nRF903 Nordic VLSI, nRF903 Datasheet - Page 18

• Manufacturer Part Number: nRF903
• Description: Multichannel RF Transceiver 433/868/915MHz
• Manufacturer: Nordic VLSI

PRODUCT SPECIFICATION
The external 1
Center frequency should be positioned at 10.7MHz, and bandwidth should not be less than the
channel spacing. 180kHz is a suitable bandwidth. Note that variations in absolute center
frequency and bandwidth may differ for different vendors.
This filter may be replaced with a 10nF capacitor between the FILT1- and FILT2-pins, at the
expense of sensitivity (approx. 3dB degradation), blocking performance and adjacent channel
selectivity. In this case, only the internal (second) IF-filter is used. The image frequency
resulting from the second mixing will then appear in the baseband. This image is centered at
691kHz above the signal of interest.
The synthesiser loopfilter is an external, single-ended third order lag-lead filter as shown in
Figure 10.
The startup and switching times of the transceiver is dependent on the loopfilter bandwidth. A
high loopfilter bandwidth reduces switching time, but necessitates efficient scrambling or
biphase (Manchester) encoding of data.
If a filter with lower bandwidth is chosen, normal data may be transmitted without scrambling
requirements at the expense of longer switching times.
The recommended filter component values are listed in Table 17.
Nordic VLSI ASA
Revision: 3.1
Chequers electronic
muRata
TDK
Table 16. Vendors and part no. for suitable 10.7MHz ceramic filters.
st
IF-filter is a piezoelectric ceramic filter with 330 input/output impedance.
-
Table 17. Loopfilter component values and tolerances
www.chequers-electronic.com
www.murata.com
www.tdk.co.jp
Vestre Rosten 81, N-7075 Tiller, Norway
470 ( 5%)
27 ( 5%)
Figure 10. Loopfilter configuration

LF1
(2)
C
2
220 ( 5%)
12 ( 5%)
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R

V
1
DD
C
1
LTCV10.7MS3A10-A
SFECV10.7MS3S-A-TC (SMD-package)
FFE1070MS (Through-mount)
0.47 ( 5%)
6.8 ( 5%)
C
-
3

Phone [phone]
LF2
R
(3)
2
150 ( 1%)
330 ( 1%)
(SMD-package)
:

-
Fax [phone]
150 ( 1%)
330 ( 1%)
December 2002
: