SM1211E915 Semtech, SM1211E915 Datasheet - Page 29

• Manufacturer Part Number: SM1211E915
• Description: Dev Kit Accessory
• Manufacturer: Semtech

Specifications of SM1211E915

• Modulation Type: FSK, OOK
• Data Rate Max: 200Kbps
• Frequency Range: 902MHz To 928MHz
• Supply Voltage Range: 2.1V To 3.6V
• Module Interface: SPI
• Supply Current: 25mA
• Accessory Type: RF Module
• Sensitivity: -105dBm
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Package Type: TQFN EP
• Operating Supply Voltage (min): 2.1V
• Operating Supply Voltage (typ): 2.5/3.3V
• Operating Supply Voltage (max): 3.6V
• Sensitivity (dbm): -105dBm
• Rohs Compliant: NA
• Lead Free Status / RoHS Status: na
• Lead Free Status / RoHS Status: na

In peak threshold mode the comparison threshold level is the peak value of the RSSI, reduced by 6dB. In the
absence of an input signal or during the reception of a logical “0”, the acquired peak value is decremented by one
RXPAram_OOK_thresh_step every RXParam_OOK_thresh_dec_period.
When the RSSI output is null for a long time (for instance after a long string of “0” received, or if no transmitter is
present), the peak threshold level will continue falling until it reaches the “Floor Threshold” that is programmed
through the register MCParam_OOK_floor_thresh.
The default settings of the OOK demodulator lead to the performance stated in the electrical specification.
However, in applications in which sudden signal drops are awaited during a reception, the three parameters shall
be optimized accordingly.
MCParam_OOK_floor_thres determines the sensitivity of the OOK receiver, as it sets the comparison threshold for
weak input signals (i.e. those close to the noise floor). Significant sensitivity improvements can be generated if
configured correctly.
Note that the noise floor of the receiver at the demodulator input depends on:
It is therefore important to note that the setting of MCParam_OOK_floor_thresh will be application dependant. The
following procedure is recommended to optimize MCParam_OOK_floor_thresh.
Rev 7 – Sept 2
ADVANCED COMMUNICATIONS & SENSING
The noise figure of the receiver.
The gain of the receive chain from antenna to base band.
The matching - including SAW filter.
The bandwidth of the channel filters.
nd
RSSI
(dB)
, 2008
3.4.10.1. Optimizing the Floor Threshold
Figure 22: OOK Demodulator Description
Zoom
Zoom
RXParam_OOK_thresh_dec_period
RXPAram_OOK_thresh_step
Decay in dB as defined in
Period as defined in
Page 29 of 92
Fixed 6dB difference
‘’Peak -6dB’’ Threshold
‘’Floor’’ threshold defined by
MCParam_OOK_floor_thresh
Noise floor of
receiver
Time
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