ata5724p3c-tkqy ATMEL Corporation, ata5724p3c-tkqy Datasheet - Page 9

• Manufacturer Part Number: ata5724p3c-tkqy
• Description: Uhf Ask/fsk Receiver
• Manufacturer: ATMEL Corporation

5. Receiving Characteristics
9248A–RKE–09/11
The Atmel
a SAW front-end filter. In a typical automotive application, a SAW filter is used to achieve bet-
ter selectivity and large signal capability. The receiving frequency response without a SAW
front-end filter is illustrated in
ATA5724C”. This example relates to ASK mode. 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 3dB 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
t h e s u m o f t h e d e v i a t i o n o f t h e c r y s t a l a n d t h e X T O d e v i a t i o n o f t h e A t m e l
ATA5723C/ATA5724C/ATA5728C. Low-cost crystals are specified to be within ±90ppm over
t o l e r a n c e , t e m p e r a t u r e , a n d a g i n g . T h e X T O d e v i a t i o n o f t h e A t m e l
ATA5723C/ATA5724C/ATA5728C is an additional deviation due to the XTO circuit. This devi-
ation is specified to be ±10ppm worst case for a crystal with CM = 7fF. If a crystal of ±90ppm
is used, the total deviation is ±100ppm 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.
®
-10
-20
-30
-40
-50
-60
-70
RF receiver ATA5723C/ATA5724C/ATA5728C can be operated with and without
10
0
430
Narrow Band Receiving Frequency Response Atmel ATA5724C
Atmel ATA5723C/ATA5724C/ATA5728C
431
Image Rejection versus RF Frequency
432
Figure 5-1
433
(MHz)
434
“Narrow Band Receiving Frequency Response
435
436
437
438
4.5V -40
5V -40
5.5V -40
4.5V 25
5V 25
5.5V 25
4.5V 105
5V 105
5.5V 105
˚
˚
C
C
˚
˚
˚
˚
˚
C
C
C
C
C
˚
˚
C
C
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