System and method for generating multicarrier spread spectrum signals with constant envelope
View Patent ↗A method of generating a multicarrier spread spectrum signal having a constant envelope includes partitioning multiple spreading codes into at least a first portion of spreading codes and a second portion of spreading codes. First and second modulating signals, respectively, are formed from the first and second portions of spreading codes. A first carrier spread spectrum signal is modulated with the first modulating signal to form a first modulated carrier signal, and a second carrier spread spectrum signal is modulated with the second modulating signal to form a second modulated carrier signal. The first and second modulated carrier signals are summed to form the multicarrier spread spectrum signal. The method includes combining spreading codes from the multiple spreading codes using majority voting logic to form the first and second portions of spreading codes.
1. A method of generating a multicarrier spread spectrum signal having a constant envelope, comprising the steps of:
(a) partitioning multiple spreading codes into at least a first portion of spreading codes and a second portion of spreading codes;
(b) forming first and second modulating signals, respectively, from the first and second portions of spreading codes;
(c) modulating a first carrier spread spectrum signal with the first modulating signal to form a first modulated carrier signal;
(d) modulating a second carrier spread spectrum signal with the second modulating signal to form a second modulated carrier signal; and
(e) summing the first and second modulated carrier signals to form the multicarrier spread spectrum signal;
wherein step (a) includes
partitioning the multiple spreading codes into an odd number of spreading codes to form the first portion of spreading codes,
partitioning the multiple spreading codes into another odd number of spreading codes to form the second portion of spreading codes, and
forming a third portion of spreading codes, if other spreading codes are present in the multiple spreading codes that are not included in the first and second portions of spreading codes.
2. The method of claim 1 wherein
step (a) includes combining spreading codes from the multiple spreading codes using majority voting logic to form the first and second portions of spreading codes.
3. The method of claim 2 wherein
combining the spreading codes includes combining an odd number of spreading codes from the multiple spreading codes using majority voting logic.
4. The method of claim 3 wherein
combining the spreading codes includes combining three different spreading codes from the multiple spreading codes using majority voting logic.
5. The method of claim 2 wherein
the spreading codes have chip values of +1 and −1, and
combining the spreading codes includes selecting an amplitude of +1 or −1, at a specific point in time, as a majority vote, based on inspecting a set of +1 or −1 chip values among the spreading codes at the specific point in time.
6. The method of claim 1 wherein
step (c) includes modulating either an in-phase carrier or a quadrature carrier of the first carrier spread spectrum signal with the first modulating signal, and
step (d) includes modulating either an in-phase carrier or a quadrature carrier of the second carrier spread spectrum signal with the second modulating signal.
7. The method of claim 1 wherein
step (b) includes forming a third modulating signal from the third portion of spreading codes, and modulating a third carrier spread spectrum signal to form a third modulated carrier signal; and
step (e) includes summing the third modulated carrier signal with the first and second modulated carrier signals.
8. The method of claim 7 wherein
the third carrier spread spectrum signal is either an in-phase or a quadrature carrier of the first carrier spread spectrum signal.
9. The method of claim 8 wherein
the multicarrier spread spectrum signal has the following form:
s
(
t
)
=
P
s
[
s
1
(
t
)
+
s
2
(
t
)
s
3
(
t
)
]
sin
2
π
f
1
t
+
P
s
[
s
2
(
t
)
+
s
1
(
t
)
s
3
(
t
)
]
cos
2
π
f
1
t
+
P
s
2
[
s
3
(
t
)
-
s
1
(
t
)
s
2
(
t
)
]
sin
2
π
f
2
t
and the modulating signals are
s 1 (t)=MV(C 1 , C 2 , C 3 )
s 2 (t)=C 7
s 3 (t)=MV(C 4 ,C 5 ,C 6 )
and MV =majority voting logic,
f 1 =a first carrier frequency,
f 2 =a second carrier frequency,
C 1 -C 7 =multiple spreading codes,
P s =signal power.
10. A method of generating a multicarrier spread spectrum signal having a constant envelope and a set of multiple spreading codes, comprising the steps of:
(a) combining an odd number of spreading codes using majority voting logic into a first modulating signal;
(b) modulating a first carrier signal with the first modulating signal;
(c) receiving a second modulating signal;
(d) modulating a second carrier signal with the second modulating signal; and
(e) summing the first and second modulated carrier signals to form the multicarrier spread spectrum signal having a constant envelope;
wherein an odd number of spreading codes from the set of multiple spreading codes is used in the combining of step (a) to form the first modulating signal, and
another odd number of spreading codes from the set of multiple spreading codes is used in the combining of step (c) to form the second modulating signal, and
the method further includes the steps of:
combining any remaining odd number of spreading codes from the set of multiple spreading codes using majority voting logic to form a third modulating signal, and
modulating either the first or second carrier signal with the third modulating signal.
11. The method of claim 10 wherein
the first modulating signal modulates either an in-phase component or a quadrature component of the first carrier signal, and
the second modulating signal modulates either an in-phase component or a quadrature component of the second carrier signal.
12. The method of claim 10 wherein
the spreading codes have chip values of +1 and −1, and
combining the odd number of spreading codes includes selecting an amplitude of +1 or −1, at a predetermined time interval, as a majority vote, based on inspecting a set of +1 or −1 chip values among the odd number of spreading codes at the predetermined time interval.
13. A system for generating a multicarrier spread spectrum signal having a constant envelope comprising
a first majority voting module for combining an odd number of spreading codes using majority voting logic to form a first modulating signal,
a second majority voting module for combining another odd number of spreading codes using majority voting logic to form a second modulating signal,
a third majority voting module for combining still another odd number of spreading codes using majority voting logic to form a third modulating signal,
at least one modulator for spreading at least a first carrier using the first, second and third modulating signals, and
a summer for combining the first spread carrier with a second spread carrier to form the multicarrier spread spectrum signal.
14. The system of claim 13 including
a second modulator for spreading another carrier to form the second spread carrier using the first, second and third modulating signals, and
a summing module for combining the first and second spread carriers to form the multicarrier spread spectrum signal.
15. The system of claim 13 including a set of multiple spreading codes, wherein
the first modulating signal is formed from the odd number of spreading codes from the set of multiple spreading codes,
the second modulating signal is formed from the other odd number of spreading codes from the set of multiple spreading codes, and
the third modulating signal is formed from the still other odd number of spreading codes from the set of multiple spreading codes, being any remaining number of spreading codes from the set of multiple spreading codes.
16. The system of claim 13 wherein
the one modulator spreads an in-phase component or a quadrature component of the first spread carrier, and
a second modulator spreads an in-phase component or a quadrature component of a second carrier using the first, second and third modulating signals to form the second spread carrier.
17. The system of claim 13 wherein
the spreading codes have chip values of +1 and −1, and
combining an odd number of spreading codes includes selecting an amplitude of +1 or −1, at a predetermined time interval, as a majority vote, based on inspecting a set of +1 or −1 chip values among the odd number of spreading codes at the predetermined time interval.