Satellite Signal Acquisition, Tracking, and Data Demodulation - Understanding GPS: Principles and Applications - page 167

ATAN2( QI

PS

, ) Q PS

PS

180

150

120

90

60

30

0

− 30

− 60

90 −

120

−

150 −

180 −

− 180 − 150 − 120 − 90 − 60 − 30

0 30 60 90 120 150

True input error (degrees)

(a)

* QI

PS PS

ATAN( QI

PS PS

)

Q PS *Sign( I PS ) Q PS I PS

180

160

140

120

100

80

60

40

20

0

20 −

− 40

− 60

80 −

100

−

− 120

− 140

160 −

180

−

− 180 − 150 − 120 − 90 − 60 − 30 0 30 60 90 120 150 180

True input error (degrees)

(b)

Figure 5.9 (a) Comparison of PLL discriminators, and (b) comparison of Costas PLL
discriminators.

sine function is in-phase with the incoming SV carrier signal (converted to IF), this
results in a sine squared product at the I output, which produces maximum I PS