CXA1999 SONY [Sony Corporation], CXA1999 Datasheet - Page 13

• Manufacturer Part Number: CXA1999
• Description: IF Amplifier for M-ary FSK Pagers
• Manufacturer: SONY [Sony Corporation]

12) M-ary (M = 2- or 4-level) FSK Demodulation System
[4-level FSK demodulating waveform]
[NRZ OUT] Polarity discrimination output
[L.C. OUT] MSB comparator output
Polarity discrimination output and MSB comparator output are used to demodulate the 4-level waveform
shown below.
The 4-level FSK demodulating data is divided into an NRZ OUT and L.C. OUT shown above. Here, the
NRZ OUT corresponds to a conventional NRZ comparator output. The L.C. OUT is made comparing the
demodulated waveform amplitude to the IC internal reference voltage levels. When the threshold value of
L.C. OUT is not appropriate to the detector output, the resistance value on Pin 8 should be adjusted for
the detector output level adjustment.
For the 2-level FSK demodulation, it corresponds to a conventional NRZ comparator output.
POS
NEG
1.6kHz
4.8kHz
–1.6kHz
–4.8kHz
+4.8kHz
+1.6kHz
01
1
0
(When the input frequency is higher than the local frequency)
00
0
0
—13—
10
0
1
11
1
1
01
1
0
10
0
1
00
0
0
The polarity can be inverted
by setting the local frequency
higher
frequency.
than
the
CXA1999N
input