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 centre-
frequency 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.
INPUT+
2
GND
3
INPUT-
1
12
GND
11
GND
4
GND
DW9255
GND
5
10
GND
GND
6
7
8
9
GND
LCS12/1
FEATURES
INPUT +
s
Insertion Loss of 17dB
±1dB
(typical)
s
1dB Bandwidth 1.9MHz (typical)
s
Passband Ripple 0.8dB (typical)
s
Low Profile Ceramic Surface Mount Package
s
Operating Temperature Range -40° to +85°C
GND
3
2
INPUT -
s
Centre Frequency of 35.42MHz
1
12
GND
GND
4
11
GND
DW9255
APPLICATION
s
Commercial Global Positioning
GND
5
10
GND
GND
6
7
OUTPUT +
9
8
OUTPUT -
GND
RELATED PRODUCTS AND PUBLICATIONS
Part
GP2010
GP2015
Description
GPS receiver RF Front-end
Miniature GPS receiver
RF Front-end
Data
Reference
DS4056
DS4374
LCS12/4
Fig.1 Pinout
1
DW9255
GPS Antenna
SAW
1st IF Filter
LNA
GP2010/15
RF Front End
DW9255
Clock
Crystal
GP2021
12 channel
Correlator
+ Support
Functions
DATA BUS
ADDRESS BUS
TO
PROCESSOR
TCXO
2 x Serial
Communications Ports
(Programmable UARTS)
Fig.2 DW9255 used with GPS chipset
ELECTRICAL CHARACTERISTICS
(Typ. @ 25°C)
Parameter
Centre Frequency
1dB Bandwidth
Insertion Loss
Amplitude Ripple
(34.62 to 36.22MHz)
Relative Attenuation
<28MHz
(relative to insertion loss) <31MHz
<33.5MHz
>37.5MHz
>40MHz
>50MHz
>63MHz
>73 - 110MHz
Group Delay Ripple
(34.62 to 36.22MHz)
Maximum Group Delay
(34.62 to 36.22MHz)
Operating Temperature Range
Min
-
1.6
16
-
35
30
21
21
25
30
28
40
-
-
-40
Typ
35.42
1.9
17
0.8
40
35
25
25
30
40
35
45
190
1.6
-
Max
-
-
18
1.6
-
-
-
-
-
-
-
-
300
1.7
+85
Units
MHz
MHz
dB
dB (pk to pk)
dB
dB
dB
dB
dB
dB
dB
dB
ns
µs
°C
2
DW9255
DW9255 used as 2nd IF filter for GP2010/15
Centre Frequency
Pass Band
Insertion loss
3rd IF Image frequency at 2nd IF
Source Impedance
Load Impedance
35.42MHz
±1.0MHz
(within
±1.0dB)
14-18dB
26.8MHz
500Ω typical
1000Ω typical
than 20dB) beyond this bandwidth, and so should have a brick-
wall type response at these extremes. The DW9255 SAW
filter provides a 1dB Bandwidth of typically 1.9MHz centred on
35.42MHz, with a typical pass band ripple of 0.8dB, when the
SAW input and output capacitance is resonantly matched with
inductors of optimum value. The out-of-band signal rejection is
better than 21dB at
±2.0MHz,
and better than 35dB at
±7.5MHz.
The frequency response of the DW9255 SAW filter with
matching components is shown in Fig. 3. The matching
components used with the GP2010/15 device are shown in
Fig. 4.
The second external IF filter is connected between the output
of Stage 2 and input of Stage 3. It is required to define the
bandwidth of the RF section of the GPS receiver, hence it is
critical to the receiver performance. The filter should be flat
across the 2MHz bandwidth of the GPS Coarse-Acquisition
(C/A) code signal. It should also have high rejection (greater
5
0
Insertion Loss (dB)
- 5
-10
-15
-20
-25
-30
-35
-40
32
33
34
35
FREQUENCY (MHz)
36
37
38
Fig.3 Typical frequency response of DW9255 SAW filter used as 2nd IF filter
3
DW9255
VCC
L1
L2
IP+
OP+
SOURCE
IMPEDANCE
= 500Ω
MIX
2
O/P
IP-
DW9255
OP-
2.2µH
MIX
3
I/P
LOAD
IMPEDANCE
= 1KΩ
COILCRAFT
1008
GP2010
GP2010 or GP2015
L1, L2 = 560nH COILCRAFT 1008
Fig.4 Typical matching components when used with GP2010 or GP2015 GPS Front-end IC
680nH
IP+
COILCRAFT 1008
OP+
910nF
COILCRAFT 1008
DW9255
15pF VITRAMON
(VJ0805A150JXA)
IP-
OP-
Pin 1 = IP-
Pin 2 = IP+
Pin 7 = OP+
Pin 8 = OP-
Fig.5 50
Ω
Matching network
4
http://www.mitelsemi.com
World Headquarters - Canada
Tel: +1 (613) 592 2122
Fax: +1 (613) 592 6909
North America
Tel: +1 (770) 486 0194
Fax: +1 (770) 631 8213
Asia/Pacific
Tel: +65 333 6193
Fax: +65 333 6192
Europe, Middle East,
and Africa (EMEA)
Tel: +44 (0) 1793 518528
Fax: +44 (0) 1793 518581
Information relating to products and services furnished herein by Mitel Corporation or its subsidiaries (collectively “Mitel”) is believed to be reliable. However, Mitel assumes no
liability for errors that may appear in this publication, or for liability otherwise arising from the application or use of any such information, product or service or for any infringement of
patents or other intellectual property rights owned by third parties which may result from such application or use. Neither the supply of such information or purchase of product or
service conveys any license, either express or implied, under patents or other intellectual property rights owned by Mitel or licensed from third parties by Mitel, whatsoever.
Purchasers of products are also hereby notified that the use of product in certain ways or in combination with Mitel, or non-Mitel furnished goods or services may infringe patents or
other intellectual property rights owned by Mitel.
This publication is issued to provide information only and (unless agreed by Mitel in writing) may not be used, applied or reproduced for any purpose nor form part of any order or
contract nor to be regarded as a representation relating to the products or services concerned. The products, their specifications, services and other information appearing in this
publication are subject to change by Mitel without notice. No warranty or guarantee express or implied is made regarding the capability, performance or suitability of any product or
service. Information concerning possible methods of use is provided as a guide only and does not constitute any guarantee that such methods of use will be satisfactory in a specific
piece of equipment. It is the user’s responsibility to fully determine the performance and suitability of any equipment using such information and to ensure that any publication or
data used is up to date and has not been superseded. Manufacturing does not necessarily include testing of all functions or parameters. These products are not suitable for use in
any medical products whose failure to perform may result in significant injury or death to the user. All products and materials are sold and services provided subject to Mitel’s
conditions of sale which are available on request.
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