Satellite Signal Acquisition, Tracking, and Data Demodulation - Understanding GPS: Principles and Applications - page 197

PRN code: modulation

P(Y) code: BPSK-R(10) C/A code: BPSK-R(1) M code: BOC (10,5)

s

5 5

DLL noise bandwidth: B = 0.2 Hz

n

BPSK-R( ) modulation codes: P(Y) and C/A n

Predetection integration time: T = 0.020 s

4 4

E-L correlator spacing: D = 1 chip

Normalized bandwidth: b = 2

Db =2

BOC ( , ) modulation code: M
Predetection integration time: T = 0.1 s (TDDM)
E-L correlator spacing: = 1/8 chip
Front end bandwidth (MHz):

mn

3 3

D

B = 24 MHz

fe

2 2

1 1

0 0

20 20 25 25 30 30 35 35 40 40 45 45

( C/N 0 dB ) (dB-Hz)

(a)

E E-L correlator spacing

D = 1/4chip D = 1/2chip D = 1-chip

0.2

1/6-chip threshold

13.2 dB-Hz

Modulation: BPSK-R( )
DLL noise bandwidth: = 0.2 Hz
Predetection integration time: = 0.020 s
Normalized front end bandwidth:

n

0.15

B

n

T

b = 17

Db > 3.1416

0.1

1/12-chip threshold

14.2 dB-Hz

0.05

1/24-chip threshold

15.6 dB-Hz

0

5 10 15 20 25 30

( C/N 0 dB ) (dB-Hz)

(b)

Figure 5.28 Delay lock loop jitter versus ( C / N 0 ) dB : (a) comparison of P(Y) code, C/A code, and M
code DLL accuracy, (b) comparison of DLL jitter for different correlator spacing, (c) effect of noise
bandwidth on DLL jitter, and (d) effect of predetection integration time on DLL jitter.