Texas Instruments 2000 series, Reference Manual

Page: 41 / 52

41
Adjustment of Oscillator Signal Pulse
Width
The RA-RFM has an in-built-in feature to allow setting of the pulse width of the
transmitter signal coming from the oscillator. This enables the generated field
strength to be reduced from 50% down to 0%.
For this purpose a pulse width setting resistor may be inserted between J4 pins 3
and 4 on the RA-RFM. Inserting a smaller resistance value decreases the pulse
width and thus also the field strength. As default, no resistor is connected, thus
selecting the maximum pulse width of 50% and the maximum field strength. By
connecting a shorting bridge, the smallest pulse width of approximately 0% is
selected.
Table 16 provides an overview of oscillator signal pulse width and corresponding
field strength reduction when different oscillator signal pulse widths are selected by
connecting different resistor values.
Table 16: Oscillator Signal Pulse Width versus Resistor Value (estimated
values)
Resistor value
[k
Ω Ω Ω Ω
]
Oscillator signal
pulse width [%]
Field strength
reduction [dB]
open 50 0
151 37 -3
59 25 -6
17 12 -12
10 6 -18
shorted 0
∞
Appendix 2