SLRC400 Datasheet, PDF (89/130 Pages) NXP Semiconductors – I·CODE Reader IC

Philips Semiconductors
I•CODE Reader IC
Product Specification Rev. 2.0 November 2001
SL RC400
14 RECEIVER CIRCUITRY
14.1 General
The SL RC400 employs an integrated quadrature-demodulation circuit which extracts the sub-carrier signal
from the 13.56 MHz ASK-modulated signal applied to pin RX. The quadrature-demodulator uses two
different clocks, Q- and I-clock, with a phase shift of 90° between them. Both resulting subcarrier signals are
amplified, filtered and forwarded to the correlation circuitry. The correlation results are evaluated, digitised
and passed to the digital circuitry.
For all processing units various adjustments can be made to obtain optimum performance.
14.2 Block Diagram
Figure 14-1 shows the block diagram of the receiver circuitry. The receiving process includes several steps.
First the quadrature demodulation of the carrier signal of 13.56 MHz is done. To achieve an optimum in
performance an automatic clock Q calibration is recommended (see 14.3.1). The demodulated signal is
amplified by an adjustable amplifier. A correlation circuit calculates the degree of similarity between the
expected and the received signal. The bit phase register allows to align the position of the correlation
intervals with the bit grid of the received signal. In the evaluation and digitizer circuitry the valid bits are
detected and the digital results are send to the FIFO register. Several tuning steps in this circuit are possible.
ClockQDelay[4:0] ClockQCalib ClockQ180°
I to Q
Conversion
clock
I-clock
Q-clock
Gain[1:0]
13.56 MHz
RX
Demodulator
BitPhase[7:0]
Correlation
Circuitry
CollLevel[3:0] RcvClkSelI
MinLevel[3:0] RxWait[7:0]
Evaluation and Digitizer
Circuitry
s_valid
s_data
s_coll
s_clock
VRxFollQ
VRxFoll I
VRxAmpQ
VRxAmpI
VCorrNI VCorrNQ
VCorrDI VCorrDQ
VEvalR
VEvalL
to
TestAna
OutSel
Figure 14-1: Block Diagram of Receiver Circuitry
The user may observe the signal on its way through the receiver as shown in the block diagram above. One
signal at a time may be routed to pin AUX using the TestAnaSelect-Register as described in 18.3.
89
Preliminary