GPS Receiver-Related Subjects - Fundamentals of Global Positioning System Receivers: A Software Approach - page 335

acquisition is performed on the data. The S / N in dB of the GPS signal is obtained
after the acquisition. This operation is performed 500 times. Each time a different
noise sequence with zero mean and the same standard deviation is used. The
results are shown in Table 12.5.
As is shown in the table, if the input signals are digitized with an ADC having
a high number of bits, the output S / N is close to 14.4 dB, which is the result
without the cw jamming signal. If the number of bits decreases, the S / N also
decreases, and this represents the bit reduction effect of the ADC. The S / N
value of 14 dB is arbitrarily chosen as the desired value. The number of bits is

TABLE 12.5 Output S/Nin dB of the GPS Signal after Processing

J / S in dB 120 100 80 60 40 20

Number of Bits

20 14.35

19 14.01

18 12.88 14.52

17 14.32

16 14.20

15 13.43 14.54

14 11.11 14.40

13 14.32

12 13.71 14.46

11 12.10 14.35

10 14.35

9 14.01

8 12.60 14.42

7 14.40

6 14.08 14.4

5 13.02 14.06

4 13.98

3 12.77