SM1211E915TOPIC Semtech, SM1211E915TOPIC Datasheet - Page 27

• Manufacturer Part Number: SM1211E915TOPIC
• Description: KIT PICTAIL EXT FOR SX1211
• Manufacturer: Semtech
• Type: Transceiver, UHFr

Specifications of SM1211E915TOPIC

• Frequency: 915MHz
• For Use With/related Products: SX1211
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

In OOK mode, the RSSI evaluates the signal strength by sampling I(t) and Q(t) signals 16 times in each period of
the chosen IF2 frequency (refer to section 3.4.1). In FSK mode, the signals are sampled 16 times in each Fdev
period, Fdev being the frequency deviation of the companion transmitter. An average is then performed over a
sliding window of 16 samples. Hence, the RSSI output register RXParam_RSSI is updated 16 times in each Fdev
or IF2 period.
The following settings should be respected:
The dynamic range of the RSSI is over 70 dB, extending from the nominal sensitivity level. The IF gain setting
available in MCParam_IF_gain is used to achieve this dynamic range:
The RSSI response versus input signal is independent of the receiver filter bandwidth. However in the absence of
any input signal, the minimum value directly reflects upon the noise floor of the receiver, which is dependant on the
filter bandwidth of the receiver.
The SX1211 can also be used to detect a RSSI level above a pre-configured threshold. The threshold is set in
IRQParam_RSSI_irq_thresh and the IRQ status stored in IRQParam_RSSI_irq (cleared by writing a “1”).
An
IRQParam_Rx_stby_irq1. Figure 21 shows the timing diagram of the RSSI interrupt source, with
IRQParam_RSSI_irq_thresh set to 28.
Rev 7 – Sept 2
ADVANCED COMMUNICATIONS & SENSING
FSK Mode: Ensure that the Fdev parameter (as described in MCParam_Fdev) remains consistent with the
actual frequency deviation of the companion transmitter.
OOK reception: Ensure that the Fdev parameter (as described in MCParam_Fdev) is equal with the frequency
of I(t) and Q(t) signals, i.e. the second Intermediate Frequency, IF2, of the receiver (Note that this equals Fo,
the center frequency of the polyphase filter).
interrupt
nd
, 2008
can
3.4.7.3. Dynamic Range
3.4.7.4. RSSI IRQ Source
180
160
140
120
100
80
60
40
20
be
0
-120
mapped
-100
to
Figure 20: RSSI Dynamic Range
the
IF_Gain=00
-80
IRQ0
Page 27 of 92
RSSI Response
IF_Gain=01
or
Pin [dBm]
-60
IRQ1
IF_Gain=10
pins
-40
IF_Gain=11
via
bits
-20
IRQParam_Rx_stby_irq0
0
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SX1211
or