CN101902288A - 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 a kind of method of measurement of spread spectrum modulator Delay Measurement, 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 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,, adopt modulation-demodulation device in the transceiver usually with complex modulation system in order to reach purposes such as anti-noise, anti-interference, secure communication.Modulator is as the part of communication link, and the time delay component of himself has certain influence to The ultimate results, has only the time delay of this part is made accurate measurement can to guarantee to locate precision with time service.

The domestic and international at present research to time-delay measuring method mainly concentrates on the two big class measured pieces: the one, and most with the frequency devices; The 2nd, on a small quantity as the simple relatively frequency conversion device of this class working method of frequency mixer.For 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 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, through the relatively more reasonable feasible frequency converter method of measurement of experimental verification wide-band oscilloscope method and network analyzer frequency conversion mensuration are arranged, accuracy of measurement is at nanosecond order.

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

The wide-band oscilloscope method is to utilize wide-band oscilloscope to have the characteristics of high-speed data acquisition speed and big storage depth, measured piece input and output waveform 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 it is when measurand is spread spectrum modulator, no longer suitable in this way.Information code for example to be transmitted is 1010, spreading code is 7 PN sign indicating numbers 1001110, as seen become for 0 the moment in information code by 1, saltus step does not take place in spreading code, the output signal of measured piece is continuous, no temporal information characteristic point does 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 to commutation 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 accurately measure 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 is set up the latency measurement system

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

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

The second step high speed data acquisition system acquired signal

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 a reference channel; Another road signal enters high speed data acquisition system behind cable B, tested direct sequence spread spectrum binary phase shift keying modulator, cable C, this road is a test channel.High speed data acquisition system carries out synchronous high-speed, high precision sampling to this two paths of signals.

The data demodulates computing of the 3rd step demodulation module

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 that with digital section Stas ring the modulated bandpass signal that receives is transformed into analytic signal, and the carrier frequency and the initial phase of signal are done the estimation computing, the estimation range of carrier frequency is carrier frequency ± 1% carrier frequency.The estimation of carrier wave initial phase is carried out Hilbert transform with the Hilbert transform method of operational formula (1) to acquired signal x (t) and is got analytic signal

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 the formula (1) ₊(t) multiply by such carrier frequency ω that band is estimated _cAnd phase place Complex signal after promptly obtain the low pass complex envelope of original signal As shown in Equation (3).

When loop is all estimated correctly carrier frequency and phase place, then the real part of low pass complex envelope be exactly need to recover with spread baseband signal.

The data despreading computing of the 4th step despreading module

The despreading module is finished 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 then _s/ f _PnΔ f _PnBe the maximum of PN sign indicating number frequency deviation, then chip maximum deviation of PN sign indicating number is counted

The sampling number that is provided with 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 with 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 the formula (4), x (k Δ t) is the signal after the despreading, and y (k Δ t) is the PN coded signal in the PN code correlator, and N counts for the PN coded signal, R _XyBe correlation.Get R _XyMaximum R _Max, with (2N ₁+ 1) individual different PN sign indicating number by formula (4) relevant with despread signal, obtain (2N ₁+ 1) individual maximum correlation R _MaxThis (2N ₁+ 1) the maximum in the individual maximum is the PN sign indicating number chip-rate in the 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 the abscissa value of maximum related value correspondence is the synchronization point of code phase.Again PN sign indicating number and restituted signal on synchronous are multiplied each other, promptly finish despreading, the baseband signal m that is restored _c

The time delay computing of the 5th step time delay correlation module

With the baseband signal m that recovers _cWith the baseband signal m that directly collects 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, the transverse axis coordinate of note relevant peaks maximum correspondence 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, the refinement relevant peaks that obtains, and the abscissa of the relevant peaks maximum correspondence of refinement is the time delay T of tested direct sequence spread spectrum binary phase shift keying modulator constantly ₁

The 6th step was set up the time delay calibration system

With the tested direct sequence spread spectrum binary phase shift keying modulator in the measuring system, demodulation module, the deletion of despreading module.Baseband signal generator links to each other with power splitter, and power splitter links to each other with high speed data acquisition system by cable A.Another road of power splitter links to each other with high speed data acquisition system by cable B, cable C, and high speed data acquisition system links to each other with the time delay correlation module by data/address bus.Obtain a kind of calibration system of method of measurement of delay of direct sequence spread spectrum binary phase shift keying modulator.

The initial time delay of the 7th pacing amount

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 behind 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 handled.

Data processing method in the time delay correlation module by formula (5) carries out related operation to the two paths of signals that delay of direct sequence spread spectrum binary phase shift keying modulator calibration system high speed data acquisition unit collects, m (t) is for entering the data in the high speed data acquisition system, m through cable A _c(t) for to enter the data in the high speed data acquisition system through cable B, cable C, two groups of data pointwises are multiplied each other, and the multiplied result addition obtains a correlation, again with m _c(t) signal slides behind the data collection point to multiply each other with the pointwise of m (t) signal and results added is obtained second correlation again, by that analogy, finally obtains correlation curve.

Obtain the maximum of relevant peaks, the transverse axis coordinate of note relevant peaks maximum correspondence 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, the refinement relevant peaks that obtains, and the abscissa of the relevant peaks maximum correspondence 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, the time delay initial value 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

Be to improve accuracy of measurement, should choose as the signal source of baseband signal generator and have narrow pulse code type generator along characteristic, the operated by rotary motion rise and fall are 0.8ns along the time; High speed data acquisition system is the sampling rate of 4GSap/s, is 250ps to guarantee sampling resolution; Cooperate 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, idea 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 that the input and output waveform of tested direct sequence spread spectrum binary phase shift keying modulator is carried out high-speed sampling, kept the time delay information between the two.With data processing method demodulation despreading 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 demodulation despreading algorithm can guarantee not introduce additional time delay in measuring process, when the data collecting card sample rate is 4GSap/s, after the refinement of employing relevant peaks, 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. power splitters 3. tested direct sequence spread spectrum binary phase shift keying modulators

4. high speed data acquisition system 5. demodulation modules 6. despreading modules 7. time delay correlation modules 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 is set up the latency measurement system

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

Baseband signal generator 1 links to each other with power splitter 2, and power splitter 2 links to each other with high speed data acquisition system 4 by cable A8.Power splitter 2 another roads link to each other with tested direct sequence spread spectrum binary phase shift keying modulator 3 by cable B9, and tested direct sequence spread spectrum binary phase shift keying modulator 3 output ports link to each other with high speed data acquisition system 4 by cable C10.High speed data acquisition system 4 links to each other with demodulation module 5 by data/address bus, is linked to each other by data/address bus between demodulation module 5 and the despreading module 6, is linked to each other by data/address bus between despreading module 6 and the time delay correlation module 7.

Second step high speed data acquisition system 4 acquired signal

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 a reference channel; Another road signal enters high speed data acquisition system 4 behind cable B9, tested direct sequence spread spectrum binary phase shift keying modulator 3, cable C10, this road is a test channel.High speed data acquisition system 4 carries out synchronous high-speed, high precision sampling to this two paths of signals.

The data demodulates computing of the 3rd step demodulation module 5

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 that with digital section Stas ring the modulated bandpass signal that receives is transformed into analytic signal, and the carrier frequency and the initial phase of signal are done the estimation computing, the estimation range of carrier frequency is carrier frequency ± 1% carrier frequency.The estimation of carrier wave initial phase is carried out Hilbert transform with the Hilbert transform method of operational formula (1) to acquired signal x (t) and is got analytic signal

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

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

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

As shown in Equation (3).

When loop is all estimated correctly carrier frequency and phase place, then the real part of low pass complex envelope be exactly need to recover with spread baseband signal.

The data despreading computing of the 4th step despreading module 6

Despreading module 6 is finished the despreading computing of data, and the chip-rate that receiving terminal is known is f _Pn=10MHz, sample rate is f _s=4GHz, then the sampling number N=f that spread-spectrum code chip is interior _s/ fpn=400.Δ f _Pn=25kHz is the maximum of PN sign indicating number frequency deviation, and then chip maximum deviation of PN sign indicating number is counted

The sampling number that is provided with in spread-spectrum code chip of receiving terminal PN code correlator is (399:401), with 3 different PN code correlators respectively with 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 the formula (4), x (k Δ t) is the signal after the despreading, and y (k Δ t) is the PN coded signal in the PN code correlator, and N counts for the PN coded signal, R _XyBe correlation.Get R _XyMaximum R _Max, with (2N ₁+ 1) individual different PN sign indicating number by formula (4) relevant with despread signal, obtain 3 maximum correlation R _MaxThe maximum in these 3 maximums is the PN sign indicating number chip-rate in the tracking.

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

The time delay computing of the 5th step time delay correlation module 7

With the baseband signal m that recovers _cWith the baseband signal m that directly collects 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, the transverse axis coordinate of note relevant peaks maximum correspondence 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, the refinement relevant peaks that obtains, the abscissa of the relevant peaks maximum correspondence 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 was set up the time delay calibration system

With the tested direct sequence spread spectrum binary phase shift keying modulator 3 in the measuring system, demodulation module 5,6 deletions of despreading module.Baseband signal generator 1 links to each other with power splitter 2, and power splitter 2 links to each other with high speed data acquisition system 4 by cable A8.Another road of power splitter 2 links to each other with high speed data acquisition system 4 by cable B9, cable C10, and high speed data acquisition system 4 links to each other with time delay correlation module 7 by data/address bus.Obtain a kind of calibration system of method of measurement of delay of direct sequence spread spectrum binary phase shift keying modulator.

The initial time delay of the 7th pacing amount

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 behind 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 handled.

Data processing method in the time delay correlation module 7 by formula (5) carries out related operation to the two paths of signals that delay of direct sequence spread spectrum binary phase shift keying modulator calibration system high speed data acquisition unit 4 collects, m (t) is for entering the data in the high speed data acquisition system 4, m through cable A8 _c(t) for to enter the data in the high speed data acquisition system 4 through cable B9, cable C10, two groups of data pointwises are multiplied each other, and the multiplied result addition obtains a correlation, again with m _c(t) signal slides behind the data collection point to multiply each other with the pointwise of m (t) signal and results added is obtained second correlation again, by that analogy, finally obtains correlation curve.

Obtain the maximum of relevant peaks, the transverse axis coordinate of note relevant peaks maximum correspondence 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, the refinement relevant peaks that obtains, the abscissa of the relevant peaks maximum correspondence 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 measurements, the time delay initial value 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.

Be to improve accuracy of measurement, should choose as the signal source of baseband signal generator 1 and have narrow pulse code type generator along characteristic, the operated by rotary motion rise and fall are 0.8ns along the time; High speed data acquisition system 4 should have the sampling rate of 4GSap/s, is 250ps to guarantee sampling resolution; Cooperate 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 this method are:

The first step is set up the latency measurement system

The described measuring system of a kind of method of measurement of delay of direct sequence spread spectrum binary phase shift keying modulator 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);

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

Second step high speed data acquisition system (4) acquired signal

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 a reference channel; Another road signal enters high speed data acquisition system (4) behind cable B (9), tested direct sequence spread spectrum binary phase shift keying modulator (3), cable C (10), this road is a test channel; High speed data acquisition system (4) carries out synchronous high-speed, high precision sampling to this two paths of signals;

The data demodulates computing of the 3rd step demodulation module (5)

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 that with digital section Stas ring the modulated bandpass signal that receives is transformed into analytic signal, and the carrier frequency and the initial phase of signal are done the estimation computing, the estimation range of carrier frequency is carrier frequency ± 1% carrier frequency; The estimation of carrier wave initial phase is carried out Hilbert transform with the Hilbert transform method of operational formula (1) to acquired signal x (t) and is got analytic signal

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

Complex signal after promptly obtain the low pass complex envelope of original signal As shown in Equation (3);

When loop is all estimated correctly carrier frequency and phase place, then the real part of low pass complex envelope be exactly need to recover with spread baseband signal;

The data despreading computing of the 4th step despreading module (6)

Despreading module (6) is finished 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 then _s/ f _PnΔ f _PnBe the maximum of PN sign indicating number frequency deviation, then a chip maximum deviation of PN sign indicating number points N ₁=f _s/ Δ f _PnThe sampling number that is provided with 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 with 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 the formula (4), x (k Δ t) is the signal after the despreading, and y (k Δ t) is the PN coded signal in the PN code correlator, and N counts for the PN coded signal, R _XyBe correlation; Get R _XyMaximum R _Max, with (2N ₁+ 1) individual different PN sign indicating number by formula (4) relevant with despread signal, obtain (2N ₁+ 1) individual maximum correlation R _MaxThis (2N ₁+ 1) the maximum in the individual maximum is the PN sign indicating number chip-rate in the tracking;

The synchronous slip related operation of use of code phase in the despreading module (6), at first synchronous spreading code of general and restituted signal by formula (4) carry out related operation, obtain correlation, the abscissa value of maximum related value correspondence is the synchronization point of code phase; Again PN sign indicating number and restituted signal on synchronous are multiplied each other, promptly finish despreading, the baseband signal m that is restored _c

The time delay computing of the 5th step time delay correlation module (7)

With the baseband signal m that recovers _cWith the baseband signal m that directly collects 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, the transverse axis coordinate of note relevant peaks maximum correspondence 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), the refinement relevant peaks that obtains, and the abscissa of the relevant peaks maximum correspondence of refinement is the time delay T of tested direct sequence spread spectrum binary phase shift keying modulator (3) constantly ₁

The 6th step was set up the time delay calibration system

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

The initial time delay of the 7th pacing amount

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) behind 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 handled;

Data processing method in the time delay correlation module (7) by formula (5) carries out related operation to the two paths of signals that delay of direct sequence spread spectrum binary phase shift keying modulator calibration system high speed data acquisition unit (4) collects, m (t) is for entering the data in the high speed data acquisition system (4), m through cable A (8) _c(t) for to enter the data in the high speed data acquisition system (4) through cable B (9), cable C (10), two groups of data pointwises are multiplied each other, and the multiplied result addition obtains a correlation, again with m _c(t) signal slides behind the data collection point to multiply each other with the pointwise of m (t) signal and results added is obtained second correlation again, by that analogy, finally obtains correlation curve;

Obtain the maximum of relevant peaks, the transverse axis coordinate of note relevant peaks maximum correspondence 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), the refinement relevant peaks that obtains, and the abscissa of the relevant peaks maximum correspondence 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, the time delay initial value 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

Be to improve accuracy of measurement, should choose as the signal source of baseband signal generator (1) and have narrow pulse code type generator along characteristic, the operated by rotary motion rise and fall are 0.8ns along the time; High speed data acquisition system (4) is the sampling rate of 4GSap/s, is 250ps to guarantee sampling resolution; Cooperate data processing calculating can guarantee time delay measures uncertainty＜500ps after satisfying above-mentioned condition.

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