ATA5744 ATMEL Corporation, ATA5744 Datasheet - Page 6

• Manufacturer Part Number: ATA5744
• Description: Ata5744 Uhf Ask Receiver
• Manufacturer: ATMEL Corporation

Figure 3-3.
4. Analog Signal Processing
4.1
4.2
6
IF Amplifier
RSSI Amplifier
ATA5744
f
RF
Input Matching Network without SAW Filter
RF
IN
= 433.92 MHz
C3
15p
3.3p
Please note that for all coupling conditions (see
wire inductivity of the LNA ground is compensated. C3 forms a series resonance circuit together
with the bond wire. L = 25 nH is a feed inductor to establish a DC path. Its value is not critical but
must be large enough not to detune the series resonance circuit. For cost reduction, this induc-
tor can be easily printed on the PCB. This configuration improves the sensitivity of the receiver
by about 1 dB to 2 dB.
The signals coming from the RF front end are filtered by the fully integrated 4th-order IF filter.
T h e I F c e n t e r f r e q u e n c y i s f
f
mine the center frequency.
The receiver ATA5744 employs an IF bandwidth of B
the U2741B in ASK mode.
The subsequent RSSI amplifier enhances the output signal of the IF amplifier before it is fed into
the demodulator. The dynamic range of this amplifier is DRRSSI = 60 dB. If the RSSI amplifier is
operated within its linear range, the best S/N ratio is maintained. If the dynamic range is
exceeded by the transmitter signal, the S/N ratio is defined by the ratio of the maximum RSSI
output voltage and the RSSI output voltage due to a disturber. The dynamic range of the RSSI
amplifier is exceeded if the RF input signal is about 60 dB higher compared to the RF input sig-
nal at full sensitivity.
RF
22n
= 433.92 MHz is used. For other RF input frequencies, refer to
TOKO LL2012
25n
100p
F22NJ
8
9
LNAGND
LNA_IN
ATA5744
I F
= 1 M H z f o r a p p l i c a t i o n s w h e r e f
RF
f
IN
RF
= 315 MHz
Figure 3-2 on page 5
C3
33p
3.3p
IF
= 600 kHz and can be used together with
39n
TOKO LL2012
25n
100p
F39NJ
Table 3-1 on page 5
8
9
and
ATA5744
LNAGND
LNA_IN
Figure
R F
= 3 1 5 M H z o r
3-3), the bond
4893A–RKE–11/05
to deter-