UM10381
User manual for the BGU7005 GPS Front end evaluation
board
Rev. 01 — 21 October 2009
User manual
Document information
Info
Keywords
Abstract
Content
LNA, FE, GPS, SAW, BGU7005, Mobile Phones Co-habitation
This document explains the BGU7005 GPS front-end evaluation board
NXP Semiconductors
UM10381
BGU7005 GPS FE EVB
Revision history
Rev
01
Date
Description
21 October 2009 First release
Contact information
For additional information, please visit:
http://www.nxp.com
For sales office addresses, please send an email to:
salesaddresses@nxp.com
UM10381_1
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 01 — 21 October 2009
2 of 18
NXP Semiconductors
UM10381
BGU7005 GPS FE EVB
1. Introduction
NXP Semiconductors’ BGU7005 Global Positioning System Front-End Evaluation Board
(BGU7005 GPS FE EVB) is designed to evaluate the performance of the GPS front-end
using:
•
NXP Semiconductors’ BGU7005 GPS low-noise amplifier;
•
a matching inductor;
•
a decoupling capacitor;
•
two identical GPS band-pass filters.
It has a gain of 14.6 dB and a noise figure of 1.8 dB at a current consumption of 4.8mA.
Its superior linearity performance removes interference and noise from co-habitation
cellular transmitters, while retaining sensitivity. The front-end components occupy a total
area of approximately 3 x 3 mm.
In this document, the application diagram, board layout, bill of materials, and typical
results are given, as well as some explanations on GPS related performance parameters
like out-of-band input third-order intercept point O_IIP3, gain compression under jamming
and noise under jamming.
Fig 1. BGU7005 GPS front-end evaluation board
UM10381_1
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 01 — 21 October 2009
3 of 18
NXP Semiconductors
UM10381
BGU7005 GPS FE EVB
2. General description
Modern cellular phones have multiple radio systems, so problems like co-habitation are
quite common. A GPS receiver implemented in a mobile phone requires the following
factors to be taken into account.
All the different transmit signals that are active in a phone can cause problems like
intermodulation and compression.
Since the GPS receiver needs to receive signals with an average power level of
-130 dBm, sensitivity is very important. Currently there are several GPS chipsets on the
market that can be implemented in cell phones, PDAs etc. Although many of these GPS
ICs do have integrated LNA front ends, the noise performance, and as a result the
system sensitivity is not always adequate. The GPS receiver sensitivity is a measure for
how accurate the coordinates are calculated. The GPS signal reception can be improved
by a so called GPS front-end, which improves the sensitivity by filtering out the unwanted
jamming signals and by amplifying the wanted GPS signal with a low-noise amplifier.
The pre-filters and post filters are needed to improve the overall linearity of the system as
well as to avoid overdriving the integrated LNA stage of the GPS receiver.
3. BGU7005 GPS front-end evaluation board
The BGU7005 front-end evaluation board simplifies the RF evaluation of the BGU7005
GPS LNA applied in a GPS front end, that is often used in mobile cell phones. The
evaluation board enables testing of the device RF performance and requires no
additional support circuitry. The board is fully assembled with the BGU7005, including the
input series inductor, decoupling capacitor as well as two SAW filters to optimize the
linearity performance. The board is supplied with two SMA connectors for input and
output connection to RF test equipment. The BGU7005 can operate from a 1.5 V to 2.85
V single supply and consumes about 5 mA.
3.1 Application Circuit
The circuit diagram of the evaluation board is shown in
Fig 2
With jumper JU1 the enable input can be connected either to V
cc
or GND.
X3
GND
V
en
V
cc
X4
JU1
C1
5
RF in
X1
SAW
L1
4
3
SAW
6
RF out
X2
BGU7005
1
2
Fig 2. Circuit diagram of the BGU7005 front-end evaluation board
UM10381_1
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 01 — 21 October 2009
4 of 18
NXP Semiconductors
UM10381
BGU7005 GPS FE EVB
3.2 Board Layout
Fig 3.
Printed-circuit board layout of the BGU7005 front-end evaluation board
3.3 PCB layout
A good PCB layout is an essential part of an RF circuit design. The front-end evaluation
board of the BGU7005 can serve as a guideline for laying out a board using the
BGU7005. Use controlled impedance lines for all high frequency inputs and outputs.
Bypass V
CC
with decoupling capacitors, preferably located as close as possible to the
device. For long bias lines it may be necessary to add decoupling capacitors along the
line further away from the device. Proper grounding of the GND pins is also essential for
good RF performance. Either connect the GND pins directly to the ground plane or
through vias, or do both, which is recommended. The out-of-band rejection of the SAW
filters also depends on the grounding of the filter. The material that has been used for the
evaluation board is FR4 using the stack shown in
Fig 4.
20um Cu
20um Cu
0.2mm FR4 critical
0.8mm FR4 only for
mechanical rigidity of PCB
20um Cu
(1) Material supplier is ISOLA DURAVER;
εr
= 4.6 - 4.9:
Τanδ
= 0.02
Fig 4. Stack of the PCB material
UM10381_1
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 01 — 21 October 2009
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