Rev. 3.5

RI-RFM-006A

Page 18 of 19

Wiring for Antenna Circuit

As previously described, the FSK signals sent from a remote TIRIS transponder are normally found

within a band of 120 kHz to 140 kHz. Therefore, the signal receiving circuit of this TIRIS Transmitter-

Receiver System is designed so that the signal amplification factor is necessarily highest within this band.

Because of this, all signals and noises which are produced by other devices and whose frequencies fall

within this band greatly affect the system performance, especially, its available data communication

distance with the remote TIRIS transponder among others.

In the same way, they have quite the undesirable effect not only upon the environment in which the

proper antenna for the system is found, but also upon the wire used to connect it with the IC’s “A1IN” pin

which works as the first-phase amplifier for received signals. Furthermore, if there are wires for square or

pulse wave logic signals containing high-frequency components (even though their fundamental

frequencies are low) very close to this antenna connection wire, the system’s available data

communication distance with the remote TIRIS transponder is further shortened due to the adverse

effects of such wires. For all that, if there is no other alternative than to use a long wiring between the IC

and its external antenna, it is suggested that a shielded wire be used for antenna wiring in either way as

illustrated below. With this, the antenna wiring will be less susceptible to the aforementioned adverse

effects.

a. When the antenna is driven first.

b. When the capacitor is driven first.

RI45538NS

7

8

TXLO

TXHI

To receiver amplifier

Shielded wire

Antenna

Antenna resonance capacitor

RI45538NS

78

TXLO

TXHI

To receiver amplifier

Shielded wire

Antenna

Antenna resonance capacitor