Receiver; Rfm Connectors And Jumpers; Rfm Top View; Timing Characteristics - Texas Instruments 2000 Series Reference Manual

Receiver

1.3 Receiver
The signal received from the transponder is a frequency shift keying (FSK) signal with typical low and high
bit frequencies of 134.2 kHz and 123.2 kHz respectively. The signal is received from the antenna
resonator, which is capacitively coupled to the receiver.
The signal RXCK is the reference clock signal to decode the RXDT data stream. The RXCK signal
changes from low to high level during each data bit and the RXDT signal is valid before and after this
positive slope for a certain time window. For more details refer to
The receiver also has a built-in RF receive signal strength detector. The receive signal strength is
indicated by the digital output RXSS-.
RXSS- becomes active ( logic low level) when the received RF signal strength exceeds a defined level.
This threshold level can be adjusted with a potentiometer (R409) on the RFM. The potentiometer is
located near SW1 on the board. See
The RXSS- output is used for detection of other transmitting reading units and thus can be used for
wireless read cycle synchronization of several reading units.
1.4

RFM Connectors and Jumpers

There are a number of connectors, jumpers and other components on the RFM available for use.
These are:
J1 Connector for supply voltages and interface signal lines to and from the RFM
J2 Connector for the (optional) Antenna Tuning Indicator (ATI), which can be used for easy
antenna tuning during installation.
J3 Connector for antenna resonance tuning, used to connect the required tuning capacitors.
J4 Connector for field strength adjustment resistor and also direct access to receiver input.
J5 Additional antenna damping Jumper.
J6 Common-mode noise choke bypass.
R409 RXSS noise level adjustment potentiometer.
SW1 Default all on. (SW1/1 CPS setting see
ANT1/ANT2 (Two M3 screw connectors) Connect the transmit/receive (TX/RX) antenna to the RFM.
10 Product Description
Figure

1-3, RFM Top View.

Appendix
Table

2-3, Timing Characteristics.

E.)
SCBU022 – November 2002
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