ATA5423_06 ATMEL [ATMEL Corporation], ATA5423_06 Datasheet - Page 11

• Manufacturer Part Number: ATA5423_06
• Description: UHF ASK/FSK Transceiver
• Manufacturer: ATMEL [ATMEL Corporation]

3.2
4841C–WIRE–05/06
Input Matching at RF_IN
A low-IF architecture is also less sensitive to second-order intermodulation (IIP2) than direct
conversion receivers, where every pulse or AM-modulated signal (especially the signals from
TDMA systems like GSM) demodulates to the receiving signal band at second-order
non-linearities.
Note:
The measured input impedances as well as the values of a parallel equivalent circuit of these
impedances can be seen in
of these impedances to the source impedance of 50Ω
Table 3-1.
The matching of the LNA Input to 50Ω was done with the circuit shown in
values given in
value changes of C
measured typical FSK and ASK Manchester code sensitivities with a Bit Error Rate (BER) of 10
are shown in
tors having a quality factor according to
0.8 dB at 315 MHz, 0.8 dB at 345 MHz, 0.7 dB at 433.92 MHz, 0.7 dB at 868.3 MHz and 0.7 at
915 MHz. These losses can be estimated when calculating the parallel equivalent resistance of
the inductor with R
With an ideal inductor, for example, the sensitivity at 433.92 MHz/FSK/20 Kbit/s/
±16 kHz/Manchester can be improved from –106 dBm to –106.7 dBm. The sensitivity depends
on the control logic which examines the incoming data stream. The examination limits must be
programmed in control registers 5 and 6. The measurements in
page 12
Figure 3-1.
–
are based on the values of registers 5 and 6 according to
120 dBC/Hz at ±1 MHz and
f
433.92
RF
868.3
Table 3-3
315
345
915
/MHz
Measured Input Impedances of the RF_IN Pin
Input Matching to 50Ω
Table 3-2 on page
loss
1
and L
= 2 × π × f × L × Q
and
1
Table 3-4 on page
may be necessary to compensate for individual board layouts. The
Table
C1
–
12. The reflection coefficients were always ≤10 dB. Note that
3-1. The highest sensitivity is achieved with power matching
75 dBC at ±FREF at 433.92 MHz
(44
(40
(32
Z(RF_IN)
Table
(21
(18
L
and the matching loss with 10 log(1 + R
L1
-
-
-
-
-
j233)Ω
j211)Ω
j169)Ω
j78)Ω
j70)Ω
4
12. These measurements were done with induc-
3-2, resulting in estimated matching losses of
RF_IN
ATA5423/ATA5425/
ATA5428/ATA5429
ATA5423/25/28/29
Table 9-3 on page
Table 3-3
1278Ω//2.1 pF
1153Ω//2.1 pF
Figure 3-1
925Ω//2.1 pF
311Ω//2.2 pF
290Ω//2.3 pF
R
p
and
//C
p
Table 3-4 on
p
and with the
/R
61.
loss
).
11
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