NCD1015ZP

4

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R02

2. Functional Overview and Description

2.1 Overview

The reader and the pre-programmed NCD1015ZP

transponder comprise the two elements of a

half-duplex wireless communications system

operating in a sequential mode with time-separated

power and data transmission cycles. Power transfer to

the transponder (tag) is accomplished by

electromagnetic coupling of the transponder and

reader antennae.

2.2 Power Transfer

As shown below in Figure 1, an activation field

sourced by the reader supplies power to the

transponder at the beginning of a read request. The

reader generates an electromagnetic field for 50 ms

using an activation frequency of 134.2 kHz to energize

the resonant circuit of the transponder. During this

Powering Phase, circuitry within the transponder

rectifies the induced voltage to charge an internal

storage capacitor. Energy held by the storage

capacitor provides the means by which the

transponder transmits it’s stored data. The reader

terminates the activation field to indicate it is ready to

receive data from the transponder.

Figure 1: Activation and Read Phases: Voltage at

the Reader’s Exciter and Transponder Coils

2.3 Communication Interface - Tag to Reader

Frequency Shift Keying (FSK) modulation is employed

by the NCD1015ZP to transmit the stored data

immediately after detecting the end of the reader’s

activation field. As can be seen in Figure 1, the tag’s

transmit (Response phase) directly follows the

Powering phase.

Transfer of the stored digital information is

accomplished by using two discrete frequencies, one

for a logic “1” (High) and another for a logic “0” (Low).

The nominal frequencies used for data transmission

are:

2.3.1 Data Bit Structure

Data bits are transmitted as 16 cycles of their

respective frequency. Because a logic high (1) data bit

uses a lower frequency than that for a logic low (0), the

duration of a 1 bit is longer than a 0 bit. The duration

for logic 1 and logic 0 bits is given below.

Figure 2 illustrates the FSK encoding principle used to

transmit the stored data.

Figure 2: FSK Transmission Used During the

Read Phase

2.3.2 Transponder Data Rate and Data Coding

The data coding is based on the NRZ method thus

achieving an average data rate of ~8kbit/s based on

an equal distribution of '0' and '1' data bits.

2.3.3 Completion of Transmission

Following the output of the last bit, the transponder

deactivates.