ATA5423 ATMEL Corporation, ATA5423 Datasheet - Page 11

• Manufacturer Part Number: ATA5423
• Manufacturer: ATMEL Corporation

3.2
4841A–RKE–02/05
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 50
Table 3-1.
The matching of the LNA Input to 50
the values given in
that value changes of C
The measured typical FSK and ASK Manchester code sensitivities with a Bit Error Rate (BER) of
10
inductors having a quality factor according to
of 1.0 dB at 315 MHz, TBD dB at 345 MHz, 1.2 dB at 433.92 MHz, 0.6 dB at 868.3 MHz and
TBD dB at 915 MHz. These losses can be estimated when calculating the parallel equivalent
resistance of the inductor with R
10 log(1 + R
With an ideal inductor, for example, the sensitivity at 433.92 MHz/FSK/20 kBaud/
±16 kHz/Manchester can be improved from -106 dBm to –107.2 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.
–3
are shown in
–
are based on the values of registers 5 and 6 according to
120 dBC/Hz at ±1 MHz and
f
433.92
RF
p
868.3
/R
315
345
915
/MHz
Measured Input Impedances of the RF_IN Pin
Input Matching to 50
loss
).
Table 3-3
Table 3-2 on page
1
and L
Table
and
1
may be necessary to compensate for individual board layouts.
Table 3-4 on page
C1
–
3-1. The highest sensitivity is achieved with power matching
ATA5423/25/28/29 [Preliminary]
75 dBC at ±FREF at 433.92 MHz
los s
12. The reflection coefficients were always 10 dB. Note
was done with the circuit shown in
(44
(32
= 2
(21
Z(RF_IN)
–
TBD
–
TBD
L1
–
j233)
j169)
j78)
Table
4
RF_IN
ATA5423/ATA5425/
ATA5428/ATA5429
3-2, resulting in estimated matching losses
f
12. These measurements were done with
L
Q
L
and the matching loss with
Table 9-3 on page
Table 3-3
1278 //2.1 pF
925 //2.1 pF
311 //2.2 pF
R
Figure 3-1
TBD
TBD
p
and
//C
p
Table 3-4 on
61.
and with
11