Design Of Rfid Reader Computer Science Essay

Radio Frequency Identification ( RFID ) is an automatic designation method, utilizing hand-held reader or another device that can read and hive away remotely and recovering informations. RFID usage devices called RFID tickets or transponders. The RFID engineering is non a recent engineering, instead it has been used for decennaries by different organisations. However, ab initio, the cost of implementing RFID engineering was really high. This is the ground, non many people knew about RFID engineering. The RFID engineering is progressing twenty-four hours by twenty-four hours and researches are on to assist cut down the cost that can take to easy handiness of the RFID services. Research and survey is carried out on RFID reader design. The attack of the work starts by planing the RF aerial so continue with planing the addition phase for the reader.

Radio Frequency Identification ( RFID ) systems use radio frequence to place, turn up and track people, assets, and animate beings. Passive RFID systems are composed of three constituents: a reader, a inactive ticket, and a host computing machine. A ticket has an designation figure ( ID ) and a reader recognizes the information from the ticket. The reader sends out a signal which supplies power to a ticket. The ticket transmits its ID to the reader and the reader consults an external database with standard ID to acknowledge the information.

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The ticket is composed of an antenna spiral and a Si bit that includes basic transition circuitry and non-volatile memory. The ticket is energized by a time-varying electromagnetic wireless frequence ( RF ) wave that is transmitted by the reader. This RF signal is called a bearer signal. When the RF field passes through an antenna spiral, there is an AC electromotive force generated across the spiral. This electromotive force is rectified to provide power to the ticket. The information stored in the ticket is transmitted back to the reader. This is frequently called backscattering. By observing the backscattering signal, the information stored in the ticket can be to the full identified.

Data decryption for the standard signal is accomplished utilizing a microcontroller. The microcontroller is written in such a manner to convey the RF signal, decrypt the entrance informations and communicate with the host computing machine. Typical, reader is a read merely device. RFID reader is a device that activates the ticket and retrieves the information stored in its IC and so passes the information to a computing machine for processing.

The focal point of this undertaking is to plan a hardware portion of a RFID reader which consists of planing the aerial, filters and programming a microcontroller. The reader can observe informations from a inactive ticket and so subsequently send the informations received from the ticket to the host system.

Problem Statement

Normally, UTP will purchase the RFID reader that is dearly-won for any undertaking or applications. University normally bought the reader that might be around RM350 and supra. This undertaking will plan RFID reader that can recover informations from the inactive ticket and send the information to the host computing machine.

Aim

The chief aims of this undertaking are:

To plan a resonating aerial circuit utilizing a spiral that can have the ID from RFID ticket.

To plan an active low base on balls filter and active bandpass filter for the RFID reader

To plan and develop a low cost RFID reader utilizing a microcontroller ( PIC16F628A ) that capable of reading a 125 kilohertz RFID ticket.

To plan a reader that can read the RFID ticket Numberss and convey them to a host computing machine for informations aggregation and storage

Scope of Study

The chief range of this undertaking is the survey of RFID concentrating on planing the RFID reader portion. The undertaking includes the design a spiral aerial, low base on balls filter, bandpass filter and programming a microcontroller for the reader.

Chapter 2

LITERATURE REVIEW AND THEORY

2.1 RFID Components

The intent of an RFID system is to enable informations to be transmitted by a portable device, called a ticket, which is read by an RFID reader and processed harmonizing to the demands of a peculiar application. A reader sends an electromagnetic signal to the ticket. Upon having the reader ‘s signal, the ticket transmits its codification to the reader. The information transmitted by the ticket may supply designation or location information, or particulars about the merchandise tagged, such as monetary value, colour or day of the month of purchase.

A basic RFID system consists of three hardware constituents which are RFID ticket, reader and host system.

Figure 1: RFID basic constituents

Addition Phase

High Voltage Phase

Low Pass

Band Pass

Detector

125 kHz Signal Beginning

Microcontroller

To PC

Control

Coder/ Decoder

Modulator/ Demodulator

Figure 2: RFID reader block diagram

The occupation of the reader circuit is to direct out a signal which supplies power to a ticket, retrieve the informations stored in the ticket and expose the information to the host computing machine. In order to construe the information, the bearer frequence must be removed, and the enfolding frequences must be magnified into something measureable.

2.2 Resonant Antenna Circuit

Passive RFID ticket work in such a manner that they are really powered by an external signal, which, in most instances is the bearer signal from the reader circuit. The reader and ticket communicate utilizing magnetic matching since their several aerials can feel alterations in magnetic field, which is observed as a alteration in electromotive force in the reader circuit.

One of the restricting factors in low frequence inactive RFID is reading distance. Maximal reading distance is determined by frequence, power and signal intervention. Typical reading distance for RFID is merely a few centimetres. Because increasing power and frequence is non ever practical, a common solution to increase reading distance is modify antenna being used.

The magnetic initiation type aerial used for low frequence RFID is constructed from multiple bends of magnetic wore in a cringle. Generally, a bigger radius of a cringle will ensue in a greater reading distance.

By and large, RF aerial is a series resonance circuit of opposition ( R ) , induction ( L ) and capacitance ( C ) . The relation of constituent L and C is [ 1 ] :

f = resonate frequence ( Hertz )

L = induction ( Henries )

C = Capacitance ( Farad )

An CRO can be used to analyze how the LC circuit responds to the frequence green goods by sine moving ridge generator. The peak response will be at the frequence of natural resonance of the circuit.

Figure 3: Series Resonant Circuit

The induction of antenna spiral is dependent on form, size and the figure of bends in the aerial spiral [ 1 ] . To build an aerial with the necessary induction, a spiral of Cu wire is used. Inductance of a rectangular spiral is determined by the undermentioned equation:

L = induction ( µH )

ten = breadth of the spiral ( centimeter )

y = length of the spiral ( centimeter )

H = tallness ( centimeter )

B = breadth across the carry oning portion of the spiral ( centimeter )

N = figure of bends

2.3 Gain Phase

Filters are indispensable constituents in any electrical systems. In the RFID reader, filters are required to take unsought signals at different phases of the receiving procedure, such as noise from incoming signals the aerial receives, unsought signals at the image frequence, and harmonics after the commixture operation. All linear filters fall in one of two classs: passive or active. In this low frequence RFID system, active filters are used because of the undermentioned advantages:

Active filter can bring forth addition larger than one.

Higher order filters can easy be cascaded since each Op-amp can be 2nd order.

Filters are little in size every bit long as no inductances are used, which make it really utile as incorporate circuit.

An active low base on balls filter will reject unsought bearer signal and take majority of bearer frequence. The active set base on balls filter is to pull out the FSK signal and reject the signals outside 10-20 kilohertz signals. These are because the ID signals from the ticket are 12.5 kilohertzs and 15.65 kilohertz and signal power is really low [ 2 ] .

2.3.1 Low Pass Filter

A Low-Pass Filter is a frequence selective device which passes low frequences and blocks high frequences. It has a individual passband and a individual stopband. fC is defined as the frequence that separates the two sets. This is besides known as the cutoff frequence and is the point at which the amplitude is 3 dubnium below its maximal value.

Figure 4: Active low base on balls filter

Cutoff frequence:

Addition:

The negative mark indicates that the inverting amplifier generates a 180 & A ; deg ; phase switch from the filter input to the end product.

2.3.2 Active Band Pass Filter

The simplest design of a band-pass filter is the connexion of a high-pass filter and a low base on balls filter in series, which is normally done in wide-band filter applications.

Figure 5: Active set base on balls filter

Centre frequence is the frequence at the centre of the set which typically the extremums of the frequence response curve.

Addition:

The filter bandwidth ( BW ) is the difference between the upper and lower passband frequences. A expression associating the bandwidth is:

The quality factor, or Q of the filter is a step of the distance between the upper and lower frequence points and is defined as ( Center Frequency / BW ) so that as the passband gets narrower around the same centre frequence, the Q factor becomes higher. The quality factor represents the acuteness of the filter,

For a individual op-amp bandpass filter with both capacitances the same value, the Q factor must be greater than the square root of half the addition.

Resistors value:

Capacitor values:

Chapter 3

Methodology

3.1 Flow of Work

The development of the undertaking adopts the methodological analysis flow as figure below:

Undertaking Low-level formatting

Start

Problem Designation

Literature Review

Feasibilities Surveies

Survey on RFID Reader Design

Antenna Design

Design Analysis and Circuit Diagram

Low Pass and Bandpass Filter

No

Simulation and Experiment

Successful

Microcontroller Programming

Yes

Integrating hardware with the microcontroller ( Generate Code )

No

Successful

Yes

Prototyping

Testing

Concluding Integration

Figure 6: Undertaking Development Phase

Chapter 4

RESULT AND DISCUSSION

4.1 Resonant Antenna Design

In a RFID system, runing frequence is fixed, accordingly the resonating frequence is fixed [ 3 ] which are 125 kilohertzs. In order to be able to cipher approximately the electrical capacity C of the spiral, it is necessary to gauge the induction L of the circuit. The induction is determined and the estimated value of the spiral induction is 220µH. As a consequence, electrical capacity C is:

C = 7.369µF = 7369pF

However, there is no electrical capacity value of 7369pF. The nearest electrical capacity values available are 6800pF and 8200pF.

The Numberss of bends for the rectangular spiral with the breadth, x and length, Y of the spiral are 6cm and the thickness, H is 0.3cm. The induction value used is 220µH and below is the estimated figure of bends for the rectangular spiral aerial:

N = 40 bends

6cmThe figure of bends out to be 40 bends and finished spiral is extracted and secured with tape.

0.3cm

6cm

Figure 7: Rectangular spiral aerial

To ticket tune the resonating frequence of the full system is merely by altering the electrical capacity value until the CRO displayed the highest resonating electromotive force from the bearer frequence. Below are the consequence obtain signifier the CRO for the resonating electromotive force after tuned the aerial. From the CRO, observed that electrical capacity value of 6800pF gives the highest resonating electromotive force compared to 8200pF capacitance value.

we

Figure 8: Resonant electromotive force for 6800pF electrical capacity

Figure 9: Resonant electromotive force for 8200pF electrical capacity

4.2 Gain Phase

4.2.1 Active Low Pass Filter circuit design

The frequence involved in this undertaking is rather low, so the low frequence public presentation of the TL062 Op-amp should non be an issue. The values for the low base on balls filter constituents are calculated, and the circuits are so simulated utilizing Pspice. Take the value for R2 = 160ka„¦ and C = 100pF.

The cut-off frequence calculated:

fc = 9.947 kilohertz

Addition:

K = 16

Figure 10: Active low base on balls filter conventional

4.2.2 Active Low Pass Filter simulation

Figure 11: Active Low Pass Filter Response

From the simulation, it could be observed that the cut-off frequence for the active low base on balls filter is 9.880 kilohertz

4.2.3 Active Bandpass Filter circuit design

The circuits are composed of one Op-amps, three resistances, and two capacitances. The amplifiers are based on the TL062. Assume the capacitance value, C = C1= C2 = 1nF. The bandpass filter with a centre frequence of fc = 17 kilohertz, a quality factor of Q = 6, and a addition of A = -30. All value of capacitances are obtained:

BW = 3.183k

Figure 12: Active bandpass filter conventional

4.2.4 Active Bandpass Filter simulation

Figure 13: Bandpass Filter Response

As can be seen from figure 13, the bandpass filter largely isolates the base on balls set ( 10-20 KHz ) , with approximately unity addition for all frequences outside the base on balls set. The Centre frequence is 17.113 kilohertz which about to the deliberate value. The fake consequences satisfy the system demands, these circuit constructions are suited for the designed RFID application.

Chapter 5

Decision

A basic passive RFID system is composed of three chief constituents which are reader, inactive ticket, and host computing machine. This undertaking focal point on planing an RFID reader which can direct out a signal to supplies power to a ticket, retrieve the informations stored in the ticket and expose the information to the host computing machine. The reader composed of an aerial, a low base on balls filter and bandpass filter every bit good as a microcontroller. The RF aerial is a series resonance circuit and was designed in a rectangular form utilizing a spiral. The addition phase consists of an active low base on balls filter and an active set base on balls filter. An active low base on balls filter was designed to reject unsought bearer signal and take majority of bearer frequence. The active set base on balls filter is to pull out the FSK signal and reject the signals outside 10-20 kilohertz signals. The active low base on balls and set base on balls filter constituents were calculated and simulated in Pspice. The undertaking will continue to programming the PIC16F628A microcontroller