Philips NXP BGU7004 GPS LNA, User Manual

Page: 6 / 15

NXP Semiconductors
UM10491
BGU7004 GPS LNA EVB
UM10491 © NXP B.V. 2011. All rights reserved.
User manual Rev. 1.0 — 14 June 2011 6 of 15
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
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. The material that has been used for the evaluation board is FR4 using the stack
shown in Fig 4
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 Value Supplier Name/type Comment
Ac BGU7004 1.45x1.1mm LNA MMIC
PCB v2.1 35x20mm BGU7004 GPS LNA EVB
C1 Capacitor 0402 1nF
Murata GRM1555
Decoupling
L1 Inductor 0402 5.6nH
Murata/LQW15A High Q low Rs
Input matching
X1,X2 SMA RF
connector
- - Johnson, End launch SMA
142-0701-841 RF input/ RF
output
X3 DC header - - Molex, PCB header, Right Angle, 1
row, 3 way 90121-0763
Bias connector
X4 JUMPER
stage
- - Molex, PCB header, Vertical, 1 row,
3 way 90120-0763
Connect V
en
to
V
cc
or separate
V
en
voltage
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
s
).
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
s
the noise performance will degrade.
0.2mm FR4 critical
0.8mm FR4 only for
mechanical rigidity of PCB
20um Cu
20um Cu
20um Cu