MITEL DW9255 Datasheet
The DW9255 is a Surface Acoustic Wave (SAW) bandpass
filter for use with the GP2000 Global Positioning System
(GPS) receiver chip-set, available from Mitel Semiconductor.
It is pre-tuned to the exact 2nd IF filter requirements of the
GP2010 & GP2015 RF front-end devices, with a centrefrequency of 35.42MHz. The response is tuned for a flat
passband, steep stopband and uniform passband group-delay
with 3 external inductors. The device is realised on a Lithium
Tantalate substrate and housed in a small leadless ceramic
Surface Mount package.
The DW9255 gives significant improvement in correlated
GPS Signal-to-Noise Ratio (SNR) performance compared to
conventional LC bandpass filter schemes. This aids satellite
signal acquisition and tracking capability from the GP2000
GPS chip-set. This device effectively filters out-of-band
(unwanted) noise in the GPS signal. The Automatic Gain
Control (AGC) within the GP2010 and GP2015 RF Front-end
devices will then operate only on in-band noise for optimum
gain and superior correlated GPS signal strength.
FEATURES
■ Centre Frequency of 35.42MHz
■ Insertion Loss of 17dB ±1dB (typical)
■ 1dB Bandwidth 1.9MHz (typical)
■ Passband Ripple 0.8dB (typical)
■ Low Profile Ceramic Surface Mount Package
■ Operating Temperature Range -40° to +85°C
APPLICATION
■ Commercial Global Positioning
DW9255
DW9255
35.42MHz SAW Filter for GPS Receivers
DS3861 - 3.1 November 1997
INPUT+
21
GND
GND
GND
GND
GND
GND
GND
GND
3
4
DW9255
5
6
78
OUTPUT+
INPUT +
21
3
4
DW9255
5
6
12
11
10
9
OUTPUT- INPUT-
INPUT -
12
11
10
9
GND
GND
GND
GND
LCS12/1
GND
GND
GND
GND
RELATED PRODUCTS AND PUBLICATIONS
Part
GP2010
GP2015
Description
GPS receiver RF Front-end
Miniature GPS receiver
RF Front-end
Data
Reference
DS4056
DS4374
78
OUTPUT +
OUTPUT -
Fig.1 Pinout
LCS12/4
1
DW9255
GPS Antenna
SAW
1st IF Filter DW9255
LNA
GP2010/15
RF Front End
Clock
Crystal
GP2021
12 channel
Correlator
DATA BUS
+ Support
Functions
ADDRESS BUS
TCXO
2 x Serial
Communications Ports
(Programmable UARTS)
Fig.2 DW9255 used with GPS chipset
ELECTRICAL CHARACTERISTICS (Typ. @ 25°C)
Parameter Min Typ Max Units
TO
PROCESSOR
Centre Frequency - 35.42 - MHz
1dB Bandwidth 1.6 1.9 - MHz
Insertion Loss 16 17 18 dB
Amplitude Ripple - 0.8 1.6 dB (pk to pk)
(34.62 to 36.22MHz)
Relative Attenuation <28MHz 35 40 - dB
(relative to insertion loss) <31MHz 30 35 - dB
<33.5MHz 21 25 - dB
>37.5MHz 21 25 - dB
>40MHz 25 30 - dB
>50MHz 30 40 - dB
>63MHz 28 35 - dB
>73 - 110MHz 40 45 - dB
Group Delay Ripple - 190 300 ns
(34.62 to 36.22MHz)
Maximum Group Delay - 1.6 1.7 µs
(34.62 to 36.22MHz)
Operating Temperature Range -40 - +85 °C
2
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