Note: Descriptions are shown in the official language in which they were submitted.
SIDE PEAK TRACKING DETECTION
BACKGROUND
[00011 In conventional systems, Global Navigation Satellite System (GNSS)
signals are
employing new modulation techniques to increase the overall system
performance. However,
these modulations introduce multiple peaks to the autocorrelation function.
This can cause a
receiver to track a wrong peak of the autocorrelation function resulting in
biased pseudorange
measurements.
[00021 For example, in conventional systems, the incoming signal may have
multiple peaks
in its autocorrelation function. Typically, in order to reduce the complexity
of the receiver,
this signal is being tracked by correlating the incoming signal with a locally
generated binary
offset carrier (BOC) signal replica. This incoming signal may be a composite
binary offset
carrier (CBOC) or any other complex 130C signal, The cross-correlation
function of the
BOC signal shows two side peaks located at a given offset (for example, 0.5
chips) from
the center peak. The receiver can lock to these side peaks unless some
protection mechanism
is utilized to prevent side peak tracking.
[0003] Conventionally, the baseband channel in the ONSS receiver responsible
for tracking
HOC modulated signals includes five correlators: Very Early, Early, Prompt,
Late, and Very
Late. The Prompt correlator is responsible for tracking the center peak and
the Very Early
and the Very Late correlators are spaced at +0,5 chip distance apart from the
Prompt
correlator. If a side peak is tracked, it can be detected by observing a
higher amplitude in
either of the two correlators with respect to the prompt correlator. If the
amplitude in one of
these two correlators is larger than the amplitude of the prompt correlator
for several
integration periods, it is concluded that the receiver is tracking a side peak
of the signal and
the local signal replica is moved by the given offset. This is known as the
bump jumping
technique. However, the inclusion and use of the Very Early and Very Late
Correlators in
the conventional bump jumping technique leads to an increased complexity in
the baseband
tracking channel design, thus, increasing the cost of the ONSS receiver.
[0004] For the reasons stated above and for other reasons stated below, it
will become
apparent to those skilled in the art upon reading and understanding the
specification, there is a
need in the art for a less complex baseband tracking channel design with fewer
correlators to
detect side peak tracking in the baseband tracking channel,
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SUMMARY
[000$1 A global navigation satellite system (GNSS) receiver having at least
one processor
configured to implement at least one baseband tracking channel is provided.
The baseband
tracking channel comprises: at least one code generator to generate a local
signal correlating
with an incoming signal received by the GNSS receiver; a multiplier that
multiplies the local
signal with a baseband signal corresponding to an incoming signal received by
the GNSS
receiver to generate a code removed signal; at least one prompt correlator
including at least
two integration registers, wherein a first of the at least two integration
registers integrates the
samples of the code removed signal corresponding to a first portion of each
pseudorandom
noise (PRN) code chip of the local signal to provide a first integration
register output, and
wherein a second of the at least two integration registers integrates the
samples of the code
removed signal corresponding to a second portion of the PEN code chip of the
local signal to
provide a second integration register output; and a side peak tracking
detection module that
receives integration results from the at least first and second of the at
least two integration
registers and generates information indicating when side peak tracking is
occurring based on
the integration results from the at least first and second of the at least two
integration
registers.
DRAWINGS
[0006] Understanding that the drawings depict only exemplary embodiments and
are not
therefore to be considered limiting in scope, the exemplary embodiments will
be described
with additional specificity and detail through the use of the accompanying
drawings, in
which:
[0007] Figure 1 is a block diagram of an example GNSS receiver according to
one
embodiment of the present disclosure.
[0008] Figure 2 is a block diagram of an example baseband tracking channel
included in
GNSS receiver of Figure 1 according to one embodiment of the present
disclosure.
[00091 Figure 315 a flow diagram of an example side peak tracking detection
module
included in baseband tracking channel according to one embodiment of the
present
disclosure.
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[0010) Figure 4 is a flow diagram of an exemplary method for detecting side
peak tracking
by GNSS receiver according to one embodiment of the present disclosure.
[0011] Figure 5 is another flow diagram of an exemplary method for detecting
side peak
tracking by GNSS receiver according to one embodiment of the present
disclosure.
[0012] In accordance with common practice, the various described features are
not drawn to
scale but are drawn to emphasize specific features relevant to the exemplary
embodiments.
DETAILED DESCRIPTION
[0013] In the following detailed description, reference is made to the
accompanying drawings
that form a part hereof, and in which is shown by way of illustration specific
illustrative
embodiments, However, it is to be understood that other embodiments may be
utilized and
that logical, mechanical, and electrical changes may be made. Furthermore, the
method
presented in the drawing figures and the specification is not to be construed
as limiting the
order in which the individual steps may he performed. The following detailed
description is,
therefore, not to be taken in a limiting sense.
[00141 Embodiments of the present description provide systems and methods for
detecting
side peak tracking in a baseband tracking channel of a GNSS receiver.
Specifically, a prompt
correlator including a plurality of integrators allow integration of the local
signal to be
divided into different parts such that each part of the pseudorandom noise
(PRN) code chip of
the local signal is integrated in one of the plurality of integrators, and a
side peak tracking
detection module generates information indicating when side peak tracking is
occurring
based on the integration results from the plurality of integrators. If side
peak tracking is
detected, the receiver can be adjusted to shift the prompt correlator offset
and the receiver can
be prevented from locking to side peak tracking,
[00151 Figure 1 is a block diagram of an example GNSS receiver 100 for one
embodiment of
the present disclosure. GNSS receiver 100 includes or is coupled to at least
one antenna 155
that receives an incoming GNSS signal, at least one radio frequency front end
(RF-PE) 150
and a processor 185 that processes the digitized samples output by RF.FE 150.
At least one
GNSS signal is received by the GNSS receiver 100 through antenna 155 and fed
into RF-FE
150. The GNSS signal received by the GNSS receiver 100 may include noise
and/or
interference in the signal, In exemplary embodiments, RF-FE 150 down-converts
and
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digitizes the received GNSS signal into digitized samples. The digitized
samples of the
received GNSS signal are then received by the at least one processor 185.
[0016] In exemplary embodiments, the at least one processor 185 implements at
least some
of the processing described herein. In exemplary embodiments, the at least one
processor
185 includes at least one programmable processor, such as a microprocessor, a
rnicrocontroller, an application-specific integrated circuit (ASIC), a field-
programmable gate
array (FPGA), a field programmable object array (FPOA), or a programmable
logic device
(PLO). In exemplary embodiments, the at least one processor 185 can be any
other suitable
processor (such as, digital signal processor (DSP), etc,) The at least one
processor 185
described above may include or function with software programs, firmware or
other
computer readable instructions for carrying out various methods, process
tasks, calculations,
and control functions, described herein.
[0017] These instructions, and the data used and generated by the processor
185, are typically
stored on any appropriate computer readable medium used for storage of
computer readable
instructions or data structures, such as memory 188. The computer readable
medium can be
implemented as any available non-transient and tangible media that can be
accessed by a
general purpose or special purpose computer or processor, or any programmable
logic device,
Suitable processor-readable media may include storage or memory media such as
magnetic or
optical media, For example, storage or memory media may include conventional
hard disks,
Compact Disk - Read Only Memory (CD-ROM), volatile or nonvolatile media such
as
Random Access Memory (RAM) (including, but not limited to, Synchronous Dynamic
Random Access Memory (SDRAM), Double Data Rate (DDR) RAM, RAMBUS Dynamic
RAM (RDRAM), Static RAM (SRAM), etc.), Read Only Memory (ROM), Electrically
Erasable Programmable ROM (EEPROM), and flash memory, etc.
[0018] The at least one processor 185 implements at least one baseband
tracking channel
110, As shown in Figure 1, bascband tracking channel 110 includes at least one
code
generator 140 that is coupled to at least one prompt correlator 120. In
exemplary
embodiments, prompt correlator 120 includes at least two integration registers
122 and 124.
The code removed signal is generated by multiplier 166 by multiplication of
carrier removed
incoming signal produced by multiplier 162 with local PRN code signal
modulated also with
a BOC signal generated by code generator 140. This code removed signal is
split, such that
samples corresponding to one portion of each chip of the PRN code modulated
with a BOC
signal generated by the code generator 140 is received by the first
integration register 122 and
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samples corresponding to a second portion of each chip of the PRN code
modulated with a
BOC signal generated by the code generator 140 is received by the second
integration register
124. In one implementation, the first portion is the first half of each chip
of the PRN code
modulated with a BOC signal and the second portion is the second half of each
chip of the
PRN code modulated with a BOC signal, In one implementation, the first and the
second
portion are determined by BOC chip signal (control signal) locally generated
by code
generator 140,
[0019] In exemplary embodiments, integration registers 122 and 124 are
implemented by a
single integration register 125. In such an example, a single integration
register 125 performs
the function of both integration registers 122 and 124. That is, the code
signal generated by
code generator 140 is received by integration register 125, wherein
integration register 125
integrates in an additive mode for samples of code removed signal
corresponding to a first
portion of each chip of the local PRN code modulated with the BOC signal and
integrates in a
subtractive mode for samples of code removed signal corresponding to a second
portion of
each chip of the local PRN code modulated with the BOC signal. Accordingly,
integration
register 125 is configured to switch between the additive mode and subtractive
mode of
integration register 125 based on the portion of the chip that samples being
integrated
correspond to, In exemplary embodiments, this switching between modes is
controlled by a
BOC chip signal generated by code generator 140.
[0020] The prompt correlator 120 is further coupled with a side peak tracking
detection
module 130 that receives the outputs from the first integration register 122
and the second
integration register 124. In some implementations, the side peak tracking
detection module
130 is coupled with code generator 140. In some implementations, the baseband
tracking
channel is coupled to memory 188. In some implementations, memory 188 is
included in
processor 185.
[0021] As illustrated in Figure 2, baseband tracking channel 110 includes a
carrier generator
170 that generates a local carrier signal, which is an estimate of the
remaining intermediate
frequency and Doppler frequency of the incoming GNSS signal, The digitized
samples of the
incoming GNSS signal are converted into baseband by multiplying the local
signal with the
incoming signal using multiplier 162,
[0022] Baseband tracking channel 110 further includes a code generator 140
that generates at
least one local pseudorandom noise code signal to correlate with the incoming
signal. The
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product of the baseband signal output from multiplier 162 and at least one
local PRN code
signal is then integrated for correlation. In the example shown in Figure 1,
three PRN code
signals are generated by the code generator for correlation: Early, Prompt,
and Late.
[0023] The product of the baseband signal with Early przN code signal (shown
in Figure 2 at
164) is sent into integration and dump filter 112 and the product of baseband
signal with Late
PRN code signal (shown in Figure 2 at 168) is sent into integration and clump
filter 114. The
output of integration and dump filters 112 and 114 are numerical values
indicating how much
the PRN code signal correlates with the code in the incoming signal.
[0024] The product 166 of the baseband signal and the prompt PRN code signal,
is a code
removed signal and is received by a switch 126 included in baseband tracking
channel 110.
In exemplary embodiments, switch 126 is a binary offset carrier (BOC) switch.
Baseband
tracking channel 110 further includes at least two integration registers 122
and 124, Switch
126 facilitates code removed signal to be divided into two parts, wherein one
part of each
PRN chip of the code removed signal is integrated by integration register 122
and a second
part of each PRN chip of the code removed signal is integrated by integration
register 124.
The switching between registers 122 and 124 is controlled via a control signal
generated by
code generator 140. In one implementation, the control signal is a BOC chip
signal. In the
example shown in Figure Z the code removed signal is output from multiplier
166 after the
BOC modulated PRN code signal generated by code generator 140 has been
multiplied by the
baseband signal output from multiplier 162.
[0025] A BOC chip is a signal indicating whether the current PRN sequence
sample is
modulated by a value of either +1 or -1, In BOC (1,1) modulation, each chip in
the PRN
sequence is divided into two parts. One part of the chip is multiplied with +1
and the second
part of the chip is multiplied with -1, AS shown in Figure 2, the BOC chip
signal generated
by code generator 140 indicates the current modulation of the locally
generated PRN code
signal, wherein the samples corresponding to first portion of the chip
(multiplied by 1) are
integrated by integration register 122 and the samples corresponding to second
portion of the
chip (multiplied by -1) are integrated by integration register 124,
Accordingly, this BOC chip
signal controls switch 126 to determine whether the code removed signal is
accumulated by
first integration register 122 or second integration register 124.
[0026] Multiplication of the first portion of each chip of the local PRN code
modulated with
the BOC signal and the second portion of each chip of the local PRN code
modulated with
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the BOO signal depends on the value of the PRN chip. In exemplary embodiments,
samples
of code removed signal corresponding to first portion of each chip of the
local PRN code
modulated with the BOC signal is multiplied by 1, and samples of code removed
signal
corresponding to a second portion of each chip of the local PRN code modulated
with the
BOC signal is multiplied by .l. In exemplary embodiments when the value of PRN
code chip
is -1, samples of code removed signal corresponding to first portion of each
chip of the local
PRN code modulated with the BOC signal is multiplied by 1, and samples of code
removed
signal corresponding to a second portion of each chip of the local PRN code
modulated with
the BOC signal is multiplied by -1. Samples corresponding to the first portion
are integrated
by integration register 122 and samples corresponding to the second portion
are integrated by
integration register 124.
[0027] A comparison of the output from the first integration register 122 and
second
integration register 124 provides a result indicating whether side peak
tracking is occurring.
In exemplary embodiments, a first result is obtained by subtraction of
integrated samples
corresponding to the first portion and integrated samples corresponding to the
second portion
of each chip of local PRN code modulated with the BOC signal. In exemplary
embodiments
this result is normalized. When GNSS receiver 100 is tracking a main peak the
subtraction
result is close to zero. However, when tracking channel 110 is tracking a side
peak, the
normalized subtraction result between the integrated samples corresponding to
the first
portion and the integrated samples corresponding to the second of each chip is
close to an
offset value consistent with code offset between a side peak and a main peak
tracked by the
tracking channel 110. Accordingly, in exemplary embodiments, side peak
tracking can be
detected by subtracting the integrated samples corresponding to the second
portion of each
chip of local PRN code modulated with the BOC signal from the integrated
samples
corresponding to the first portion of each chip of local PRN code modulated
with the BOC
signal.
[0028] Integration registers 122 and 124 output numerical values that indicate
correlation
between the PRN code signal and the code in the incoming GNSS signal. In some
implementations, the output of the integration registers 122 and 124 are sent
to a summing
node 180. The sum of the integration registers 122 and 124 provide a
correlation result of the
prompt eorrelator 120. That is, the sum of integration register 122 and 124
provides a result
indicating the correlation between the PRN code signal of the prompt
correlatot 120 and the
code in the incoming GNSS
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[0029] In some implementations, the output from the summing node 180 is then
fed back
through a carrier tracking loop where the output is received by a carrier
discriminator 174,
which is then sent to a carrier loop filter 172 before being received by the
carrier generator
170. Similarly, outputs from integrate and dump filters 112 and 114 go through
a code
tracking loop where the output is received by a code discriminator 144, which
is then sent to
a code loop filter 142 before being received by the code generator 140.
100301 The output of the integration registers 122 and 124 are also sent to
the side peak
tracking detection module 130 to detect when tracking channel 110 is tracking
a side peak in
the correlation function. In some implementations, side peak tracking
detection module is
coupled to code generator 140 and the information indicating when side peak
tracking is
occurring is provided to code generator 140.
[0031] Figure 3 shows a flow diagram of one example embodiment of a process
for side peak
tracking detection which may be implemented by the side peak tracking
detection module
130 in tracking channel 110. It should be understood that process shown in
Figure 3 may be
implemented in conjunction with any of the various embodiments and
implementations
described in this disclosure above or below. As such, elements of this process
may be used in
conjunction with, in combination with, or substituted for elements of those
embodiments,
Further, the functions, structures and other description of elements for such
embodiments
described herein may apply to like named elements of this method and vice
versa,
[0032] In the example shown in Figure 3, the side peak tracking detection
module 130
receives the first integration register output RI from the. first integration
register 122 and a
second integration register output R2 from the second integration register
124, The first
integration register output R1 is compared with the second integration
register output R2 and
an absolute value of the comparison result is determined. In the example shown
in Figure 3,
the comparison result is a difference between R1 and R2. That is, the second
integration
output R2 is subtracted from the first integration output R1 to provide a
difference (310).
The difference, R1-R2, is also referred to herein as subtraction result.
[0033] As shown in Figure 3, side peak tracking detection module 130 is
further configured
to determine the absolute value of the difference and compare the absolute
value with an
amplitude threshold (312, 322). In some implementations, the amplitude
threshold is
predetermined. In some implementations, the amplitude threshold can be stored
in a memory
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such as memory 188 and is accessed by the side peak tracking module 130 during
implementation
[00341 When the absolute value of the difference exceeds an amplitude
threshold, the side
peak tracking detection module 130 increases a jump count by one (314, 324),
When the
absolute value of the difference does not exceed the threshold, the jump count
is decreased by
one, Thus, as discussed below, jump count is the number of time the absolute
value of the
difference has exceeded the amplitude threshold minus the number of time the
absolute value
has not exceeded the amplitude threshold. The jump count has a minimum value
of zero. As
shown in Figure 3, when the difference of the second integration register
output subtracted
from the first integration register output is less than zero, the jump count
is defined as
positive jump (324, 326, 332, 334), Similarly, when the difference of the
second integration
register output subtracted from the first integration register output is
greater than or equal to
zero, the jump count is defined as negative jump (314, 316, 342, 344),
[0035] The jump count is then compared with a predefined count threshold (316,
326).
When the jump count is greater than or equal to count threshold, the side peak
tracking
detection module can determine that side peak tracking is occurring, Thus, the
count
threshold is the value that the jump count needs to be greater than or equal
to for the side
peak tracking detection module to determine that side peak tracking is
occurring. When the
jump count is less than the count threshold, detection for the integration
period is ended (350)
and side peak tracking detection module waits for integration results for a
subsequent
integration period.
[0036] When the side peak tracking detection module 130 receives the first
integration
register output RI and a second integration register output R2 for a
subsequent period, it
performs the detection for the subsequent period. If the absolute value of the
difference (R1-
R2) for the subsequent period exceeds the amplitude threshold, the jump count
is increased
by one and compared to the count threshold,
[0037] When the jump count is greater than or equal to the count threshold,
the side peak
tracking detection module 130 generates information indicating that the side
peak tracking is
occurring. In some implementations, information indicating detection of side
peak tracking is
provided to code generator 140 so that the code generator is shifted by a
given offset value,
[00381 When the jump count is at least equal to the count threshold, it can be
determined that
tracking channel 110 is locked on to that side peak. The code generator 140
has to be shifted
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by a given offset value so that the prompt correlator is located at the main
peak and the
tracking channel 110 can track the main peak for subsequent integration
period(s).
[0039] As shown in Figure 3, when the jump count is greater than or equal to
the count
threshold, side peak tracking detection module 130 determines that the local
PRN code signal
is to be shifted by an offset value (318, 328). The offset value is consistent
with a code offset
between detected side peak and the main peak. In some implementations, the
offset value is
defined by BOC modulation of the focally generated PRN code signal. In some
implementations, the offset value is 0.5 chips.
[0040] When the difference of the second integration register output
subtracted from the first
integration register output is less than zero by a value larger than the
amplitude threshold for
at least a number of times equal to the count threshold, the offset value is
positive and code
register 140 is to be shifted by the positive offset value (328), When the
difference of the
second integration register output subtracted from the first integration
register output is
greater than zero by a value larger than the amplitude threshold for at least
a number of times
equal to the count threshold, the offset value is negative and code register
140 is to be shifted
by negative offset value (318). The jump count, both positive jump and
negative jump, are
set to wro (315) and detection of side peak tracking is restarted (351).
10041] When the absolute value of the difference is less than or equal to an
amplitude
threshold, the side peak tracking detection module 130 is configured to
determine if the jump
count is greater than zero (342, 332). When the absolute value of the
difference is less than
or equal to an amplitude threshold, and the jump count is greater than zero,
the side peak
tracking detection module 130 has detected side peak tracking for at least one
previous
iteration. In such an example, the jump count is decreased by one (344, 334)
and the
detection for the integration period has ended (350). Accordingly, the jump
count is the
number of times the absolute value of the difference has exceeded the
amplitude threshold
minus the number of time the absolute value of the difference has not exceeded
the amplitude
threshold. In some implementations, the jump count can be stored in a memory
such as
memory 188 for later retrieval in subsequent iterations,
[0042] When the absolute value of the difference is less than or equal to an
amplitude
threshold or when the jump count is less than the count threshold the tracking
channel 110 is
assumed to be tracking the main peak. Accordingly, the side peak tracking
detection module
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130 is configured to end (350). In some implementations, the side peak
tracking detection
module 130 generates information that main peak tracking is occurring.
[0043] In some implementations, baseband tracking channel 110 is implemented
in at least
one of an application specific integrated circuit (ASIC), a field programmable
gate array
(FPGA), a field programmable object array (FPOA), a programmable logic device
(PLD), a
digital signal processor (DSP) or a general purpose processor (GPP). The BQC
switch can be
implemented with a hardware adjustment or a software adjustment based on
whether the
integration is performed on a FPGA or ASIC, or whether the integration is
performed on a
DSP or a GM
[0044] Figure 4 is a flow diagram of an example method 400 of detecting side
peak tracking
by a GNSS receiver, such as the GNSS receiver disclosed with respect to
Figures 1-3. It
should be understood that method 400 may be implemented in conjunction with
any of the
various embodiments and implementations described in this disclosure above or
below, As
such, elements of method 400 may be used in conjunction with, in combination
with, or
substituted for elements of those embodiments. Further, the functions,
structures and other
description of elements for such embodiments described herein may apply to
like named
elements of method 400 and vice versa.
[0045] Method 400 begins at block 402 with receiving at least one incoming
radio frequency
(RF) signal. The at least one incoming RF signal is digitized using a radio
frequency front
end (RF-FE), such as an RF-FE 150, into a digital samples. Method 400 proceeds
to block
404 with multiplying a locally generated carrier signal with the incoming
signal to provide a
baseband signal, wherein the locally generated carrier signal is generated in
a carrier
generator, such as carrier generator 170, of a baseband tracking channel, such
as baseband
tracking channel 110 of the GNSS receiver.
[0046] Method 400 proceeds to block 406 with multiplying a locally generated
code signal
with the baseband signal to provide a code removed signal, wherein the locally
generated
code signal is generated in a code generator, such a code generator 140, of a
baseband
tracking channel, such as baseband tracking channel 110 of the GNSS receiver.
The locally
generated code signal is provided in a prompt correlator, such as a prompt
correlator 120 of
the baseband tracking channel. In one example of method 400, the locally
generated signal is
a BOC (1,1) modulated code signal which is multiplied with the baseband signal
to provide a
code removed signal.
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[0047] Method 400 then proceeds to block 408 with integrating samples of code
removed
signal corresponding to the first portion of each chip of a pseudorandom noise
code
modulated with a BOC signal in a first integration register, such as
integration register 122,
of the baseband tracking channel to provide a first integration register
output. Method 400
then proceeds to block 410 with integrating samples of code removed signal
corresponding to
the second portion of each chip of a pseudorandom noise code modulated with a
BOC signal
in a second integration register, such as integration register 124, of the
baseband tracking
channel to provide a second integration register output. In exemplary
embodiments, first
portion is a first half of each chip and second portion is the second half of
each chip of the
FRN code modulated with a BOC signal,
[0048] Finally, method 400 proceeds to block 412 with detecting when side peak
tracking is
occurring based on the first integration register output and the second
integration register
output, In one implementation, a side peak tracking detection module, such as
side peak
tracking detection module 130, is implemented to detect when side peak
tracking is
occurring.
[0049] In one implementation of method 400, detecting when side peak tracking
is occurring
further comprises subtracting the second integration register output from the
first integration
register output to provide a difference and determining the absolute value of
the difference,
When the absolute value of the subtraction result of the second integration
register output
from the first integration register output exceeds an amplitude threshold,
this implementation
of method 400 further comprises increasing a jump count by one, When the
absolute value of
the subtraction result of the second integration register output from the
first integration
register output does not exceed an amplitude threshold, this implementation of
method 400
comprises decreasing the jump count by one. Finally, when the jump count is
greater than or
equal to a predefined number of times, this implementation of method 400
comprises
generating information indicating that side peak tracking is occurring.
[0050] In a further implementation of method 400, detecting when side peak
tracking is
occurring further comprises shifting the code generator by an offset value
consistent with a
code offset between detected side peak and a main peak. In an even further
implementation,
shifting the code generator by an offset value further comprises shifting the
code generator by
a negative code offset value when the subtraction result is greater than or
equal to zero and
the absolute value of the difference exceeds the amplitude threshold by a
predefined number
of times, and shifting the code generator by a positive code offset value when
the subtraction
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result is less than zero and the absolute value of the difference exceeds the
amplitude
threshold by a predefined number of times. In one implementation, shifting the
code
generator by an offset value further comprises shifting the code generator by
a negative code
offset value when the subtraction result is greater than or equal to zero by a
value larger than
a predetermined threshold and the absolute value of the difference exceeds the
amplitude
threshold by a predefined number of times, and shifting the code generator by
a positive code
offset value when the subtraction result is less than zero by a value larger
than a
predetermined threshold and the absolute value of the difference exceeds the
amplitude
threshold by a predefined number of times, In one implementation, the value of
the code
offset is 0,5 chips. Accordingly, in such an implementation, when the code
generator is
shifted by a negative code offset, the value of the code offset is -0.5 chips,
and when the code
generator is shifter by a positive code offset, the value of the code offset
is +0.5 chips,
[00511 In one implementation of method 400, detecting when side peak tracking
is occurring
further comprises subtracting the second integration register output from the
first integration
register output to provide a difference, determining an absolute value of the
difference, and
generating information indicating that main peak tracking is occurring when
the absolute
value of the difference is less than or equal to an amplitude threshold, and
wherein a juinp
count is less than a count threshold. The jump count is the number of time the
absolute value
of the difference has exceeded the amplitude threshold.
[00521 In an implementation, method 400 further comprises summing the first
integration
register output and the second integration register output to provide a prompt
correlation
result indicating the correlation between the locally generated code signal
and the incoming
RF signal, In one implementation, first integration register output and the
second integration
register output are summed via a summing node, such as summing node 180.
[00531 Figure 5 is a flow diagram of another example method 500 embodiment for
detecting
side peak tracking by a GNSS receiver, such as the GNSS receiver 100 as
disclosed with
respect to Figures 1-3. It should be understood that method 500 may be
implemented in
conjunction with any of the various embodiments and implementations described
in this
disclosure above or below, As such, elements of method 500 may be used in
conjunction
with, in combination with, or substituted for elements of those embodiments,
Further, the
functions, structures and other description of elements for such embodiments
described
herein may apply to like named elements of method 500 and vice versa,
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[0054] Method 500 begins with block 502 with receiving a first integration
register output
from a first integration register, such a first integration register 122, in a
baseband tracking
channel, such as baseband channel 110 of the GNSS receiver, such as GNSS
receiver 100, In
one implementation of method 500, receiving i first integration register
output from a first
integration register further comprises receiving samples of code removed
signal
corresponding to a first half of each chip of a pseudorandom noise code
modulated with a
BOC signal.
[0055] Method 500 then proceeds to block 504 with receiving a second
integration register
output from a second integration register, such as second integration register
124, in the
baseband tracking channel of the GNSS receiver. In one implementation of
method 500,
receiving a second integration register output from a second integration
register further
comprises receiving samples of a code removed signal corresponding to a second
half of each
chip of the pseudorandom noise code modulated with a 130C signal.
[0056] Method 500 then proceeds to block 506 with comparing the second
integration
register output with the first integration register output to provide an
integration comparison
result. In one example, comparing the second integration register output with
the first
integration register output to provide an integration comparison result
further comprises
subtracting the second integration register output from the first integration
register output to
provide a difference and determining an absolute value of the difference,
[0057] Method 300 then proceeds to block 508 with comparing the absolute value
of the
difference with an amplitude threshold. Finally, method 500 proceeds to block
510 with
generating information indicating when side peak tracking is occurring based
the integration
comparison result and a jump count and the absolute value of the difference.
The jump count
is the number of times the absolute value of the integration comparison result
(ex, the
difference) has exceeded the amplitude threshold minus the number of times the
integration
comparison result has not exceeded the amplitude threshold. in an
implementation of method
500, when the absolute value of the integration comparison result exceeds an
amplitude
threshold and the jump count is greater than or equal to a predefined count
threshold; method
500 comprises generating information indicating that side peak tracking is
occurring,
EXAMPLE EMBODIMENTS
[0058] Example 1 includes a global navigation satellite system (GNSS) receiver
having at
least one processor configured to implement at least one baseband tracking
channel, the
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baseband tracking channel comprising: at least one code generator to generate
a local signal
correlating with an incoming signal received by the GNSS receiver; a
multiplier that
multiplies the local signal with a baseband signal corresponding to an
incoming signal
received by the GNSS receiver to generate a code removed signal; at least one
prompt
correlator including at least two integration registers, wherein a first of
the at least two
integration registers integrates the samples of the code removed signal
corresponding to a
first portion of each pseudorandom noise code chip of the local signal to
provide a first
integration register output, and wherein a second of the at least two
integration registers
integrates the samples of the code removed signal corresponding to a second
portion of the
PRN code chip of the local signal to provide a second integration register
output; and a side
peak tracking detection module that receives integration results from the at
least first and
second of the at least two integration registers and generates information
indicating when side
peak tracking is occurring based on the integration results from the at least
first and second of
the at least two integration registers.
[0059] Example 2 includes the GNSS receiver of Example 1, wherein the baseband
tracking
channel further comprises at least one carrier generator to generate a local
carrier signal to
multiply with the incoming signal.
[0060] Example 3 includes the GNSS receiver of any of Examples 1-2, wherein
the baseband
tracking channel further comprises a summing node that receives the first
integration register
output and the second integration register output, and wherein the summing
node provides a
prompt correlator result indicating the correlation between the local signal
and the incoming
[0061] Example 4 includes the GNSS receiver of any of Examples 1-3, wherein
when
absolute value of a subtraction result of the second integration register
output from the first
integration register output exceeds an amplitude threshold , the side peak
tracking detection
module increases a jump count by one, wherein when absolute value of a
subtraction result of
the second integration register output from the first integration register
output does not
exceed an amplitude threshold, the side peak tracking detection module
decreases the jump
count by one, and when the jump count is greater than or equal a predefined
number of times,
the side peak tracking detection module generates information indicating that
side peak
tracking is occurring.
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[0062] Example 5 includes the GNSS receiver of Example 4, wherein the code
generator is
shifted by an offset value consistent with a code offset between detected side
peak and a main
peak.
[00631 Example 6 includes the GNSS receiver of Example 5, wherein when the
jump count is
greater than or equal to the predefined number of times and the subtraction
result is greater
than zero, the code generator is shifted by a negative code offset value, and
wherein when the
jump count is greater than or equal to the predefined number of times and the
subtraction
result is less than zero, the code generator is shifted by a positive code
offset value.
[0064] Example 7 includes the GNSS receiver of any of Examples 1-6, wherein
wherein the
value of the code offset is positive or negative 0.5 chips.
[00651 Example 8 includes the GNSS receiver of any of Examples 1-7, wherein
the first of
the at least two integration registers integrates the samples of the code
removed signal
corresponding to a first half of a pseudorandom noise code chip of the local
signal to provide
a first integration register output, and wherein a second of the at least two
integration
registers integrates the samples of the code removed signal corresponding to a
second half of
the PRN code chip of the local signal to provide a second integration register
output.
[00661 Example 9 includes the GNSS receiver of any of Examples 1-8, wherein
the baseband
tracking channel is implemented in at least one of an application specific
integrated circuit
(ASIC), a field programmable gate array (FPGA), a digital signal processor
(DSP) and a
general purpose processor (GPP),
[0067] Example 10 includes a method of detecting side peak tracking by a GNSS
receiver,
the method comprising: receiving an incoming radio frequency (RF) signal;
multiplying a
locally generated carrier signal with the incoming signal to provide a
baseband signal;
multiplying a locally generated code signal with the baseband signal to
provide a code
removed signal; integrating samples corresponding to a first portion of each
pseudorandom
noise code chip of the locally generated code signal to provide a first
integration register
output; integrating samples corresponding to a second portion of each PRN code
chip of the
locally generated code signal to provide a second integration register output;
and detecting
when side peak tracking is occurring based on the first integration register
output and the
second integration register output.
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[0068] Example 11 includes the method of Example 10, wherein integrating
samples
corresponding to a first portion of each pseudorandom noise code chip of the
locally
generated code signal further comprises integrating samples corresponding to
the first portion
of each PRN code chip of the locally generated code signal in a first
integration register of
the baseband tracking channel; and integrating samples corresponding to a
second portion of
each PRN code chip of the locally generated code signal further comprises
integrating
samples corresponding to the second portion of each PRN code chip of the
locally generated
code signal in a second integration register of the baseband tracking channel
different from
the first integration register.
[00691 Example 12 includes the method of any of Examples 10-11, further
comprising
summing the first integration register output and the second integration
register output to
provide a prompt correlation result indicating the correlation between the
locally generated
code signal and the incoming RF signal.
[0070] Example 13 includes the method of any of Examples 10-12, wherein
detecting when
side peak tracking is occurring further comprises: subtracting the second
integration register
output from the first integration register output to provide a difference;
determining the
absolute value of the difference; when the absolute value of the subtraction
result of the
second integration register output from the first integration register output
exceeds an
amplitude threshold, increasing a jump count by one; when the absolute value
of the
subtraction result of the second integration register output from the first
integration register
output does not exceed an amplitude threshold, decreasing the jump count by
one; and when
the jump count is greater than or equal to a predefined number of times,
generating
information indicating that side peak tracking is occurring.
[0071] Example 14 includes the method of Example 13, further comprising
shifting the code
generator by an offset value consistent with a code offset between detected
side peak and a
main peak,
[0072] Example 15 includes the method of Example 14, wherein shifting the code
generator
by au offset value further comprises: when the subtraction result is greater
than zero and the
jump count is greater than or equal to the predefined number of times,
shifting the code
generator by a negative code offset value; and when the subtraction result is
less than zero
and the jump count is greater than or equal to the predefined number of times,
shifting the
code generator by a positive code offset value.
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[00731 Example 16 includes the method of any of Examples 14-15, wherein
shifting the code
generator by an offset value is shifting the code generator by a value of
positive or negative
0.5 chips.
[0074] Example 17 includes the method of any of Examples 10-]6, wherein
integrating
samples corresponding to a first portion of each pseudorandom noise code chip
of the locally
generated code signal further comprises integrating samples corresponding to a
first half of
the PRN code chip of the locally generated code signal to provide a first
integration register
output; and integrating samples corresponding to a second portion of each
pseudorandom
noise code chip of the locally generated code signal further comprises
integrating samples
corresponding to a second half of the PRN code chip of the locally generated
code signal to
provide a second integration register output.
[0075] Example 18 includes a global navigation satellite system (GNSS)
receiver having at
least one processor configured to implement at least one baseband tracking
channel, the
baseband tracking channel comprising: at least one code generator to
generate a local
signal correlating with an incoming signal received by the GNSS receiver; a
multiplier that
multiplies the local signal with a baseband signal corresponding to an
incoming signal
received by the GNSS receiver to generate a code removed signal; at least one
prompt
correlator including at least one integration register, wherein the at least
one integration
register integrates the samples of the code removed signal corresponding to a
first portion of
each pseudorandom noise code chip of the code removed signal to provide a
first integration
register output, and wherein the at least one integration register integrates
the samples of the
code removed signal corresponding to a second portion of each PRN code chip of
the code
removed signal to provide a second integration register output; and a side
peak tracking
detection module that receives integration results from the at least one
integration register and
generates information indicating when side peak tracking is occurring based on
the first
integration register output and the second integration register output,
[0076] Example 19 includes the receiver of Example 18, wherein the at least
one prompt
correlator includes at least two integration registers, wherein the first of
the at least two
integration registers integrates the samples of the code removed signal
corresponding to the
first potion of a PRN code chip of the local signal to provide a first
integration register
output, and wherein the second integration register integrates the samples of
the code
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removed signal corresponding to a second portion of the PRN code chip of the
local signal to
provide a second integration register output,
[00771 Example 20 includes the receiver of any of Examples 18-19, wherein when
absolute
value of a subtraction result of the second integration register output from
the first integration
register output exceeds an amplitude threshold the side peak tracking
detection module
increases a jump count by one, wherein when absolute value of a subtraction
result of the
second integration register output from the first integration register output
does not exceed an
amplitude threshold, the side peak tracking detection module decreases the
jump count by
one, and when the jump count is greater than or equal to a predefined number
of times, the
side peak tracking detection module generates information indicating that side
peak tracking
is occurring.
[0078] In various alternative embodiments, system elements, method steps, or
examples
described throughout this disclosure (such as the baseband tracking channel,
prompt
correlator, side peak tracking modulator, and/or sub-parts of any thereof, for
example) may
be implemented using one or more computer systems, field programmable gate
arrays
(FPGAs), or similar devices and/or comprising a processor coupled to a memory
and
executing code to realize those elements, processes, steps or examples, said
code stored on a
non-transient data storage device, Therefore other embodiments of the present
disclosure
may include elements comprising program instructions resident on computer
readable media
which when implemented by such computer systems, enable them to implement the
embodiments described herein. As used herein, the term "computer readable
media" refers to
tangible memory storage devices having non-transient physical forms. Such non-
transient
physical forms may include computer memory devices, such as but not limited to
punch
cards, magnetic disk or tape, any optical data storage system, flash read only
memory
(ROM), non-volatile ROM, programmable ROM (PROM), erasable-programmable ROM (E-
PROM), random access memory (RAM), or any other form of permanent, semi-
permanent,
or temporary memory storage system or device having a physical, tangible form,
Program
instructions include, but are not limited to computer-executable instructions
executed by
computer system processors and hardware description languages such as Very
High Speed
Integrated Circuit (VHSIC) Hardware Description Language (VHDL).
[0079] Although specific embodiments have been illustrated and described
herein, it will be
appreciated by those of ordinary skill in the art that any arrangement, which
is calculated to
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achieve the same purpose, may be substituted for the specific embodiment
shown. This
application is intended to cover any adaptations or variations of the
presented embodiments.
Therefor; it is manifestly intended that embodiments be limited only by the
claims and the
equivalents thereof.
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