MLX71121 Datasheet, PDF (14/28 Pages) Melexis Microelectronic Systems – 300 to 930MHz FSK/FM/ASK Receiver

MLX71121
300 to 930MHz
FSK/FM/ASK Receiver
2.2 Calculation of Frequency Settings
The receiver has two predefined receive frequency plans which can be selected by the RFSEL control pin.
Depending on the logic level of RFSEL pin the sideband selection of the second mixer and the counter set-
tings for N₁ and N₂ are changed accordingly.
RFSEL
Injection
f_RFmin [MHz]
f_RFmax [MHz]
N₁
N₂
0
high-low
300
470
4
6
1
low-high
610
930
2
12
The following table shows the relationships of several internal receiver frequencies for the two input fre-
quency ranges.
f_RF [MHz]
300 to 470
610 to 930
f_IF1
f _RF + N₁f _IF2
N₁ −1
f _RF − N₁f _IF2
N₁ +1
f_LO1
N₁ (f _RF + f _IF2 )
N₁ −1
N₁ (f _RF + f _IF2 )
N₁ +1
f_LO2
f _RF + f _IF2
N₁ −1
f _RF + f _IF2
N₁ +1
f_RO
f _RF + f _IF2
N ₂ (N₁ − 1)
f _RF + f _IF2
N ₂ (N₁ + 1)
Given IF2 = 1.8MHz and the corresponding N₁, N₂ counter settings, above equations can be transferred into
the following table.
f_RF [MHz]
300 to 470
610 to 930
f_IF1
f_RF + 7.2MHz
3
f_RF − 3.6MHz
3
f_LO1
4(f_RF + 1.8MHz)
3
2(f_RF + 1.8MHz)
3
f_LO2
f_RF + 1.8MHz
3
f_RO
f_RF + 1.8MHz
18
f_RF + 1.8MHz
36
39010 71121
Rev. 007
Page 14 of 28
Data Sheet
Feb/08