CN101620264B - Method for adjusting simulating medium-frequency level ensuring data quantification correctness in GNSS signal collection experiment - Google Patents

Abstract

The invention discloses a method for adjusting simulating medium-frequency level which ensures data quantification correctness in GNSS signal collection experiment. A GNSS signal collection experiment system comprises a GNSS antenna, a down-conversion module, an A/D module, a collection module and a PC machine, wherein an extracting module of medium-frequency adjusting information is stored in the PC machine; the GNSS antenna converts a received radio-frequency signal f1 into a simulating medium-frequency signal f2 by the down-conversion module; the simulating medium-frequency signal f2 after being quantified by the A/D module outputs a digital medium-frequency signal f3, and the digital medium-frequency signal f3 after being encrypted, locked and stored by the collection module outputs a digital medium-frequency signal code flow f4 to the PC machine; and the digital medium-frequency signal code flow f4 carries out probability statistics in the extracting module of the medium-frequency adjusting information of the PC machine to obtain the adjusting information f5 of the simulating medium-frequency signal f2. The extracting module of the medium-frequency adjusting information analyzes the received digital medium-frequency signal code flow f4 by a digitizing means, the number of each quantification level can be effectively obtained, and the conditions that the signal-to-noise ratio of the simulating medium-frequency signal is low and a user is not easy to accurately observe by depending on observation simply are fully considered.

Description

Guarantee the correct analog intermediate frequency level method of adjustment of data-measuring in the GNSS signal collection experiment

Technical field

The invention belongs to the signal processing technology field, relate to the correct analog intermediate frequency level method of adjustment of assurance data-measuring in a kind of GNSS signal collection experiment.

Background technology

The purpose of GNSS signal collection experiment is to gather the GNSS digital medium-frequency signal.GNSS signal collection experiment system has generally comprised GNSS antenna 1, down conversion module 2, A/D module 3 and acquisition module 4, as shown in Figure 1.GNSS antenna 1 is with the radiofrequency signal f that receives ₁Become analog if signal f through down conversion module 2 ₂Analog if signal f ₂Quantize back output digital medium-frequency signal f via A/D module 3 ₃, this digital medium-frequency signal f ₃Behind acquisition module 4 codings, be latched in the acquisition module 4.

In GNSS signal collection experiment system as shown in Figure 1, down conversion module 2 is with the radiofrequency signal f that receives ₁Be converted into analog if signal f ₂, this analog if signal f ₂Need carry out being quantized by A/D module 3, wherein the level of A/D quantification is fixed, and in order to compensate the level-shift that causes owing to down conversion module 2, it is correct to guarantee to quantize output level, need be to the analog if signal f of down conversion module 2 outputs ₂Adjust.

In the GNSS signal collection experiment, the amplitude limit of the intermediate-freuqncy signal that analog intermediate frequency level method of adjustment can not show according to oscillograph, observe the limit and adjust.The first, do not consider the influence of A/D quantization level drift like this; The second, be superimposed with noise on the analog if signal, signal to noise ratio (S/N ratio) is very low, is not easy to observe accurately.

The analog intermediate frequency level is generally without adjustment in traditional GNSS signal collection experiment.If the analog intermediate frequency level is not adjusted, the level-shift of the analog if signal of drift of A/D quantization level or the output snr loss that can cause signal Processing then.

Summary of the invention

In order to solve in the GNSS signal collection experiment, because the level-shift that the quantification of down conversion module 2 produces is given analog if signal f ₂The snr loss who introduces, the present invention propose to guarantee in the GNSS signal collection experiment the correct analog intermediate frequency level method of adjustment of data-measuring.

Guarantee the correct analog intermediate frequency level method of adjustment of data-measuring in a kind of GNSS signal collection experiment of the present invention, this GNSS signal collection experiment system is by the GNSS antenna, and down conversion module, A/D module, acquisition module and PC are formed;

Store intermediate frequency adjustment information extraction module in this PC, the digital medium-frequency signal code stream f of intermediate frequency adjustment information extraction module to receiving ₄The treatment step that carries out is:

The first step is added up the number of quantization level number

The A/D module adopts 1bit to quantize, the digital medium-frequency signal f of A/D module output ₃Code stream form by code stream 0 and code stream 1, wherein, code stream 0 is decoded into-1 quantization level number, code stream 1 is decoded into+1 quantization level number;

Statistics in an acquisition time T, the number of-1 quantization level number, number N promptly-1 (1);

Statistics in an acquisition time T, the number of+1 quantization level number, number N promptly+1 (+1);

The total data number of quantization level number is designated as N _T=N (1)+N (+1);

In second step, the number of calculating the data of each quantization level accounts for the ratio of total data number

-1 number N (1) accounts for total data number N _TRatio be $P_{-1}=\frac{N(-1)}{N_T};$

+ 1 number N (+1) accounts for total data number N _TRatio be $P_{+1}=\frac{N(+1)}{N_T};$

In the 3rd step, the foundation of intermediate-freuqncy signal is adjusted in acquisition

When | P _-1-P _{+ 1}|, finish the GNSS signal collection experiment at≤8% o'clock;

When | P _-1-P _{+ 1}|＞8% o'clock, to the analog if signal f of down conversion module output ₂Adjust, its adjustment amount to down conversion module is by k (P _-1-P _{+ 1}) determine, k represents scale-up factor, its value is 0.2V;

As k (P _-1-P _{+ 1}) when being positive number, raise analog if signal f ₂The level of output;

As k (P _-1-P _{+ 1}) when being negative, downward modulation analog if signal f ₂The level of output.

The advantage that guarantees the analog intermediate frequency level method of adjustment that data-measuring is correct in the GNSS signal collection experiment of the present invention is:

(1) utilizes PC as carrier, adopt the digital medium-frequency signal code stream f of intermediate frequency adjustment information extraction module acquisition module 4 outputs ₄Carry out the analysis of digitizing means, can obtain the number of each quantization level effectively, it is low to have taken into full account the analog if signal signal to noise ratio (S/N ratio), and simple dependence is observed and is not easy to observe situation accurately.

(2) adopt intermediate frequency adjustment information extraction module that the number of each quantization level has been carried out record, the ratio that accounts for the total data number for the number of the data of calculating each quantization level provides foundation.

(3) adopt Matlab 7.0 software programming intermediate frequency adjustment information extraction modules, language is simple, the counting yield height.

(4) the digital medium-frequency signal code stream f that acquisition module 4 is exported ₄Carry out the analysis of digitizing means.This module can be considered the influence that the drift of A/D module 3 quantization levels causes fully.

Description of drawings

Fig. 1 is the structured flowchart of traditional GNSS signal collection experiment system.

Fig. 2 is the structured flowchart of GNSS signal collection experiment of the present invention system.

Fig. 3 is the intermediate frequency adjustment information extraction module interface displayed of storing in the PC that utilizes of the present invention.

Embodiment

The present invention is described in further detail below in conjunction with drawings and Examples.

In order to solve in GNSS signal collection experiment system, because the level-shift that the quantification of A/D module 3 produces is given digital medium-frequency signal f ₃The snr loss who introduces the invention provides and a kind ofly connects a PC on the output terminal of acquisition module 4, and stores intermediate frequency adjustment information extraction module in this PC.

See also shown in Figure 2ly, GNSS signal collection experiment of the present invention system is by GNSS antenna 1, and down conversion module 2, A/D module 3, acquisition module 4 and PC 5 are formed.

GNSS antenna 1 is with the radiofrequency signal f that receives ₁Become analog if signal f through down conversion module 2 ₂Analog if signal f ₂Quantize back output digital medium-frequency signal f via A/D module 3 ₃, this digital medium-frequency signal f ₃Output digital medium-frequency signal code stream f after acquisition module 4 codings latch ₄Give PC 5; This digital medium-frequency signal code stream f ₄In the intermediate frequency adjustment information extraction module of PC 5, carry out probability statistics and obtain analog if signal f ₂Adjustment information f ₅

Described intermediate frequency adjustment information extraction module adopts Matlab 7.0 software programmings.

The minimalist configuration of PC is CPU 2GHz, internal memory 2GB, hard disk 10GB; Operating system is windows2000/2003/XP.

Referring to shown in Figure 3, in the present invention, the digital medium-frequency signal code stream f of intermediate frequency adjustment information extraction module to receiving ₄The treatment step that carries out is:

The first step is added up the number of quantization level number

In the present invention, A/D module 3 adopts 1bit to quantize, the digital medium-frequency signal f of A/D module 3 outputs ₃Code stream form by code stream 0 and code stream 1, wherein, code stream 0 is decoded into-1 quantization level number, code stream 1 is decoded into+1 quantization level number;

Statistics in an acquisition time T, the number of-1 quantization level number, number that should-1 quantization level number is designated as N (1), abbreviates-1 number N (1) as;

Statistics in an acquisition time T, the number of+1 quantization level number, number that should+1 quantization level number is designated as N (+1), abbreviates as+1 number N (+1);

The total data number of quantization level number is designated as N _T=N (1)+N (+1);

In the present invention, acquisition time T is set up on their own by the inventor, can be 1 second, 10 seconds, 30 seconds, 60 seconds or 600 seconds.

In second step, the number of calculating the data of each quantization level accounts for the ratio of total data number

-1 number N (1) accounts for total data number N _TRatio be $P_{-1}=\frac{N(-1)}{N_T},$ Abbreviate-1 number ratio as $P_{-1}=\frac{N(-1)}{N_T};$

+ 1 number N (+1) accounts for total data number N _TRatio be $P_{+1}=\frac{N(+1)}{N_T},$ Abbreviate as+1 number ratio $P_{+1}=\frac{N(+1)}{N_T};$

In the 3rd step, the foundation of intermediate-freuqncy signal is adjusted in acquisition

When | P _-1-P _{+ 1}|, finish the GNSS signal collection experiment at≤8% o'clock;

When | P _-1-P _{+ 1}|＞8% o'clock, to the analog if signal f of down conversion module 2 outputs ₂Adjust, its adjustment amount to down conversion module 2 is by k (P _-1-P _{+ 1}) determine, k represents scale-up factor, its value is 0.2V.

In the present invention, k (P _-1-P _{+ 1}) when being positive number, with analog if signal f ₂The level of output is transferred big (rise level); K (P _-1-P _{+ 1}) when being negative, with analog if signal f ₂The level of output is turned (downward modulation level) down.

Embodiment 1:

Carry out analog if signal f according to Fig. 2, shown in Figure 3 GNSS signal collection experiment of the present invention system ₂Adjustment process be:

Adjust for the first time, at acquisition time T=30 in second, if P appears in the quantization level number that the intermediate frequency adjustment information extraction module interface that shows in the display of PC calculates _{+ 1}=30%, P _-1During=70% situation: | P _-1-P _{+ 1}|=40%, 40%＞8%, then should be to the analog if signal f of down conversion module 2 outputs ₂The adjustment size be k (P _-1-P _{+ 1})=0.08V, i.e. analog if signal f ₂Level need raise 0.08V.

After adjusting for the first time, because-1 number ratio P _-1With+1 number ratio P _{+ 1}The absolute value of difference greater than 8%, therefore need carry out for the second time or adjustment for the third time, until satisfying | P _-1-P _{+ 1}|≤8% could finish the GNSS signal collection experiment.

Adjust for the second time, at acquisition time T=30 in second, if P appears in the quantization level number that the intermediate frequency adjustment information extraction module interface that shows in the display of PC calculates _{+ 1}=40%, P _-1During=60% situation: | P _-1-P _{+ 1}|=20%, 20%＞8%, then should be to the analog if signal f of down conversion module 2 outputs ₂The adjustment size be k (P _-1-P _{+ 1})=0.04V, i.e. analog if signal f ₂Level need raise 0.04V.

Adjust for the third time, at acquisition time T=30 in second, if P appears in the quantization level number that the intermediate frequency adjustment information extraction module interface that shows in the display of PC calculates _{+ 1}=49%, P _-1During=51% situation: | P _-1-P _{+ 1}|=2%, 2%＜8%, then finish test.

In whole adjustment process, the inventor utilizes the intermediate frequency adjustment information extraction module interface displayed (as shown in Figure 3) of storing in the PC to carry out the setting of acquisition time T, carrying out " parameter setting " by objective interface, clicking " gathering beginning " to the acquisition time end, can show relevant parameter information in a plurality of squares in the interface, clicking " adjust and judge " then then has the parameter that raises voltage and downward modulation voltage to show, when satisfying | and P _-1-P _{+ 1}|, finish the GNSS signal collection experiment at≤8% o'clock.

Embodiment 2:

Carry out analog if signal f according to Fig. 2, shown in Figure 3 GNSS signal collection experiment of the present invention system ₂Adjustment process be:

Adjust for the first time, at acquisition time section T=10 in second, if P appears in the quantization level number that the intermediate frequency adjustment information extraction module interface that shows in the display of PC calculates _{+ 1}=55%, P _-1During=45% situation: | P _-1-P _{+ 1}|=10%, 10%＞8%, then to the analog if signal f of down conversion module 2 output ₂The adjustment size be k (P _-1-P _{+ 1}The 0.02V of)=-, i.e. analog if signal f ₂Level need reduce 0.02V.

Adjust for the second time, at acquisition time section T=30 in second, if P appears in the quantization level number that the intermediate frequency adjustment information extraction module interface that shows in the display of PC calculates _{+ 1}=48%, P _-1During=52% situation: | P _-1-P _{+ 1}|=4%, 4%≤8%, then finish test.

In the present invention, utilize PC, use the interface of intermediate frequency adjustment information extraction module as shown in Figure 3 and carry out numerical information demonstration directly perceived as carrier.The present invention adopts the digital medium-frequency signal code stream f of intermediate frequency adjustment information extraction module to acquisition module 4 outputs ₄Carry out the analysis of digitizing means, can obtain the number of each quantization level effectively, it is low to have taken into full account the analog if signal signal to noise ratio (S/N ratio), and simple dependence is observed and is not easy to observe situation accurately.Simultaneously, adopt intermediate frequency adjustment information extraction module that the number of each quantization level has been carried out record, the ratio that accounts for the total data number for the number of the data of calculating each quantization level provides foundation.

Claims (2)

1. guarantee the correct analog intermediate frequency level method of adjustment of data-measuring in a GNSS signal collection experiment, it is characterized in that: this GNSS signal collection experiment system is made up of GNSS antenna (1), down conversion module (2), A/D module (3), acquisition module (4) and PC (5); Wherein, store intermediate frequency adjustment information extraction module in this PC (5);

GNSS antenna (1) is with the radiofrequency signal f that receives ₁Become analog if signal f through down conversion module (2) ₂Analog if signal f ₂Quantize back output digital medium-frequency signal f via A/D module (3) ₃, this digital medium-frequency signal f ₃Output digital medium-frequency signal code stream f after acquisition module (4) coding latchs ₄Give PC (5); This digital medium-frequency signal code stream f ₄In the intermediate frequency adjustment information extraction module of PC (5), carry out probability statistics and obtain analog if signal f ₂Adjustment information f ₅

The digital medium-frequency signal code stream f of intermediate frequency adjustment information extraction module to receiving ₄The treatment step that carries out is:

The first step, the number of quantization level number is added up:

A/D module (3) adopts 1bit to quantize, the digital medium-frequency signal f of A/D module (3) output ₃Code stream form by code stream 0 and code stream 1, wherein, code stream 0 is decoded into-1 quantization level number, code stream 1 is decoded into+1 quantization level number;

Statistics in an acquisition time T, the number of-1 quantization level number, number N promptly-1 (1);

Statistics in an acquisition time T, the number of+1 quantization level number, number N promptly+1 (+1);

The total data number of quantization level number is designated as N _T=N (1)+N (+1);

In second step, the number of calculating the data of each quantization level accounts for the ratio of total data number:

-1 number N (1) accounts for total data number N _TRatio be

+ 1 number N (+1) accounts for total data number N _TRatio be

In the 3rd step, the foundation of intermediate-freuqncy signal is adjusted in acquisition:

When | P _-1-P _{+ 1}|, finish the GNSS signal collection experiment at≤8% o'clock;

When | P _-1-P _{+ 1}|＞8% o'clock, to the analog if signal f of down conversion module (2) output ₂Carry out the first time and adjust, its adjustment amount to down conversion module (2) is by k (P _-1-P _{+ 1}) determine, k represents scale-up factor, its value is 0.2V;

As k (P _-1-P _{+ 1}) when being positive number, with analog if signal f ₂The level of output is transferred big;

As k (P _-1-P _{+ 1}) when being negative, with analog if signal f ₂The level of output is turned down;

After adjusting for the first time, because-1 number ratio P _-1With+1 number ratio P _{+ 1}The absolute value of difference greater than 8%, therefore need carry out for the second time or adjustment for the third time, until satisfying | P _-1-P _{+ 1}|≤8% could finish the GNSS signal collection experiment.

2. guarantee the correct analog intermediate frequency level method of adjustment of data-measuring in a kind of GNSS signal collection experiment according to claim 1, it is characterized in that: acquisition time T is meant 1 second, 10 seconds, 30 seconds, 60 seconds or 600 seconds.

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