Global Positioning System Reference
In-Depth Information
4.
Within Chapter 4, the thermal noise power was computed for a 2 MHz band-
width (approximate null-null bandwidth of the GPS C/A code signal) at 290
◦
K
(typically considered to be ambient temperature).
(a) What would the noise power be for a temperature of 100
◦
K?
(b) What would the noise power be if the two primary lobes of the Galileo L1
BOC (1,1) signal were utilized to define the bandwidth while maintaining
the 290
◦
K temperature?
Comment on the dependence of the resulting noise power from changes in tem-
perature and bandwidth.
5.
What is the noise figure of the system depicted in Figure 4.2? What would
it be if a passive antenna were utilized (move the filter and amplifier within the
antenna to after the RF cable)?
6.
160 dBW,
how many satellites must be a collected data set where the front end has a 2 dB
noise figure and the C/A code sinc spectrum appears 2 dB above the filter shape
in the collected data? Now redo the computation assuming the same 2 dB above
the filter shape but now all the power results from a single satellite?
Assuming the received GPS signal power from each satellite is
−
7.
Assume it is possible to implement an ideal bandpass filter. Further assume
that the transmitted signal has infinite bandwidth.
(a) What filter bandwidth is required to capture 98% of the GPS C/A code
power? 98% of the Galileo L1 BOC(1,1) power?
(b) If the filter was designed to capture the first main spectrum lobe [lobes for
the Galileo BOC(1,1) signal] what percent of the total power would that
provide for the GPS C/A code signal? the Galileo L1 BOC(1,1)?
8.
The collected data from the front end are represented as 8-bit samples (signed
char format). Develop an
M
-file to convert this to
(a) 1 bit (
±
1) values,
(b) 2 bit (
±
1
,
±
3).
9.
The
M
-file
codegen
generates any of the 32 PRN codes used in GPS. Com-
pute the autocorrelation function for PRN 1 and notice the maximum and mini-
mum values. Plot the resulting correlation function.
Hint: The correlation function between two sequences can be computed as
1022
R
xy
(
n
)
=
x
(
l
)
y
(
l
+
n
),
l
=
0
or you may use the
M
-function
xcorr
.
Search WWH ::
Custom Search