AMIS-53050 Datasheet, PDF (59/107 Pages) AMI SEMICONDUCTOR – Frequency Agile Transceiver

AMIS-53050 Frequency Agile Transceiver
Data Sheet
AM Data Recovery with RSSI
The logarithmic AM detector, used with OOK/ASK modulated signals, produces an RSSI output signal with approximately 18mV/dB
output level. A low pass filter provides additional filtering matched to the AM signal data rate (1.2, 1.8, 2.4, 4.8, 7.2, 9.6, 14.4,
19.2kbps). This filtered signal is sampled and compared to the slice threshold to recover the digital data. The slice threshold can be set
to a fixed value or it can use a signal tracking circuit to set a peak or average threshold.
The RSSI output signal can also be applied to a clock and data recovery circuit, which synchronizes an AMIS-53050 internal clock with
the incoming data rate (see CDR Operation).
Register descriptions:
Slice Threshold- The slice operation needs to be selected, fixed or automatic. The value for the fixed threshold needs to be
set.
Filter/Slice- Filter settings and slice mode need to be selected.
Slice Threshold
Sets the data slice level for AM reception. This threshold is used when the slice method sets in the AM data filter and slice options
register is set to DAC.
Table 36: Slice Threshold - 0X1D [29]
Bit Name
Comment
7:0 _{SL_THRESH [7:0]} AM slice threshold in DAC mode = SL_THRESH*7.8125mV
AM Data Filter and Slice Options
This register contains settings for determining the method of slicing for AM receive mode.
AM_FILTER: Sets the post-detection filter bandwidth for RSSI during AM receive. These filter bandwidths are set for the
corresponding data rates. These filter settings can also be used with custom data rates.
AM_HYST: Sets the amount of hysteresis in the AM slice comparator.
AM_SLICE: Used to select the method for providing a reference to the AM slice comparator.
DAC Mode: This is a fixed threshold level programmed into the slice threshold register.
Average Mode: This is an automatic threshold level where the AMIS-53050 sets the threshold level to the average
level of the RSSI signal. An external capacitor is required on the PEAK pin to set a bandwidth for the low pass filter
response of the averaging circuit. .
Peak Mode: This is similar to the average mode, but only the highest level is determined from the incoming signal
and the AMIS-53050 sets the threshold to a level 6dB lower than the peak value. An external capacitor on the PEAK
pin determines a bleed off (discharge) rate for the peak detector circuit. The value of this capacitor is discussed in
the application note “Setting up the AMIS-52100 Data Slicing Modes” which applies also to this AMIS-53050
parameter.
AMI Semiconductor – Jan. 07, M-20639-002
59
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