ATA5760 ATMEL Corporation, ATA5760 Datasheet - Page 8

• Manufacturer Part Number: ATA5760
• Description: Ata5760 Uhf Ask/fsk Receiver
• Manufacturer: ATMEL Corporation

5. Receiving Characteristics
8
ATA5760/ATA5761
The RF receiver ATA5760/ATA5761 can be operated with and without a SAW front-end filter. In
a typical automotive application, a SAW filter is used to achieve better selectivity and large sig-
nal capability. The receiving frequency response without a SAW front-end filter is illustrated in
Figure 5-1
sion ATA5760N3. FSK mode exhibits a similar behavior. The plots are printed relatively to the
maximum sensitivity. If a SAW filter is used, an insertion loss of about 3 dB must be considered,
but the overall selectivity is much better.
When designing the system in terms of receiving bandwidth, the LO deviation must be consid-
ered as it also determines the IF center frequency. The total LO deviation is calculated, to be the
sum of the deviation of the crystal and the XTO deviation of the ATA5760/ATA5761. Low-cost
crystals are specified to be within ±90 ppm over tolerance, temperature and aging. The XTO
deviation of the ATA5760/ATA5761 is an additional deviation due to the XTO circuit. This devia-
tion is specified to be ±30 ppm worst case for a crystal with CM = 7 fF. If a crystal of ±90 ppm is
used, the total deviation is ±120 ppm in that case. Note that the receiving bandwidth and the
IF-filter bandwidth are equivalent in ASK mode but not in FSK mode.
Figure 5-1.
Figure 5-2.
and
Narrow Band Receiving Frequency Response (B
Wide Band Receiving Frequency Response (B
Figure 5-2 on page
-100.0
-20.0
-30.0
-40.0
-60.0
-50.0
-10.0
-20.0
-30.0
-40.0
-60.0
-80.0
-90.0
-50.0
-70.0
-10.0
0.0
0.0
-4.0
-12.0
-3.0
-9.0
8. This example relates to ASK mode and the 600 kHz ver-
-2.0
-6.0
-3.0
-1.0
df (MHz)
df (MHz)
0.0
0.0
3.0
1.0
IF
2.0
6.0
= 600 kHz)
IF
= 600 kHz)
9.0
3.0
12.0
4.0
4896C–RKE–04/06