ATA5823 ATMEL Corporation, ATA5823 Datasheet - Page 17

• Manufacturer Part Number: ATA5823
• Description: Uhf Ask/fsk Transceiver Ata5823 Ata5824
• Manufacturer: ATMEL Corporation

7.8
7.9
4829D–RKE–06/06
Inband Disturbers, Data Filter, Quasi-peak Detector, Data Slicer
TEST3 Output
Figure 7-7.
This high blocking performance makes it even possible for some applications using quarter
wave whip antennas to use a simple LC band-pass filter instead of a SAW filter in the receiver.
W h e n d e s i g n i n g s u c h a L C f i l t e r , t a k e i n t o a c c o u n t t h a t t h e 3 d B b l o c k i n g a t
433.92 MHz/2 = 216.96 MHz is 42 dBC and at 433.92 MHz/3 = 144.64 MHz is 47 dBC and at
2
cially that at 3
LO harmonic receiving frequency with only 17 dBC blocking.
If a disturbing signal falls into the received band, or a blocker is not a continuous wave, the per-
formance of a receiver strongly depends on the circuits after the IF filter. Hence the
demodulator, data filter and data slicer are important in that case.
The data filter of the ATA5823/ATA5824 implies a quasi-peak detector. This results in a good
suppression of above mentioned disturbers and exhibits a good carrier to noise performance.
The required ratio of useful signal to disturbing signal, at a BER of 10
mode and less than 3 dB (BR_Range_0 ... BR_Range_2) and 6 dB (BR_Range_3) in FSK
mode. Due to the many different possible waveforms these numbers are measured for signal as
well as for disturbers with peak amplitude values. Note that these values are worst case values
and are valid for any type of modulation and modulating frequency of the disturbing signal as
well as the receiving signal. For many combinations, lower carrier to disturbing signal ratios are
needed.
The internal raw output signal of the demodulator Demod_Out is available at pin TEST3. TEST3
is an open drain output and must be connected to a pull-up resistor if it is used (typically 100 k ),
otherwise no signal is present at that pin. This signal is mainly used for debugging purposes dur-
ing the setup of a new application, since the received data signal can be seen there without any
digital processing.
(433.92 MHz + 226 kHz) +
±50 MHz Blocking Characteristic for
(433.92 MHz + 226 kHz)+226 kHz = 1302.664 MHz the receiver has a second
-10.0
-20.0
-30.0
-40.0
-50.0
-60.0
-70.0
-80.0
-90.0
0.0
-50.0
Distance of Interfering to Receiving Signal [MHz]
-40.0
–
-30.0
226 kHz = 868.066 MHz/868.518 MHz is 50 dBC. And espe-
-20.0
-10.0
0.0
–
85 dBm Useful Signal at 433.92 MHz
10.0
20.0
ATA5823/ATA5824
30.0
40.0
-3
is less than 12 dB in ASK
50.0
17