ATA5811-PLQX Atmel, ATA5811-PLQX Datasheet - Page 21

• Manufacturer Part Number: ATA5811-PLQX
• Manufacturer: Atmel

Specifications of ATA5811-PLQX

• Operating Temperature (min): -40C
• Operating Temperature (max): 105C
• Operating Temperature Classification: Industrial
• Product Depth (mm): 7mm
• Product Height (mm): 0.9mm
• Product Length (mm): 7mm
• Lead Free Status / Rohs Status: Compliant

Matching Network in TX Mode
Matching Network in RX Mode In RX mode the RF_OUT pin has a high impedance of about 7 k in parallel with 1.0 pF
4689B–RKE–04/04
Figure 17. Equivalent Circuit of the Switch
In TX mode the 20 mm long and 0.4 mm wide transmission line which is much shorter
than /4 is approximately switched in parallel to the capacitor C
connection between C
mission line into the loop antenna with pin RF_OUT, L
(using a C
approximated with a 16 nH inductor in series with a 1.5
be approximated according to Table 10 on page 20 with the series connection of 1.6 nH
and 5
power going into it looking from the loop antenna into the transmission line a capacitor of
about 7.6 pF to GND is needed at the beginning of the transmission line (this capacitor
is later absorbed into C
keep the 50
also about 7.6 pF. This reduces the TX power by about 0.5 dB at 433.92 MHz compared
to the case the where the LNA path is completely disconnected.
at 433.92 MHz as can be seen in Table 11 on page 22. This together with the losses of
the inductor L
RF_OUT. Since the optimum load impedance in TX mode for the power amplifier at
RF_OUT is 890
estimated to be 10
loop antenna without L
433.92 MHz, about an inductor of 1.6 nH in series with the parallel connection of 2.5 pF
and 2.0 k . Since the impedance level at pin RX_TX1 in RX mode is about 50
only negligiblably dampens the received signal by about 0.1 dB. When matching the
LNA to the loop antenna the transmission line and the 7.6 pF part of C
into account when choosing the values of C
the loop antenna into the transmission line with the 7.6 pF capacitor connected is 50 .
Since the loop antenna in RX mode is loaded by the LNA input impedance the loaded Q
of the loop antenna is lowered by about a factor of 2 in RX mode hence the antenna
bandwidth is higher than in TX mode.
in this mode. To have a parallel resonant high impedance circuit with little RF
9
without the added 7.6 pF as discussed later). The transmission line can be
impedance in RX mode at the end of this transmission line C
2
with 120 nH and Q
the loss associated with the inductor L
log(1 + 890/3700) = 0.95 dB compared to the optimum matched
8
and C
9
ATA5811/ATA5812 [Preliminary]
which is then higher as needed for 50
2
and RF_OUT. The switch represents, in this mode at
9
has an impedance of about 50
2.5 pF
11
L2
1.6 nH
= 25 gives about 3.7 k
RX_TX1
TX
11
and L
5
1
so that the impedance seen from
resistor, the closed switch can
2
2
, C
and the RF_OUT pin can be
10
, C
9
locking from the trans-
to GND. The antenna
8
loss impedance at
transformation). To
and C
9
has to be taken
9
7
connected
has to be
this
21