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3.3 PCB layout
A good PCB layout is an essential part of an RF circuit design. The evaluation board of
the BGU7004 can serve as a guideline for laying out a board using the BGU7004. Use
controlled impedance lines for all high frequency inputs and outputs. Bypass V
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. The material that has been used for the evaluation board is FR4 using the stack
shown in
Fig 4. Stack of the PCB material
Material supplier is ISOLA DURAVER; r = 4.6 - 4.9: Tan= 0.02
3.4 Bill of materials
Table 1 BOM of the BGU7004 GPS LNA EVB v2.1
Designator
Description Footprint
Ac
BGU7004
PCB
v2.1
C1
Capacitor
L1
Inductor
X1,X2
SMA RF
connector
X3
DC header
X4
JUMPER
stage
JU1
Jumper
3.4.1 Series inductor
The evaluation board is supplied with Murata LQW15series inductor of 5.6nH. This is a
wire wound type of inductor with high quality factor (Q) and low series resistance (R
This type of inductor is recommended in order to achieve the best noise performance.
High Q inductors from other suppliers can be used. If it is decided to use other low cost
inductors with lower Q and higher R
UM10491
User manual
Fig 4
20um Cu
20um Cu
20um Cu
Value
1.45x1.1mm
35x20mm
BGU7004 GPS LNA EVB
0402
1nF
0402
5.6nH
-
-
-
-
-
-
Rev. 1.0 — 14 June 2011
0.2mm FR4 critical
0.8mm FR4 only for
mechanical rigidity of PCB
Supplier Name/type
Murata GRM1555
Murata/LQW15A High Q low Rs
Johnson, End launch SMA
142-0701-841
Molex, PCB header, Right Angle, 1
row, 3 way 90121-0763
Molex, PCB header, Vertical, 1 row,
3 way 90120-0763
the noise performance will degrade.
s
UM10491
BGU7004 GPS LNA EVB
with
cc
Comment
LNA MMIC
Decoupling
Input matching
RF input/ RF
output
Bias connector
Connect V
to
en
V
or separate
cc
V
voltage
en
).
s
© NXP B.V. 2011. All rights reserved.
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