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| U3745BM Datasheet, PDF (7/29 Pages) ATMEL Corporation – UHF ASK RECEIVER IC | |||
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U3745BM
Figure 3. Input Matching Network with SAW Filter
8 LNAGND
U3745BM
C3
L
9 LNA_IN
22p
25n
fRF = 433.92 MHz
C16
C17
100p
L3
27n
8.2p
TOKO LL2012
F27NJ
L2
RFIN
TOKO LL2012
F33NJ
1 IN
B3555
5
OUT
C2
33n
2 IN_GND
OUT_GND 6
CASE_GND
8.2p
3,4 7,8
Figure 4. Input Matching Network without SAW Filter
fRF = 433.92 MHz
15p
25n
8 LNAGND
U3745BM
9 LNA_IN
RFIN
3.3p
22n
100p
TOKO LL2012
F22NJ
8 LNAGND
U3745BM
C3
L
9
LNA_IN
47p
25n
fRF = 315 MHz
C16
C17
100p
L3
47n
22p
TOKO LL2012
F47NJ
L2
RFIN
TOKO LL2012
F82NJ
1 IN
B3551
5
OUT
C2
82n
2 IN_GND
OUT_GND 6
CASE_GND
10p
3,4 7,8
fRF = 315 MHz
8 LNAGND
U3745BM
9
33p
25n
LNA_IN
RF
IN
3.3p
39n
100p
TOKO LL2012
F39NJ
Please note that for all coupling conditions (see Figure 3 and Figure 4), the bond 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 inductor can be easily printed on the PCB. This configuration
improves the sensitivity of the receiver by about 1 dB to 2 dB.
7
4663AâRKEâ06/03
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