CN102694610B - 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 for radiodetermination-satellite service passage is demarcated.

Background technology

Satellite navigation system can send 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 has completed first generation Big Dipper navigation positioning system and has set up, this system adopts RDSS (Radio Determination Satellite Service radiodetermination-satellite service) mode of operation, and has obtained application in various fields.In addition, the time that usually adopts satellite Transparent Transponder to carry out between monitoring station and time service central station in 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 demarcation of passage null value.The null value stated accuracy of passage will directly affect range accuracy and the time transmitting accuracy of RDSS service-user.

At present, the system of demarcating for frequency translation passage null value, main two classes:

(1) the null value calibration system based on vector network analyzer.Adopt vector frequency mixer collimation technique, this technology is Agilent company (Agilent) invention, and it adopts calibration frequency mixer to calibrate the test macro based on vector network analyzer.This method needs transponder self that local oscillation signal is provided, and need to 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 null value calibration system.Be adapted to transponder and cannot provide the situation of local oscillation signal to test and time delay calibration system.When frequency modulating signal is much smaller than carrier frequency, can meet arrowband hypothesis time, envelope delay just can approximate representation group delay.Modulation method is by 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.Transponder input radio frequency carries out frequency sweep on a band frequency, and transponder output signal is demodulated, by the phase bit comparison of the phase place of restituted signal and original baseband signal, thereby obtains the time delay of the each Frequency point of passage.The time delay that the method obtains is the absolute time delay of each Frequency point in transmission passband, can not accurately reflect the passage null value of the specific RDSS business of RDSS channel transfer spread-spectrum signal.

Document " the Group Delay Measurement method research based on spread-spectrum signal " (always 312 phase pp8～11 of " modern electronic technology " the 1st phase in 2010, author: the sea of sand, Zhu Xiangwei, Zhang Guozhu, Sun Guangfu) relevant group delay method of testing of employing spread-spectrum signal of proposition, but the method requires the input and output of measured piece necessary with frequently, and the input and output frequency difference of radio determination service passage, therefore the 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 deficiencies in the prior art, the passage null value calibration system that a kind of stated accuracy is high, can accurately reflect transmission specific spread spectrum code rate RDSS business spread-spectrum signal 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, the first attenuator, the second attenuator, control and process computer and vector network analyzer, wherein:

Spread-spectrum signal source: produce the spread-spectrum signal of an intermediate frequency carrier modulation, 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 intermediate frequency carrier modulated spread spectrum signal that spread-spectrum signal source is produced is carried out frequency translation, and the centre frequency that the signal center frequency after conversion is corresponding with radiodetermination-satellite service channel input signal is consistent;

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

The first attenuator: the input of sending into radiodetermination-satellite service passage after the signal transmitting is decayed;

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

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

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

Carrier wave rotary module: in two complex data groups that channel data orthogonalization module is obtained one as with reference to array, another is as processing array, by carrier wave circulator, with reference frequency and the difference on the frequency f that processes frequency _ccentered by, stepping amount is f _t, within the scope of ± Δ f, generate frequency sweep point

carry out carrier wave rotation to processing 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, and processing frequency is the centre frequency of processing array;

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

Null value computing module: the peak value of the amplitude square that search circulation auto-correlation processing module obtains, determine the sample point sequence number value that peak point is corresponding, and sample point sequence number value corresponding peak point is multiplied 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 more than the twice of highest frequency in radiodetermination-satellite service passage input spread-spectrum signal or output spread-spectrum signal.

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

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

l _codefor the chip number comprising in the pseudo noise code cycle; And L=2 ^k, k is an integer.

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

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

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

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

(4) system of the present invention has been utilized 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 relevant treatment does not affect the accuracy of measurement, can greatly reduce operand; And the input/output signal of passage carries out cross correlation process, do not need signal to carry out the acquisition and tracking of spread-spectrum signal, reduce complexity and the operand processed, calibration algorithm is realized simple.

Accompanying drawing explanation

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

Fig. 2 is the channel input signal spectrogram of simulating in the embodiment of the present invention;

Fig. 3 is the passage output signal spectrum figure simulating in the embodiment of the present invention;

Fig. 4 is input-output wave shape figure when channel time delay is 300ns in the embodiment of the present invention;

Fig. 5 is the relevant amplitude square curve chart of input and output in the embodiment of the present invention with peak value.

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 for generation of the spread-spectrum signal of an intermediate frequency carrier modulation, and 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 product intermediate frequency synthetical baseband processor CORTEX QRT-XL of company 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.

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

The output signal merit of frequency converter is divided into two-way by power divider, and a road is input to oscillographic the first input channel of two-channel digital, and the first attenuator is sent on another road; Here, adopting power divider is Agilent formula product 11636B, and it is 5dB that signal distributes Insertion Loss.

Attenuator 1 is sent into the input of radiodetermination-satellite service passage after the signal transmitting is decayed; Here attenuator 1 is chosen as 1dB～121dB adjustable attenuator, operating frequency range 0～10GHz.

Attenuator 2 is sent into oscillographic the second input channel of two-channel digital after the output signal of radiodetermination-satellite service passage is decayed; Selecting attenuator 2 is 30dB250W high power attenuator, operating frequency range 0～10GHz.

Two-channel digital oscilloscope: the signal of two input channels is carried out to synchronized sampling, and when synchronized sampling, unitary sampling duration length equals the pseudo noise code cycle of a radiodetermination-satellite service signal; 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 single channel storage depth is 100M.

Control and the processing such as process computer completes 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 for proofreading and correct the time delay of stube cable, attenuator, power splitter.Here the E8362B that adopts Agilent company, working frequency range is up to 26.5GHz, and time delay calibrated error is 0.1ns.

Concrete demarcation implementation procedure is as follows:

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

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

3, the time delay and link Insertion Loss in the path delay of time that outputs to A/D converter 2 with vector network analyzer calibration RDSS service channel, this chain-circuit time delay amount is t _downns, 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 to RDSS passage, and passage to be measured powers up and calibration system device power-on.

5, control and process computer operation digital oscilloscope initialization module, complete the connection setup that oscillographic network is connected, controlled process computer and digital oscilloscope, the sample rate of digital oscilloscope is set, more than requiring the twice of proportion higher than RDSS passage input and output signal highest frequency.Here RDSS passage is output as 3950.3MHz.Selection has adopted as 10GSa/s, triggering mode single step mode, to RDSS passage, binary channels synchronous data collection is carried out in input and output, and sampled data length is 1ms, the sampled data output number of RDSS passage input and output signal is 1e7, between each sample point, is spaced apart 0.1ns;

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

between an integer, wherein N is the sampled point number comprising in pseudo noise code cycle in radiodetermination-satellite service signal, requirement l _codefor the chip number comprising 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,

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, L=1048576.

Start anew, intercept input sampling data:

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

To input sampling data, Hilbert transform forms plural number:

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

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

Start anew, intercept output sampled data:

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

To output sampled data, Hilbert transform forms plural number:

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

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

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

For two complex data groups, using one of them complex data group as with reference to array, the centre frequency of reference array is reference frequency f _ref, another one complex data group, as processing array, is processed the centre frequency of array for processing frequency f _process; Frequency difference f between computing reference frequency and processing frequency _c.

f _c＝f _ref-f _process (7)

With f _ccentered by, stepping amount is f _t, within the scope of ± Δ f, generate 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 take RDSS passage output center frequency as reference frequency f _ref=3950.3MHz, input centre frequency is for processing frequency f _process=1615.7MHz, the frequency difference f between reference frequency and processing frequency _c=3950.3-1615.7=2334.6MHz, stepping amount f _tget 200Hz, Δ f gets 1kHz, and 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.

Frequency sweep frequency

shi Zaibo rotation value is:

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

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

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 completing the plural ordered series of numbers Fourier transform respectively of the postrotational input and output of carrier wave, then carry out conjugate multiplication:

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

In formula, FFT () represents ordered series of numbers in () to carry out fast fourier transform.

Then carry out inverse Fourier transform and amplitude square:

A＝|IFFT(Y)| ² (14)

In formula, IFFT () represents ordered series of numbers in () to carry out fast adverse Fourier transform.

For frequency sweep point, carrier wave rotary module carries out carrier wave rotation to the plural array of reference successively to be processed, and after often 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, carry out peak value searching to all outputs of circulation auto-correlation module, obtains the sample point sequence number N that peak point is corresponding _channel, calculate passage 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 formula: t _lrepresent that RDSS service signal source outputs to the path delay of time of A/D converter 1;

T _uprepresent that RDSS service signal source outputs to the path delay of time of RDSS service channel input;

T _downrepresent that 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.Have the amplitude square curve of correlation peak as shown in Figure 5, on ground, there is amplitude peak in 3000 sample places, is 3000 sample points thereby obtain passage null value.Sample frequency is 10GHz, and sample point is spaced apart 0.1ns, and therefore, passage null value is 3000 × 0.1=300ns, consistent with emulation set point.

The content not being described in detail in 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, the first attenuator, the second attenuator, control and process computer and vector network analyzer, wherein:

Spread-spectrum signal source: produce the spread-spectrum signal of an intermediate frequency carrier modulation, 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 intermediate frequency carrier modulated spread spectrum signal that spread-spectrum signal source is produced is carried out frequency translation, and the centre frequency that the signal center frequency after conversion is corresponding with radiodetermination-satellite service channel input signal is consistent;

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

The first attenuator: the input of sending into radiodetermination-satellite service passage after the signal transmitting is decayed;

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

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

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

Carrier wave rotary module: in two complex data groups that channel data orthogonalization module is obtained one as with reference to array, another is as processing array, by carrier wave circulator, with reference frequency and the difference on the frequency f that processes frequency _ccentered by, stepping amount is f _t, within the scope of ± Δ f, generate frequency sweep point carry out carrier wave rotation to processing 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, and processing frequency is the centre frequency of processing array;

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

Null value computing module: the peak value of the amplitude square that search circulation auto-correlation processing module obtains, determine the sample point sequence number value that peak point is corresponding, and sample point sequence number value corresponding peak point is multiplied 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 more than the twice of highest frequency in radiodetermination-satellite service passage input spread-spectrum signal or output 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 is

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

l _codefor the chip number comprising in the pseudo noise code cycle; And L=2 ^k, k is an integer.

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