Furuno GN-86F User Manual page 9

Figure 2-5 shows Transmission Loss-Frequency characteristics of the microstrip line shown in Figure 2-4. It
is simulated by Agilent ADS
MSub
MSUB
MSub1
H=0.178 mm
Er=4.3
Mur=1
Cond=5.96e7
Hu=1000 mm
T=0.043 mm
TanD=0.018
Rough=0.00127 mm
Figure 2-5 Simulation Result on Transmission Loss-Frequency Characteristics of the Microstrip line
Usually the microstrip line is routed at the surface layer of the PCB, and it is not protected from the radio
interference. So sometimes the interference causes the degradation of the receiver performance. In such
case, the guarding ground plane can improve the performance with decoupling the interference noise
source. The guarding ground plane is the ground placed around the microstrip line as shown in Figure 2-6.
The important thing for designing and layouting the guarding ground plane is to keep the gap between the
microstrip line and guarding ground plane wider than the microstrip line width. Otherwise this line is not able
to work as microstrip line but coplanar line.
FURUNO ELECTRIC CO., LTD. All rights reserved.
FURUNO GPS/GNSS Receiver 86/87 Series User's Design Guide
TM
.
Term
Term1
Num=1
Z=50 Ohm
Transmission, dB
0.00
-0.25
m1
freq= 1.589GHz
-0.50
dB(S(2,1))=-0.181
-0.75
-1.00
-1.25
-1.50
-1.75
-2.00
0.0 0.5 1.0
by Agilent ADS
Figure 2-6 Example of Layout of Microstrip Line
MLIN
TL7
Subst="MSub1"
W=0.31 mm
L=23.5 mm
m1
1.5 2.0 2.5
freq, GHz
TM
5
SE13-900-001-06
Term
Term2
Num=2
Z=50 Ohm
3.0