Carrier and Code Tracking - A Software-Defined GPS and Galileo Receiver: A Single-Frequency Approach - page 101

I E Code tracking loop

Integrate
& dump

E

I I P Navigation data

Integrate
& dump

P

I L

Integrate
& dump

L

PRN code
generator

Code loop
discriminator

L

Integrate
& dump Q L

P

Q

Integrate
& dump Q P

E

Integrate
& dump Q E

Incoming
signal

I

Lowpass
filter

NCO carrier
generator

Carrier loop
filter

Carrier loop
discriminator

90°

Lowpass
filter

Q Carrier tracking loop

FIGURE 7.19. Block diagram of the combined DLL and PLL tracking loops.

We note that in MATLAB the ACF can be coded as

R=(1 - abs(tau)) * heaviside(1 - abs(tau));

Next we determine the multipath error envelope for Galileo BOC(1,1). The result
is plotted in Figure 7.18. Comparing Figures 7.17 and 7.18 for correlator spacing
d 1 we see that the C/A code multipath error envelop is sensitive for multipath

signals with a relative path delay up to 300 m. The resulting range errors

= 0 .

τ are

between ± 4 m. For BOC(1,1) the corresponding value is 150 m and range errors

of 4 m. This demonstrates that BOC(1,1) signals are better to handle multipath

signals than C/A code signals!
The multipath error envelopes are computed from equations like (7.29) and
(7.30). Figures 7.17 and 7.18 are plotted by using the powerful ezplot command.
With correlator spacing d

±

= 0 . 1 and multipath delays δ in the range 0-157 m