RF-

GND

Figure 6: RFID Block Diagram

2.1.3. Demodulator

The demodulator (or data extractor) circuit extracts digital data stream from the envelope of the RF signal which is detected by the peak detector block. The input signal level of the demodulator circuit can be as low as 0.5mV which is extracted from 20mV RF signal.

2.1.4. Oscillator (clock generator)

This circuit generates the clock signal for digital circuits. The oscillator consumes less than 1uA when operating (it is turned on when there is input signal or a request from digital part). Due to cost considerations, there is no external reference clock in RFID tags.

2.2. Digital architecture

Figure 7 shows the architecture of the digital part of the RFID chip. As shown in this figure, the extracted data and generated clock in analog front-end are applied to the clock/data recovery circuit to recover the required clock and data for other digital blocks. According to the ISO180004 standard the data rate can be between 20-40 kHz. So the RFID chip has two options for processing on incoming data stream. The first option is over-sampling with higher clock frequency. But over-sampling causes higher power consumption in the digital section due to more transitions. As a second solution, the circuit should generate a clock signal with the exact data rate while can be from 20 to 40 kHz. Our innovative clock/data recovery circuit recovers a clock signal with input data rate with less than 8% accuracy.

The digital circuit is optimized for power. Various power optimization techniques are used in different design phases such as design, implementation, synthesis and place and route to achieve very low power consumption. The total current consumption of the digital section is about 5uA. The total digital core area is less than 1mm2.

Figure 7: Digital Section Architecture

2.3. Electrical Characteristics

The Cronos110 electrical characteristic is as follows:

Absolute Maximum Ratings

Storage Temperature........................................... -55°C to +150°C Supply voltage......................................................... 3.6 V Maximum Antenna Input Voltage............................. 3.6 VP-P

The operating characteristics which are measured in the standard operating condition and operating temperature (-20°C to +70°C) are shown in Table 4.

2.4. PEDM RFID Reader

The complete PEDM RFID solution also includes a multi-protocol RFID reader, utilizing RFID read/write technology, which supports EPCglobal complete set of protocols and also ISO18000. Utilizing multi-frequency technology compliant with FCC (902-928 MHz), ETSI – Europe (868 MHz) and 2.45GHz ISM band, PEDM RFID reader is designed to ensure compatibility today and as new RFID tags and protocols evolve tomorrow.

Another important issue in designing the RFID reader is the cost. Most existing RFID readers are very expensive and aren’t suitable for low cost high volume applications. PEDM’s main goal is to reduce the cost as low as possible, so a broader range of application could be able to use our solution.

2.5. Conclusions

PEDM has planned to produce RFID readers and tags with sensor interface and eventually single chips consisting of a sensor and an EPC compliant RFID tag. Our target is to:

As discussed in previous sections, PEDM has a very low power dual mode (passive and semi-passive), wide frequency range RFID tag which is compatible with ISO 18000 part 4.1 and 6B standards. The chip has been fabricated in 0.35um CMOS process with EEPROM memory. The effective area of the chip (excluding test pads) is less than 1.5mm2. Some advantages and differentiations of the chip are:

z Ultra low power circuits (<10uA @ full operation)

z Using turn on/off method to reduce power consumption

z Innovative demodulating and clock/data recovery techniques

z Easily customizable for customer's needs

Table 4: Operating Charactersitics

Parameters Symbol Min Typ Max Units Conditions
Operation temperature TA -40 25 85 ° C
Passive
RF voltage level Vin 0.4 1 Vp
Operating Voltage Xdc 1.5 1.8 3.6 V
Current consumption Idd 3 5 8 uA
Semi-passive
RF voltage level Vin 5 mVp
Operating Voltage Vdd 1.5 1.8 3.6 V
Current consumption Idd 5 8 12 uA Vdd = 2 V
Electrical Characteristics VDD= 2.0V, TA=+25°C (unless otherwise stated)
Operating voltage VDD or Vpon 3.6 V
Xdc
Current consumption Idd 5.0 15 uA (semi-passive)
Power On Reset Rise Vpon 1.2 1.5 1.8 V
Power On Reset Fall Vpoff 1.0 1.3 1.6 V
oscillator frequency Fosc 250 450 650 KHz Over full voltage
and temperature
range
Carrier frequency FRF 500 2450 3000 MHz
Bit rate BR 20 32 40 Kb/s
Bit Rate Accuracy ± 5 ± 15 %
EEPROM (Memory) Writing Time Tw 4 5 8 mSec  
Receive to Transmit Turn Around Time (Quiet time) Tq 8 16 31 1/Bit rate programmable

 

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