CN101902288B - Method for measuring delay of direct sequence spread spectrum binary phase shift keying modulator - Google Patents

Abstract

The invention discloses a method for measuring delay of a direct sequence spread spectrum binary phase shift keying modulator. Data despreading and demodulation and delay dependence are taken as cores, the delay measurement of input/output signals with different frequencies and different waveforms of the direct sequence spread spectrum binary phase shift keying modulator is converted into the delay measurement of signals with the same frequency and the same waveform, and is implemented by a created system. Digital signals are divided into two paths by a baseband signal generator (1) through a power divider (2), one path of digital signals pass through a direct sequence spread spectrum binary phase shift keying modulator (3) to be tested and enter a high-speed data acquisition unit (4), and the other path of digital signals are directly output by the power divider (2) to the high-speed data acquisition unit (4). A demodulation module (5) and a dispreading module (6) respectively perform demodulation and despreading processing on the acquired signals, and a delay-dependent module (7) calculates the delay of the two paths of signals. The method ensures that additional delay caused by hardware is not introduced in the measuring process, and can ensure the delay measuring accuracy less than 500ps when the sampling rate is 4GSa/s.

Description

A kind of method of measurement of delay of direct sequence spread spectrum binary phase shift keying modulator

Technical field

The present invention relates to the method for measurement of a kind of method of measurement of spread spectrum modulator time delay, particularly a kind of delay of direct sequence spread spectrum binary phase shift keying modulator.

Background technology

Along with the develop rapidly of science and technology, the requirement of the accuracy of measurement of adjusting the distance in the fields such as satellite fix, satellite navigation, space flight range finding is more and more higher, and accurately the key of measuring distance is the accurate measurement of time delay.In Modern Communication System, in order to reach the purposes such as anti-noise, anti-interference, secure communication, usually adopt the modulation-demodulation device with complex modulation system in transceiver.Modulator is as the part of communication link, and the time delay component of himself has certain impact to final measurement result, only has the time delay of this part is made accurate measurement can to guarantee to locate precision with time service.

Domestic and international research to time-delay measuring method at present mainly concentrates on two large class measured pieces: the one, and most with the frequency devices; The 2nd, a small amount of frequency conversion device as relatively simple in this class working method of frequency mixer.For the latency measurement with the frequency device, its measuring instrument and method of measurement develop comparatively perfectly, as use the network analyzer of high accuracy to carry out latency measurement accurately to devices such as air line, cable, altimeters, its accuracy of measurement can reach picosecond magnitude; Latency measurement for the frequency conversion device of the relative complex such as frequency mixer had obtained paying close attention to widely in the last few years, each research institution has also carried out a large amount of research, frequency converter method of measurement through experimental verification comparison reasonable has wide-band oscilloscope method and network analyzer frequency conversion mensuration, and accuracy of measurement is at nanosecond order.

Network analyzer frequency conversion mensuration is realized by vector network analyzer, vector network analyzer can the Measurement accuracy time delay prerequisite be that measured piece has good linear phase characteristic, and for spread spectrum modulator, its output signal has been passed through the complicated modulation system such as band spectrum modulation, binary phase shift keying modulation for input signal, video stretching, signal form is complicated, this system under test (SUT) is non linear system, be not suitable for fully with vector network analysis, its phase place being measured, can't have measured its time delay.

The wide-band oscilloscope method is to utilize wide-band oscilloscope to have the characteristics of high-speed data acquisition speed and large storage depth, the measured piece input-output wave shape is sampled, for the temporal information characteristic point, as rising edge, commutation point etc., calculate in the variation that enters the measured piece front and back position time delay is estimated.Yet when measurand is spread spectrum modulator, no longer applicable in this way.For example information code to be transmitted is 1010, spreading code is 7 PN codes 1001110, as seen become for 0 the moment in information code by 1, saltus step does not occur in spreading code, the output signal of measured piece is continuous, without the temporal information characteristic point, do not have and base band benchmark relatively, so can't measure the time delay of spread spectrum modulator with the wide-band oscilloscope method yet.On the other hand, the accuracy of this method depends on the judgement of exchange phase point position, and accuracy of measurement is not high.

Summary of the invention

The object of the present invention is to provide a kind of method of measurement of delay of direct sequence spread spectrum binary phase shift keying modulator, solve the problem that existing routine techniques is difficult to the Measurement accuracy delay of direct sequence spread spectrum binary phase shift keying modulator.

A kind of concrete steps of method of measurement of delay of direct sequence spread spectrum binary phase shift keying modulator are:

The first step, set up the latency measurement system, described latency measurement system comprises: baseband signal generator, power splitter, tested direct sequence spread spectrum binary phase shift keying modulator, high speed data acquisition system, demodulation module, despreading module, time delay correlation module, cable A, cable B, cable C.

Wherein, baseband signal generator is connected with power splitter, and the cable A of leading up to of power splitter is connected with high speed data acquisition system.Another road of power splitter is connected with tested direct sequence spread spectrum binary phase shift keying modulator by cable B, and the output port of tested direct sequence spread spectrum binary phase shift keying modulator is connected with high speed data acquisition system by cable C.High speed data acquisition system is connected with demodulation module by data/address bus, is connected by data/address bus between demodulation module and despreading module, is connected by data/address bus between despreading module and time delay correlation module.

Second step, the high speed data acquisition system collection signal is specially:

The baseband signal that baseband signal generator produces is divided into two-way through power splitter, and one the tunnel enters high speed data acquisition system through cable A, and this road is reference channel; Another road signal enters high speed data acquisition system after cable B, tested direct sequence spread spectrum binary phase shift keying modulator, cable C, this road is test channel.High speed data acquisition system carries out synchronous high-speed, high precision sampling to this two paths of signals.

In the 3rd step, demodulation module carries out the data demodulates computing, is specially:

Demodulation module carries out the demodulation computing to the data of the test channel that collects from high speed data acquisition system, and modulated spread spectrum signal is reverted to spread baseband signal.

The demodulation computing realizes with Digital Costas Loop, and the modulated bandpass signal that receives is transformed into analytic signal, and carrier frequency and the initial phase of signal are done the estimation computing, and the estimation range of carrier frequency is carrier frequency ± 1% carrier frequency.Following steps are adopted in the estimation of carrier wave initial phase: with the Hilbert transform method of operational formula (1), collection signal x (t) is carried out Hilbert transform and get analytic signal x ₊(t), the imaginary part of analytic signal is orthogonal signalling

$H\left[x\left(t\right)\right]=x_{+}\left(t\right)=x\left(t\right)+j\hat{x}\left(t\right)---\left(1\right)$

With these orthogonal signalling

Be divided by with formula (2) with original signal x (t) and do arctangent cp cp operation, the phase place that obtains estimating

With the analytic signal x in formula (1) ₊(t) multiply by such carrier frequency ω that band is estimated _cAnd phase place

Complex signal after namely obtain the low pass complex envelope of original signal

As shown in formula (3).

When loop is all estimated when correct carrier frequency and phase place, the real part of low pass complex envelope is exactly to need the spread baseband signal recovered.

In the 4th step, the despreading module is carried out data despreading computing, is specially:

The despreading module is completed the despreading computing of data, and the chip-rate that receiving terminal is known is f _pn, sample rate is f _s, the sampling number N=f in spread-spectrum code chip _s/ f _pnΔ f _pnBe the maximum of PN code frequency deviation, chip maximum deviation of PN code is counted The sampling number that arranges in spread-spectrum code chip of receiving terminal PN code correlator is (N-N ₁: N+N ₁), with (2N ₁+ 1) individual different PN code correlator respectively to demodulation after signal do and slide relevantly, related operation is (4) calculating by formula:

$R_{\mathrm{xy}}\left(\mathrm{m\Δt}\right)=\left|\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(\mathrm{k\Δt}\right)y\right[(k+m)\mathrm{\Δt}\left]\right|---\left(4\right)$

In formula (4), x (k Δ t) is the signal after despreading, and y (k Δ t) is the PN coded signal in the PN code correlator, and N is that the PN coded signal is counted, R _xyBe correlation.Get R _xyMaximum R _max, with (2N ₁+ 1) individual different PN code by formula (4) relevant to despread signal, obtain (2N ₁+ 1) individual maximum correlation R _maxThis (2N ₁+ 1) the maximum in individual maximum is the PN code chip-rate in tracking.

The synchronous slip related operation of using of code phase in the despreading module, spreading code that at first will be synchronous and restituted signal by formula (4) carry out related operation, obtain correlation, and abscissa value corresponding to maximum related value is the synchronization point of code phase.Again PN code and restituted signal on synchronous are multiplied each other, namely complete despreading, the baseband signal m that is restored _c

In the 5th step, the time delay correlation module carries out the time delay computing, is specially:

With the baseband signal m that recovers _cWith the baseband signal m that is directly collected by high speed data acquisition system deliver to the time delay correlation module by formula (5) carry out related calculation:

$R_{{\mathrm{mm}}_c}=\left|\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}m\left(\mathrm{k\Δt}\right)m_c\right[(k+m)\mathrm{\Δt}\left]\right|---\left(5\right)$

Obtain the maximum of relevant peaks, transverse axis coordinate corresponding to note relevant peaks maximum is X _N, getting abscissa is X _N-2, X _N-1, X _N, X _N+1, X _N+2These five points are done the cubic spline interpolation computing in the time delay correlation module, obtain the relevant peaks of refinement, and abscissa corresponding to the relevant peaks maximum of refinement is the time delay T of tested direct sequence spread spectrum binary phase shift keying modulator constantly ₁

The 6th step, set up the time delay calibration system, be specially:

With the tested direct sequence spread spectrum binary phase shift keying modulator in the latency measurement system, demodulation module, the deletion of despreading module.Baseband signal generator is connected with power splitter, and the cable A of leading up to of power splitter is connected with high speed data acquisition system.Another road of power splitter is connected with high speed data acquisition system by cable B, cable C, and high speed data acquisition system is connected with the time delay correlation module by data/address bus, thereby obtains the time delay calibration system.

The 7th step, measure initial time delay, be specially:

The baseband signal that baseband signal generator produces is divided into two-way through power splitter, and one the tunnel enters high speed data acquisition system through cable A; Another road signal enters high speed data acquisition system after cable B, cable C, high speed data acquisition system carries out the high-speed, high precision sampling to the signal of two passages simultaneously, and sampled data is delivered to the time delay correlation module and processed.

Data processing method in the time delay correlation module by formula (5) carries out related operation to the two paths of signals that time delay calibration system high speed data acquisition unit collects, and m (t) is for entering the data in high speed data acquisition system, m through cable A _c(t) for to enter the data in high speed data acquisition system through cable B, cable C, be respectively m (k Δ t) and m after two groups of data process high speed data acquisition systems (4) _c(k Δ t) is with m (k Δ t) and m _c(k Δ t) pointwise is multiplied each other, and the results added that multiplies each other obtains a correlation, then with m _c(k Δ t) signal slides to multiply each other with m (k Δ t) signal pointwise behind a data collection point and results added is obtained second correlation again, by that analogy, finally obtains correlation curve.

Obtain the maximum of relevant peaks, transverse axis coordinate corresponding to note relevant peaks maximum is X ' _N, getting abscissa is X ' _N-2, X ' _N-1, X ' _N, X ' _N+1, X ' _N+2These five points are done the cubic spline interpolation computing in the time delay correlation module, obtain the relevant peaks of refinement, and abscissa corresponding to the relevant peaks maximum of refinement is the time delay T of two paths of signals constantly ₀, be initial time delay.In the result that tested delay of direct sequence spread spectrum binary phase shift keying modulator is measured, initial time delay is deducted, obtain the time delay value Δ T of tested direct sequence spread spectrum binary phase shift keying modulator, Δ T=T ₁-T ₀

Have narrow pulse pattern generator along characteristic for improving accuracy of measurement, should choosing as the signal source of baseband signal generator, it is 0.8ns along the time that rise and fall are set; High speed data acquisition system has the sampling rate of 4GSa/s, to guarantee that sampling resolution is as 250ps; Coordinate data processing calculating can guarantee time delay measures uncertainty＜500ps after satisfying above-mentioned condition.

The delay of direct sequence spread spectrum binary phase shift keying modulator method of measurement that the present invention proposes, the thought of software radio is introduced in the delay of direct sequence spread spectrum binary phase shift keying modulator measurement, adopt high speed data acquisition system to carry out high-speed sampling to the input-output wave shape of tested direct sequence spread spectrum binary phase shift keying modulator, the Delay between having kept both.With the data processing method demodulation with the modulating wave of output revert to can with baseband signal baseband waveform relatively, with difference frequently between different wave mode signals the latency measurement problem convert to frequently with wave mode signal measurement problem.Solve at present existing measuring instrument and method of measurement and can't measure the problem of delay of direct sequence spread spectrum binary phase shift keying modulator.And the demodulation algorithm can guarantee not introduce additional time delay in measuring process, when the data collecting card sample rate is 4GSap/s, after adopting the relevant peaks refinement, can guarantee latency measurement accuracy＜500ps.

Description of drawings

The described measuring system figure of the method for measurement of a kind of delay of direct sequence spread spectrum binary phase shift keying modulator of Fig. 1;

The described calibration system figure of the method for measurement of a kind of delay of direct sequence spread spectrum binary phase shift keying modulator of Fig. 2.

1. baseband signal generator 2. tested direct sequence spread spectrum binary phase shift keying modulators of power splitter 3.

4. high speed data acquisition system 5. demodulation module 6. despreading module 7. time delay correlation module 8. cable A

9. cable B 10. cable C

Embodiment

A kind of concrete steps of method of measurement of delay of direct sequence spread spectrum binary phase shift keying modulator are:

The first step, set up the latency measurement system, described latency measurement system comprises: baseband signal generator 1, power splitter 2, tested direct sequence spread spectrum binary phase shift keying modulator 3, high speed data acquisition system 4, demodulation module 5, despreading module 6, time delay correlation module 7, cable A8, cable B9, cable C10.

Wherein, baseband signal generator 1 is connected with power splitter 2, and the cable A8 of leading up to of power splitter 2 is connected with high speed data acquisition system 4.Another road of power splitter 2 is connected with tested direct sequence spread spectrum binary phase shift keying modulator 3 by cable B9, and the output port of tested direct sequence spread spectrum binary phase shift keying modulator 3 is connected with high speed data acquisition system 4 by cable C10.High speed data acquisition system 4 is connected with demodulation module 5 by data/address bus, is connected by data/address bus between demodulation module 5 and despreading module 6, is connected by data/address bus between despreading module 6 and time delay correlation module 7.

Second step, high speed data acquisition system 4 collection signals are specially:

The baseband signal that baseband signal generator 1 produces is divided into two-way through power splitter 2, and one the tunnel enters high speed data acquisition system 4 through cable A8, and this road is reference channel; Another road signal enters high speed data acquisition system 4 after cable B9, tested direct sequence spread spectrum binary phase shift keying modulator 3, cable C10, this road is test channel.High speed data acquisition system 4 carries out synchronous high-speed, high precision sampling to this two paths of signals.

In the 3rd step, demodulation module 5 carries out the data demodulates computing, is specially:

5 pairs of demodulation modules carry out the demodulation computing from the data of the test channel that high speed data acquisition system 4 collects, and modulated spread spectrum signal is reverted to spread baseband signal.

The demodulation computing realizes with Digital Costas Loop, and the modulated bandpass signal that receives is transformed into analytic signal, and carrier frequency and the initial phase of signal are done the estimation computing, and the estimation range of carrier frequency is carrier frequency ± 1% carrier frequency.Following steps are adopted in the estimation of carrier wave initial phase: with the Hilbert transform method of operational formula (1), collection signal x (t) is carried out Hilbert transform and get analytic signal x ₊(t), the imaginary part of analytic signal is orthogonal signalling

$H\left[x\left(t\right)\right]=x_{+}\left(t\right)=x\left(t\right)+j\hat{x}\left(t\right)---\left(1\right)$

With these orthogonal signalling

Be divided by with formula (2) with original signal x (t) and do arctangent cp cp operation, the phase place that obtains estimating

With the analytic signal x in formula (1) ₊(t) multiply by such carrier frequency ω that band is estimated _cAnd phase place

Complex signal after namely obtain the low pass complex envelope of original signal

As shown in formula (3).

When loop is all estimated when correct carrier frequency and phase place, the real part of low pass complex envelope is exactly to need the spread baseband signal recovered.

In the 4th step, despreading module 6 is carried out data despreading computing, is specially:

Despreading module 6 is completed the despreading computing of data, and the chip-rate that receiving terminal is known is f _pn=10MHz, sample rate is f _s=4GHz, the sampling number N=f that spread-spectrum code chip is interior _s/ f _pn=400.Δ f _pn=25kHz is the maximum of PN code frequency deviation, and chip maximum deviation of PN code is counted The sampling number that arranges in spread-spectrum code chip of receiving terminal PN code correlator is (399:401), with 3 different PN code correlators respectively to demodulation after signal do and slide relevantly, related operation is (4) calculating by formula:

$R_{\mathrm{xy}}\left(\mathrm{m\Δt}\right)=\left|\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(\mathrm{k\Δt}\right)y\right[(k+m)\mathrm{\Δt}\left]\right|---\left(4\right)$

In formula (4), x (k Δ t) is the signal after despreading, and y (k Δ t) is the PN coded signal in the PN code correlator, and N is that the PN coded signal is counted, R _xyBe correlation.Get R _xyMaximum R _max, with (2N ₁+ 1) individual different PN code by formula (4) relevant to despread signal, obtain 3 maximum correlation R _maxThe maximum in these 3 maximums is the PN code chip-rate in tracking.

The synchronous slip related operation of using of code phase in despreading module 6, spreading code that at first will be synchronous and restituted signal by formula (4) carry out related operation, obtain correlation, and abscissa value corresponding to maximum related value is the synchronization point of code phase.Again PN code and restituted signal on synchronous are multiplied each other, namely complete despreading, the baseband signal m that is restored _c

In the 5th step, time delay correlation module 7 carries out the time delay computing, is specially:

With the baseband signal m that recovers _cWith the baseband signal m that is directly collected by high speed data acquisition system 4 deliver to time delay correlation module 7 by formula (5) carry out related calculation:

$R_{{\mathrm{mm}}_c}=\left|\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}m\left(\mathrm{k\Δt}\right)m_c\right[(k+m)\mathrm{\Δt}\left]\right|---\left(5\right)$

Obtain the maximum of relevant peaks, transverse axis coordinate corresponding to note relevant peaks maximum is 11232, getting abscissa is that 11230,11231,11232,11233,11234 these five points are done the cubic spline interpolation computing in time delay correlation module 7, obtain the relevant peaks of refinement, abscissa corresponding to the relevant peaks maximum of refinement is the time delay T of tested direct sequence spread spectrum binary phase shift keying modulator 3 constantly ₁=49.55ns.

The 6th step, set up the time delay calibration system, be specially:

With the tested direct sequence spread spectrum binary phase shift keying modulator 3 in the latency measurement system, demodulation module 5,6 deletions of despreading module.Baseband signal generator 1 is connected with power splitter 2, and the cable A8 of leading up to of power splitter 2 is connected with high speed data acquisition system 4.Another road of power splitter 2 is connected with high speed data acquisition system 4 by cable B9, cable C10, and high speed data acquisition system 4 is connected with time delay correlation module 7 by data/address bus, thereby obtains the time delay calibration system.

The 7th step, measure initial time delay, be specially:

The baseband signal that baseband signal generator 1 produces is divided into two-way through power splitter 2, and one the tunnel enters high speed data acquisition system 4 through cable A8; Another road signal enters high speed data acquisition system 4 after cable B9, cable C10, high speed data acquisition system 4 carries out the high-speed, high precision sampling to the signal of two passages simultaneously, and sampled data is delivered to time delay correlation module 7 and processed.

Data processing method in time delay correlation module 7 by formula (5) carries out related operation to the two paths of signals that time delay calibration system high speed data acquisition unit 4 collects, and m (t) is for entering the data in high speed data acquisition system 4, m through cable A8 _c(t) for to enter the data in high speed data acquisition system 4 through cable B9, cable C10, be respectively m (k Δ t) and m after two groups of data process high speed data acquisition systems (4) _c(k Δ t) is with m (k Δ t) and m _c(k Δ t) pointwise is multiplied each other, and the results added that multiplies each other obtains a correlation, then with m _c(k Δ t) signal slides to multiply each other with m (k Δ t) signal pointwise behind a data collection point and results added is obtained second correlation again, by that analogy, finally obtains correlation curve.

Obtain the maximum of relevant peaks, transverse axis coordinate corresponding to note relevant peaks maximum is 11192, getting abscissa is that 11190,11191,11192,11193,11194 these five points are done the cubic spline interpolation computing in time delay correlation module 7, lead the relevant peaks of refinement, abscissa corresponding to the relevant peaks maximum of refinement is the time delay T0 of two paths of signals constantly, is initial time delay.In the result of tested direct sequence spread spectrum binary phase shift keying modulator 3 latency measurements, initial time delay is deducted, obtain the time delay value Δ T=39.73ns of tested direct sequence spread spectrum binary phase shift keying modulator 3, Δ T=T ₁-T ₀=9.82ns.

Have narrow pulse pattern generator along characteristic for improving accuracy of measurement, should choosing as the signal source of baseband signal generator 1, it is 0.8ns along the time that rise and fall are set; High speed data acquisition system 4 has the sampling rate of 4GSa/s, to guarantee that sampling resolution is as 250ps; Coordinate data processing calculating can guarantee time delay measures uncertainty＜500ps after satisfying above-mentioned condition.

Claims (1)

1. the method for measurement of a delay of direct sequence spread spectrum binary phase shift keying modulator is characterized in that the concrete steps of the method are:

The first step, set up the latency measurement system, described latency measurement system comprises: baseband signal generator (1), power splitter (2), tested direct sequence spread spectrum binary phase shift keying modulator (3), high speed data acquisition system (4), demodulation module (5), despreading module (6), time delay correlation module (7), cable A (8), cable B (9), cable C (10);

Wherein, baseband signal generator (1) is connected with power splitter (2), and the cable A (8) of leading up to of power splitter (2) is connected with high speed data acquisition system (4); Another road of power splitter (2) is connected with tested direct sequence spread spectrum binary phase shift keying modulator (3) by cable B (9), and the output port of tested direct sequence spread spectrum binary phase shift keying modulator (3) is connected with high speed data acquisition system (4) by cable C (10); High speed data acquisition system (4) is connected with demodulation module (5) by data/address bus, be connected by data/address bus between demodulation module (5) and despreading module (6), be connected by data/address bus between despreading module (6) and time delay correlation module (7);

Second step, high speed data acquisition system (4) collection signal is specially:

The baseband signal that baseband signal generator (1) produces is divided into two-way through power splitter (2), and one the tunnel enters high speed data acquisition system (4) through cable A (8), and this road is reference channel; Another road signal enters high speed data acquisition system (4) after cable B (9), tested direct sequence spread spectrum binary phase shift keying modulator (3), cable C (10), this road is test channel; High speed data acquisition system (4) carries out synchronous high-speed, high precision sampling to this two paths of signals;

In the 3rd step, demodulation module (5) carries out the data demodulates computing, is specially:

Demodulation module (5) carries out the demodulation computing to the data of the test channel that collects from high speed data acquisition system (4), and modulated spread spectrum signal is reverted to spread baseband signal;

The demodulation computing realizes with Digital Costas Loop, and the modulated bandpass signal that receives is transformed into analytic signal, and carrier frequency and the initial phase of signal are done the estimation computing, and the estimation range of carrier frequency is carrier frequency ± 1% carrier frequency; Following steps are adopted in the estimation of carrier wave initial phase: with the Hilbert transform method of operational formula (1), collection signal x (t) is carried out Hilbert transform and get analytic signal x ₊(t), the imaginary part of analytic signal is orthogonal signalling

$H\left[x\left(t\right)\right]=x_{+}\left(t\right)=x\left(t\right)+j\hat{x}\left(t\right)---\left(1\right)$

With these orthogonal signalling Be divided by with formula (2) with original signal x (t) and do arctangent cp cp operation, the phase place that obtains estimating

With the analytic signal x in formula (1) ₊(t) multiply by such carrier frequency ω that band is estimated _cAnd phase place

Complex signal after namely obtain the low pass complex envelope of original signal

As shown in formula (3);

When loop is all estimated when correct carrier frequency and phase place, the real part of low pass complex envelope is exactly to need the spread baseband signal recovered;

In the 4th step, despreading module (6) is carried out data despreading computing, is specially:

Despreading module (6) is completed the despreading computing of data, and the chip-rate that receiving terminal is known is f _pn, sample rate is f _s, the sampling number N=f in spread-spectrum code chip _s/ f _pnΔ f _pnBe the maximum of PN code frequency deviation, chip maximum deviation points N of PN code ₁=f _s/ Δ f _pnThe sampling number that arranges in spread-spectrum code chip of receiving terminal PN code correlator is (N-N ₁: N+N ₁), with (2N ₁+ 1) individual different PN code correlator respectively to demodulation after signal do and slide relevantly, related operation is (4) calculating by formula:

$R_{\mathrm{xy}}\left(\mathrm{m\Δt}\right)=\left|\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}x\left(\mathrm{k\Δt}\right)y\right[(k+m)\mathrm{\Δt}\left]\right|---\left(4\right)$

In formula (4), x (k Δ t) is the signal after despreading, and y (k Δ t) is the PN coded signal in the PN code correlator, and N is that the PN coded signal is counted, R _xyBe correlation; Get R _xyMaximum R _max, with (2N ₁+ 1) individual different PN code by formula (4) relevant to despread signal, obtain (2N ₁+ 1) individual maximum correlation R _maxThis (2N ₁+ 1) the maximum in individual maximum is the PN code chip-rate in tracking;

The synchronous slip related operation of using of code phase in despreading module (6), spreading code that at first will be synchronous and restituted signal by formula (4) carry out related operation, obtain correlation, and abscissa value corresponding to maximum related value is the synchronization point of code phase; Again PN code and restituted signal on synchronous are multiplied each other, namely complete despreading, the baseband signal m that is restored _c

In the 5th step, time delay correlation module (7) carries out the time delay computing, is specially:

With the baseband signal m that recovers _cWith the baseband signal m that is directly collected by high speed data acquisition system (4) deliver to time delay correlation module (7) by formula (5) carry out related calculation:

$R_{{\mathrm{mm}}_c}=\left|\frac{1}{N}\underset{k=0}{\overset{N-1}{\mathrm{\Σ}}}m\left(\mathrm{k\Δt}\right)m_c\right[(k+m)\mathrm{\Δt}\left]\right|---\left(5\right)$

Obtain the maximum of relevant peaks, transverse axis coordinate corresponding to note relevant peaks maximum is X _N, getting abscissa is X _N-2, X _N-1, X _N, X _N+1, X _N+2These five points are done the cubic spline interpolation computing in time delay correlation module (7), obtain the relevant peaks of refinement, and abscissa corresponding to the relevant peaks maximum of refinement is the time delay T of tested direct sequence spread spectrum binary phase shift keying modulator (3) constantly ₁

The 6th step, set up the time delay calibration system, be specially:

With the tested direct sequence spread spectrum binary phase shift keying modulator (3) in the latency measurement system, demodulation module (5), despreading module (6) deletion; Baseband signal generator (1) is connected with power splitter (2), and the cable A (8) of leading up to of power splitter (2) is connected with high speed data acquisition system (4); Another road of power splitter (2) is connected with high speed data acquisition system (4) by cable B (9), cable C (10), high speed data acquisition system (4) is connected with time delay correlation module (7) by data/address bus, thereby obtains the time delay calibration system;

The 7th step, measure initial time delay, be specially:

The baseband signal that baseband signal generator (1) produces is divided into two-way through power splitter (2), and one the tunnel enters high speed data acquisition system (4) through cable A (8); Another road signal enters high speed data acquisition system (4) after cable B (9), cable C (10), high speed data acquisition system (4) carries out the high-speed, high precision sampling to the signal of two passages simultaneously, and sampled data is delivered to time delay correlation module (7) and processed;

Data processing method in time delay correlation module (7) by formula (5) carries out related operation to the two paths of signals that time delay calibration system high speed data acquisition unit (4) collects, m (t) is for entering the data in high speed data acquisition system (4), m through cable A (8) _c(t) for to enter the data in high speed data acquisition system (4) through cable B (9), cable C (10), be respectively m (k Δ t) and m after two groups of data process high speed data acquisition systems (4) _c(k Δ t) is with m (k Δ t) and m _c(k Δ t) pointwise is multiplied each other, and the results added that multiplies each other obtains a correlation, then with m _c(k Δ t) signal slides to multiply each other with m (k Δ t) signal pointwise behind a data collection point and results added is obtained second correlation again, by that analogy, finally obtains correlation curve;

Obtain the maximum of relevant peaks, transverse axis coordinate corresponding to note relevant peaks maximum is X ' _N, getting abscissa is X ' _N-2, X ' _N-1, X ' _N, X ' _N+1, X ' _N+2These five points are done the cubic spline interpolation computing in time delay correlation module (7), obtain the relevant peaks of refinement, and abscissa corresponding to the relevant peaks maximum of refinement is the time delay T of two paths of signals constantly ₀, be initial time delay; In the result of tested direct sequence spread spectrum binary phase shift keying modulator (3) latency measurement, initial time delay is deducted, obtain the time delay value Δ T of tested direct sequence spread spectrum binary phase shift keying modulator (3), Δ T=T ₁-T ₀

Have narrow pulse pattern generator along characteristic for improving accuracy of measurement, should choosing as the signal source of baseband signal generator (1), it is 0.8ns along the time that rise and fall are set; High speed data acquisition system (4) has the sampling rate of 4GSa/s, to guarantee that sampling resolution is as 250ps; Coordinate data processing calculating can guarantee time delay measures uncertainty＜500ps after satisfying above-mentioned condition.

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