ATA5811_06 ATMEL [ATMEL Corporation], ATA5811_06 Datasheet - Page 16

• Manufacturer Part Number: ATA5811_06
• Description: UHF ASK/FSK TRANSCEIVER
• Manufacturer: ATMEL [ATMEL Corporation]

5.10
5.11
16
Frequency Synthesizer
FSK/ASK Transmission
ATA5811/ATA5812
Figure 5-6.
The synthesizer is a fully integrated fractional-N design with internal loop filters for receive and
transmit mode. The XTO frequency f
The bits FR0 to FR8 in control registers 2 and 3 (see
page
has a phase noise of
loop bandwidth allowing the direct modulation of the carrier with 20 Kbit/s Manchester data. Due
to the closed loop modulation any spurious caused by this modulation are effectively filtered out
as can be seen in
–120 dBC/Hz at 1 MHz and spurious of
The initial tolerances of the crystal oscillator due to crystal tolerances, internal capacitor toler-
ances and the parasitics of the board have to be compensated at manufacturing setup with
control registers 2 and 3 as can be seen in
synthesizer needed for ASK, FSK and receive/transmit switching are calculated internally. The
RF (Radio Frequency) resolution is equal to the XTO frequency divided by 16384 which is
777.1 Hz at 315.0 MHz, 808.9 Hz at 433.92 MHz and 818.59 Hz at 868.3 MHz.
Due to the fast modulation capability of the synthesizer and the high resolution, the carrier can
be internally FSK modulated which simplifies the application of the transceiver. The deviation of
the transmitted signal is ±20 digital frequency steps of the synthesizer which is equal to
±15.54 kHz for 315 MHz, ±16.17 kHz for 433.92 MHz and ±16.37 kHz for 868.3 MHz.
Due to closed loop modulation with PLL filtering the modulated spectrum is very clean, meeting
ETSI and CEPT regulations when using a simple LC filter for the power amplifier harmonics as it
is shown in
ter of the FSK transmission and the power amplifier is switched on and off to perform the
modulation.
ulation with pseudo random data with 20 Kbit/s/±16.17 kHz/Manchester and 5 dBm output
power.
36) are used to adjust the deviation of f
Figure 3-1 on page
Figure 5-7 on page 17
Typical RSSI Characteristic versus Temperature and Supply Voltage
Figure 5-9 on page
–
111 dBC/Hz at 1 MHz and spurious at FREF of
1000
1100
900
800
700
600
500
400
-120
7. In ASK mode the frequency is internally connected to the cen-
-110
Min.
to
Figure 5-9 on page 18
XTO
-100
–
18. In RX mode the synthesizer has a phase noise of
75 dBC.
is the reference frequency FREF for the synthesizer.
Table 6-1 on page
PRF_IN (dBm)
-90
XTO
Typ.
. In transmit mode, at 433.92 MHz, the carrier
-80
Table 9-7 on page 36
-70
Max.
show the spectrum of the FSK mod-
25. The other control words for the
-60
-50
–
66 dBC with a high PLL
-40
and
Table 9-10 on
4689F–RKE–08/06