GPS write up MPD

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Product Feature: GPS Diplexer
by Lorch Microwave
G
satellites constantly circling
mum over temperature. The 3 dB
bandwidth is 100 MHz nominal. The
Pass Band as previously stated is .5
tbe earth. These satellites transmit
very low power radio signals allowing
dB relative over tbe center 30 MHz
(1212 to 1242). The Return loss is 14
PS or Global Positioning
System refers to a group of
anyone witb a GPS receiver to deter­
mine tbeir current location. Each
satellite transmits on several frequen­
cies designated as L 1, L2, etc. The
signals travel line of sight meaning
they will pass through clouds, glass
and plastic, bur will not go through
most solid objects such as buildings
and mountains. These line of sight sig­
nals are also susceptible to other inter­
fering signals such as US ATC Radar.
Lorch Microwave has developed a fil­
ter to provide the teleco=unications
industry with an of the shelf product
that addresses the ever increasing fre­
quency interference problem with
today's crowded frequency spectrum.
·1227t,575_,_,
.OldB
ripple
Chebychev
transfer
of band attenuation. The Passband
bandwidth is specified as .5 dB flat­
ness minimum over 30 MHz. A three
pole filter response was chosen to
provide adequate
minimum size.
attenuation and
Typical performance for the 3DP91227/1575-M is shown in Figure 1:
Of,"_._..
.-tD'•l
..
.
....,..
_,,..... ...
....,
. ... ..
13-.... .....
...
dB minimum and 17 dB typical over
the center 30 MHz of the band.
Isolation between the two channeIs is
typically greater than 25 dB.
The filter is packaged on an open
Figure 1: 1227.6 MHZ
less nickel gold plate on our carrier
boards for ease of solder. We build
ture connector configurations. We can
provide the part in a hermetically
sealed housing if tbe environmental
function was chosen to provide mini­
mum insertion loss and maximum out
1.
,.
.... ... .
(1560 to 1590). The Return Joss is 14
mount GPS diplexer that has been
Loss is typically the most important
design concern as it directly affects
the overall system noise figure. A
•t..liW41
The 3 dB
bandwidth is 100 MHz nominal. The
Pass Band on the upper channel is also
.5 dB relative over the center 30 MHz
designed to provide excellent in band
performance while achieving excel­
lent out of band attenuation in a small
mechanical configuration. Insertion
.. "•k-•
��l1dl
au
-l�--
typical and specified as 1.5 dB maxi­
mum over temperature.
figuration. However, this ftlter can be
made available in a variety of other
custom packages with SMA or minia­
3DP9-1227/1575-M is a surface
..... .. ...
.
the center 30 MHz of the band.
Please see Figure 2: 1575.42 MHz.
The upper band of the Diplexer is
centered on 1575.42 MHz.
The
Insertion Loss at Mid Band is 1.3 dB
our components with s/n 96 solder to
withstand reflow conditions of 215°C
for 15 seconds. The filter is suitable
for various applications, both military
and commerical. Lorch has designed
this filter to be in a surface mount con­
GPS Diplexer
14148t15
dB minimum and 17dB typical over
framed FR4 carrier PCB 1.25" long by
.50" wide. The overall height of the
package is .38". We use an electro­
UlJlfb 3DP9
-
' ".. 2..!
v ...... ..
L
.......
' ... '"' ....
11 �"' •••
7 Mr 201S
,
. .....".
liLt�·
.1••••••2
UII .. MHI
OHMr••,.._
lilt....., ..
-l,..... Ntl
ll1&.34d
u.
.... ....
conditions warrant it. The typical
operating temperature is -4o•c to
+70•c. Lorch Microwave has tested
these filters at the operating tempera­
CMlftar'tt.,...
&JU•l
'21"'.ltnt ..
-u..... ,...
....41llcil
1S.MIIM4a.
ture extremes of -40, +25, and +70
degrees Celsius. The typical tempera­
ture drift has been measured at less
than I 0 ppM per degrees Celsius over
the frequency and bandwidth.
The 3DP9-1227/1575-M diplexer
has also been used as ftltering for
LNA (low noise amplifiers). By tak­
ing the diplexer and combining this
unit with an LNA you are able to pro­
1227.6 MHz.
The lower band of the Diplexer is
vide a GPS preamplifier with different
gain variations as well as selectivity.
The filter has very little affect to the
centered on 1227.6 MHz.
The
Insertion Loss at Mid Band is 1.3 dB
typical and specified as 1.5 dB maxi-
low mid-band insertion loss. There are
otber standard designs available that
system overall noise figure due to the
Figure 2: 1575.42 MHZ
provide more selectivity with a slight
increase in package size and insertion
Joss. If you would like more informa­
tion on this product please feel free to
contact Lorch Microwave at 410-860-
51 00 or visit our web
www.lorchmicrowave.com.
site
at
LORCH MICROWAVE
CIRCLE READER SERVICE NO.
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