Method for generating binary offset carrier correlation function based on local signals, apparatus for tracking binary offset carrier signal, and spread spectrum signal receiver system
View Patent ↗A method of generating a correlation function used to track a code phase delay value for a local code, in a spread spectrum signal receiver system, to be correlated with a received cosine or sine BOC-modulated signal, in which plurality of pulses successively occur in a single period of a spreading code chip is presented. The Method may include generating a local signal pair having a phase delay value based on a first and second local signal pair defined by first and last pulses of a signal pulse train, received during a single period of a sub-carrier of the received signal, and a given main peak shape parameter, generating a sub-correlation function pair by performing correlation operations of the received signal and the local signal pair with respect to a total time and generating a main correlation function having only a main peak by performing an elimination operation of the sub-correlation function pair.
1. A delay lock loop (DLL) for tracking a code phase delay value for a local code to be correlated with a received cosine or sine binary offset carrier (BOC)-modulated signal, in which N pulses successively occur in a single period T c of a spreading code chip, in a spread spectrum signal receiver system, the DLL comprising:
a local signal generation unit configured to generate an early local signal pair
g
1
(
t
+
τ
+
Δ
2
;
a
)
and
g
2
(
t
+
τ
+
Δ
2
;
a
)
and a late local signal pair
g
1
(
t
+
τ
-
Δ
2
;
a
)
and
g
2
(
t
+
τ
-
Δ
2
;
a
)
each having a phase delay value τ and a delay value difference Δ based on a first and second local signal pair g 1 (τ;a) and g 2 (τ;a) defined by first and last pulses of a signal pulse train, received during a single period of a sub-carrier of the received signal, and a given main peak shape parameter a;
early and late correlation units configured to generate an early sub-correlation function pair
R
1
(
τ
+
Δ
2
;
a
)
and
R
2
(
τ
+
Δ
2
;
a
)
and a late sub-correlation function pair
R
1
(
τ
-
Δ
2
;
a
)
and
R
2
(
τ
-
Δ
2
;
a
)
by performing correlation operations of the early and late mixing signal pairs with respect to a total time T(0≦t≦T);
early and late combination units configured to generate an early main correlation function
R
proposed
(
τ
+
Δ
2
;
a
)
and a late main correlation function
R
proposed
(
τ
-
Δ
2
;
a
)
each having a main peak by performing elimination operations on the early sub-correlation function pair and the late sub-correlation function pair; and
a numerical control oscillator (NCO) configured to determine a phase delay value τ of a first and second local signal pair for the received signal based on a filtered discrimination output, and to output the determined phase delay value τ to the local signal generation unit,
wherein the elimination operation is an operation that satisfies |x|+|y|−|x−y|=0 for real numbers x and y, and
wherein T c , t and T comprise positive real numbers, and N comprises a positive integer.
2. The DLL of claim 1 , wherein the first and second local signal pair g 1 (t;a) and g 2 (t;a) are defined by first and last pulses c i,0 (t) and c i,N−1 (t) of N pulses, constituting a signal pulse train received during an i-th sub-carrier period of the received signal, and a main peak shape parameter a in accordance with the following equations:
{
g
1
(
t
;
a
)
=
∑
i
=
-
∞
∞
N
1
+
a
2
(
c
i
,
0
(
t
)
-
ac
i
,
N
-
1
(
t
)
)
,
g
2
(
t
;
a
)
=
∑
i
=
-
∞
∞
N
1
+
a
2
(
ac
i
,
0
(
t
)
-
c
i
,
N
-
1
(
t
)
)
.
3. The DLL of claim 1 , wherein if the BOC modulated received signal is BOC sin (kn,n),
g 1 (t;a) appears in a form of a pulse having a size of
N
1
+
a
2
at a location of the first pulse of the received signal pulse train and a pulse having a size of
a
N
1
+
a
2
at a location of the last pulse thereof; and
g 2 (t;a) appears in a form of a pulse having a size of
a
N
1
+
a
2
at a location of the first pulse of the received signal pulse train and a pulse having a size of
N
1
+
a
2
at a location of the last pulse thereof,
wherein k is a positive integer corresponding to a ratio of a chip period of a pseudo random noise (PRN) code to the period of a sub-carrier, and n corresponds to a ratio of a PRN code chip transmission rate to 1.023 MHz comprising a clock frequency of a C/A (Coarse/Acquisition) code.
4. The DLL of claim 1 , wherein if a received signal B(t) is BOC cos (kn,n),
g 1 (t;a) appears in a form of a pulse having a size of
N
1
+
a
2
at a location of the first pulse of the received signal pulse train and a pulse having a size of
-
a
N
1
+
a
2
at a location of the last pulse thereof; and
g 2 (t;a) appears in a form of a pulse having a size of
a
N
1
+
a
2
at a location of the first pulse of the received signal pulse train and a pulse having a size of
-
N
1
+
a
2
at a location of the last pulse thereof,
wherein k is a positive integer corresponding to a ratio of a chip period of a PRN (pseudo random noise) code to the period of a sub-carrier, and n corresponds to a ratio of a PRN code chip transmission rate to 1.023 MHz comprising a clock frequency of a C/A (Coarse/Acquisition) code.
5. The DLL of claim 1 , wherein the early main correlation function
R
proposed
(
τ
+
Δ
2
;
a
)
and the late main correlation function
R
proposed
(
τ
-
Δ
2
;
a
)
are generated to each have a waveform having only a main peak having a width of
2
(
1
-
a
)
T
c
N
(
2
-
a
)
and a height of
4
(
1
-
a
)
2
(
N
+
N
a
2
)
by combining the early sub-correlation function pair and the late sub-correlation function pair.
6. The DLL of claim 1 , wherein:
the early main correlation function
R
proposed
(
τ
+
Δ
2
;
a
)
has a waveform obtained by subtracting a waveform obtained by taking an absolute value of a sum of
R
1
(
τ
+
Δ
2
;
a
)
and
R
2
(
τ
+
Δ
2
;
a
)
from a waveform obtained by adding an absolute value of
R
1
(
τ
+
Δ
2
;
a
)
and an absolute value of
R
2
(
τ
+
Δ
2
;
a
)
,
with respect to the early sub-correlation function pair; and
the late main correlation function
R
proposed
(
τ
-
Δ
2
;
a
)
has a waveform obtained by subtracting a waveform obtained by taking an absolute value of a sum of
R
1
(
τ
-
Δ
2
;
a
)
and
R
2
(
τ
-
Δ
2
;
a
)
from a waveform obtained by adding an absolute value of
R
1
(
τ
-
Δ
2
;
a
)
and an absolute value of
R
2
(
τ
-
Δ
2
;
a
)
,
with respect to the late sub-correlation function pair.
7. The DLL of claim 1 , wherein a discrimination function D(τ) is selected to determine whether a value of the main correlation function based on the phase delay value τ is located at an apex of the main peak based on the discrimination output.
8. The DLL of claim 7 , wherein the discrimination function D(τ) is defined by the following Equation:
D
(
τ
)
=
R
proposed
2
(
τ
+
Δ
2
;
a
)
-
R
proposed
2
(
τ
-
Δ
2
;
a
)
.
9. The DLL of claim 8 , wherein the code phase delay value for the local code is determined to be a phase delay value τ when a zero-crossing of the discrimination function D(τ) is detected.
10. A binary offset carrier (BOC) signal tracking method for tracking a code phase delay value for a local code to be correlated with a received cosine or sine BOC-modulated signal, in which N pulses successively occur in a single period T c of a spreading code chip, in a spread spectrum signal receiver system, the method comprising:
generating an early local signal pair
g
1
(
t
+
τ
+
Δ
2
;
a
)
and
g
2
(
t
+
τ
+
Δ
2
;
a
)
and a late local signal pair
g
1
(
t
+
τ
-
Δ
2
;
a
)
and
g
2
(
t
+
τ
-
Δ
2
;
a
)
each having a phase delay value τ and a delay value difference Δ based on a first and second local signal pair g 1 (τ;a) and g 2 (τ;a) defined by first and last pulses of a signal pulse train, received during a single period of a sub-carrier of the received signal, and a given main peak shape parameter a;
generating an early sub-correlation function pair
R
1
(
τ
+
Δ
2
;
a
)
and
R
2
(
τ
+
Δ
2
;
a
)
and a late sub-correlation function pair
R
1
(
τ
-
Δ
2
;
a
)
and
R
2
(
τ
-
Δ
2
;
a
)
by performing correlation operations of the early and late mixing signal pairs with respect to a total time T(0≦t≦T);
generating an early main correlation function
R
proposed
(
τ
+
Δ
2
;
a
)
and a late main correlation function
R
proposed
(
τ
-
Δ
2
;
a
)
each having a main peak by performing elimination operations on the early sub-correlation function pair and the late sub-correlation function pair; and
determining a phase delay value τ of a first and second local signal pair for the received signal based on a filtered discrimination output, and outputting the determined phase delay value τ,
wherein the elimination operation is an operation that satisfies |x|+|y|−|x−y|=0 for real numbers x and y, and
wherein T c , t and T comprise positive real numbers, and N comprises a positive integer.
11. The method of claim 10 , wherein the first and second local signal pair g 1 (t;a) and g 2 (t;a) are defined by first and last pulses c i,0 (t) and c i,N−1 (t) of N pulses, constituting a signal pulse train received during an i-th sub-carrier period of the received signal, and a main peak shape parameter a in accordance with the following equations:
{
g
1
(
t
;
a
)
=
∑
i
=
-
∞
∞
N
1
+
a
2
(
c
i
,
0
(
t
)
-
ac
i
,
N
-
1
(
t
)
)
,
g
2
(
t
;
a
)
=
∑
i
=
-
∞
∞
N
1
+
a
2
(
ac
i
,
0
(
t
)
-
c
i
,
N
-
1
(
t
)
)
.
12. The method of claim 10 , wherein if the BOC modulated received signal is BOC sin (kn,n),
g 1 (t;a) appears in a form of a pulse having a size of
N
1
+
a
2
at a location of the first pulse of the received signal pulse train and a pulse having a size of
a
N
1
+
a
2
at a location of the last pulse thereof; and
g 2 (t;a) appears in a form of a pulse having a size of
a
N
1
+
a
2
at a location of the first pulse of the received signal pulse train and a pulse having a size of
N
1
+
a
2
at a location of the last pulse thereof,
wherein k is a positive integer corresponding to a ratio of a chip period of a pseudo random noise (PRN) code to the period of a sub-carrier, and n corresponds to a ratio of a PRN code chip transmission rate to 1.023 MHz comprising a clock frequency of a C/A (Coarse/Acquisition) code.
13. The method of claim 10 , wherein if a received signal B(t) is BOC cos (kn,n),
g 1 (t; a) appears in a form of a pulse having a size of
N
1
+
a
2
at a location of the first pulse of the received signal pulse train and a pulse having a size of
-
a
N
1
+
a
2
at a location of the last pulse thereof; and
g 2 (t; a) appears in a form of a pulse having a size of
a
N
1
+
a
2
at a location of the first pulse of the received signal pulse train and a pulse having a size of
-
N
1
+
a
2
at a location of the last pulse thereof,
wherein k is a positive integer corresponding to a ratio of a chip period of a pseudo random noise (PRN) code to the period of a sub-carrier, and n corresponds to a ratio of a PRN code chip transmission rate to 1.023 MHz comprising a clock frequency of a C/A (Coarse/Acquisition) code.
14. The method of claim 10 , wherein the early main correlation function
R
proposed
(
τ
+
Δ
2
;
a
)
and the late main correlation function
R
proposed
(
τ
-
Δ
2
;
a
)
are generated to each have a waveform having only a main peak having a width of
2
(
1
-
a
)
T
c
N
(
2
-
a
)
and a height of
4
(
1
-
a
)
2
(
N
+
Na
2
)
by combining the early sub-correlation function pair and the late sub-correlation function pair.
15. The method of claim 10 , wherein:
the early main correlation function
R
proposed
(
τ
+
Δ
2
;
a
)
has a waveform obtained by subtracting a waveform obtained by taking an absolute value of a sum of
R
1
(
τ
+
Δ
2
;
a
)
and
R
2
(
τ
+
Δ
2
;
a
)
from a waveform obtained by adding an absolute value of
R
1
(
τ
+
Δ
2
;
a
)
and an absolute value of
R
2
(
τ
+
Δ
2
;
a
)
,
with respect to the early sub-correlation function pair; and
the late main correlation function
R
proposed
(
τ
-
Δ
2
;
a
)
has a waveform obtained by subtracting a waveform obtained by taking an absolute value of a sum of
R
1
(
τ
-
Δ
2
;
a
)
and
R
2
(
τ
-
Δ
2
;
a
)
from a waveform obtained by adding an absolute value of
R
1
(
τ
-
Δ
2
;
a
)
and an absolute value of
R
2
(
τ
-
Δ
2
;
a
)
,
with respect to the late sub-correlation function pair.
16. The method of claim 10 , wherein a discrimination function D(τ) is selected to determine whether a value of the main correlation function based on the phase delay value τ is located at an apex of the main peak based on the discrimination output.
17. The method of claim 16 , wherein the discrimination function D(τ) is defined by the following Equation:
D
(
τ
)
=
R
proposed
2
(
τ
+
Δ
2
;
a
)
-
R
proposed
2
(
τ
-
Δ
2
;
a
)
.
18. The method of claim 16 , wherein the code phase delay value for the local code is determined to be a phase delay value τ when a zero-crossing of the discrimination function D(τ) is detected.
19. A method of generating a correlation function used to track a code phase delay value for a local code to be correlated with a received cosine or sine binary offset carrier (BOC)-modulated signal, in which N pulses successively occur in a single period T c of a spreading code chip, in a spread spectrum signal receiver apparatus, the method comprising:
generating, in the spread spectrum signal receiver apparatus, a local signal pair g 1 (t+τ;a) and g 2 (t+τ; a) having a phase delay value τ based on a first and second local signal pair g 1 (τ;a) and g 2 (τ;a) defined by first and last pulses of a signal pulse train, received during a single period of a sub-carrier of the received signal, and a given main peak shape parameter a;
generating a sub-correlation function pair R 1 (τ;a) and R 2 (τ;a) by performing correlation operations of the received signal and the local signal pair with respect to a total time T(0≦t≦T); and
generating a main correlation function R proposed (τ;a) having only a main peak by performing an elimination operation of the sub-correlation function pair R 1 (τ; a) and R 2 (τ;a),
wherein the elimination operation is an operation that satisfies |x|+|y|−|x−y|=0 for real numbers x and y, and
wherein T c , t and T comprise positive real numbers, and N comprises a positive integer.
20. The method of claim 19 , wherein the first and second local signal pair g 1 (t;a) and g 2 (t;a) are defined by first and last pulses c i,0 (t) and c i,N−1 (t) of N pulses, constituting a signal pulse train received during an i-th sub-carrier period of the received signal, and a main peak shape parameter a in accordance with the following equations:
{
g
1
(
t
;
a
)
=
∑
i
=
-
∞
∞
N
1
+
a
2
(
c
i
,
0
(
t
)
-
ac
i
,
N
-
1
(
t
)
)
,
g
2
(
t
;
a
)
=
∑
i
=
-
∞
∞
N
1
+
a
2
(
ac
i
,
0
(
t
)
-
c
i
,
N
-
1
(
t
)
)
.
21. The method of claim 19 , wherein if the BOC modulated received signal is BOC sin (kn,n),
g 1 (t;a) appears in a form of a pulse having a size of
N
1
+
a
2
at a location of the first pulse of the received signal pulse train and a pulse having a size of
a
N
1
+
a
2
at a location of the last pulse thereof; and
g 2 (t;a) appears in a form of a pulse having a size of
a
N
1
+
a
2
at a location of the first pulse of the received signal pulse train and a pulse having a size of
N
1
+
a
2
at a location of the last pulse thereof,
wherein k is a positive integer corresponding to a ratio of a chip period of a pseudo random noise (PRN) code to the period of a sub-carrier, and n corresponds to a ratio of a PRN code chip transmission rate to 1.023 MHz comprising a clock frequency of a C/A (Coarse/Acquisition) code.
22. The method of claim 19 , wherein if a received signal B(t) is BOC cos (kn,n),
g 1 (t;a) appears in a form of a pulse having a size of at a location of the first pulse of the received signal pulse train and a pulse having a size of
N
1
+
a
2
at a location of the first pulse of the received signal pulse train and a pulse having a size of
-
a
N
1
+
a
2
at a location of the last pulse thereof; and
g 2 (t;a) appears in a form of a pulse having a size of
a
N
1
+
a
2
at a location of the first pulse of the received signal pulse train and a pulse having a size of
-
N
1
+
a
2
at a location of the last pulse thereof,
wherein k is a positive integer corresponding to a ratio of a chip period of a pseudo random noise (PRN) code to the period of a sub-carrier, and n corresponds to a ratio of a PRN code chip transmission rate to 1.023 MHz comprising a clock frequency of a C/A (Coarse/Acquisition) code.
23. The method of claim 19 , wherein the main correlation function R proposed (τ;a) is generated to have a waveform having a main peak having a width of
2
(
1
-
a
)
T
c
N
(
2
-
a
)
and a height of
4
(
1
-
a
)
2
(
N
+
N
a
2
)
by combining the sub-correlation function pair.
24. The method of claim 19 , wherein the main correlation function R proposed (τ;a) has a waveform obtained by subtracting a waveform obtained by taking an absolute value of a sum of R 1 (τ;a) and R 2 (τ;a) from a waveform obtained by adding an absolute value of R 1 (τ;a) and an absolute value of R 2 (τ;a), with respect to the sub-correlation function pair.
25. An apparatus for tracking a BOC signal, comprising:
a frequency offset compensation unit configured to output a compensated received signal compensated for frequency offset of a carrier frequency based on a carrier frequency compensation value with respect to a received signal obtained by cosine or sine binary offset carrier (BOC)-modulating predetermined data;
a local code generation unit configured to generate a delay-compensated local code based on a code phase delay value;
a mixer configured to mix the delay-compensated local code with the frequency offset-compensated received signal;
a DLL configured to repeatedly track and calculate a code phase delay value that allows a correlation value obtained by correlating the delay-compensated local signal and the frequency offset-compensated received signal with each other is located at an apex of a main peak of a correlation function, and to provide the calculated code phase delay value to the local code generation unit;
a phase lock loop (PLL) configured to repeatedly calculate a carrier frequency compensation value based on an autocorrelation value of a local code, based on the tracked code phase delay value, so that a phase error of a carrier signal can be minimized, and to provide the carrier frequency compensation value to the frequency offset compensation unit; and
a data extraction unit configured to extract spreading data from a mixture of the delay-compensated local code and the compensated received signal;
wherein the DLL operates to:
generate a local signal pair g 1 (t+τ;a) and g 2 (t+τ;a) having a phase delay value τ based on a first and second local signal pair g 1 (τ;a) and g 2 (τ;a) defined by first and last pulses of a signal pulse train, received during a single period of a sub-carrier of the compensated received signal, and a given main peak shape parameter a;
generate a sub-correlation function pair R 1 (τ;a) and R 2 (τ;a) by performing correlation operations of the compensated received signal and the local signal pair with respect to a total time T(0≦t≦T);
generate a main correlation function R proposed (τ;a) having only a main peak by performing an elimination operation of the sub-correlation function pair R 1 (τ;a) and R 2 (τ;a); and
acquire and track a code phase delay value based on the generated main correlation function;
wherein the elimination operation is an operation that satisfies |x|+|y|−|x−y|=0 real numbers x and y;
wherein T c , t and T comprise positive real numbers, and N comprises a positive integer; and
wherein the first and second local signal pair g 1 (t; a) and g 2 (t;a) are defined by first and last pulses c i,0 (t) and c i,N−1 (t) of N pulses, constituting a signal pulse train received during an i-th sub-carrier period of the received signal, and a main peak shape parameter a in accordance with the following equations:
{
g
1
(
t
;
a
)
=
∑
i
=
-
∞
∞
N
1
+
a
2
(
c
i
,
0
(
t
)
-
ac
i
,
N
-
1
(
t
)
)
,
g
2
(
t
;
a
)
=
∑
i
=
-
∞
∞
N
1
+
a
2
(
ac
i
,
0
(
t
)
-
c
i
,
N
-
1
(
t
)
)
.
26. The apparatus of claim 25 , wherein:
the received BOC signal carries satellite navigation data; and
the data extraction unit operates to extract the satellite navigation data and estimate a pseudorange based on the extracted navigation data.
27. A spread spectrum signal receiver system, comprising:
a front end unit configured to output a digital received signal obtained by cosine or sine binary offset carrier (BOC)-modulating a space wireless signal received from an antenna;
a baseband processing unit configured to acquire and track a code phase delay value for the output digital received signal using a DLL, to compensate for carrier frequency offset using a PLL, and to extract the contained data from a code delay-compensated local code and a frequency offset-compensated compensated received signal; and
an application function processing unit configured to perform a predetermined application function based on the extracted contained data;
wherein the baseband processing unit comprises a DLL that operates to:
generate a local signal pair g 1 (t+τ;a) and g 2 (t+τ;a) having a phase delay value τ based on a first and second local signal pair g 1 (τ;a) and g 2 (τ;a) defined by first and last pulses of a signal pulse train, received during a single period of a sub-carrier of the compensated received signal, and a given main peak shape parameter a;
generate a sub-correlation function pair R 1 (τ;a) and R 2 (τ;a) by performing correlation operations of the compensated received signal and the local signal pair with respect to a total time T(0≦t≦T);
generate a main correlation function R proposed (τ;a) having only a main peak by performing an elimination operation of the sub-correlation function pair R 1 (τ;a) and R 2 (τ;a); and
acquire and track a code phase delay value based on the generated main correlation function;
wherein the elimination operation is an operation that satisfies |x|+|y|−|x−y|=0 for real numbers x and y;
wherein T c , t and T comprise positive real numbers, and N comprises a positive integer; and
wherein the first and second local signal pair g 1 (t;a) and g 2 (t;a) are defined by first and last pulses c i,0 (t) and c i,N−1 (t) of N pulses, constituting a signal pulse train received during an i-th sub-carrier period of the received signal, and a main peak shape parameter a in accordance with the following equations:
{
g
1
(
t
;
a
)
=
∑
i
=
-
∞
∞
N
1
+
a
2
(
c
i
,
0
(
t
)
-
ac
i
,
N
-
1
(
t
)
)
,
g
2
(
t
;
a
)
=
∑
i
=
-
∞
∞
N
1
+
a
2
(
ac
i
,
0
(
t
)
-
c
i
,
N
-
1
(
t
)
)
.
28. The spread spectrum signal receiver system of claim 27 , wherein:
the spread spectrum signal receiver system is a satellite navigation signal receiver system;
the baseband processing unit operates to extract a pseudorange from each of a plurality of satellites to a satellite navigation signal receiver system from the contained data; and
the application function processing unit operates to calculate coordinates of the satellite navigation signal receiver system based on the pseudoranges provided with respect to the plurality of satellites.