CN102694610A - Calibration system for RDSS channel zero value - Google Patents

Abstract

A calibration system for RDSS (Radio Determination Satellite Service) channel zero value comprises a spread spectrum signal source, a microwave signal source, a frequency converter, a power divider, a double-channel digital oscilloscope, a first attenuator, a second attenuator, a control and processing computer and a vector network analysis instrument, wherein the spread spectrum signal source generates simulated RDSS spread spectrum signals; spread spectrum signal source outcoming signals are subjected to frequency conversion by the microwave signal source and the frequency converter so as to generate frequency points suitable for RDSS service channel input; a high-sampling rate digital oscilloscope is used for synchronously sampling the input/output signals of the RDSS service channel; and the control and processing computer is used for completing initialization of the oscilloscope, acquisition and loading of the oscilloscope channel data, orthogonalization of the channel data, carrier rotation, circulating autocorrelation, peak value searching, and zero value calculation and processing, so as to eventually obtain the absolute time delay of the RDSS service channel. According to the system provided by the invention, the signals consistent with the RDSS service system are adopted to serve as the reference, the calibration zero value can reflect the real conditions and the calibration precision is high.

Description

A kind of calibration system of radiodetermination-satellite service passage null value

Technical field

The present invention relates to the system that a kind of null value that is used for the radiodetermination-satellite service passage is demarcated.

Background technology

Satellite navigation system can be sent high accuracy, round-the-clock, round-the-clock navigation, location and time service information, is the indispensable important space infrastructure of current national economy and national defense construction.In order to set up independent China Satecom navigation system, avoid situation under one's control, China just builds in the development of acceleration satellite navigation system.Since 2000, China accomplished first generation Big Dipper navigation positioning system and has set up, and this system adopts RDSS (Radio Determination Satellite Service radiodetermination-satellite service) mode of operation, and had obtained application in various fields.In addition; The time of usually adopting the satellite Transparent Transponder to carry out between monitoring station and the time service central station in the time dissemination system transmits and calibration; The channel unit time delay of satellite is the part that whole link transmits, and in time dissemination system comes into operation, must carry out the passage null value and demarcate.The null value stated accuracy of passage will directly influence the range accuracy and the time transmitting accuracy of RDSS service-user.

At present, for the system of frequency translation passage null value demarcation, main two types:

(1) based on the null value calibration system of vector network analyzer.Adopt vector frequency mixer collimation technique, this technology is Agilent company (Agilent) invention, and it adopts the calibration frequency mixer that the test macro based on vector network analyzer is calibrated.This method needs transponder self that local oscillation signal is provided, and need calibrate frequency converter with the high-accuracy time delay of transponder I/O respective frequencies transformation relation to be measured.

(2) based on carrier modulation the null value calibration system.Being adapted to transponder provides the situation of local oscillation signal can't for test and time delay calibration system.When frequency modulating signal much smaller than carrier frequency, promptly can satisfy arrowband when hypothesis, envelope delay just can the approximate representation group delay.Modulation method is through being realized radio-frequency carrier amplitude modulation (AM), frequency modulation (FM) or phase modulation (PM) by the sinusoidal wave baseband signal of a lower frequency.The transponder input radio frequency carries out frequency sweep on a band frequency, transponder output signal is by demodulation, with the bit comparison mutually of the phase place of restituted signal and original baseband signal, thereby obtains the time delay of each Frequency point of passage.The resulting time delay of this method is the absolute time delay of each Frequency point in the transmission passband, can not accurately reflect the passage null value of the professional spread-spectrum signal of the specific RDSS of RDSS channel transfer.

(" modern electronic technology " 2010 the 1st phases are 312 phase pp8～11 always for document " based on the group delay method of measuring of spread-spectrum signal "; Author: the sea of sand, Zhu Xiangwei, Zhang Guozhu, Sun Guangfu) proposes one and adopt the relevant group delay method of testing of spread-spectrum signal; But this method requires the input and output of measured piece necessary with frequently; And the input and output frequency of radio determination service passage is different, so this method can not be used for the demarcation of radio determination service passage null value.

Summary of the invention

Technology of the present invention is dealt with problems and is: overcome the deficiency of prior art, the passage null value calibration system that a kind of stated accuracy is high, can accurately reflect the professional spread-spectrum signal of transmission specific spread spectrum code rate RDSS is provided.

Technical solution of the present invention is: a kind of calibration system of radiodetermination-satellite service passage null value; Comprise spread-spectrum signal source, microwave signal source, frequency converter, power divider, two-channel digital oscilloscope, first attenuator, second attenuator, control and process computer and vector network analyzer, wherein:

Spread-spectrum signal source: produce the spread-spectrum signal of an IF carrier modulation, the spread-spectrum signal modulation system is consistent with the system of radiodetermination-satellite service channel transmission signal with spread-spectrum code rate;

Microwave signal source and frequency converter: the IF carrier modulated spread spectrum signal that spread-spectrum signal source produces is carried out frequency translation, and the centre frequency that the signal center frequency after the conversion and radiodetermination-satellite service channel input signal are corresponding is consistent;

Power divider: the output signal merit of frequency converter is divided into two-way, and one the tunnel is input to oscillographic first input channel of two-channel digital, and first attenuator is sent on another road;

First attenuator: the input of sending into the radiodetermination-satellite service passage after the signal that transmits decayed;

Second attenuator: send into oscillographic second input channel of two-channel digital after the output signal of radiodetermination-satellite service passage decayed;

The two-channel digital oscilloscope: the signal to two input channels carries out synchronized sampling, and unitary sampling duration length equals the pseudo noise code cycle of a radiodetermination-satellite service signal during synchronized sampling;

Control and process computer: comprise channel data orthogonalization module, carrier wave rotary module, circulation auto-correlation processing module and null value computing module,

Channel data orthogonalization module:,, and sample point is carried out Hilbert transform respectively form two complex data groups respectively from the sample point of same position intercepting similar number to the two-way sampled data of two-channel digital oscilloscope output; Sample point begins to utilize the positive integer serial number from interception position;

The carrier wave rotary module: in two complex data groups that channel data orthogonalization module is obtained one array as a reference, another is as handling array, through the carrier wave circulator, with reference frequency and the difference on the frequency f that handles frequency _cBe the center, the stepping amount is f _t, in ± Δ f scope, generate the frequency sweep point

Carry out the carrier wave rotation to handling array,

Wherein

Stepping amount f _tGet the fixed value that is not more than 500Hz, Δ f gets the fixed value that is not more than 5kHz; Reference frequency is the centre frequency of reference array, handles frequency for handling the centre frequency of array;

Circulation auto-correlation processing module: to reference array and each time the postrotational processing array of carrier wave carry out conjugate multiplication behind the Fourier transform respectively, multiplied result is carried out inverse Fourier transform, and the time domain data amplitude behind the inverse Fourier transform is asked square;

Null value computing module: the peak value of the amplitude square that search loop auto-correlation processing module obtains; Confirm peak point corresponding sample point sequence number value; And peak point corresponding sample point sequence number value multiply by the sampling period; And then deduct the time delay adjustment value of stube cable, attenuator, power splitter, obtain the absolute time delay of radiodetermination-satellite service passage;

Vector network analyzer: the time delay to stube cable, attenuator, power splitter is proofreaied and correct.

The oscillographic sampling clock frequency of described two-channel digital is perhaps exported more than the twice of highest frequency in the spread-spectrum signal for radiodetermination-satellite service passage input spread-spectrum signal.

The length L value of the sampled data of described channel data orthogonalization module intercepts does

Between an integer, wherein N is the sampled point number that is comprised in pseudo noise code cycle in the radiodetermination-satellite service signal,

L _CodeIt is the chip number that is comprised in the pseudo noise code cycle; And L=2 ^k, k is an integer.

The present invention's advantage compared with prior art is:

(1) system of the present invention adopts the test input of RDSS service signal as the RDSS service channel, and calibration result can reflect accurately, truly that navigation satellite carries out the passage null value under the transmission specific spread spectrum code rate situation in the RDSS business;

(2) system of the present invention carries out over-sampling to the microwave modulating signal of the input and output of RDSS service channel, and the stated accuracy of system depends on sample frequency, and certainty of measurement is high;

(3) system of the present invention utilizes the carrier wave rotary module to realize the carrier wave rotation, two signal data centre frequency deviations that guarantee cross correlation process in allowed limits, thereby can obtain tangible correlation peak;

(4) system of the present invention has utilized the good autocorrelation performance and the their cross correlation of spread-spectrum pseudo code, and the pseudo-random signal of intercepting certain-length is carried out the accuracy that relevant treatment does not influence measurement, can greatly reduce operand; And the input/output signal of passage carries out cross correlation process, need not carry out the acquisition and tracking of spread-spectrum signal to signal, reduces complexity and the operand handled, and calibration algorithm is realized simple.

Description of drawings

Fig. 1 is the theory of constitution block diagram of system of the present invention;

The channel input signal spectrogram of Fig. 2 for simulating in the embodiment of the invention;

The passage output signal spectrum figure of Fig. 3 for simulating in the embodiment of the invention;

Input and output oscillogram when Fig. 4 is 300ns for channel time delay in the embodiment of the invention;

The input and output relevant amplitude square curve chart of Fig. 5 for having peak value in the embodiment of the invention.

Embodiment

As shown in Figure 1, calibration system of the present invention comprises spread-spectrum signal source, frequency converter, power divider, high sampling rate digital oscilloscope, control and process computer, attenuator, test cable, network interface cable and vector network analyzer.Wherein:

Spread-spectrum signal source is used to produce the spread-spectrum signal of an IF carrier modulation, and the spread-spectrum signal modulation system is consistent with the system of radiodetermination-satellite service channel transmission signal with spread-spectrum code rate; Here the French IN-SNEC Company products intermediate frequency synthetical baseband processor CORTEX QRT-XL that samples can produce the spread-spectrum signal of the BPSK carrier modulation of centre frequency 70MHz, sets RDSS service signal spread spectrum code check 2.046MHz, pseudo-code cycle 1ms.

Microwave signal source and frequency converter carry out frequency translation with the IF carrier modulated spread spectrum signal that spread-spectrum signal source produces, and the centre frequency that the signal center frequency after the conversion and radiodetermination-satellite service channel input signal are corresponding is consistent; Here, microwave signal source is the signal source 8257D of Agilent company, and spread-spectrum signal source is exported the RDSS service signal that the 70MHz signal up-converts to RDSS input channel centre frequency, supposes that RDSS passage incoming frequency is the signal of 1615.7MHz.

Power divider is divided into two-way with the output signal merit of frequency converter, and one the tunnel is input to oscillographic first input channel of two-channel digital, and first attenuator is sent on another road; Here, adopting power divider is Agilent formula product 11636B, and the signal allocation Insertion Loss is 5dB.

After decaying, 1 pair of signal that transmits of attenuator sends into the input of radiodetermination-satellite service passage; Here attenuator 1 is chosen as 1dB～121dB adjustable attenuator, operating frequency range 0～10GHz.

After decaying, the output signal of 2 pairs of radiodetermination-satellite service passages of attenuator sends into oscillographic second input channel of two-channel digital; Selecting attenuator 2 is the 30dB250W high power attenuator, operating frequency range 0～10GHz.

The two-channel digital oscilloscope: the signal to two input channels carries out synchronized sampling, and unitary sampling duration length equals the pseudo noise code cycle of a radiodetermination-satellite service signal during synchronized sampling; Here, high sampling rate digital oscilloscope model is the DSO090804A four-way digital oscilloscope of Agilent company, and sample rate is up to 40Gsa/s, and the single channel storage depth is 100M.

Processing such as control and process computer are accomplished with the communicating by letter of testing equipment, test data is written into and channel data orthogonalization, carrier wave are rotated, circulation auto-correlation and null value calculating.

Test cable 1, test cable 2, test cable 3, test cable 4 and test cable 5 are radio frequency cable.

Vector network analyzer is used for the time delay of stube cable, attenuator, power splitter is proofreaied and correct.Here adopt the E8362B of Agilent company, working frequency range is up to 26.5GHz, and the time delay calibrated error is 0.1ns.

Concrete demarcation implementation procedure is following:

1, output to the combination time delay and the link Insertion Loss in the path of A/D converter 1 with vector network analyzer calibration RDSS service signal source, delay volume is t ₁Ns, the Insertion Loss amount is Loss ₁DB.

2, output to the path delay of time and the link Insertion Loss of the input of RDSS service channel with vector network analyzer calibration RDSS service signal source, delay volume is T ₂Ns, the Insertion Loss amount is Loss ₂DB;

3, output to the time delay and link Insertion Loss in the path delay of time of A/D converter 2 with vector network analyzer calibration RDSS service channel, this chain-circuit time delay amount is t _DownNs, the Insertion Loss amount is Loss ₃DB.

4, press Fig. 1 mode, select suitable frequency converter output level P ₁, guarantee P ₁-Loss ₁In the OK range of channel oscilloscope input; The attenuation of attenuator 1 is set, guarantees P ₁-Loss ₂In the RDSS service channel input range of regulation, and P ₁-Loss ₂+ G-Loss ₃In the OK range of channel oscilloscope input; Each part of calibration system is connected the RDSS passage, and passage to be measured powers up and the calibration system device power-on.

5, control and process computer operation digital oscilloscope initialization module; Completion to oscillographic network connect, the foundation of communicating by letter of control and treatment computer and digital oscilloscope; The sample rate of digital oscilloscope is set, requires to adopt frequency to be higher than more than the twice of RDSS passage input and output signal highest frequency.Here the RDSS passage is output as 3950.3MHz.Selection has been adopted and has been 10GSa/s; The triggering mode single step mode, the binary channels synchronous data collection is carried out in input and output to the RDSS passage, and sampled data length is 1ms; Then the sampled data output number of RDSS passage input and output signal is 1e7, is spaced apart 0.1ns between each sample point;

6, the data that insmod the oscilloscope collection of control and process computer operation image data are loaded into control and process computer, and channel input signal spread-spectrum signal frequency spectrum is as shown in Figure 2; The frequency spectrum of passage output spread-spectrum signal is as shown in Figure 3;

7, control and process computer operation channel data orthogonalization module, its processing procedure:

Select intercepted length L.The intercepted length L value of sampled data does

Between an integer, wherein N is the sampled point number that is comprised in pseudo noise code cycle in the radiodetermination-satellite service signal, requirement

L _CodeIt is the chip number that is comprised in the pseudo noise code cycle; And, also require L=2 ^k, k is an integer.

Here, the cycle chip number L of a pseudo noise code _Code=2046,

Be M≤10.23, then Therefore L can select an integer between 977518～10e6, in order to improve Fourier transform and inverse Fourier transform speed, requires L=2 ^k, k is an integer, gets k=20 here, then L=1048576.

Start anew the intercepting input sampling data:

${\stackrel{\→}{D}}_{\mathrm{in}}=\left[\begin{array}{cccc}{d}_{\mathrm{in}}\left(1\right)& d_{\mathrm{in}}\left(2\right)& ...& d_{\mathrm{in}}\left(L\right)\end{array}\right]---\left(1\right)$

Hilbert transform forms plural number to input sampling data:

${\stackrel{\→}{D}}_{\mathrm{Zin}}={\stackrel{\→}{D}}_{\mathrm{in}}+\mathrm{Hibert}\left({\stackrel{\→}{D}}_{\mathrm{in}}\right)---\left(2\right)$

${\stackrel{\→}{D}}_{\mathrm{Zin}}=\left[\begin{array}{cccc}{d}_{\mathrm{zin}}\left(1\right)& d_{\mathrm{zin}}\left(2\right)& ...& d_{\mathrm{zin}}\left(L\right)\end{array}\right]---\left(3\right)$

Start anew intercepting output sampled data:

${\stackrel{\→}{D}}_{\mathrm{out}}=\left[\begin{array}{cccc}{d}_{\mathrm{out}}\left(1\right)& d_{\mathrm{out}}\left(2\right)& ...& d_{\mathrm{out}}\left(L\right)\end{array}\right]---\left(4\right)$

Hilbert transform forms plural number to the output sampled data:

${\stackrel{\→}{D}}_{\mathrm{Zout}}={\stackrel{\→}{D}}_{\mathrm{out}}+\mathrm{Hibert}\left({\stackrel{\→}{D}}_{\mathrm{out}}\right)---\left(5\right)$

${\stackrel{\→}{D}}_{\mathrm{Zout}}=\left[\begin{array}{cccc}{d}_{\mathrm{zout}}\left(1\right)& d_{\mathrm{zout}}\left(2\right)& ...& d_{\mathrm{zout}}\left(L\right)\end{array}\right]---\left(6\right)$

8, control and process computer operating carrier rotary module, its processing procedure:

For two complex data groups, with one of them complex data group array as a reference, the centre frequency of reference array is reference frequency f _Ref, another one complex data group is as handling array, and the centre frequency of handling array is for handling frequency f _ProcessCalculate reference frequency and handle the frequency difference f between the frequency _c

f _c＝f _ref-f _process (7)

With f _cBe the center, the stepping amount is f _t, in ± Δ f scope, generate the frequency sweep point

${\tilde{f}}_m=f_c-\mathrm{\Δf}+m\·f_t,m=\mathrm{0,1},...,\frac{2\mathrm{\Δf}}{f_t}---\left(8\right)$

Stepping amount f _tGet the fixed value that is not more than 500Hz, Δ f gets the fixed value that is not more than 5kHz;

Here be reference frequency f with RDSS passage output center frequency _Ref=3950.3MHz, the input centre frequency is for handling frequency f _Process=1615.7MHz, then the frequency difference f between reference frequency and the processing frequency _c=3950.3-1615.7=2334.6MHz, stepping amount f _tGet 200Hz; Δ f gets 1kHz, and then the frequency sweep point of carrier wave circulator is 2334.599MHz, 2334.5992MHz, 2334.5994MHz, 2334.5996MHz, 2334.5998MHz, 2334.6MHz, 2334.602MHz, 2334.604MHz, 2334.606MHz, 2334.608MHz, 2334.61MHz.

Carrier wave rotation value is during frequency sweep frequency

:

$\stackrel{\→}{R}=\left[\begin{array}{cccc}r\left(1\right)& r\left(2\right)& ...& r\left(L\right)\end{array}\right]---\left(9\right)$

$r\left(m\right)=\exp (j\·m\·{\tilde{f}}_m\·\frac{1}{f_S})---\left(10\right)$

The postrotational value of input signal carrier wave is:

${\stackrel{\→}{D}}_{\mathrm{Zin}\_R}=\left[\begin{array}{cccc}{d}_{\mathrm{zin}\_r}\left(1\right)& d_{\mathrm{zin}\_r}\left(2\right)& ...& d_{\mathrm{zin}\_r}\left(L\right)\end{array}\right]---\left(11\right)$

d _{zin_r}(m)＝d _zin(m)·r(m) (12)

9, control and process computer operation circulation auto-correlation processing module, to accomplishing the plural ordered series of numbers difference Fourier transform of the postrotational input and output of carrier wave, carry out conjugate multiplication then:

$Y={\left[\mathrm{FFT}\left({\stackrel{\→}{D}}_{\mathrm{Zin}\_R}\right)\right]}^{*}\·\mathrm{FFT}\left({\stackrel{\→}{D}}_{\mathrm{Zout}}\right)---\left(13\right)$

FFT () expression is carried out FFT to ordered series of numbers in () in the formula.

Carry out inverse Fourier transform and amplitude square then:

A＝|IFFT(Y)| ² (14)

IFFT () expression is carried out fast adverse Fourier transform to ordered series of numbers in () in the formula.

To the frequency sweep point, the carrier wave rotary module carries out the carrier wave rotation processing to the plural array of reference successively, and after whenever finishing dealing with, circulation auto-correlation processing module is also corresponding carries out single treatment.

10, control and process computer operation null value computing module carries out peak value searching to all outputs of circulation auto-correlation module, obtains peak point corresponding sample point sequence number N _Channel, compute channel null value t _Channel:

$t_{\mathrm{channel}}=N_{\mathrm{channel}}\·\frac{1}{f_S}+t_l-t_{\mathrm{up}}-t_{\mathrm{down}}---\left(13\right)$

In the formula: t _lExpression RDSS service signal source outputs to the path delay of time of A/D converter 1;

t _UpExpression RDSS service signal source outputs to the path delay of time of RDSS service channel input;

t _DownExpression RDSS service channel outputs to the path delay of time of A/D converter 2;

The time delay of setting RDSS is 300ns, i.e. 3000 sample points, and the use waveform of RDSS passage input and output is as shown in Figure 4.Amplitude square curve with correlation peak is as shown in Figure 5, and amplitude peak appears in 3000 sample places on ground, is 3000 sample points thereby obtain the passage null value.Sample frequency is 10GHz, and sample point is spaced apart 0.1ns, and therefore, the passage null value is 3000 * 0.1=300ns, and is consistent with the emulation set point.

The content of not doing to describe in detail in the specification of the present invention belongs to those skilled in the art's known technology.

Claims (3)

1. the calibration system of a radiodetermination-satellite service passage null value; It is characterized in that comprising: spread-spectrum signal source, microwave signal source, frequency converter, power divider, two-channel digital oscilloscope, first attenuator, second attenuator, control and process computer and vector network analyzer, wherein:

Spread-spectrum signal source: produce the spread-spectrum signal of an IF carrier modulation, the spread-spectrum signal modulation system is consistent with the system of radiodetermination-satellite service channel transmission signal with spread-spectrum code rate;

Microwave signal source and frequency converter: the IF carrier modulated spread spectrum signal that spread-spectrum signal source produces is carried out frequency translation, and the centre frequency that the signal center frequency after the conversion and radiodetermination-satellite service channel input signal are corresponding is consistent;

Power divider: the output signal merit of frequency converter is divided into two-way, and one the tunnel is input to oscillographic first input channel of two-channel digital, and first attenuator is sent on another road;

First attenuator: the input of sending into the radiodetermination-satellite service passage after the signal that transmits decayed;

Second attenuator: send into oscillographic second input channel of two-channel digital after the output signal of radiodetermination-satellite service passage decayed;

The two-channel digital oscilloscope: the signal to two input channels carries out synchronized sampling, and unitary sampling duration length equals the pseudo noise code cycle of a radiodetermination-satellite service signal during synchronized sampling;

Control and process computer: comprise channel data orthogonalization module, carrier wave rotary module, circulation auto-correlation processing module and null value computing module,

Channel data orthogonalization module:,, and sample point is carried out Hilbert transform respectively form two complex data groups respectively from the sample point of same position intercepting similar number to the two-way sampled data of two-channel digital oscilloscope output; Sample point begins to utilize the positive integer serial number from interception position;

The carrier wave rotary module: in two complex data groups that channel data orthogonalization module is obtained one array as a reference, another is as handling array, through the carrier wave circulator, with reference frequency and the difference on the frequency f that handles frequency _cBe the center, the stepping amount is f _t, in ± Δ f scope, generate the frequency sweep point

Carry out the carrier wave rotation to handling array,

Wherein

Stepping amount f _tGet the fixed value that is not more than 500Hz, Δ f gets the fixed value that is not more than 5kHz; Reference frequency is the centre frequency of reference array, handles frequency for handling the centre frequency of array;

Circulation auto-correlation processing module: to reference array and each time the postrotational processing array of carrier wave carry out conjugate multiplication behind the Fourier transform respectively, multiplied result is carried out inverse Fourier transform, and the time domain data amplitude behind the inverse Fourier transform is asked square;

Null value computing module: the peak value of the amplitude square that search loop auto-correlation processing module obtains; Confirm peak point corresponding sample point sequence number value; And peak point corresponding sample point sequence number value multiply by the sampling period; And then deduct the time delay adjustment value of stube cable, attenuator, power splitter, obtain the absolute time delay of radiodetermination-satellite service passage;

Vector network analyzer: the time delay to stube cable, attenuator, power splitter is proofreaied and correct.

2. the calibration system of a kind of radiodetermination-satellite service passage null value according to claim 1 is characterized in that: the oscillographic sampling clock frequency of described two-channel digital is perhaps exported more than the twice of highest frequency in the spread-spectrum signal for radiodetermination-satellite service passage input spread-spectrum signal.

3. the calibration system of a kind of radiodetermination-satellite service passage null value according to claim 1 is characterized in that: the length L value of the sampled data of described channel data orthogonalization module intercepts does

Between an integer, wherein N is the sampled point number that is comprised in pseudo noise code cycle in the radiodetermination-satellite service signal,

L _CodeIt is the chip number that is comprised in the pseudo noise code cycle; And L=2 ^k, k is an integer.

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