Rev. 3.5

RI-RFM-006A

Page 15 of 19

! Typical Receiver Circuit Configuration

Three simple CMOS inverter type amplifiers are integrated in this RF-module IC in order to amplify the

FSK signals received from a remote TIRIS transponder up to a satisfactory logic level. The IC is

designed so as to permit their amplification factor and frequency characteristics to be selected within a

certain range by the use of appropriate external parts and/or circuits. A typical applied receiver circuit is

illustrated below.

In general, the FSK signals sent from a remote TIRIS transponder are found within a band of 120 kHz to

140 kHz, mainly due to dispersion of workmanship during manufacture and ambient temperature

fluctuation during transmitting operation. Therefore, by damping signals that fall out of the above band

range as much as possible, noise suppression performance can be improved. In the illustrated circuit

configuration, amplifier input coupling capacitors C2, C4 and C6 are used to reduce extremely

low-frequency noise signals, and amplifier output load capacitors C1, C3 and C5 to reduce

high-frequency noises. If you desire to enhance the noise resistance of the circuit still more, it is

necessary to install a required number of external wide band amplifiers with high amplification factor and

add an active band pass filter, LC resonance circuit, etc.

D1, D2 and R4 for input into the first amplifier (A1) form a circuit to prevent high-voltage signals for

power transmission and similar signals from entering the IC, thereby keeping from occurrence of

latch-up or other adverse situations. This circuit or otherwise, an equivalent protector, must be inserted

without fail.

1

2

3

4

5

6

To FSK signal demodulator

RI45538NS

R1

R2

R3

R4

C1

C2

C4

C5

A3OP

A3IN

A2OP

A2IN

A1OP

A1IN

From Antenna

C3

D2

D1

C6