CN107300709B - The spaceborne offset dual-frequency navigation signal generator of one kind and generation method - Google Patents
The spaceborne offset dual-frequency navigation signal generator of one kind and generation method Download PDFInfo
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- CN107300709B CN107300709B CN201710594931.2A CN201710594931A CN107300709B CN 107300709 B CN107300709 B CN 107300709B CN 201710594931 A CN201710594931 A CN 201710594931A CN 107300709 B CN107300709 B CN 107300709B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/13—Receivers
- G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
- G01S19/29—Acquisition or tracking or demodulation of signals transmitted by the system carrier including Doppler, related
Abstract
The present invention provides a kind of spaceborne offset dual-frequency navigation signal generator and generation methods, the generator includes signal component generation module, offset phase look-up table means, bandpass filter, Amplitude Compensation filter, sub-carrier phase counter, generates spaceborne offset dual-frequency navigation signal upper side band I circuit-switched data code UI, the road upper side band Q pilot code UQ, lower sideband I circuit-switched data code LI, the road lower sideband Q pilot code LQ and sub-carrier phase；According to upper side band I circuit-switched data code UI, the road upper side band Q pilot code UQ, lower sideband I circuit-switched data code LI, the road lower sideband Q pilot code LQ and sub-carrier phase, sinusoidal phase look-up table, cosine phase look-up table are searched, I, Q component I (n) and Q (n) after obtaining frequency shift (FS)；Filter out the out of band signal of I, Q component I (n) and Q (n), and by filtered I, Q component IBP(n)、QBP(n) it is forwarded to Amplitude Compensation filter；Amplitude Compensation filtering is carried out to signal, obtains the real part of spaceborne offset dual-frequency navigation signalAnd imaginary part
Description
Technical field
The present invention relates to a kind of satellite-based navigation signalling means generator and generation method, in particular to a kind of satellite drift double frequency
The generator and generation method of navigation signal, belong to satellite navigation and positioning and navigation field.
Background technique
In modernization satellite navigation system, double frequency perseverance envelope navigation signal is a kind of important signal.Using double frequency perseverance
Envelope navigation signal can by be located at two adjacent bands navigation signal base band perseverance envelope multiplex be a signal, to drop
Low signal implementation complexity.
Earliest for navigation system double frequency perseverance envelope navigation signal be Galileo E5 signal use AltBOC (15,
10) signal, Galileo E5 signal band include two frequency bands of E5a and E5b, center frequency point be respectively 1176.45MHz and
1207.14MHz, E5a and E5b include a data component and a weight of pilot frequency, are modulated using QPSK (10).It is double to realize
The permanent envelope multiplex of frequency, Centre National D'etudes Spatiales (CNES) propose permanent envelope alternate binary offset carrier (AltBOC)
Technology, and applied for 7561103 B2 of United States Patent (USP) US.To the generating mode of AltBOC signal, especially by look-up table reality
The mode of existing AltBOC signal is protected.
And in Beidou down navigation signal, Beidou B2 signal is as a kind of high-precision civil signal, with Galileo
E5 signal it is similar, have the characteristics that big bandwidth, double frequency perseverance envelope multiplex.Domestic scholars propose a variety of double frequency constant envelope signals
Technology, representational technology includes TD-AltBOC, ACE-BOC and broad sense AltBOC etc., and has applied for patent at home,
Respectively " a kind of navigation signal modulation method " (patent No.: 102209056 B of CN), " Heng Bao of four component spread-spectrum signal of double frequency
Network multiplexing method, device and method of reseptance " (patent No.: 103023598 A of CN), a kind of " non-constant power quadrature phase shift keying letter
Number modulator approach and modulating device " (patent No.: CN 201310180096.X).
The protection core of above-mentioned patent is the base band generation method of signal, is according to original phase look-up table or arithmetic
Expression formula generates.But navigation signal generation faces following constraint on star: 1) with state-of-the art, to guarantee reliability, number
Word domain clock rate is generally no more than 400MHz.2) navigation signal is stringent to demand on signal quality, to ensure signal quality, respectively
It must satisfy stringent corresponding relationship between frequency, integral frequency divisioil generation carried out by the same frequency.Navigation signal generation is divided into number
Word base band scheme and digital intermediate frequency scheme, digital baseband scheme generates digital baseband signal, after DA, I, Q is recycled just to hand in
Frequency conversion is to radio frequency；Digital intermediate frequency scheme generates intermediate-freuqncy signal in numerical portion, after DA, then is converted to radio frequency.Digital base
Band scheme is easy to make navigation signal deterioration there are I, Q imbalance problem, therefore, digital intermediate frequency scheme is commonly used.
However, digital intermediate frequency scheme needs to generate IF carrier, clock frequency requires stringent.For example, patent is " a kind of parallel
AltBOC navigation signal intermediate frequency generation method " (patent No.: CN 105116425A) provides a kind of two-frequency signal intermediate frequency generation side
Method, clock rate need to be four times of IF frequency, and therefore, the selection of IF frequency is limited, and flexibility is insufficient.
Summary of the invention
Technology of the invention solves the problems, such as: overcoming the deficiencies of the prior art and provide a kind of spaceborne offset dual-frequency navigation letter
Number generator and generation method, devise carrier frequency shift phase look-up table, without using IF carrier modulation premise
Under, frequency shift (FS) navigation signal is generated according to look-up table, reduces the constraint designed clock rate.
The technical solution of the invention is as follows: a kind of spaceborne offset dual-frequency navigation signal generator, and the spaceborne offset is double
Frequency navigation signal is bit rate Rc=10.23Mchip/s, sub-carrier frequencies fsThe satellite navigation signals of=15 × 10.23MHz,
Its off center frequency is foffset=F × 15 × 10.23MHz, wherein F is integer, and | F |≤min (2K, 4K-4), min
() expression is minimized, and K is integer, K >=2, fclkFor processed clock signal frequency, the generation
Device includes signal component generation module, offset phase look-up table means, bandpass filter, Amplitude Compensation filter, subcarrier phase
Digit counter, in which:
Signal component generation module is f in frequencyclkClock control under, generate spaceborne offset dual-frequency navigation signal top
Band I circuit-switched data code UI, the road upper side band Q pilot code UQ, lower sideband I circuit-switched data code LI, the road lower sideband Q pilot code LQ, export to inclined
Jayrator look-up table means；
Sub-carrier phase counter, carries out sub-carrier phase counting under CLK clock domain, and output width is
Sub-carrier phase, be sent to offset phase look-up table means；
Offset phase look-up table means, according to upper side band I circuit-switched data code UI, the road upper side band Q pilot code UQ, the road lower sideband I
Numeric data code LI, the road lower sideband Q pilot code LQ and sub-carrier phase search sine offset phase look-up table, cosine offset phase is looked into
Table is looked for, the I, Q component I (n) after obtaining frequency shift (FS) and Q (n) are sent to bandpass filter module；
Bandpass filter, filters out the out of band signal of I, Q component I (n) and Q (n), and by filtered I, Q component IBP(n)、
QBP(n) it is forwarded to Amplitude Compensation filter；
Amplitude Compensation filter carries out Amplitude Compensation filtering to the signal of bandpass filter output, it is double to obtain spaceborne offset
The real part of frequency navigation signalAnd imaginary part
The objective function of the amplitude-frequency response of the Amplitude Compensation filter is
Element in the sinusoidal phase look-up table, cosine phase look-up table is respectively offset phase look-up table corresponding element
Sine, cosine value.
The offset phase look-up table is the column of 8K row 16, and wherein element is θm,n, under 0≤m≤8K-1,1≤n≤16 meets
Column relationship:
Wherein,For downward rounding operation；C is arbitrary constant；
For in baseband phase look-up table pth row n-th arrange element, wherein 0≤p≤7,1≤n≤16.
The bandpass filter is obtained by following method:
(1), the N rank low-pass FIR filter of a linear phase is designed, N is even number, and the bilateral bandwidth BW of filter is greater than etc.
In the main lobe bandwidth of spaceborne offset dual-frequency navigation signal, the selection of N meets Nfoffset/fCLK=NF/ (8K) is integer；
(2), the low-pass filter coefficients h obtained according to step (1)LP(n), bandpass filter coefficient is calculatedWherein:
hBP,I(n)=hLP(n)cos(ωoffsetn)
hBP,Q(n)=hLP(n)sin(ωoffsetn)
In formula, ωoffset=2 π foffset/fCLK。
Another technical solution provided by the invention is: a kind of spaceborne offset dual-frequency navigation signal creating method, institute
Stating spaceborne offset dual-frequency navigation signal is bit rate Rc=10.23Mchip/s, sub-carrier frequencies fs=15 × 10.23MHz's
Satellite navigation signals, off center frequency are foffset=F × 15 × 10.23MHz, wherein F is integer, and | F |≤min
(2K, 4K-4), min () expression are minimized, and K is integer, K >=2,fclkFor processed clock signal
Frequency, this method comprises the following steps:
It (1), is f in frequencyclkClock control under, generate spaceborne offset dual-frequency navigation signal upper side band I circuit-switched data code
UI, the road upper side band Q pilot code UQ, lower sideband I circuit-switched data code LI, the road lower sideband Q pilot code LQ；
It (2), is f in frequencyclkClock control under, carry out sub-carrier phase counting, output width be's
Sub-carrier phase；
(3), according to the resulting spaceborne offset dual-frequency navigation signal upper side band I circuit-switched data code UI of step (1), the road upper side band Q
The sub-carrier phase that pilot code UQ, lower sideband I circuit-switched data code LI, the road lower sideband Q pilot tone LQ and step (2) obtain is searched sinusoidal
Phase look-up table, cosine phase look-up table, I, Q component I (n) and Q (n) after obtaining frequency shift (FS), are sent to bandpass filter
Module；Element in the sinusoidal phase look-up table, cosine phase look-up table is respectively offset phase look-up table corresponding element
Sinusoidal, cosine value, the offset phase look-up table are the column of 8K row 16, and wherein element is θm,n, 0≤m≤8K-1,1≤n≤16 are expired
Sufficient following relationship:
Wherein,For downward rounding operation, c is arbitrary constant；
For in baseband phase look-up table pth row n-th arrange element, wherein 0≤p≤7,1≤n≤16；
(4), it to I, the Q component I (n) and Q (n) progress bandpass filtering after frequency shift (FS), filters out and believes except I, Q component main lobe
Number；
(5), Amplitude Compensation filtering is carried out to the signal after bandpass filtering, obtains the real part of spaceborne offset dual-frequency navigation signalAnd imaginary partThe objective function of the amplitude-frequency response of the Amplitude Compensation filter is
Compared with the prior art, the invention has the advantages that:
(1), the present invention devises frequency offset phase look-up table, under the premise of without using IF carrier modulation, generates
Frequency shift (FS) navigation signal；
(2), present invention reduces the constraints designed clock rate, for given sample frequency, it is only necessary to change offset
Phase look-up table can be achieved with different frequency shift (FS)s；
(3), frequency shift (FS) navigation signal generation method provided by the present invention, the double frequency perseverance envelope suitable for mainstream navigate
Signal, including AltBOC, TD-AltBOC, ACE-BOC, broad sense AltBOC signal.
Detailed description of the invention
Fig. 1 is that offset dual-frequency navigation signal disclosed by the invention generates conceptual scheme；
Fig. 2 is the amplitude-frequency response that 32 rank of the embodiment of the present invention answers FIR bandpass filtering；
Fig. 3 is the amplitude-frequency response of 32 rank Amplitude Compensation filter of the embodiment of the present invention；
Fig. 4 is the power spectrum that the embodiment of the present invention deviates dual-frequency navigation signal；
Fig. 5 is that the embodiment of the present invention deviates dual-frequency navigation signal constellation (in digital modulation) figure.
Specific embodiment
Below in conjunction with the drawings and specific embodiments, the present invention is described in detail.
Spaceborne offset dual-frequency navigation signal is bit rate Rc=10.23Mchip/s, sub-carrier frequencies fs=15 ×
The satellite navigation signals of 10.23MHz, off center frequency are foffset=F × 15 × 10.23MHz, wherein F is integer, and
| F |≤min (2K, 4K-4), min () expression are minimized, and K is integer, K >=2,fclkFor signal
Handle clock frequency.
Due to sub-carrier coefficient difference, double frequency constant envelope signal is divided into AltBOC and ACE-BOC signal etc..
The expression formula of double frequency constant envelope signal may be expressed as:
In formula, sUI(t)、sLI(t)、sUQ(t)、sLQ(t) be four binary components, respectively upper side band I circuit-switched data code,
Lower sideband I circuit-switched data code, the road upper side band Q pilot code, the road lower sideband Q pilot code, value are { -1,1 }.
Each subcarrier period is divided into 8 equal portions, and the waveform in a cycle is expressed as:
In formula,Ts=1/fsFor the subcarrier period.
The difference of dual-frequency navigation signal is exactly sub-carrier coefficientValue is different, these values
It can be acquired by phase look-up table.
Following table is exactly the coefficient of AltBOC, whereinNote that ACE-BOC
In,
Expression formula after offset multiplied by the offset complex carrier signal of a cycle by obtaining:
soffset(t)=s (t) scoffset
Moreover, scoffsetPeriod be also Ts, it is expressed as
In formula,
Expression formula after offset are as follows:
In formula,Other are successively similar, and one at this time
The subcarrier period is with regard to equal part for 8K equal portions.
Below by taking ACE_BOC signal as an example, the present invention will be described in detail.
As shown in Figure 1, the generator includes signal the present invention provides a kind of spaceborne offset dual-frequency navigation signal generator
Component generation module, offset phase look-up table means, bandpass filter, Amplitude Compensation filter, sub-carrier phase counter,
In:
(1), signal component generation module
Signal component generation module is f in frequencyclkClock control under, generate spaceborne offset dual-frequency navigation signal top
Band I circuit-switched data code UI, the road upper side band Q pilot code UQ, lower sideband I circuit-switched data code LI, the road lower sideband Q pilot code LQ, export to inclined
Jayrator look-up table means.It is upper side band I circuit-switched data code UI, the road upper side band Q pilot code UQ, lower sideband I circuit-switched data code LI, following
The band road Q pilot code LQ is 0 or 1.
(2), sub-carrier phase counter
Sub-carrier phase counter carries out sub-carrier phase counting under CLK clock domain, and output width is
Sub-carrier phase, be sent to offset phase look-up table means.
(3), offset phase look-up table means
Offset phase look-up table means are according to upper side band I circuit-switched data code UI, the road upper side band Q pilot code UQ, lower sideband I number
According to code LI, the road lower sideband Q pilot code LQ and sub-carrier phase, sinusoidal phase look-up table, cosine phase look-up table are searched, obtains frequency
I, Q component I (n) and Q (n) after rate offset, are sent to bandpass filter module.The sinusoidal phase look-up table, cosine phase
Element in look-up table is respectively the sine of offset phase look-up table corresponding element, cosine value.
Offset phase look-up table is acquired using the baseband phase look-up table of dual-frequency navigation signal:
(a), baseband phase look-up table is established
As shown in table 1, baseband phase look-up table is usually a 8*16 table, upper side band I circuit-switched data code UI, the road upper side band Q
Tetra- pilot code UQ, lower sideband I circuit-switched data code LI, the road lower sideband Q pilot code LQ binary components constitute signal phasor, signal arrow
Amount shares 16 kinds of values, corresponding to every a line in table；8 equal portions of each subcarrier period point, corresponding to each column of table, base band
Phase look-up table (LUT) is denoted asMinimum sample rate is 120*1.023MHz.
1 ACE_BOC signal baseband phase look-up table of table
(b), minimum sample rate is risen to K times, is equivalent to and the every a line of baseband phase look-up table LUT is extended to K row, obtains
Look-up table { φ after to extensionm,n, 0≤m≤8K-1,1≤n≤16 }, have To be rounded downwards.
By the look-up table { φ after extensionm,n, 0≤m≤8K-1,1≤n≤16 } and m row phase value addsC is arbitrary constant, can take but be not limited to 0, obtain frequency offset phase look-up table { θm,n,0≤
M≤8K-1,1≤n≤16 }, have
That is:
Wherein,For downward rounding operation, c is arbitrary constant；
For in baseband phase look-up table pth row n-th arrange element, wherein 0≤p≤7,1≤n≤16, such as 2 institute of table
Show:
2 frequency offset phase look-up table of table
(c), according to offset phase look-up table { θm,n, 0≤m≤8K-1,1≤n≤16 } phase value, calculate sinusoidal phase
Look-up table (cos (θm,n)) and cosine phase look-up table sin (θm,n), it is stored according to the mode for arranging preferential, the size of each table is
128K。
Sub-carrier phase counting is carried out under CLK clock domain, counter isBit,To round up,
Count range is 0~8K-1.
(d) under CLK clock domain, by the subcarrier phase of the value of four binary components and the output of sub-carrier phase counter
Position is incorporated as address, altogetherBit searches sinusoidal phase look-up table and cosine phase look-up table, obtains frequency
I, Q component I (n) and Q (n) after rate offset.
Sub-carrier phase is located at low level, upper side band I circuit-switched data code UI, lower sideband I circuit-switched data code LI, upper side band Q circuit-switched data
Code UQ, lower sideband Q circuit-switched data code LQ are located at a high position, and high-low-position splicing becomes the address value of memory block, it is inclined can to obtain frequency
I, Q component I (n) and Q (n) after shifting.
(4), bandpass filter
Bandpass filter filters out the out of band signal of I, Q component I (n) and Q (n), and by filtered I, Q component IBP(n)、
QBP(n) it is forwarded to Amplitude Compensation filter.
Under CLK clock domain, bandpass filtering is carried out using multiple FIR filter, bandpass filtering is carried out to I (n) and Q (n).
The unit impulse response of N rank multiple FIR filter is denoted as:According to sample rate and signal
Bandwidth determines filter coefficient, exports I after bandpass filtering, Q component is denoted as respectively: IBP(n) and QBP(n)。
Bandpass filter is obtained by following method:
(4.1), the N rank low-pass FIR filter h of a linear phase is designedLP(n), i.e. hLP(n)=hLP(N-n) low pass,
The main lobe bandwidth for the spaceborne offset dual-frequency navigation signals such as N is even number, and the bilateral bandwidth BW of filter is more than or equal to, in the present embodiment,
The main lobe bandwidth of spaceborne offset dual-frequency navigation signal is 51.15MHz, takes BW >=70.61MHz, includes the outer two sides each one of main lobe
A sideband.hLP(n) transmission function are as follows:
Under CLK clock domain, digital filter device bandwidth is ± 2 π BW/fCLK, filter coefficient hLP(n) by excellent
Change algorithm to obtain.
(4.2), the low-pass filter coefficients h obtained according to step (1)LP(n), bandpass filter coefficient is calculatedBandpass filterTransmission function pass through HLP(ejω) translation obtain:
Bandpass filter coefficient are as follows:
hBP,I(n)=hLP(n)cos(ωoffsetn)
hBP,Q(n)=hLP(n)sin(ωoffsetn)
In formula, ωoffset=2 π foffset/fCLK.The selection of N meets Nfoffset/fCLK=NF/ (8K) is integer, at this time
hBP,I(n) and hBP,Q(n) there is linear phase.
(4.3), bandpass filtering is carried out to I (n) and Q (n), obtains exporting I after bandpass filtering, Q component is denoted as respectively: IBP
(n) and QBP(n):
(5), Amplitude Compensation filter
Since frequency shift (FS) is by using offset complex carrier signal scoffsetIt realizes, and scoffsetIt is equivalent to an ideal
Linear deflection complex carrier signalIt being sampled to obtain, sampling leads to the decaying of the amplitude presentation sinc shape of different frequency,
Therefore it will appear sinc decaying from the signal that bandpass filter exports.The signal that Amplitude Compensation filter exports bandpass filter
Amplitude Compensation filtering is carried out, keeps the frequency spectrum of shifted signal consistent with the frequency spectrum of baseband signal, obtains spaceborne offset dual-frequency navigation letter
Number real partAnd imaginary part
The Amplitude Compensation filter is that M rank linear phase amplitude compensates FIR filtering, is obtained by the following method:
(5.1), the amplitude-frequency response of Amplitude Compensation FIR filtering, the transmission function of the FIR filter are determined are as follows:
The objective function of amplitude-frequency response are as follows:
(5.2), according to the objective function of the amplitude-frequency response of Amplitude Compensation FIR filter, filter coefficient h is calculatedMag(n)
Value.
(5.3), to IBP(n) and QBP(n) Amplitude Compensation filtering is carried out:
Generate offset two-frequency signal:
I branch can be used only in practical application
The present invention also provides a kind of spaceborne offset dual-frequency navigation signal creating method, the spaceborne offset dual-frequency navigation letter
Number be bit rate Rc=10.23Mchip/s, sub-carrier frequencies fsThe satellite navigation signals of=15 × 10.23MHz, offset in
Frequency of heart is foffset=F × 15 × 10.23MHz, wherein F is integer, and | F |≤min (2K, 4K-4), min () expression take
Minimum value, K are integer, K >=2, fclkFor processed clock signal frequency, this method includes following step
It is rapid:
It (1), is f in frequencyclkClock control under, generate spaceborne offset dual-frequency navigation signal upper side band I circuit-switched data code
UI, upper side band Q circuit-switched data code UQ, lower sideband I circuit-switched data code LI, lower sideband Q circuit-switched data code LQ；
It (2), is f in frequencyclkClock control under, carry out sub-carrier phase counting, output width be's
Sub-carrier phase；
(3), according to the resulting spaceborne offset dual-frequency navigation signal upper side band I circuit-switched data code UI of step (1), the road upper side band Q
The carrier frequency shift address that pilot code UQ, lower sideband I circuit-switched data code LI, the road lower sideband Q pilot code LQ and step (2) obtain,
Sinusoidal phase look-up table, cosine phase look-up table are searched, I, Q component I (n) and Q (n) after obtaining frequency shift (FS) are sent to band
Allpass filter block；Element in the sinusoidal phase look-up table, cosine phase look-up table is respectively offset phase look-up table pair
Sine, the cosine value of element are answered, the offset phase look-up table is the column of 8K row 16, and wherein element is θm,n,0≤m≤8K-1,1≤
N≤16 meet following relationship:
Wherein,For downward rounding operation,；C is arbitrary constant；
For in baseband phase look-up table pth row n-th arrange element, wherein 0≤p≤7,1≤n≤16；
(4), to I, the Q component I (n) and Q (n) progress bandpass filtering after frequency shift (FS), I, Q component out of band signal are filtered out；
(5), Amplitude Compensation filtering is carried out to the signal after bandpass filtering, the objective function for obtaining the amplitude-frequency response of Amplitude Compensation filter described in the real and imaginary parts of spaceborne offset dual-frequency navigation signal is
Embodiment
To make the objectives, technical solutions, and advantages of the present invention more comprehensible, below with reference to attached drawing 1, to the present invention into
One step is described in detail.
Generate ACE-BOC (15,10) signal of a frequency shift (FS), Rc=10.23Mchip/s, sub-carrier frequencies fs
=15*1.023MHz, clock rate are selected as fCLK=240*1.023MHz, K=2, off center frequency are foffset=45*
1.023MHz i.e. F=3.Signal double frequency bandwidth BW=71.61MHz.
The operating procedure of method disclosed by the invention is as follows:
(1) according to the original phase look-up table of ACE-BOC (15,10), frequency offset phase look-up table is generated.Original phase
Look-up table isSize is 8*16, is given in Table 2, at this time K=2, and frequency offset phase is looked into
Looking for table is { θm,n, 0≤m≤8K-1,1≤n≤16 }, size is the table of 16*16, and phase value isIt obtains
Offset phase table it is as shown in table 3.
(2) under 240*1.023MHz clock domain, four signal components UI, LI, UQ, LQ, four signal component values are generated
Belong to { 1,0 }.
(3) under 240*1.023MHz clock domain, using four signal component values and 4 bit sub-carrier phase values as ground
Sine, the cosine table of offset phase look-up table are searched in location, I, Q component I (n) and Q (n) after generating frequency shift (FS).
(4) under 240*1.023MHz clock domain, band logical filter is carried out to I (n) and Q (n) using N rank multiple FIR filter
Wave.N's selects to make 3N/16 integer, and in this example, N is selected as 32.First the 32 rank low passes an of linear phase are obtained with optimization method
FIR filter hLP(n), hLP(n)=hLP(n-32), the bilateral bandwidth BW=70.61MHz of filter, 17 are before low-pass filter
A several results are provided in following table:
| n | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| hLP(n) | 0.0001 | 0.0042 | 0.0045 | -0.0014 | -0.0098 | -0.0119 | -0.0013 | 0.0170 | 0.0266 |
| n | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | |
| hLP(n) | 0.0119 | -0.0244 | -0.0554 | -0.0440 | 0.0299 | 0.01477 | 0.2570 | 0.3014 |
32 ranks answer FIR bandpass filteringCoefficient are as follows:
hBP,I(n)=h (n) cos (π/8 3n)
hBP,Q(n)=h (n) sin (π/8 3n)
Fig. 2 gives multiple band logical FIR filterAmplitude-frequency response.I (n) and Q (n) are after bandpass filter
I, Q component are as follows:
(5) under 240*1.023MHz clock domain, Amplitude Compensation is carried out using M rank Symmetric FIR Filters, is then generated inclined
Move dual-frequency navigation signal.The unit impulse response of Amplitude Compensation FIR filter is denoted as: hMag(n).Amplitude loss is due to frequency
Caused by offset, hMag(n) objective function of amplitude-frequency response are as follows:
It in this example, is illustrated, selects M=32, hMag(n)=hMag(32-n), a result of preceding 17 coefficients is under
Table provides:
| n | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
| hMag(n) | 0.0000 | -0001 | 0.0001 | -0.0001 | 0.0002 | -0.0004 | 0.0006 | -0.0009 | 0.0013 |
| n | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | |
| hMag(n) | -0.0020 | 0.0031 | -0.0049 | 0.0082 | -0.0152 | 0.0332 | -0.1059 | 1.1663 |
Fig. 3 is to give the amplitude-frequency response of the filter.To IBP(n) and QBP(n) Amplitude Compensation filtering is carried out:
The offset two-frequency signal finally generated are as follows:
The power spectrum of offset two-frequency signal is shown in Fig. 4.
Fig. 5 give offset dual-frequency navigation signal be down-converted to the planisphere after base band, it is found that with through baseband phase
The baseband signal constellation diagram that look-up table obtains is consistent.
The present invention is that the common knowledge for partly belonging to those skilled in the art is described in detail.
Claims (6)
1. a kind of spaceborne offset dual-frequency navigation signal generator, the spaceborne offset dual-frequency navigation signal is bit rate Rc=
10.23Mchip/s, sub-carrier frequencies fsThe satellite navigation signals of=15 × 10.23MHz, off center frequency are foffset
=F × 15 × 10.23MHz, wherein F is integer, and | F |≤min (2K, 4K-4), min () expression are minimized, and K is whole
Number, K >=2,fclkFor processed clock signal frequency, it is characterised in that generate mould including signal component
Block, offset phase look-up table means, bandpass filter, Amplitude Compensation filter, sub-carrier phase counter, in which:
Signal component generation module is f in frequencyclkClock control under, generate spaceborne offset dual-frequency navigation signal upper side band I
Circuit-switched data code UI, the road upper side band Q pilot code UQ, lower sideband I circuit-switched data code LI, the road lower sideband Q pilot code LQ, output to offset phase
Position look-up table means；
Sub-carrier phase counter, carries out sub-carrier phase counting under CLK clock domain, and output width isSon
Carrier phase is sent to offset phase look-up table means；
Offset phase look-up table means, according to upper side band I circuit-switched data code UI, the road upper side band Q pilot code UQ, lower sideband I circuit-switched data
Code LI, the road lower sideband Q pilot code LQ and sub-carrier phase, search sine offset phase look-up table, cosine offset phase look-up table,
I, Q component I (n) and Q (n) after obtaining frequency shift (FS), are sent to bandpass filter module；
Bandpass filter, filters out the out of band signal of I, Q component I (n) and Q (n), and by filtered I, Q component IBP(n)、QBP(n)
It is forwarded to Amplitude Compensation filter；
Amplitude Compensation filter carries out Amplitude Compensation filtering to the signal of bandpass filter output, obtains spaceborne offset double frequency and lead
The real part of boat signalAnd imaginary part。
2. the spaceborne offset dual-frequency navigation signal generator of one kind according to claim 1, it is characterised in that: the amplitude is mended
The objective function for repaying the amplitude-frequency response of filter is
3. the spaceborne offset dual-frequency navigation signal generator of one kind according to claim 1, it is characterised in that: the sine phase
Element in position look-up table, cosine phase look-up table is respectively the sine of offset phase look-up table corresponding element, cosine value.
4. the spaceborne offset dual-frequency navigation signal generator of one kind according to claim 1, it is characterised in that: the offset phase
Position look-up table is the column of 8K row 16, and wherein element is θm,n, 0≤m≤8K-1,1≤n≤16 meet following relationship:
Wherein,For downward rounding operation；C is arbitrary constant；
For in baseband phase look-up table pth row n-th arrange element, wherein 0≤p≤7,1≤n≤16.
5. the spaceborne offset dual-frequency navigation signal generator of one kind according to claim 1, it is characterised in that: the band logical filter
Wave device is obtained by following method:
(1), the N rank low-pass FIR filter of a linear phase is designed, N is even number, and the bilateral bandwidth BW of filter is more than or equal to star
The main lobe bandwidth of offset dual-frequency navigation signal is carried, the selection of N meets Nfoffset/fCLK=NF/ (8K) is integer；
(2), the low-pass filter coefficients h obtained according to step (1)LP(n), bandpass filter coefficient is calculatedWherein:
hBP,I(n)=hLP(n)cos(ωoffsetn)
hBP,Q(n)=hLP(n)sin(ωoffsetn)
In formula, ωoffset=2 π foffset/fCLK。
6. a kind of spaceborne offset dual-frequency navigation signal creating method, the spaceborne offset dual-frequency navigation signal is bit rate Rc=
10.23Mchip/s, sub-carrier frequencies fsThe satellite navigation signals of=15 × 10.23MHz, off center frequency are foffset
=F × 15 × 10.23MHz, wherein F is integer, and | F |≤min (2K, 4K-4), min () expression are minimized, and K is whole
Number, K >=2,fclkFor processed clock signal frequency, it is characterised in that include the following steps:
It (1), is f in frequencyclkClock control under, generate spaceborne offset dual-frequency navigation signal upper side band I circuit-switched data code UI, on
The road sideband Q pilot code UQ, lower sideband I circuit-switched data code LI, the road lower sideband Q pilot code LQ；
It (2), is f in frequencyclkClock control under, carry out sub-carrier phase counting, output width beSon carry
Wave phase；
(3), according to the resulting spaceborne offset dual-frequency navigation signal upper side band I circuit-switched data code UI of step (1), the road upper side band Q pilot tone
The sub-carrier phase that code UQ, lower sideband I circuit-switched data code LI, the road lower sideband Q pilot tone LQ and step (2) obtain, searches sinusoidal phase
Look-up table, cosine phase look-up table, I, Q component I (n) and Q (n) after obtaining frequency shift (FS), are sent to bandpass filter module；
Element in the sinusoidal phase look-up table, cosine phase look-up table be respectively offset phase look-up table corresponding element sine,
Cosine value, the offset phase look-up table are the column of 8K row 16, and wherein element is θm,n, 0≤m≤8K-1,1≤n≤16 meet following
Relationship:
Wherein,For downward rounding operation, c is arbitrary constant；
For in baseband phase look-up table pth row n-th arrange element, wherein 0≤p≤7,1≤n≤16；
(4), to I, the Q component I (n) and Q (n) progress bandpass filtering after frequency shift (FS), the external signal of I, Q component main lobe are filtered out；
(5), Amplitude Compensation filtering is carried out to the signal after bandpass filtering, obtains the real part of spaceborne offset dual-frequency navigation signalAnd imaginary partThe objective function of the amplitude-frequency response of the Amplitude Compensation filter is
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