CN202177705U

CN202177705U - High-precision caesium optical pump signal processor

Info

Publication number: CN202177705U
Application number: CN2011201370652U
Authority: CN
Inventors: 许庆丰; 周捷; 马凯; 郭梦华; 姚奇
Original assignee: SHANGHAI GENERAL SATELLITE NAVIGATION Co Ltd
Current assignee: SHANGHAI GENERAL SATELLITE NAVIGATION Co Ltd
Priority date: 2011-05-03
Filing date: 2011-05-03
Publication date: 2012-03-28
Anticipated expiration: 2021-05-03

Abstract

The utility model relates to a high-precision caesium optical pump signal processor, which is a high-precision signal frequency discriminating circuit based on a large scale programming logic device, FPGA, wherein an optical pump signal undergoes signal demodulation and difference frequency/shaping, and then is input into the programmable logic device and then output to a PC104ISA bus interface by the programmable logic device, under the cooperation of a high stability constant temperature crystal oscillator module, etc., and the programmable logic device is formed by connecting a difference frequency counter, a sampling controller, a main counter, a sampling counter, an interruption controller, a built-in self-check BIT interface, and an ISA bus interface together, and used for completing a main frequency discriminating algorithm and realizing interfaces. Software employs a mu C/OS-II real time operation system to accomplish signal reading, digital filtering and data storing and displaying. The high-precision caesium optical pump signal processor can output a signal with a resolution of 0.005 nT (same as the foreign level) to the caesium optical pumping probe under a sampling frequency of 200 Hz (better than the foreign level), can receive three channels of signals, can be used for aviation precision magnetism measure, has undergone aviation flight test, can reach to the design indices and fills the domestic blank in this field.

Description

High precision caesium optical pump signal processor

Technical field

The utility model relates to a kind of accurate high precision aviation caesium optical pump signal processor of surveying the magnetic purposes.

Background technology

At weak magnetic field detection, caesium optical pumping probe is widely used as the most general in the world Magnetic Sensor.Be applied to the geophysical measurement of ground or aviation, like resource exploration, underwater salvage, archaeological excavation or the like.Caesium optical pumping probe is domestic still to be belonged to blankly, is import all, mainly contains the CS-3 of Canadian Sinitrix company, the G-838 of U.S. Geometrix company, G-858.One of output and the proportional frequency signal of external magnetic field during the work of caesium optical pumping probe, the relation of frequency and external magnetic field is f=3.498577Hz/nT, and the external magnetic field changes 1nT, and the frequency signal of optical pumping probe output changes 3.498577Hz.Caesium optical pumping probe is very fast to the response speed of external magnetic field; In applications such as magnetic air spies; Can not consider the response time of magnetic sensing probe itself, the inromation bandwidth that whole magnetic is visited system only depends on the signal processing system of back, the i.e. response time of optical pump signal device.The static noise peak-to-peak value of the commercial caesium optical pumping probe of at present external main flow can reach and be superior to 0.002nT, and this just requires supporting with it signal processor can detect the change of frequency of this order of magnitude, and competence exertion goes out the effect of probe.For example: the regularity of distribution in magnetic field of the earth is that two-stage is stronger; The equator a little less than; Average about 50000nT closes 0.5 Gauss, and this moment, the frequency signal of caesium optical pumping probe output was about 50000*3.498577=175kHz; Detect the variable quantity of 0.002nT, just the follow-up signal processor want can reliable detection 175kHz ± 0.007Hz frequency signal.In addition, also require signal processor that certain bandwidth is arranged, the sampling rate of 10Hz will be arranged at least, the signal processor that is used for aircraft equipment also requires to have higher sampling rate.This has very high requirement to supporting optical pump signal processor.

At weak magnetic field detection, present domestic aerial survey unit a complete set of introduce external a whole set of magnetic and visits equipment, and the MM4 type magnetic airborne surveys equipment like Canadian pcio company comprises caesium optical pumping probe, optical pump signal processor, GPS receiver, radio altimeter or the like.

The utility model content

The utility model is domestic first and the supporting optical pump signal processor of general caesium optically pumped magnetometer in the world.

The technical matters that the utility model will solve is: the aircraft equipment optical pump signal processor requirement supporting with the caesium optically pumped magnetometer has high precision and high sampling rate, and domestic also do not have and the matching used optical pump signal processor of caesium optical pumping.The utility model caesium optical pump signal processor precision has reached external like product level (0.005nT); And reach higher sampling rate (200Hz); External like product is all at tens Hz, and sampling rate is superior to external like product, has filled up domestic blank in the aerospace applications field.

The technical scheme of the utility model: be a kind of high precision optical pump signal frequency-discriminating circuit that designs to the caesium optical pumping based on scale programmable logic device FPGA.Shown in Figure of description 1; Its frequency-discriminating circuit is arranged on the optical pump signal disposable plates; Optical pump signal 1,2,3 is separated mediation difference frequency/shaping through signal; Input is connected to PLD; Be connected to the PC104ISA EBI by PLD output again, also have high stability constant-temperature crystal oscillator module to be connected with PLD with the online upgrading interface simultaneously, PLD is connected to form by difference frequency counter, sampling controller, basic counter, sample counter, interruptable controller, built in test BIT interface, isa bus interface.It has good dirigibility, broadband measurement scope (200Hz), very high measuring accuracy (0.005nT) designing requirement, can handle 3 road probe input signals at most simultaneously, and complete machine has the aviation cabinet of reinforcing and structural design reliably.

Because under weak magnetic environment; The variation of caesium optical pumping probe output frequency is very little; Under the background magnetic field of 50000nT, the external magnetic field changes 0.01nT, and the variation of output frequency has only 175kHz ± 0.03Hz; Being equivalent to detect direct such change of frequency to be very difficult, has adopted the difference frequency technology for this reason.System multiplies each other optical pumping frequency signal and the approaching fixed frequency signal of frequency of input earlier; The result has produced the signal with frequency and 2 kinds of frequencies of difference frequency; With frequency higher use the wave filter filtering with the frequency signal, difference frequency signal is counted, just the frequency of measuring-signal more accurately.For example, establish probe output

A=sin (θ 1+ Δ θ), Δ θ are that the difference frequency frequency of benchmark is because external magnetic field changes the frequency variation that causes:

B=sin (θ 2), through exporting signal behind the analog multiplier:

AxB＝sin(θ1+Δθ)x?sin(θ2)＝(cos(θ1-θ2+Δθ)+cos(θ1+Δθ+θ2))/2。

This shows that the difference frequency process has just reduced fundamental frequency, to frequency variation and free of losses.If θ 1, θ 2 differs kHz about 175kHz, is 350kHz through 2 signal frequencies behind the analog multiplier then, 1kHz, and difference is very big, is easy to separate with wave filter.Signal behind the difference frequency has been equivalent to improve the ratio that signal changes, and detects relatively more easily.The change of frequency of for example original 175kHz ± 0.03Hz, frequency change rate is 1.7 * 10-7, if the signal behind the difference frequency is 1KHz ± 0.03Hz, then rate of change is 3 * 10-5, has improved 2 one magnitude, uses electric circuit inspection more easily before comparing difference frequency.

System comprises hardware components and software section, and the hardware components critical piece is to be the optical pump signal disposable plates of core with PLD FPGA, accomplishes main frequency discrimination algorithm, optical pump signal disposable plates and industrial computer interface, and industrial computer connects display device.Software section is mainly accomplished from optical pump signal disposable plates reading of data, carries out necessary digital filtering, accomplishes record and demonstration.

The beneficial effect of the utility model is: reach under the sampling rate 200Hz (being superior to external similar level) caesium optical pumping probe output resolution 0.005nT (with external similar level) with the supporting aircraft equipment optical pump signal processor of caesium optically pumped magnetometer; The equipment of the utility model through actual aviation flight test, has reached design objective.Filled up domestic blank in this field.

Below in conjunction with accompanying drawing and embodiment the utility model is further specified.

Description of drawings

Fig. 1 is an optical pump signal disposable plates system chart.

Among Fig. 1; The each several part functional relationship is following: optical pump signal 1,2,3 is separated mediation difference frequency/shaping through signal; Input is connected to PLD; Be connected to the PC104ISA EBI by PLD output again; Also be connected by high stability constant-temperature crystal oscillator module and online upgrading interface simultaneously frequency reference and online upgrading are provided, PLD is connected to form by difference frequency counter, sampling controller, basic counter, sample counter, interruptable controller, built in test BIT interface, isa bus interface, accomplishes main frequency discrimination algorithm and interface.

Fig. 2 is the continuous sampling signal under the standard signal source input.It is that the optical pump signal disposable plates that design is accomplished is at first tested with the delay/pulse signal generator DG535 of U.S. Stamford research system.DG535 output signal RMS shake＜50ps+10 ^-8* postpone, can think frequency signal source very accurately, actual measurement is in the incoming frequency scope of 60Khz～300Khz, and circuit resolution has reached 0.015Hz, the highest 200Hz of sampling rate.

Embodiment

1, hardware designs

In Fig. 1, differential frequency circuit is core with the PLD, cooperates signal demodulation, difference frequency/shaping to constitute, and by high stability constant-temperature crystal oscillator module frequency reference is provided.

The frequency signal the 1,2, the 3rd of optical pumping probe output is modulated on the power supply, and demodulation demodulates sinusoidal signal through signal, passes through by multiplier again, and after difference frequency/shaping that wave filter and shaping circuit are formed, signal input PLD is counted.

In the PLD just like lower module and function:

1) difference frequency counter: the function of difference frequency counter is according to input frequency signal, the signal about generation and input signal difference 1KHz, the difference frequency/shaping of giving front end.Because the variation in magnetic field is generally not too violent, difference frequency signal upgraded and once gets final product in 1 minute.Because the difference of difference frequency signal and probe signal is very little, differ greatly with frequency signal and difference frequency signal frequency through what produce behind the analog multiplier,

2) sampling controller: signal according to the SF of setting.

3) basic counter: basic counter free-running operation, the signal behind the difference frequency is counted.

4) sample counter: after controlling of sampling was sent sampled signal, the value of basic counter latched the entering sample counter, was read by isa bus interface and exterior PC 104ISA EBI.

5) interruptable controller: after each sampling finished, interruptable controller sent interrupt request, reads the sampling numerical value in the sample counter by external bus.

6) BIT interface: the duty of monitoring each logic module.

2, software design

For satisfying the real-time of optical pump signal disposable plates sampling; The operating system of system adopts μ C/OS-II real time operating system; UC/OS-II is based on the real-time kernel of the preemptive type of priority scheduling, is that the Embedded Application of computing machine designs specially, and most codes are used the C language.CPU hardware relevant portion partly is compressed to bottom line with the assembly language of compilation language, about 200 row of total amount.Can support 64 tasks among the uC/OS-II at most, the corresponding priority 0～63 of difference, wherein 0 is limit priority.63 is lowermost level, in the software design of optical pump signal processor 4 tasks:

1) the optical pump signal data read task.This task priority is the highest, has guaranteed the real-time of from the optical pumping data processing plate, sampling.

2) serial data reads task.The priority the second of this task, system design can be read in the positional information and the temporal information of GPS or other navigating instruments from serial ports, with synthetic 1 packet of the data in the task 1, write down the magnetic field data under a certain moment and the geographic coordinate.

3) digital filtering task.The priority the 3rd of this task.Magnetic field data is carried out digital filtering, remove the noise of irrelevant frequency band.

4) data storage and demonstration task.This task priority is minimum.Function is for note down the optical pumping probe data and show in real time.

Claims

1. high precision caesium optical pump signal processor; It is characterized in that: based on the high precision optical pump signal frequency-discriminating circuit of scale programmable logic device FPGA; Its frequency-discriminating circuit is arranged on the optical pump signal disposable plates; Optical pump signal 1,2,3 is separated mediation difference frequency/shaping through signal; Input is connected to PLD; Be connected to the PC104ISA EBI by PLD output again, also have high stability constant-temperature crystal oscillator module to be connected with PLD with the online upgrading interface simultaneously, PLD is connected to form by difference frequency counter, sampling controller, basic counter, sample counter, interruptable controller, built in test BIT interface, isa bus interface.