AMIS-53050 Datasheet, PDF (60/107 Pages) AMI SEMICONDUCTOR – Frequency Agile Transceiver

AMIS-53050 Frequency Agile Transceiver
Data Sheet
Table 37: AM Data Filter and Slice Options - 0X1E [30]
Bit
Name
State Comment
000
001
010
[7:5]
011
AM_FILTER[2:0] ₁₀₀
101
110
111
RSSI filter bandwidth =300Hz
RSSI filter bandwidth = 600Hz
RSSI filter bandwidth = 1.2kHz
RSSI filter bandwidth = 2.4kHz
RSSI filter bandwidth = 4.8kHz
RSSI filter bandwidth = 9.6kHz
RSSI filter bandwidth = 19.2kHz
RSSI filter bandwidth = 38.4kHz
4
NU
00
[3:2]
AM_SLICE[1:0]
01
10
11
DAC mode: Slice threshold set in register 1Bh
Average mode: AM threshold set using averaging filter
Peak detect mode: AM threshold set using peak detector
DAC mode: Slice threshold set in register 1Bh
00
[1:0]
AM_HYST[1:0]
01
10
11
0mV slice hysteresis
25mV slice hysteresis
50mV slice hysteresis
100mV slice hysteresis
FM FFT
The AMIS-53050 receiver uses a FFT function to recover data from a FM/FSK modulated signal when the data rate is higher than
20kbps. The FFT detector uses a two-bit DFFT to demodulate the incoming IF signal. This circuit also uses the same clock recovery
block (CDR) as the AM detector (see Section 6.1.4) to detect the data.
A pattern of 1’s and 0’s is required as a preamble. A SOF is not required unless Manchester encoded data is used, requiring a unique
preamble to bit-align the Manchester decoder to the recovered data.
Register descriptions:
Data Rate- Can be specified in the discrete data rate register, or specified as a 16-bit word for a user defined data rate (see
Section 7.1.3).
Peak Deviation- The peak deviation register stores the value to be used for both transmit and receive. In the FFT FM receive
mode, this value is used to set-up the FFT bins (see Sections 6.4.1.5 and 6.4.1.6).
FM PLL Detector Loop Filter- For the discrete data rates, the values for the loop filter coefficients are pre-programmed (issue
the command ROM2REGs to have the AMIS-53050 determine these values). For user defined data rates, this value needs to
be calculated. (AMI Semiconductor provides a program, helper.exe, which can help in determining the values for this register.)
CDR Loop Filter- For the discrete data rates, the values for the loop filter coefficients are pre-programmed (issue the
command ROM2REGs to have the AMIS-53050 determine these values). For user defined data rates, this value needs to be
calculated. (AMI Semiconductor provides a program, helper.exe, which can help in determining the values for this register.)
FM PLL (Low Data Rate FSK)
The AMIS-53050 uses a PLL function to recover the data from a FM/FSK modulated signal with data rates 20kbps or lower. This circuit
uses an A DPLL for demodulation, the output of which is fed to the AM CDR circuit to recover the clock, and additionally filter the output
data.
The preamble sent by the AMIS-53050 when configured as NRZ FM is a repeating sequence of 1’s and 0’s. This gives the CDR circuit
and PLL demodulator sufficient edges to acquire lock. Hence, for the NRZ case it is unnecessary to include a SOF byte. In Manchester
mode, the preamble is specified as all 1’s (or 0’s). This gives the clock recovery circuit the most edges for lock acquisition. However,
due to the ambiguity of the preamble, a SOF byte is necessary for the Manchester decoding block. The suggested SOF for this is either
#55h or #AAh. The length of preamble necessary for this mode is dependant upon the loop bandwidth for the clock recovery PLL.
AMI Semiconductor – Jan. 07, M-20639-002
60
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