MLX90108D データシートの表示（PDF） - Melexis Microelectronic Systems

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MLX90108D

64bit Read Only Transponder

Melexis Microelectronic Systems  

MLX90108

64bit Read Only Transponder

Coding schemes

Biphase/Manchester AM

Biphase and Manchester are Amplitude

Modulation encoding schemes, which rely on the

build up of the voltage on the transponder

resonant circuit during a certain period, defined

by the baudrate.

In weak RF fields the quality factor of the

transponder antenna is significant, therefore the

rising edge is much slower than the falling edge

of the envelope. Consequently a symmetrically

driven modulator gives an asymmetrical envelope

on the reader antenna. This is anticipated by

delaying each falling edge by a fixed number of

RF clock pulses. The modulator is hence driven

asymmetrical. Each ON state is reduced by 8 (4)

clocks in 2 (4) kBaud mode, and each OFF state

is prolonged by the same amount. This

guarantees good reading in strong and weak

fields, at large distance and in proximity of the

reader antenna.

Manchester:

For a “1” bit, there is a transition from 0 to 1 in the

middle of the bit period. Reciprocal, for a “0” logic

bit there is a transition from 1 to 0 in the middle of

the bit period.

Biphase:

At the beginning of each bit, a transition will

occur. A logic bit “1” will keep its state for the

whole bit duration and a logic bit “0” will show a

transition in the middle of the bit duration.

Manchester Code

Binary Data X 1 1 1 1 0 1

Memory Output

Modulation Output

Phase Shift keying (PSK) AM

PSK is an Amplitude Modulation encoding

scheme that relies on the change of phase of the

modulation. Every other period, i.e. at half the

carrier frequency, the field is modulated.

Therefore the voltage can not build up on the

transponder resonant circuit, and hence the

sensitivity level is much higher than for the other

coding schemes.

Each data bit lasts for 16 carrier periods. A 180°

phase shift occurs at the beginning of a data bit

when a logic “0” is read from the memory. There

is no phase shift when a logic “1” is read from the

memory.

PSK readers operate in the frequency domain.

Therefore the demodulation is insensitive to skew

in the time domain.

The modulation depth is still optimized for

different field strengths, and reading distances.

Speed Clocks

per Bit

2kbaud 64

(MAN/BI)

4kbaud 32

(MAN/BI)

8kBaud 16

(PSK)

Clocks ‘ON’ state Clocks ‘OFF’ state

Long ON = 64 - 8 Long ON = 64 + 8

Short ON = 32 - 8 Short ON = 32 + 8

Long ON = 32 – 4 Long ON = 32 + 4

Short ON = 16 – 4 Short ON = 16 + 4

No asymmetrical behavior

01100

Biphase Coding

Binary Data X 0 1 1 0 1 0 0 1 1 0 0

Memory Output

Modulation Output

PSK Code

Memory output

coil

Modulation output

"0" on serial out

"1" on serial out

MLX90108 64bit Read Only Transponder

Page 4 of 6

Rev1.6 5-Feb-01

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