CN112730985A - Special spectrum analyzer for surface wave marine environment surveying equipment - Google Patents

Special spectrum analyzer for surface wave marine environment surveying equipment Download PDF

Info

Publication number
CN112730985A
CN112730985A CN202011531273.0A CN202011531273A CN112730985A CN 112730985 A CN112730985 A CN 112730985A CN 202011531273 A CN202011531273 A CN 202011531273A CN 112730985 A CN112730985 A CN 112730985A
Authority
CN
China
Prior art keywords
frequency
signal
equipment
surface wave
marine environment
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
CN202011531273.0A
Other languages
Chinese (zh)
Inventor
刘文平
何克慧
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Jingmen Huiyijia Information Technology Co ltd
Original Assignee
Jingmen Huiyijia Information Technology Co ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Jingmen Huiyijia Information Technology Co ltd filed Critical Jingmen Huiyijia Information Technology Co ltd
Priority to CN202011531273.0A priority Critical patent/CN112730985A/en
Publication of CN112730985A publication Critical patent/CN112730985A/en
Withdrawn legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
    • G01R23/16—Spectrum analysis; Fourier analysis
    • G01R23/165—Spectrum analysis; Fourier analysis using filters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R23/00—Arrangements for measuring frequencies; Arrangements for analysing frequency spectra
    • G01R23/16—Spectrum analysis; Fourier analysis
    • G01R23/165—Spectrum analysis; Fourier analysis using filters
    • G01R23/167—Spectrum analysis; Fourier analysis using filters with digital filters

Landscapes

  • Physics & Mathematics (AREA)
  • Mathematical Physics (AREA)
  • General Physics & Mathematics (AREA)
  • Radar Systems Or Details Thereof (AREA)

Abstract

The special spectrum analyzer for the surface wave marine environment surveying equipment, which is provided by the invention, aims at the problems that the radio spectrum analyzing equipment in the prior art is expensive, the monitored spectrum range is too wide and far exceeds the working range of the surface wave marine environment surveying equipment, so that the resource is greatly wasted, and the special spectrum analyzer cannot well adapt to the co-station receiving and transmitting mode of the surface wave marine environment surveying equipment, and is purposefully designed for the surface wave marine environment surveying equipment, so that the spectrum analyzer can not only receive short-band interference and noise in the working environment of the surface wave marine environment surveying equipment and provide noise data for later data acquisition, but also select proper working frequency for the surveying equipment as reference, the working frequency band of the surface wave marine environment surveying equipment is clean, the influence of strong interference is avoided, and the equipment can acquire high-quality data, thereby inverting more accurate marine dynamics parameter information.

Description

Special spectrum analyzer for surface wave marine environment surveying equipment
Scope of the technology
The invention relates to a special spectrum analyzer for surveying equipment, in particular to a special spectrum analyzer for surface wave marine environment surveying equipment, and belongs to the technical field of special spectrum analyzers.
Background
The surface wave marine environment surveying equipment is a radio equipment which is developed in recent decades and can continuously survey large-area marine environment parameters, high-power high-frequency vertical polarization electromagnetic waves are projected onto the sea surface, and when the wavelength of two wave trains of sea waves which are directed to or back from the surveying equipment is equal to half of the working wavelength of the surveying equipment, the strongest scattering is generated on the electric waves of the surveying equipment, and the scattering is called first-order scattering. The sea surface state and the change characteristics thereof are reflected on the characteristics of Doppler frequency spectrums of sea wave echoes, a first-order scattering cross-section equation established by Barrick can be used for analyzing the Doppler frequency spectrums, and marine physical information such as air, waves, currents and the like can be inverted from equipment echoes through corresponding algorithms to finish real-time and all-around survey of a wide-area marine environment. In addition, hard objects moving at low speed on the sea surface can be detected according to the difference between the echo spectrum scattered by the marine objects and the echo spectrum of sea waves. Compared with other ocean remote sensing equipment in the prior art, the surface wave ocean environment surveying equipment has the advantages of large coverage area, high detection precision, moderate manufacturing cost, low running cost, all-weather operation and the like, can detect the sea area beyond the sight distance, and is one of the most ideal ocean environment detecting equipment.
With the development of distributed surface wave marine environment networking detection equipment, the distributed surface wave marine environment networking detection equipment overcomes the typical defects of small detection range, single detection mode, serious insufficient information quantity, weak anti-interference capability, low detection precision and the like of the marine detection technology in the prior art, has the capability of detecting marine environment parameters with large service area and refinement, is more suitable for diversified application requirements in the aspects of result accuracy, application flexibility and the like, and can serve the relevant industries such as marine fishing industry, marine traffic, coastal engineering, disaster early warning and the like.
However, the lower working frequency band of the surface wave marine environment surveying equipment also causes a lot of problems, and most importantly, the working environment of the surveying equipment is very complex, when strong interference and noise exist outside, a useful signal is submerged in the noise, the detection performance of the surveying equipment is greatly reduced, and even a receiver can be blocked at some time, so that the surveying equipment cannot work normally. The types of interference encountered by surface wave marine environment survey equipment are: sea clutter interference, ionospheric interference and radio frequency interference. The most remarkable strong interference is complex and dense short-wave radio station signals, the external noise interference of the surface wave marine environment surveying equipment is 20 to 40dB higher than the interference generated inside the equipment, the working frequency range of the surface wave marine environment surveying equipment is generally between 3 and 30MHz, the working bandwidth is 30 to 100KHz, a large number of short-wave radio station signals are stored in the frequency band, one or more short-wave radio station signals are always present during working, and the short-wave radio station signals enter the surveying equipment through a receiving antenna, so that the performance of the whole detecting equipment is reduced. During night, short-wave radio station interference is particularly remarkable, and during 17 to 22 o' clock at night, the distance detected by a radar is greatly reduced.
The spectrometer is a practical tool for researching a given signal and then acquiring the energy distribution of each frequency component on the frequency spectrum of the given signal, and essentially, the spectrometer decomposes a complex signal into a plurality of single signals and displays the corresponding relation between the amplitude and the frequency of each frequency component so as to obtain the frequency and the amplitude of the signal.
If the working frequency band of the surface wave marine environment surveying equipment is clean and has no influence of strong interference, the equipment can acquire high-quality data, so that more accurate marine dynamics parameter information can be inverted. Therefore, it is an important task to effectively survey the interference and noise in the working environment of the surface wave marine environment surveying equipment, and the radio frequency spectrum analysis equipment in the market is expensive, and the monitored frequency spectrum range is too wide and far exceeds the working range of the surface wave marine environment surveying equipment, which causes great waste of resources; the surface wave marine environment surveying device is not well adapted to a co-station transmitting and receiving mode of the surface wave marine environment surveying device, and a high-power transmitting signal of the device is very likely to damage a commonly used spectrum analysis device, so that a spectrum analysis device is required to be designed for the surface wave marine environment surveying device in a targeted manner at present, short-wave-band interference and noise in the working environment of the surface wave marine environment surveying device can be received, noise data are provided for later-stage data acquisition, a proper working frequency can be selected for the surveying device to be used as a reference, and the surface wave marine environment surveying device is designed and researched based on the purpose.
The invention carries out comparative analysis on a special spectrum analyzer for surface wave marine environment surveying equipment and the prior art, and aims to solve the following problems aiming at the obvious defects of the prior art:
firstly, the spectrum analysis of the surface wave marine environment surveying device in the prior art mainly adopts a narrow-band intermediate frequency digital structure and a mode of once frequency conversion and high and intermediate frequency sampling, and in order to reduce the influence of echo signals on noise and interference signal acquisition, the surface wave marine environment surveying device mainly works in the intermittent period of the work of the surveying device, namely the time between two frequency sweeping periods. The general working principle is as follows: firstly, preselecting a noise signal in a frequency band to be monitored by a band-pass filter, then generating a linear sweep frequency signal with the initial frequency of 44.5MHz and the sweep frequency interval of 10KHz, then acquiring an obtained difference frequency signal by a frequency converter through the band-pass filter with the central frequency of 40.5MHz and the bandwidth of 10KHz, then performing FFT (fast Fourier transform) operation to obtain frequency spectrum information of an input signal by taking 10KHz as an analysis bandwidth, obtaining a large number of samples of a signal to be measured after a plurality of sweep frequency cycles, and finally counting to obtain a signal spectrogram in the bandwidth to be surveyed, wherein the mode in the prior art has a large number of problems;
second, the prior art spectrum analyzer is used in a surface wave marine environment surveying device, and has major drawbacks in three aspects: firstly, a sampling time point is 38.4ms, the working intermittence period of the early marine environment surveying equipment is only 3.125ms due to various technical improvements, the interval time is greatly shortened, if only signals of the intermittence period are sampled, the number of sampling points is obviously insufficient, or the sampling frequency needs to be increased, but the problem that external noise interference cannot be accurately reflected still exists; second, the influence of echo signals on the acquisition of noise and interference signals, at TpThe low effective sampling of the pulse must have an influence on the acquisition of noise and interference signals, and if the spectrum analysis equipment according to the prior art still performs sampling in the intermittent period of the work of the survey equipment, the influence of echo signals on the acquisition of noise and interference signals still cannot be avoided, because the current intermittent period time also only has one TpThe bandwidth of each analysis of the device is 300Hz, the effective bandwidth of the working frequency of the surveying device is selected to be 30KHz, the frequency spectrum analysis range is 1500KHz bandwidth signals, the influence of the 30KHz signal bandwidth is eliminated, the selectable bandwidth of the device is quite abundant, and the device can also be comprehensively usedSelecting and judging a spectrogram result obtained by the currently selected working frequency; thirdly, the problem of image frequency caused by the frequency converter, because the invention adopts a zero intermediate frequency structure, various harmonic components generated by the frequency converter are greatly inhibited, the low-pass filter following the frequency converter has the cut-off frequency of 300Hz, the purity of the difference frequency signal after frequency mixing can be ensured, secondly, the invention adopts the low-pass filter with the cut-off frequency of 300Hz, the identification error of the surveying signal caused by the nonpolarity of the frequency converter is also removed, and finally, the modulation signal T is causedpIs a signal with a period of 3.125ms, there will be 320Hz and its harmonics in the device, which can also be filtered out by a low pass filter.
Thirdly, the lower working frequency band of the surface wave marine environment surveying equipment causes a lot of problems, and most importantly, the working environment of the surveying equipment is very complex, when strong interference and noise exist outside, a useful signal is submerged in the noise, the detection performance of the surveying equipment is greatly reduced, and even a receiver can be blocked at some time, so that the surveying equipment cannot work normally. The most remarkable strong interference is complex and dense short-wave radio station signals, the external noise interference of the surface wave marine environment surveying equipment is 20 to 40dB higher than the interference generated inside the equipment, the working frequency range of the surface wave marine environment surveying equipment is generally between 3 and 30MHz, the working bandwidth is 30 to 100KHz, a large number of short-wave radio station signals are stored in the frequency band, one or more short-wave radio station signals are always present during working, and the short-wave radio station signals enter the surveying equipment through a receiving antenna, so that the performance of the whole detecting equipment is reduced. During night, short-wave radio station interference is particularly remarkable, and during 17 to 22 o' clock at night, the distance detected by a radar is greatly reduced.
Fourth, radio spectrum analysis equipment in the market is expensive, and the monitored spectrum range is too wide, which far exceeds the working range of surface wave marine environment survey equipment, resulting in great waste of resources; the surface wave marine environment surveying equipment is not well adapted to a co-station transmitting and receiving mode of the surface wave marine environment surveying equipment, a high-power transmitting signal of the equipment is very likely to damage commonly used spectrum analysis equipment, and the spectrum analysis equipment is designed for the surface wave marine environment surveying equipment in a targeted manner, so that the spectrum analysis equipment can not only receive short-wave-band interference and noise in the working environment of the surface wave marine environment surveying equipment and provide noise data for later-stage data acquisition, but also select proper working frequency for the surveying equipment to be used as reference.
Disclosure of Invention
Aiming at the defects of the prior art, the special spectrum analyzer for the surface wave marine environment surveying equipment provided by the invention takes the detection of the sea by the surface wave marine environment surveying equipment as the background, develops the spectrum analyzer which has strong pertinence and meets the requirements, and protects the driving and the navigation of the surface wave marine environment surveying equipment. The invention mainly comprises the following steps: firstly, analyzing the working waveform of surface wave marine environment surveying equipment, and providing a zero intermediate frequency acquisition scheme integrating sweep frequency heterodyne and FFT algorithm; secondly, analyzing an intermediate frequency digital acquisition scheme of the frequency spectrum analysis of the surface wave marine environment surveying equipment, designing and developing a frequency spectrum analyzer suitable for the surface wave marine environment surveying equipment, designing an analog front end circuit, a DDS circuit, an A/D sampling circuit and a control module of an FPGA in detail, and completing the compiling of firmware of a USB data transmission part and the design and test of an upper computer; thirdly, the drawing of a schematic diagram and a PCB of the whole project is completed, after the board manufacturing is successful, the debugging of the equipment is completed by combining an oscilloscope and a signal source instrument, the correctness of the spectrum analyzer is verified, and a good foundation is laid for designing a full-digital spectrum analyzer in the later period.
In order to achieve the technical effects, the technical scheme adopted by the invention is as follows:
a special frequency spectrum analyzer for surface wave marine environment surveying equipment analyzes a working waveform of the surface wave marine environment surveying equipment, and provides a zero intermediate frequency acquisition scheme integrating sweep frequency heterodyne and FFT algorithm; secondly, analyzing an intermediate frequency digital acquisition scheme of the frequency spectrum analysis of the surface wave marine environment surveying equipment, designing and developing a frequency spectrum analyzer suitable for the surface wave marine environment surveying equipment, designing an analog front end circuit, a DDS circuit, an A/D sampling circuit and a control module of an FPGA in detail, and completing the compiling of firmware of a USB data transmission part and the design and test of an upper computer; thirdly, drawing of a schematic diagram and a PCB of the whole project is completed, after the board is successfully manufactured, debugging of equipment is completed by combining an oscilloscope and a signal source instrument, the correctness of the spectrum analyzer is verified, and a good foundation is laid for designing a full-digital spectrum analyzer in the later period;
the special spectrum analyzer for the surface wave marine environment surveying equipment comprises two parts of hardware and software: in the aspect of hardware, the amplification and demodulation functions of weak signals to be analyzed are completed by taking a filter, an amplifier and a frequency converter as cores from an analog receiving front end; generating a required local oscillation signal by using a DDS chip; ADS8505 finishes digital acquisition of analog signals; the cyclic 3 series chip of ALTERA is adopted to complete the time sequence control of the whole equipment and coordinate the operation of each digital part; the data transmission of the equipment adopts the USB3.0 technology, and the used control chip is CY7C68013 of CYPRESS company; in the aspect of software, the Visual Studio 2010 is used as a design platform to complete the reading, FFT processing, frequency spectrum display and data storage of the collected data, and finally the whole frequency spectrum analysis equipment is displayed in a form of a real object;
the frequency spectrum analyzer of the surface wave marine environment surveying equipment is based on the heterodyne structure and the FFT principle, the heterodyne structure and the FFT principle are fused and improved, and during the frequency spectrum analysis, the local oscillator output is a single-frequency signal hLOFrom local oscillator frequency and radio frequency signal hRAnd the cut-off frequency h of the low-pass filterLDetermining the frequency spectrum of the external noise signal in the frequency range hLO～hLO+hLWhen 1024 data points are collected, one sampling is completed, and at the moment, the output of the local vibration source is hLO+1KHz, the frequency survey range of the external noise obtained at this time is hLO+1KHz～hLO+1KHz+hLBy analogy, 1500 bandwidths of h are obtainedLWhen the frequency spectrum information is obtained, the frequency sweep of the 1.5MHz bandwidth is completed, and the primary frequency spectrum analysis is completed;
in the case of time-series control, the data acquisition is carried out primarily during the rest of the survey, i.e. at DqThe surface wave marine environment surveying equipment has a complete sweep period D of 125ms, and the interval of each sweep period is Dinterval3.125ms, the period D of the gating pulseq3.125ms, pulse width DpThe sampling is needed to be performed within (3.125/2) ms;
the cut-off frequency of the low-pass filter of the spectrum analyzer is 300Hz, the AD sampling frequency is 100KHz, and 8 pulse interval times (D) are sampled in each time of spectrum analysisad8 x 3.125/2) ms, 1250 points can be collected and then FFT is performed to obtain signal information within 300Hz bandwidth, and at the same time, DDS converts once frequency hLO+1KHz, sampling the next frame, and so on, and the time for completing the spectrum analysis of the whole frequency band is (8 × D)q1500 × 37500) ms; then all the collected signals are subjected to statistical analysis to obtain the frequency spectrum of the external noise signal, and a proper working frequency is selected for marine environment surveying equipment to be used as a reference.
The special spectrum analyzer for the surface wave marine environment surveying equipment further comprises a zero intermediate frequency acquisition scheme which integrates frequency sweep heterodyne and FFT algorithm, wherein the selection of the sampling rate and the cut-off frequency of a low-pass filter comprises the following steps:
firstly, a single-frequency 12MHz local oscillator signal and a received signal are mixed to obtain a signal with a bandwidth of 1.5MHz, and the reason why the scanning monitoring is performed through a narrow-band low-pass filter is that: firstly, because the narrow band of the band-pass filter can not be idealized, the narrow band can not avoid serious image interference of a frequency converter, and basically can not complete a monitoring task, secondly, a signal with a bandwidth of 1.5MHz is sampled, and the sampling rate in engineering is more than 5MHz, so that the data rate of the whole equipment can be greatly improved, great difficulty is brought to the processing of subsequent data, the power consumption of the equipment is increased, and finally, because of the shortage of the number of sampling points, the resolution of a spectrum which can be monitored is very low, taking a 1024 sampling point of 5MHz as an FFT as an example, the resolution of the spectrum is close to 5 KHz;
second, selection of 300Hz cutoff frequency: the low-pass structure is determined by the overall plant monitoring principle, and the cut-off frequency of 300Hz is to filter out the modulation signal and its harmonics (period of 3.125 ms).
The special spectrum analyzer for the surface wave marine environment surveying equipment mainly comprises an analog front end, a DDS circuit module, an A/D sampling circuit, a USB interface circuit, an FPGA control module and other auxiliary circuits;
the analog front end is mainly used for amplifying and selecting a weak signal received by an antenna, and a quasi-zero frequency signal is obtained through a mixing circuit; the DDS circuit mainly obtains a single-frequency signal at intervals of a frequency sweeping period, and the single-frequency signal is amplified and filtered to be mixed with a signal coming from an antenna; the A/D sampling circuit is used for sampling, quantizing and encoding the analog zero-frequency signal, wherein the signal from the mixing circuit is a narrow-band signal close to zero frequency; the USB interface circuit is mainly used for completing the transmission of the acquired data; and the FPGA control module is used for completing the synchronization and control coordination of the whole equipment.
Dedicated spectrum analyzer of surface wave marine environment survey equipment, further, simulation front end design: the spectrum analyzer is provided with two signal paths, wherein the first signal path mainly realizes that a receiving frequency band of a noise signal is selected through a band-pass filter, the noise signal enters an RF end of a frequency converter after two-stage amplification, and the voltage gain of the whole path is 40 dB; the second signal path is a DDS local oscillator signal end, proper gain is obtained through filtering and amplification and is transmitted to an LO end of the frequency converter, the voltage gain of the second signal path is 52dB, and devices included at an analog end are classified into three types: filters, amplifiers and frequency converters.
Designing a filter amplifying circuit: the invention requires that the analysis monitoring bandwidth is 300Hz, the cut-off frequency of a filter MAX297 is adjusted in two ways, one is to adjust the clock frequency by adjusting the size of a vibration starting capacitor, the other is to adjust the clock frequency by externally connecting a clock signal, and the ratio of the clock frequency of the filter to the passband frequency is 50: 1, the cut-off frequency is flexibly set from 0.1Hz to 50kHz, various requirements of equipment are met, the clk signal of a 1 pin of MAX297 realizes the selection of the cut-off frequency in a mode of externally connecting a capacitor, the cut-off frequency fc is determined according to the relation that the ratio of the cut-off frequency of MAX297 to the clk is 1:50, and after actual debugging, the invention selects a 2.2nF capacitor to be grounded, so that the cut-off frequency of 300Hz is realized.
The special spectrum analyzer of surface wave marine environment survey equipment, further, the selection of amplifier: the selection of each stage of amplifier in the signal path is based on: the DDS amplifier has the advantages that the DDS amplifier is suitable in gain, low in noise coefficient, large in linear range, matched in input and output impedance and enough in bandwidth, various indexes are considered comprehensively, a low-noise amplifier GALI52 produced by MINI is adopted in a gain amplification unit of an RF signal path, in order to enable a frequency converter to have high local oscillation excitation, a two-stage amplification circuit consisting of GALI54 and RF2317 produced by MICRO is adopted in a local oscillation path to amplify local oscillation signals output by the DDS;
the final path is amplification after frequency mixing and filtering, mainly drives a rear A/D converter to meet the input requirement of A/D, the level adopts an OPA277 precision operational amplifier of DI company, the noise provided by the operational amplifier is lower, the output voltage swing is wider, the operational amplifier has ultra-low offset voltage and drift and bias current, the operational amplifier adopts single-stage 5v power supply, and ten times of equidirectional amplification capability is obtained by matching a feedback resistor;
the amplification capability of the operational amplifier obtains different amplification factors by adjusting R18 and R14, adds direct current at the input end, is very important for C25 in a feedback loop, and cuts off the direct current so as not to amplify the direct current.
Dedicated spectrum analyzer of surface wave marine environment survey equipment, further, DDS circuit design: the working control of the AD9854 is realized by the configuration of an internal register, the invention adopts a serial mode operation, a two-wire system mode is adopted, one serial operation period is divided into two parts of instruction operation and data operation, a read-write mode and the address of the register are configured at the rising edges of the first eight serial clocks, wherein the read-write mode is controlled at the highest position, O represents write operation, 1 represents read operation, and the address of the register is controlled by the last four bits;
the AD9854 has five optional working modes, the frequency generated by the AD9854 is in a frequency hopping mode, but the stepping frequency is 1KHz, the residence time is 25ms, the essence of the invention is that in a linear frequency modulation pulse mode, through setting the register value, the invention is mainly configured with the following control words:
firstly, starting a frequency control word, wherein the starting frequency control word is the starting frequency of each frame of sweep frequency, the starting frequency of the invention is 13MHz, and the frequency control word is correspondingly calculated according to the clock frequency;
secondly, stepping frequency control words are the unit of each frequency change, 1KHz is used as the stepping frequency, namely downward 1Hz, and after the control words of 1KHz are obtained, complementary code operation needs to be carried out on the control words;
thirdly, residence time control words are control words for controlling the time kept after each frequency change, the residence time control words and the stepping frequency together determine the slope of the frequency sweep, the frequency band bandwidth of each survey of the invention is 1.5MHz, and the residence time is 25 ms;
and fourthly, an amplitude control word which controls the output amplitude of the DDS through programming and generates a waveform with required amplitude through adjusting the amplitude control word.
Dedicated spectrum analyzer of surface wave marine environment survey equipment, further, use DDS to realize high accuracy arbitrary frequency division: the invention uses the principle of a phase accumulator to realize arbitrary frequency division and arbitrary duty ratio, firstly, a frequency control word and the phase accumulator are given, and then a counter is split to obtain the duty ratio;
reference clock HiAt 30MHz, a frequency of h is requiredo100KHz, 9/10 duty cycle, 1000ns duration low,
the frequency control word S is:
Figure BDA0002852151790000071
the minimum frequency that can be output is:
Figure BDA0002852151790000072
the maximum frequency that can be output is:
Figure BDA0002852151790000073
setting the duty ratio, firstly determining the number of counts, and if the duty ratio is 9/10, determining the judgment value of a counter as follows:
Figure BDA0002852151790000074
the method specifically comprises the following steps:
first, when cnt is less than or equal to 429496730, h00, namely low level;
second, when cnt > 429496730, h01, namely high level;
in the implementation process, the required frequency and duty ratio can be obtained only by providing the frequency control word and the numerical value of the counter, the method is very flexible and practical, and the precision is very high.
The special spectrum analyzer of surface wave marine environment survey equipment, further, the design of AD sampling circuit: the mixed signal is a narrow-band signal of 0 to 300Hz, in order to ensure that the sampled signal is not distorted, the sampling frequency of 100KHz is taken, and the sampling theorem is completely met, the ADS 8505A/D chip of TI company is selected, bipolar input of the chip is performed, a 16-bit digital signal is output, the highest sampling rate is 250KSPS, and the data conversion time of one time is 4 ns;
ADS8505 has four important control pins, respectively
Figure BDA0002852151790000075
BYTE, ADS8505 has two ways of translation and reading: first, AD conversion and reading are performed simultaneously when
Figure BDA0002852151790000076
Switching is started when the voltage is low, and the result after the previous switching is read; second, conversion is performed before reading, in
Figure BDA0002852151790000077
After initiating the conversion, the A/D feedback signal is checked
Figure BDA0002852151790000078
When the voltage is high level, the conversion is not finished, and when the voltage is low level, the conversion is finished;
the control mode of the invention adopts the steps of firstly converting and then reading, generating a signal with the period of 10us according to a time sequence chart, and receiving the signal
Figure BDA0002852151790000079
End in which
Figure BDA00028521517900000710
The signal is pulled low and guaranteed
Figure BDA00028521517900000711
Is between 40ns and 1750ns, enabling it to drive the a/D conversion.
The special spectrum analyzer of surface wave marine environment survey equipment, further, USB firmware design and download: the firmware program is finally burnt into a program file of an 8051 kernel, the upper computer can detect new equipment and assist in finishing data exchange between the host and the equipment under the control of a kernel CPU, and when an EZ-USB FX2 chip is used for application development, a firmware framework of the EZ-USB FX2 is utilized;
in the firmware design, the design and development are mainly carried out in the integrated development environment of uVision3 of Keil to generate a solidified ic file, the designed firmware of the invention requires to realize that a USB chip is controlled to receive and respond to the request of a USB device driver, data is accurately uploaded to a host, and a firmware library is generated after a firmware framework is created, wherein the firmware library comprises the following source files: reg 80320-contains 8051 header file information; ezusb.h-completes declaration of various library functions and definition of data types; fx2regs.h-contains FX2 register header file information; firmware framework provided by fw.c. -Cypress corporation; c-the function user can customize; a51-USB descriptor list;
the framework is composed of the following program files:
first, fw.c: the main file of the USB firmware program, which contains main () function, coordinates 51 the operation of kernel;
second, Periph.c: the method comprises the following steps of USB initialization and task processing functions, wherein when a person develops firmware, the person mainly aims at the file, and adds own task codes according to needs, wherein the following important functions are specifically described:
TD _ id () function: the function is called when the USB endpoint is initialized, and is called between equipment enumeration and task scheduling enabling, and the function can be set by self;
TD _ Poll () function: completing the processing of the circular task, and completing the interactive processing of OUD or IN endpoints by inquiring the state of each endpoint;
DR _ VendorCmnd function: when the frame adopts a certain appointed vendor command, the frame is called, and the decoding work of the user-defined command is mainly completed;
third, dscr.a51 is a description table file: VID and PID can be identified after the equipment is powered on, and the original VID and PID are replaced;
the invention completes the design of the Slave FIFO interface through the configuration register, only uses the endpoint 2 and the endpoint 6 to transmit data in the configuration process, the transmission mode is synchronous batch transmission, and after the firmware code is compiled through uVision3, a hex file is generated, and the downloading mode has two types: one method is to store data and codes by using an internal RAM of a USB device, and the method has high flexibility and is mainly suitable for early firmware debugging, and the other method is to store a firmware program into an EEROM.
Dedicated spectrum analyzer of surface wave marine environment survey equipment, further, FPGA control circuit design: the FPGA is the center of the spectrum analyzer, the control module is responsible for coordinating the operation of the whole equipment, and comprises the steps of generating a required local oscillation signal for the configuration of the DDS module, carrying out time sequence control on an A/D sampler, collecting an accurate external noise signal, and controlling the USB chip to ensure that the whole back-end data is transmitted without errors;
the invention adopts an EP3C40F484C6 chip of the CYCLONE 3 series of ALREA company, and an FPGA control program mainly comprises the control of A/D sampling and the control of USB data transmission:
firstly, A/D sampling control, the A/D sampling chip used by the invention is ADS8505, the chip control is relatively simple, the control time sequence requires that the conversion time is between 40 to 1750ns, the invention is set to 1000ns, the data can be converted each time, and finally a sampling signal with a period of 10us is generated, wherein the low level duration is 1000ns, and the design method adopts any frequency division principle of the invention;
secondly, USB data transmission control, the invention samples a zero intermediate frequency structure, a narrow-band signal of 0 to 300Hz is obtained through a low-pass filter after frequency mixing, the narrow-band signal is sampled by the sampling rate of 100KHz, enters an FPGA and is to be transmitted; if a synchronous writing mode is adopted, the matching problem of data rate exists, the sampling clock is 100KHz, the clock of the USB transmission control module is 48MHz, the difference is hundreds of times, if the clock is not processed, the transmitted data has great errors, and the problem of different data rate caused by mismatching of the two clocks needs to be solved;
after the program design is finished, the FPGA chip is further configured, only a single device configuration mode is used, wherein an AS active configuration mode and a JTAG configuration mode are used, the JTAG mode is mainly used in an online debugging stage, when the debugging is finished, a burning file after the program compiling is downloaded to a configuration device EPCS in the AS mode, and then the solidified program can be operated only by electrifying.
Compared with the prior art, the invention has the following contributions and innovation points:
firstly, the special spectrum analyzer for the surface wave marine environment surveying equipment provided by the invention is developed with strong pertinence and meeting requirements by taking the surface wave marine environment surveying equipment for surveying the ocean as a background, and is used for protecting and navigating the surface wave marine environment surveying equipment. The invention mainly comprises the following steps: firstly, analyzing the working waveform of surface wave marine environment surveying equipment, and providing a zero intermediate frequency acquisition scheme integrating sweep frequency heterodyne and FFT algorithm; secondly, analyzing an intermediate frequency digital acquisition scheme of the frequency spectrum analysis of the surface wave marine environment surveying equipment, designing and developing a frequency spectrum analyzer suitable for the surface wave marine environment surveying equipment, designing an analog front end circuit, a DDS circuit, an A/D sampling circuit and a control module of an FPGA in detail, and completing the compiling of firmware of a USB data transmission part and the design and test of an upper computer; thirdly, the drawing of a schematic diagram and a PCB of the whole project is completed, after the board manufacturing is successful, the debugging of the equipment is completed by combining an oscilloscope and a signal source instrument, the correctness of the spectrum analyzer is verified, and a good foundation is laid for designing a full-digital spectrum analyzer in the later period.
Secondly, the special spectrum analyzer for the surface wave marine environment surveying equipment is designed aiming at the distributed surface wave marine environment networking detecting equipment, the structure of the creatively proposed spectrum analyzer is different from that of an intermediate frequency sampling structure, a zero intermediate frequency structure is adopted, the selection of sampling time points is also different, and the result can be used as a key technical index for selecting proper working frequency of the equipment; the digital technology is utilized to realize the flexible adjustment of working parameters, complete the spectrum analysis work of the equipment under different working environments, and can skillfully avoid the influence of modulation signals on the equipment.
Thirdly, the spectrum analyzer special for the surface wave marine environment surveying equipment provided by the invention mainly adopts a narrow-band intermediate frequency digital structure and a mode of once frequency conversion and high and intermediate frequency sampling aiming at the spectrum analysis in the prior art, and the spectrum analyzer mainly works in the intermittent period of the work of the surveying equipment, namely the time in the middle of two frequency sweep periods, and the mode has a series of problems: first, sampling time points: in the prior art, the interval time of the intermittent period is greatly shortened, if only the signal of the intermittent period is sampled, the number of sampling points is obviously insufficient, or the sampling frequency needs to be improved, but the problem that the external noise interference cannot be accurately reflected still exists; second, the echo signal collects the noise and interference signalThe influence of (a): at TpThe low effective sampling of the pulse must have an influence on the acquisition of noise and interference signals, and if the spectrum analysis equipment according to the prior art still performs sampling in the intermittent period of the work of the survey equipment, the influence of echo signals on the acquisition of noise and interference signals still cannot be avoided, because the current intermittent period time also only has one TpThe bandwidth of each time of analysis of the device is 300Hz, the effective bandwidth of the working frequency of the surveying device is selected to be 30KHz, the spectrum analysis range is 1500KHz bandwidth signals, the influence of the bandwidth of the 30KHz signals is eliminated, the selectable bandwidth is quite abundant, and the selection judgment can be made by integrating spectrogram results obtained by the currently selected working frequency; thirdly, the problem of image frequency caused by the frequency converter: because the invention adopts the zero intermediate frequency structure, various harmonic components generated by the frequency converter are greatly inhibited, the low-pass filter following the frequency converter has the cut-off frequency of 300Hz, and can ensure the purity of the difference frequency signal after frequency mixing, secondly, the invention adopts the low-pass filter with the cut-off frequency of 300Hz, and also removes the identification error of the surveying signal caused by the nonpolarity of the frequency converter, and finally, the modulation signal TpThe signal with the period of 3.125ms exists in the device, the signal with the frequency of 320Hz and harmonic wave thereof can be filtered out through a low-pass filter, and the invention has great improvement aiming at the problems in the prior art.
Fourthly, the spectrum analyzer special for the surface wave marine environment surveying equipment, provided by the invention, aims at the problems that the radio spectrum analyzing equipment in the current market is expensive, the monitored spectrum range is too wide and far exceeds the working range of the surface wave marine environment surveying equipment, so that the resource is greatly wasted; the surface wave marine environment surveying equipment is not well adapted to a co-station transmitting and receiving mode of the surface wave marine environment surveying equipment, a high-power transmitting signal of the equipment is very likely to damage commonly used spectrum analysis equipment, and the spectrum analysis equipment is designed for the surface wave marine environment surveying equipment in a targeted manner, so that the spectrum analysis equipment can not only receive short-wave-band interference and noise in the working environment of the surface wave marine environment surveying equipment and provide noise data for later-stage data acquisition, but also select proper working frequency for the surveying equipment to be used as reference.
Drawings
FIG. 1 is a schematic diagram of the heterodyne and FFT based spectral analysis of the present invention.
Fig. 2 is a schematic diagram of the spectrum monitoring signal flow of the present invention.
FIG. 3 is a schematic diagram of the structural principle of the spectrum monitor of the present invention.
FIG. 4 is a flow diagram of a firmware framework of the present invention.
Fig. 5 is a software workflow diagram of the dedicated spectrum analyzer of the present invention.
Detailed Description
The technical solutions provided by the present invention are further described below with reference to the accompanying drawings, so that those skilled in the art can better understand the present invention and can implement the present invention.
The surface wave marine environment surveying equipment utilizes high-power electromagnetic waves of 3-30 MHz to survey marine environment, the working frequency is mainly in the frequency bands of 6.8-8.4 MHz and 11.8-13.6 MHz, but a large amount of strong interference and noise exist in the frequency bands, and the operation of the equipment is seriously influenced. Therefore, the external noise condition needs to be analyzed, and a proper and effective working frequency reference is selected for equipment.
The special spectrum analyzer for the surface wave marine environment surveying equipment comprises two parts of hardware and software: in the aspect of hardware, the amplification and demodulation functions of weak signals to be analyzed are completed by taking a filter, an amplifier and a frequency converter as cores from an analog receiving front end; using DDS chip (AD9854) to generate needed local oscillation signal; ADS8505 finishes digital acquisition of analog signals; the cyclic 3 series chip (EP3C40F484) of ALTERA is adopted to complete the time sequence control of the whole equipment and coordinate the operation of each digital part; the data transmission of the equipment adopts the USB3.0 technology, and the used control chip is CY7C68013 of CYPRESS company; in the aspect of software, Visual Studio 2010 is used as a design platform to complete reading, FFT processing, spectrum display and data storage of collected data, and finally the whole spectrum analysis equipment is displayed in a form of a real object.
The invention mainly comprises the following steps: firstly, analyzing the working waveform of surface wave marine environment surveying equipment, and providing a zero intermediate frequency acquisition scheme integrating sweep frequency heterodyne and FFT algorithm; secondly, analyzing an intermediate frequency digital acquisition scheme of the frequency spectrum analysis of the surface wave marine environment surveying equipment, designing and developing a frequency spectrum analyzer suitable for the surface wave marine environment surveying equipment, designing an analog front end circuit, a DDS circuit, an A/D sampling circuit and a control module of an FPGA in detail, and completing the compiling of firmware of a USB data transmission part and the design and test of an upper computer; thirdly, the drawing of a schematic diagram and a PCB of the whole project is completed, after the board manufacturing is successful, the debugging of the equipment is completed by combining an oscilloscope and a signal source instrument, the correctness of the spectrum analyzer is verified, and a good foundation is laid for designing a full-digital spectrum analyzer in the later period.
The frequency spectrum analyzer disclosed by the invention is simple in overall structure, flexible regulation and control of working parameters are realized by utilizing a digitization technology, a technical basis is provided for a full digitization scheme of the frequency spectrum analyzer, monitoring and analysis on external strong interference noise can be better completed by verification and analysis and adopting a frequency hopping technology, and the requirement of novel surface wave marine environment surveying equipment can be met.
Frequency spectrum analysis method integrating heterodyne structure and FFT algorithm
The spectrum analyzer of the surface wave marine environment surveying equipment is based on the principles of a heterodyne structure and FFT, and is improved by fusing the two principles, as shown in FIG. 1.
During the spectrum analysis, the local oscillator output is a single frequency signal hLOFrom local oscillator frequency and radio frequency signal hRAnd the cut-off frequency h of the low-pass filterLDetermining the frequency spectrum of the external noise signal in the frequency range hLO～hLO+hLWhen 1024 data points are collected, the process is finishedSampling once, wherein the output of the local vibration source is hLO+1KHz, the frequency survey range of the external noise obtained at this time is hLO+1KHz～hLO+1KHz+hLBy analogy, 1500 bandwidths of h are obtainedLWhen the spectrum information is obtained, the frequency sweeping of the 1.5MHz bandwidth is completed, and the spectrum analysis is completed once.
In the aspect of time sequence control, because the surface wave marine environment surveying equipment works in a transmitting and receiving co-station mode, in order to avoid burning down a spectrum analyzer by a high-power transmitting signal, the data acquisition mainly works in the working intermittence period of the surveying equipment, namely in the D periodqThe surface wave marine environment surveying equipment has a complete sweep period D of 125ms, and the interval of each sweep period is Dinterval3.125ms, the period D of the gating pulseq3.125ms, pulse width DpFor better understanding of the monitoring and analyzing process of the device, see the signal flow diagram of fig. 2, a sampling needs to be made within (3.125/2) ms.
The cut-off frequency of the low-pass filter of the spectrum analyzer is 300Hz, the AD sampling frequency is 100KHz, and 8 pulse interval times (D) are sampled in each time of spectrum analysisad8 x 3.125/2) ms, 1250 points can be collected and then FFT is performed to obtain signal information within 300Hz bandwidth, and at the same time, DDS converts once frequency hLO+1KHz, sampling the next frame, and so on, and the time for completing the spectrum analysis of the whole frequency band is (8 × D)q*1500＝37500)ms。
Then all the collected signals are subjected to statistical analysis to obtain the frequency spectrum of the external noise signal, and a proper working frequency is selected for marine environment surveying equipment to be used as a reference.
The selection of the sampling rate and the cut-off frequency of the low-pass filter includes:
firstly, a single-frequency 12MHz local oscillator signal and a received signal are mixed to obtain a signal with a bandwidth of 1.5MHz, and the reason why the scanning monitoring is performed through a narrow-band low-pass filter is that: firstly, because the narrow band of the band-pass filter can not be idealized, the narrow band can not avoid serious image frequency interference of a frequency converter, a monitoring task can not be basically completed, secondly, a signal with the bandwidth of 1.5MHz is sampled, the sampling rate in engineering is above 5MHz, the data rate of the whole equipment can be greatly improved, great difficulty is brought to the processing of subsequent data, the power consumption of the equipment is increased, and finally, because of the shortage of the number of sampling points, the resolution of a spectrum which can be monitored is very low, for example, 1024 points of sampling of 5MHz are taken as FFT, and the resolution of the spectrum is close to 5 KHz.
Second, selection of 300Hz cutoff frequency: the low-pass structure is determined by the overall plant monitoring principle, and the cut-off frequency of 300Hz is to filter out the modulation signal and its harmonics (period of 3.125 ms).
Hardware design of spectrum analyzer
Overall design of hardware
The spectrum analyzer mainly comprises an analog front end, a DDS circuit module, an A/D sampling circuit, a USB interface circuit, an FPGA control module and other accessory circuits, as shown in figure 3.
The analog front end is mainly used for amplifying and selecting a weak signal received by an antenna, and a quasi-zero frequency signal is obtained through a mixing circuit; the DDS circuit mainly obtains a single-frequency signal at intervals of a frequency sweeping period, and the single-frequency signal is amplified and filtered to be mixed with a signal coming from an antenna; the A/D sampling circuit is used for sampling, quantizing and encoding the analog zero-frequency signal, wherein the signal from the mixing circuit is a narrow-band signal close to zero frequency; the USB interface circuit is mainly used for completing the transmission of the acquired data; and the FPGA control module is used for completing the synchronization and control coordination of the whole equipment.
(II) analog front end design
The spectrum analyzer is provided with two signal paths, wherein the first signal path mainly realizes that a receiving frequency band of a noise signal is selected through a band-pass filter, the noise signal enters an RF end of a frequency converter after two-stage amplification, and the voltage gain of the whole path is 40 dB; the second signal path is a DDS local oscillation signal end, proper gain is obtained through filtering and amplification and is transmitted to an LO end of the frequency converter, and the voltage gain of the path is 52 dB. The devices included at the analog side are of three types: filters, amplifiers and frequency converters.
1. Filter amplifier circuit design
(1) The selection of the filter is mainly divided into three categories:
the first type: aiming at a first signal path, the frequency band of an input noise signal is mainly selected, in the embodiment, the noise signal with the monitoring range of 12-13.5 MHz is selected, an LC band-pass filter SBP-13 is selected, and on the path, the noise signal is selected in a two-stage filtering mode, so that the signal is guaranteed to be real and reliable. In both high and low frequency bands, for monitoring signals in a bandwidth of 7 to 8.5MHz, only a 7 to 8.5MHz band-pass filter needs to be added, and when the signals need to be used, the preselection filter is switched, so too is the corresponding DDS path, and the description is not repeated below;
the second type: for the second signal path, the band-pass filter mainly used for inhibiting the DDS spurious adopts a zero intermediate frequency superheterodyne structure, so that the selected band-pass filter is SBP-13;
in the third category: and a low-pass filter MAX297 is adopted in the first-stage filter after the output of the frequency converter, and the stop band attenuation of the first-stage filter reaches 80 dB.
The invention requires that the analysis monitoring bandwidth is 300Hz, the cut-off frequency of a filter MAX297 is adjusted in two ways, one is to adjust the clock frequency by adjusting the size of a vibration starting capacitor, the other is to adjust the clock frequency by externally connecting a clock signal, and the ratio of the clock frequency of the filter to the passband frequency is 50: 1, the cut-off frequency is flexibly set from 0.1Hz to 50kHz, thereby meeting various requirements of equipment. The clk signal of the 1 pin of the MAX297 realizes the selection of cut-off frequency in a mode of externally connecting a capacitor, the cut-off frequency fc is determined according to the relation that the ratio of the cut-off frequency of the MAX297 to the clk is 1:50, and after actual debugging, the invention selects a 2.2nF capacitor to be grounded, thereby realizing the cut-off frequency of 300 Hz.
(2) Selection of amplifiers
The selection of each stage of amplifier in the signal path is based on: proper gain, low noise figure, large linear range, matching of input and output impedance and enough bandwidth. By comprehensively considering various indexes, a low-noise amplifier GALI52 produced by MINI is adopted in an RF signal path gain amplification unit, and in order to enable a frequency converter to have high local oscillation excitation, a two-stage amplification circuit consisting of GALI54 and RF2317 produced by MICRO is adopted in a local oscillation path to amplify the local oscillation signal output by the DDS.
The final path is amplification after frequency mixing and filtering, mainly drives a rear A/D converter to meet the input requirement of A/D, the level adopts an OPA277 precision operational amplifier of DI company, the noise provided by the operational amplifier is lower, the output voltage swing is wider, the operational amplifier has ultra-low offset voltage, drift and bias current and high common mode rejection, the operational amplifier adopts single-stage 5v power supply, and ten times of equidirectional amplification capability is obtained by matching a feedback resistor.
The amplification capability of the operational amplifier obtains different amplification factors by adjusting R18 and R14, adds direct current at the input end, is very important for C25 in a feedback loop, and cuts off the direct current so as not to amplify the direct current. The differences can be visually shown by using Dina90 simulation software of TI company. If no capacitor is added, the operational amplifier loses the amplification effect on the alternating current signal and even inhibits the output of the alternating current signal.
2. Mixer circuit design
The invention adopts a zero intermediate frequency digitization scheme of a primary frequency conversion scheme, which is completed by a frequency converter, and the selection of a proper frequency mixing circuit is a crucial loop. The invention adopts a double-balanced frequency converter RAY-3 produced by MINI company, and the input local oscillator of the double-balanced frequency converter RAY-3 reaches +23dBm, thereby ensuring that the input dynamic range is larger. This is critical in spectrum analyzers, because the large input dynamic range means that the converter can still keep a linear relationship between the output and the input at a higher input, and meet the requirement of measuring the drastic change of noise in a frequency band, another important parameter is the frequency conversion loss of the converter, the typical value of the frequency conversion loss is 5.53dB, the isolation degree is 50dB, and the standing wave ratio of an LO port is less than 1.5.
(III) DDS Circuit design
DDS chip type selection
The invention adopts an AD9854 chip with a linear frequency modulation function of ADI company, a high-performance D/A converter is arranged in an AD9854 digital synthesizer, the bit width of an internally integrated frequency accumulator and a phase accumulator is up to 48 bits, so that the generation of high-stability frequency, phase and amplitude is ensured, the invention uses 0.35um CMOS technology, and is provided with a programmable 4-20 times reference clock multiplier circuit, so that an internal 300M device clock can be generated by the external lower reference clock frequency in a frequency multiplication mode.
The AD9854 adopts an 80-pin LQFP surface mount packaging form and corresponds to two packaging structures: AD9854ASQ and AD9854ASD, which differ mainly in: the clock reference frequency of the ASQ reaches 300MHz, the power consumption reaches 3W, and the ASD clock reference frequency is 200MHz at most, and the power consumption is 2W. Therefore, the power consumption of the device is still very large, when the PCB is applied and designed, the heat of the chip is radiated, the chip is prevented from being burnt by overheating, when the chip is applied, a plurality of pins and internal registers are mainly configured, and the pins used by the invention comprise: number 19-A0/SDIO pin: parallel address input/bidirectional serial data input/output, a0 used only in parallel programming mode, SDIO used in two-wire communication mode; number 29-FSK/BPSK/HOLD pin: the function is selected depending on the mode of operation of the program control register. If FSK mode, logic low corresponds to F1, logic high corresponds to F2, if BPSK mode, logic low corresponds to phase 1, logic high corresponds to phase 2, in pulse mode logic high is used for hold function, so that the frequency accumulator stops at the current position, logic low can be inserted for continuation or restart; pins number 61-PLL FILTER: the external zero compensation network of the phase-locked loop filter connected with the reference clock multiplier is formed by connecting a resistor of 1.3k omega and a capacitor of 0.01uF in series; pins 71-MASTER RESET: the serial or parallel programming bus is initialized in preparation for user programming and the programming registers are set to an idle state, i.e., a default value defined by the register allocation table, logic high active, and a main reset is necessary for proper power-on operation.
DDS Circuit design
The working control of the AD9854 is realized by the configuration of an internal register, the invention adopts a serial mode operation, adopts a two-wire mode, one serial operation period is divided into two parts of instruction operation and data operation, a read-write mode and the address of the register are configured at the rising edges of the first eight serial clocks, wherein the read-write mode is controlled at the highest position, O represents write operation, 1 represents read operation, and the address of the register is controlled by the last four bits.
The AD9854 has five optional working modes, the frequency generated by the AD9854 is in a frequency hopping mode, but the stepping frequency is 1KHz, the dwell time is 25ms, and the essence is that in a linear frequency modulation pulse mode, the register value is set. The invention is mainly configured with the following control words:
firstly, starting a frequency control word, wherein the starting frequency control word is the starting frequency of each frame of sweep frequency, the starting frequency of the invention is 13MHz, and the frequency control word is correspondingly calculated according to the clock frequency;
secondly, stepping frequency control words are the unit of each frequency change, 1KHz is used as the stepping frequency, namely downward 1Hz, and after the control words of 1KHz are obtained, complementary code operation needs to be carried out on the control words;
thirdly, residence time control words are control words for controlling the time kept after each frequency change, the residence time control words and the stepping frequency together determine the slope of the frequency sweep, the frequency band bandwidth of each survey of the invention is 1.5MHz, and the residence time is 25 ms;
and fourthly, an amplitude control word which controls the output amplitude of the DDS through programming and generates a waveform with required amplitude through adjusting the amplitude control word.
3. High-precision arbitrary frequency division by using DDS
In the multi-rate signal processing, a plurality of clocks are often required in the whole design, and the hardware platform only gives out a required highest-frequency clock by a crystal oscillator, and the required other frequencies and the frequency are generally in integral multiple relation, and the highest-frequency clock can be used for frequency division to obtain other required clocks. The invention uses the principle of phase accumulator to realize arbitrary frequency division and arbitrary duty ratio. Firstly, a frequency control word and a phase accumulator are given, and then a counter is split to obtain a duty ratio.
Example reference clock HiAt 30MHz, a frequency of h is requiredo100KHz, the duty cycle is 9/10 (low level duration is 1000 ns).
The frequency control word S is:
Figure BDA0002852151790000151
the minimum frequency that can be output is:
Figure BDA0002852151790000161
the maximum frequency that can be output is:
Figure BDA0002852151790000162
setting the duty ratio, firstly determining the number of counts, and if the duty ratio is 9/10, determining the judgment value of a counter as follows:
Figure BDA0002852151790000163
the method specifically comprises the following steps:
first, when cnt is less than or equal to 429496730, h00, namely low level;
second, when cnt > 429496730, h0I.e. high, 1.
In the implementation process, the required frequency and duty ratio can be obtained only by providing the frequency control word and the numerical value of the counter, the method is very flexible and practical, and the precision is very high.
(IV) A/D sampling circuit design
The mixed signal is a narrow-band signal of 0-300 Hz, and in order to avoid the distortion of the sampled signal, the sampling frequency of 100KHz is adopted, thus completely meeting the sampling theorem. The invention selects ADS 8505A/D chip of TI company, which has bipolar input and output 16-bit digital signal, the highest sampling rate of 250KSPS, and one-time data conversion time of 4 ns.
ADS8505 has four important control pins, respectively
Figure BDA0002852151790000164
BYTE, ADS8505 has two ways of translation and reading: first, AD conversion and reading are performed simultaneously when
Figure BDA0002852151790000165
Switching is started when the voltage is low, and the result after the previous switching is read; second, conversion is performed before reading, in
Figure BDA0002852151790000166
After initiating the conversion, the A/D feedback signal is checked
Figure BDA0002852151790000167
The transition is not completed when the level is high, and the transition is completed when the level is low.
The control mode of the invention adopts the steps of firstly converting and then reading, generating a signal with the period of 10us according to a time sequence chart, and receiving the signal
Figure BDA0002852151790000168
End in which
Figure BDA00028521517900001610
The signal is pulled low and guaranteed
Figure BDA0002852151790000169
Is between 40ns and 1750ns, enabling it to drive the a/D conversion.
(V) USB data transmission circuit
Slave FIFO transfer mode
When a logic device is connected with an FX2 chip, FX2 high-speed communication is utilized, EZ-USB is used as a bridge between USB and an external logic device, a plurality of FIFO buffers are designed in the EZ-USB chip, the external logic device accesses the endpoint FIFO buffers to realize read-write operation, and data to be transmitted is communicated between a USB host and the external logic device. In the transmission process, the CPU has very high efficiency because the CPU does not intervene, and the transmission mode is designed to be a Slave FIFO transmission mode.
In the Slave FIFO mode, two read-write operation modes, namely a synchronous mode and an asynchronous mode are provided, the selection is completed by configuring IFCONFIG3, and in the synchronous mode, the value of the register is set to be 0, and in the asynchronous mode, the value is set to be 1.
USB firmware design and download
The firmware program is finally burned into a program file of the 8051 kernel, so that the upper computer can detect the new device and assist in completing data exchange between the host and the device under the control of the kernel CPU. A complete firmware program contains a plurality of functions and is complex in structure, so that when an EZ-USB FX2 chip is used for application development, the firmware framework of the EZ-USB FX2 is used, the engineering development time is greatly reduced, and the working efficiency is improved. Cypress provides a function library and a firmware framework of firmware for a user, and a normally running firmware program can be completed only by modifying the firmware framework. The complete firmware framework flow is shown in fig. 4.
In the firmware design, the design and development are mainly carried out in the integrated development environment of uVision3 of Keil to generate a solidified ic file, the designed firmware of the invention requires to realize that a USB chip is controlled to receive and respond to the request of a USB device driver, data is accurately uploaded to a host, and a firmware library is generated after a firmware framework is created, wherein the firmware library comprises the following source files: reg 80320-contains 8051 header file information; ezusb.h-completes declaration of various library functions and definition of data types; fx2regs.h-contains FX2 register header file information; firmware framework provided by fw.c. -Cypress corporation; c-the function user can customize; a51-USB descriptor list.
The framework is composed of the following program files:
first, fw.c: the main file of the USB firmware program, which contains main () function, coordinates 51 the operation of kernel;
second, Periph.c: the method comprises the following steps of USB initialization and task processing functions, wherein when a person develops firmware, the person mainly aims at the file, and adds own task codes according to needs, wherein the following important functions are specifically described:
TD _ id () function: the function is called when the USB endpoint is initialized, and is called between equipment enumeration and task scheduling enabling, and the function can be set by self;
TD _ Poll () function: completing the processing of the circular task, and completing the interactive processing of OUD or IN endpoints by inquiring the state of each endpoint;
DR _ VendorCmnd function: when the frame adopts a certain appointed vendor command, the frame is called, and the decoding work of the user-defined command is mainly completed;
third, dscr.a51 is a description table file: upon power-up of the device, the VID and PID are recognized, replacing the original VID and PID.
The invention completes the design of the Slave FIFO interface through the configuration register, only uses the endpoint 2 and the endpoint 6 to transmit data in the configuration process, and the transmission mode is synchronous batch transmission. The hex file is generated after the firmware code is compiled by uVision3, and the downloading mode has two modes: one method is to store data and codes by using an internal RAM of a USB device, and the method has high flexibility and is mainly suitable for early firmware debugging, and the other method is to store a firmware program into an EEROM.
(VI) FPGA control circuit design
The FPGA is the center of the spectrum analyzer, and the control module is responsible for coordinating the operation of the whole equipment, including generating a required local oscillation signal for the configuration of the DDS module, carrying out time sequence control on the A/D sampler, collecting an accurate external noise signal, and controlling the USB chip to ensure that the whole back-end data is transmitted without errors.
The invention adopts an EP3C40F484C6 chip of the CYCLONE 3 series of ALTREA company, the chip has low power consumption and good performance, is a programmable gate array device, has rich resources and can meet various requirements of equipment, and an FPGA control program mainly comprises the control of A/D sampling and the control of USB data transmission:
firstly, the A/D sampling control, the A/D sampling chip used by the invention is ADS8505, the chip control is relatively simple, the control time sequence requires that the conversion time is between 40 to 1750ns, the invention is set to 1000ns, the data can be converted each time, finally, a sampling signal with a period of 10us is generated, wherein the low level duration is 1000ns, and the design method adopts any frequency division principle of the invention.
Secondly, USB data transmission control, the invention samples a zero intermediate frequency structure, a narrow-band signal of 0 to 300Hz is obtained through a low-pass filter after frequency mixing, the narrow-band signal is sampled by the sampling rate of 100KHz, enters an FPGA and is to be transmitted; if a synchronous writing mode is adopted, the problem of data rate matching exists, the sampling clock is 100KHz, the clock of the USB transmission control module is 48MHz, the difference is hundreds of times, if the data are not processed, the transmitted data have great errors, and the problem of different data rates caused by mismatching of the two clocks needs to be solved. The invention is convenient and stable, and is designed by adopting an IP core module in the quartz.
In another mode, an asynchronous control mode is adopted, asynchronous FIFO writing is carried out in the Slave FIFO mode, the control of an internal FIFO clock is not related, and only a write enable signal needs to be controlled, and the process is as follows: firstly, appointing FIFO to be written in, then inquiring the full-empty zone bit of FIFO, if FIFO is not full, enabling write signal to write data on bus into FIFO, otherwise stopping writing.
The asynchronous writing mode is synchronous and simple, and can well complete the control of FIFO inside the USB through the collocation with the A/D acquisition time sequence.
And after the program design is finished, further configuring the FPGA chip. Because the FPGA control chip of the whole equipment is only one, in the configuration aspect, only a single device configuration mode is used, wherein an AS active configuration mode and a JTAG configuration mode are used, the JTAG mode is mainly used in an online debugging stage, after the debugging is finished, a burning file obtained after the program compiling is downloaded to a configuration device EPCS in the AS mode, and then the solidified program can be operated AS long AS the program is electrified. The following are the specific contents of the two configuration modes of the invention respectively:
the first method is as follows: JTAG configuration mode, when JTAG order is prior to any other configuration mode, when JTAG configuration is effective, it is not necessary to wait for other configuration mode to complete, JTAG has four pins TDI, TDO, TMS, TCK, among which, TCK pin has weak pull-down resistance, TDI and TMS have weak pull-up resistance, data port is connected with I/O port, specifically: the type of the pin TDI is test data input, test and programming data are input through a serial input pin, data transfer occurs at the rising edge of TCK, the TDI pin is powered by VCCIO, and if the PCB does not have a JTAG interface circuit, the VCCIO of the pin is forbidden; the type of the pin TDO is test data output, test and programming data are output through a serial output pin, the data transfer occurs on the falling edge of the TCK, and if the data are not transferred, the pin is in a tri-state; the type of the pin TMS is selected as a test mode, a control signal is provided by an input pin, the state of the TAP controller is determined, and the state transition occurs on the rising edge of the TCK; pin TCK, type test clock, clock input pin, allows certain operations to occur on either the rising or falling edge.
The second method comprises the following steps: compared with the JTAG mode, the AS configuration mode mainly has one more configuration chip, in the AS configuration scheme, the CYCLONE device series adopts a serial configuration mode to configure equipment, the invention adopts EPCS16 serial hlash, wherein MSELx has different connection methods for different modes and different configuration levels.
Second, software design
Design of upper computer
In order to complete the interactive communication between a spectrum analyzer and an upper computer, the invention builds upper computer software on a Visual Studio 2010 platform of Microsoft corporation to realize the reading, the storage, the FFT conversion processing, the data storage and the final spectrum display of monitoring signals of collected data, calls a dynamic link library CyUSB.dll provided by Cypress corporation, and the control function contained in the dynamic link library comprises: CyBulkEndPoint-is used for USB block transmission endpoint control, CyControlEndPoint-is used for USB control transmission endpoint, CyIsoEndPoint-is used for USB synchronous transmission endpoint control, CyUSBDevice-is used for USB device information, USBDeviceList-is used for USB device list, CyUSBendPoint-is used for USB endpoint control, CyHiddevice-is used for USB HID device control, and CyUSBStorDevice-is used for USB large-capacity storage device control. The software workflow diagram is as in figure 5.
(II) software testing and analysis
USB3.0 speed test
After a driver is correctly installed, a control program of an FPGA (field programmable gate array) for the USB equipment is designed on a quartz platform, wherein a counter generates a group of increasing data and is loaded on a 16-bit bus of the USB, the program is downloaded into hardware equipment after being successfully compiled, upper computer software is opened, data acquisition is started, a real-time data button is clicked, the change of the increasing rule of the received data is seen in a real-time data frame, an EZ-USBInterface window is opened, a Download button is clicked, a Sdream. In the test process, data can be correctly transmitted without losing data, and the transmission speed is close to 360MB/s and is in a high-speed transmission state.
2. Host computer software testing
Connecting the USB equipment to a host computer, downloading a program compiled by the FPGA, clicking a button of the host computer for connecting the USB equipment to display successful connection by using a data port of an FD bus as data after A/D sampling, clicking a button for starting acquisition, and displaying a spectrogram after a period of time. And then sequentially clicking real-time display and data storage buttons. Through analysis, the whole upper computer software runs normally, a processing part for data is added into the upper computer software, namely FFT (fast Fourier transform) conversion is carried out on the collected data, an energy value of a signal is obtained in a mode of accumulating and averaging, and then the energy value is displayed on a spectrogram.

Claims (10)

1. The special frequency spectrum analyzer for the surface wave marine environment surveying equipment is characterized in that firstly, the working waveform of the surface wave marine environment surveying equipment is analyzed, and a zero intermediate frequency acquisition scheme integrating frequency sweep heterodyne and FFT algorithm is provided; secondly, analyzing an intermediate frequency digital acquisition scheme of the frequency spectrum analysis of the surface wave marine environment surveying equipment, designing and developing a frequency spectrum analyzer suitable for the surface wave marine environment surveying equipment, designing an analog front end circuit, a DDS circuit, an A/D sampling circuit and a control module of an FPGA in detail, and completing the compiling of firmware of a USB data transmission part and the design and test of an upper computer; thirdly, drawing of a schematic diagram and a PCB of the whole project is completed, after the board is successfully manufactured, debugging of equipment is completed by combining an oscilloscope and a signal source instrument, the correctness of the spectrum analyzer is verified, and a good foundation is laid for designing a full-digital spectrum analyzer in the later period;
the special spectrum analyzer for the surface wave marine environment surveying equipment comprises two parts of hardware and software: in the aspect of hardware, the amplification and demodulation functions of weak signals to be analyzed are completed by taking a filter, an amplifier and a frequency converter as cores from an analog receiving front end; generating a required local oscillation signal by using a DDS chip; ADS8505 finishes digital acquisition of analog signals; the cyclic 3 series chip of ALTERA is adopted to complete the time sequence control of the whole equipment and coordinate the operation of each digital part; the data transmission of the equipment adopts the USB3.0 technology, and the used control chip is CY7C68013 of CYPRESS company; in the aspect of software, the Visual Studio 2010 is used as a design platform to complete the reading, FFT processing, frequency spectrum display and data storage of the collected data, and finally the whole frequency spectrum analysis equipment is displayed in a form of a real object;
the frequency spectrum analyzer of the surface wave marine environment surveying equipment is based on the heterodyne structure and the FFT principle, the heterodyne structure and the FFT principle are fused and improved, and during the frequency spectrum analysis, the local oscillator output is a single-frequency signal hLOFrom local oscillator frequency and radio frequency signal hRAnd the cut-off frequency h of the low-pass filterLDetermining the frequency spectrum of the external noise signal in the frequency range hLO～hLO+hLWhen 1024 data points are collected, one sampling is completed, and at the moment, the output of the local vibration source is hLO+1KHz, the frequency survey range of the external noise obtained at this time is hLO+1KHz～hLO+1KHz+hLBy analogy, 1500 bandwidths of h are obtainedLWhen the frequency spectrum information is obtained, the frequency sweep of the 1.5MHz bandwidth is completed, and the primary frequency spectrum analysis is completed;
in the case of time-series control, the data acquisition is carried out primarily during the rest of the survey, i.e. at DqThe surface wave marine environment surveying equipment has a complete sweep period D of 125ms, and the interval of each sweep period is Dinterval3.125ms, the period D of the gating pulseq3.125ms, pulse width DpThe sampling is needed to be performed within (3.125/2) ms;
the cut-off frequency of the low-pass filter of the spectrum analyzer is 300Hz, the AD sampling frequency is 100KHz, and 8 pulse interval times (D) are sampled in each time of spectrum analysisad8 x 3.125/2) ms, 1250 points can be collected and then FFT is performed to obtain signal information within 300Hz bandwidth, and at the same time, DDS converts once frequency hLO+1KHz, sampling the next frame, and so on, and the time for completing the spectrum analysis of the whole frequency band is (8 × D)q1500 × 37500) ms; then all the collected signals are subjected to statistical analysis to obtain the frequency spectrum of the external noise signal, and a proper working frequency is selected for marine environment surveying equipment to be used as a reference.
2. The surface wave marine environment survey instrument specific spectrum analyzer of claim 1, wherein the selection of the sampling rate and the low pass filter cut-off frequency in the zero intermediate frequency acquisition scheme that combines the swept heterodyne and FFT algorithms comprises:
firstly, a single-frequency 12MHz local oscillator signal and a received signal are mixed to obtain a signal with a bandwidth of 1.5MHz, and the reason why the scanning monitoring is performed through a narrow-band low-pass filter is that: firstly, because the narrow band of the band-pass filter can not be idealized, the narrow band can not avoid serious image interference of a frequency converter, and basically can not complete a monitoring task, secondly, a signal with a bandwidth of 1.5MHz is sampled, and the sampling rate in engineering is more than 5MHz, so that the data rate of the whole equipment can be greatly improved, great difficulty is brought to the processing of subsequent data, the power consumption of the equipment is increased, and finally, because of the shortage of the number of sampling points, the resolution of a spectrum which can be monitored is very low, taking a 1024 sampling point of 5MHz as an FFT as an example, the resolution of the spectrum is close to 5 KHz;
second, selection of 300Hz cutoff frequency: the low-pass structure is determined by the overall plant monitoring principle, and the cut-off frequency of 300Hz is to filter out the modulation signal and its harmonics (period of 3.125 ms).
3. The special spectrum analyzer for the surface wave marine environment surveying equipment of claim 1, wherein the spectrum analyzer mainly comprises an analog front end, a DDS circuit module, an a/D sampling circuit, a USB interface circuit, an FPGA control module, and other accessory circuits;
the analog front end is mainly used for amplifying and selecting a weak signal received by an antenna, and a quasi-zero frequency signal is obtained through a mixing circuit; the DDS circuit mainly obtains a single-frequency signal at intervals of a frequency sweeping period, and the single-frequency signal is amplified and filtered to be mixed with a signal coming from an antenna; the A/D sampling circuit is used for sampling, quantizing and encoding the analog zero-frequency signal, wherein the signal from the mixing circuit is a narrow-band signal close to zero frequency; the USB interface circuit is mainly used for completing the transmission of the acquired data; and the FPGA control module is used for completing the synchronization and control coordination of the whole equipment.
4. The surface wave marine environment survey instrument specific spectrum analyzer of claim 1, wherein the analog front end design: the spectrum analyzer is provided with two signal paths, wherein the first signal path mainly realizes that a receiving frequency band of a noise signal is selected through a band-pass filter, the noise signal enters an RF end of a frequency converter after two-stage amplification, and the voltage gain of the whole path is 40 dB; the second signal path is a DDS local oscillator signal end, proper gain is obtained through filtering and amplification and is transmitted to an LO end of the frequency converter, the voltage gain of the second signal path is 52dB, and devices included at an analog end are classified into three types: filters, amplifiers and frequency converters;
designing a filter amplifying circuit: the invention requires that the analysis monitoring bandwidth is 300Hz, the cut-off frequency of a filter MAX297 is adjusted in two ways, one is to adjust the clock frequency by adjusting the size of a vibration starting capacitor, the other is to adjust the clock frequency by externally connecting a clock signal, and the ratio of the clock frequency of the filter to the passband frequency is 50: 1, the cut-off frequency is flexibly set from 0.1Hz to 50kHz, various requirements of equipment are met, the clk signal of a 1 pin of MAX297 realizes the selection of the cut-off frequency in a mode of externally connecting a capacitor, the cut-off frequency fc is determined according to the relation that the ratio of the cut-off frequency of MAX297 to the clk is 1:50, and after actual debugging, the invention selects a 2.2nF capacitor to be grounded, so that the cut-off frequency of 300Hz is realized.
5. The surface wave marine environment survey instrument specific spectrum analyzer of claim 4, wherein the amplifier is selected from the group consisting of: the selection of each stage of amplifier in the signal path is based on: the DDS amplifier has the advantages that the DDS amplifier is suitable in gain, low in noise coefficient, large in linear range, matched in input and output impedance and enough in bandwidth, various indexes are considered comprehensively, a low-noise amplifier GALI52 produced by MINI is adopted in a gain amplification unit of an RF signal path, in order to enable a frequency converter to have high local oscillation excitation, a two-stage amplification circuit consisting of GALI54 and RF2317 produced by MICRO is adopted in a local oscillation path to amplify local oscillation signals output by the DDS;
the final path is amplification after frequency mixing and filtering, mainly drives a rear A/D converter to meet the input requirement of A/D, the level adopts an OPA277 precision operational amplifier of DI company, the noise provided by the operational amplifier is lower, the output voltage swing is wider, the operational amplifier has ultra-low offset voltage and drift and bias current, the operational amplifier adopts single-stage 5v power supply, and ten times of equidirectional amplification capability is obtained by matching a feedback resistor;
the amplification capability of the operational amplifier obtains different amplification factors by adjusting R18 and R14, adds direct current at the input end, is very important for C25 in a feedback loop, and cuts off the direct current so as not to amplify the direct current.
6. The surface wave marine environment survey apparatus dedicated spectrum analyzer of claim 1, wherein the DDS circuit design: the working control of the AD9854 is realized by the configuration of an internal register, the invention adopts a serial mode operation, a two-wire system mode is adopted, one serial operation period is divided into two parts of instruction operation and data operation, a read-write mode and the address of the register are configured at the rising edges of the first eight serial clocks, wherein the read-write mode is controlled at the highest position, O represents write operation, 1 represents read operation, and the address of the register is controlled by the last four bits;
the AD9854 has five optional working modes, the frequency generated by the AD9854 is in a frequency hopping mode, but the stepping frequency is 1KHz, the residence time is 25ms, the essence of the invention is that in a linear frequency modulation pulse mode, through setting the register value, the invention is mainly configured with the following control words:
firstly, starting a frequency control word, wherein the starting frequency control word is the starting frequency of each frame of sweep frequency, the starting frequency of the invention is 13MHz, and the frequency control word is correspondingly calculated according to the clock frequency;
secondly, stepping frequency control words are the unit of each frequency change, 1KHz is used as the stepping frequency, namely downward 1Hz, and after the control words of 1KHz are obtained, complementary code operation needs to be carried out on the control words;
thirdly, residence time control words are control words for controlling the time kept after each frequency change, the residence time control words and the stepping frequency together determine the slope of the frequency sweep, the frequency band bandwidth of each survey of the invention is 1.5MHz, and the residence time is 25 ms;
and fourthly, an amplitude control word which controls the output amplitude of the DDS through programming and generates a waveform with required amplitude through adjusting the amplitude control word.
7. The surface wave marine environment survey apparatus dedicated spectrum analyzer of claim 1, wherein a DDS is applied to achieve high precision arbitrary frequency division: the invention uses the principle of a phase accumulator to realize arbitrary frequency division and arbitrary duty ratio, firstly, a frequency control word and the phase accumulator are given, and then a counter is split to obtain the duty ratio;
reference clock HiAt 30MHz, a frequency of h is requiredo100KHz, 9/10 duty cycle, 1000ns duration low,
the frequency control word S is:
Figure FDA0002852151780000041
the minimum frequency that can be output is:
Figure FDA0002852151780000042
the maximum frequency that can be output is:
Figure FDA0002852151780000043
setting the duty ratio, firstly determining the number of counts, and if the duty ratio is 9/10, determining the judgment value of a counter as follows:
Figure FDA0002852151780000044
the method specifically comprises the following steps:
first, when cnt is less than or equal to 429496730, h00, namely low level;
second, when cnt > 429496730, h01, namely high level;
in the implementation process, the required frequency and duty ratio can be obtained only by providing the frequency control word and the numerical value of the counter, the method is very flexible and practical, and the precision is very high.
8. The surface wave marine environment survey instrument specific spectrum analyzer of claim 1, wherein the a/D sampling circuit design: the mixed signal is a narrow-band signal of 0 to 300Hz, in order to ensure that the sampled signal is not distorted, the sampling frequency of 100KHz is taken, and the sampling theorem is completely met, the ADS 8505A/D chip of TI company is selected, bipolar input of the chip is performed, a 16-bit digital signal is output, the highest sampling rate is 250KSPS, and the data conversion time of one time is 4 ns;
ADS8505 has four important control pins, respectively
Figure FDA0002852151780000045
BYTE, ADS8505 has two ways of translation and reading: first, AD conversion and reading are performed simultaneously when
Figure FDA0002852151780000046
Switching is started when the voltage is low, and the result after the previous switching is read; second, conversion is performed before reading, in
Figure FDA0002852151780000047
After initiating the conversion, the A/D feedback signal is checked
Figure FDA0002852151780000048
When the voltage is high level, the conversion is not finished, and when the voltage is low level, the conversion is finished;
the control mode of the invention adopts the steps of firstly converting and then reading, generating a signal with the period of 10us according to a time sequence chart, and receiving the signal
Figure FDA0002852151780000049
End in which
Figure FDA00028521517800000410
The signal is pulled low and guaranteed
Figure FDA00028521517800000411
Is between 40ns and 1750ns, enabling it to drive the a/D conversion.
9. The surface wave marine environment survey instrument specific spectrum analyzer of claim 1, wherein USB firmware is designed and downloaded: the firmware program is finally burnt into a program file of an 8051 kernel, the upper computer can detect new equipment and assist in finishing data exchange between the host and the equipment under the control of a kernel CPU, and when an EZ-USB FX2 chip is used for application development, a firmware framework of the EZ-USB FX2 is utilized;
in the firmware design, the design and development are mainly carried out in the integrated development environment of uVision3 of Keil to generate a solidified ic file, the designed firmware of the invention requires to realize that a USB chip is controlled to receive and respond to the request of a USB device driver, data is accurately uploaded to a host, and a firmware library is generated after a firmware framework is created, wherein the firmware library comprises the following source files: reg 80320-contains 8051 header file information; ezusb.h-completes declaration of various library functions and definition of data types; fx2regs.h-contains FX2 register header file information; firmware framework provided by fw.c. -Cypress corporation; c-the function user can customize; a51-USB descriptor list;
the framework is composed of the following program files:
first, fw.c: the main file of the USB firmware program, which contains main () function, coordinates 51 the operation of kernel;
second, Periph.c: the method comprises the following steps of USB initialization and task processing functions, wherein when a person develops firmware, the person mainly aims at the file, and adds own task codes according to needs, wherein the following important functions are specifically described:
TD _ id () function: the function is called when the USB endpoint is initialized, and is called between equipment enumeration and task scheduling enabling, and the function can be set by self;
TD _ Poll () function: completing the processing of the circular task, and completing the interactive processing of OUD or IN endpoints by inquiring the state of each endpoint;
DR _ VendorCmnd function: when the frame adopts a certain appointed vendor command, the frame is called, and the decoding work of the user-defined command is mainly completed;
third, dscr.a51 is a description table file: VID and PID can be identified after the equipment is powered on, and the original VID and PID are replaced;
the invention completes the design of the Slave FIFO interface through the configuration register, only uses the endpoint 2 and the endpoint 6 to transmit data in the configuration process, the transmission mode is synchronous batch transmission, and after the firmware code is compiled through uVision3, a hex file is generated, and the downloading mode has two types: one method is to store data and codes by using an internal RAM of a USB device, and the method has high flexibility and is mainly suitable for early firmware debugging, and the other method is to store a firmware program into an EEROM.
10. The surface wave marine environment survey instrument specific spectrum analyzer of claim 1, wherein the FPGA control circuit design: the FPGA is the center of the spectrum analyzer, the control module is responsible for coordinating the operation of the whole equipment, and comprises the steps of generating a required local oscillation signal for the configuration of the DDS module, carrying out time sequence control on an A/D sampler, collecting an accurate external noise signal, and controlling the USB chip to ensure that the whole back-end data is transmitted without errors;
the invention adopts an EP3C40F484C6 chip of the CYCLONE 3 series of ALREA company, and an FPGA control program mainly comprises the control of A/D sampling and the control of USB data transmission:
firstly, A/D sampling control, the A/D sampling chip used by the invention is ADS8505, the chip control is relatively simple, the control time sequence requires that the conversion time is between 40 to 1750ns, the invention is set to 1000ns, the data can be converted each time, and finally a sampling signal with a period of 10us is generated, wherein the low level duration is 1000ns, and the design method adopts any frequency division principle of the invention;
secondly, USB data transmission control, the invention samples a zero intermediate frequency structure, a narrow-band signal of 0 to 300Hz is obtained through a low-pass filter after frequency mixing, the narrow-band signal is sampled by the sampling rate of 100KHz, enters an FPGA and is to be transmitted; if a synchronous writing mode is adopted, the matching problem of data rate exists, the sampling clock is 100KHz, the clock of the USB transmission control module is 48MHz, the difference is hundreds of times, if the clock is not processed, the transmitted data has great errors, and the problem of different data rate caused by mismatching of the two clocks needs to be solved;
after the program design is finished, the FPGA chip is further configured, only a single device configuration mode is used, wherein an AS active configuration mode and a JTAG configuration mode are used, the JTAG mode is mainly used in an online debugging stage, when the debugging is finished, a burning file after the program compiling is downloaded to a configuration device EPCS in the AS mode, and then the solidified program can be operated only by electrifying.
CN202011531273.0A 2020-12-22 2020-12-22 Special spectrum analyzer for surface wave marine environment surveying equipment Withdrawn CN112730985A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN202011531273.0A CN112730985A (en) 2020-12-22 2020-12-22 Special spectrum analyzer for surface wave marine environment surveying equipment

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN202011531273.0A CN112730985A (en) 2020-12-22 2020-12-22 Special spectrum analyzer for surface wave marine environment surveying equipment

Publications (1)

Publication Number Publication Date
CN112730985A true CN112730985A (en) 2021-04-30

Family

ID=75604077

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202011531273.0A Withdrawn CN112730985A (en) 2020-12-22 2020-12-22 Special spectrum analyzer for surface wave marine environment surveying equipment

Country Status (1)

Country Link
CN (1) CN112730985A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117420527A (en) * 2023-12-19 2024-01-19 南京航天工业科技有限公司 Radar monitoring method based on broadband real-time spectrum analysis

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
唐瑞等: "高频地波雷达频谱监测仪的设计", 《雷达科学与技术》 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117420527A (en) * 2023-12-19 2024-01-19 南京航天工业科技有限公司 Radar monitoring method based on broadband real-time spectrum analysis
CN117420527B (en) * 2023-12-19 2024-03-12 南京航天工业科技有限公司 Radar monitoring method based on broadband real-time spectrum analysis

Similar Documents

Publication Publication Date Title
CN102571483B (en) Integrated network parameter tester and test method applied to pulse regime
CN100578242C (en) Multifunctional electric cable failure detector
CN100386645C (en) Method of detecting surface flow speed of river lake using radar electric wave and its radar system
CN103248444B (en) System integration method for test parameters based on unit combination
CN104237905B (en) Big Dipper detector
CN104993887B (en) Integrated pulse condition noise coefficient method of testing and tester
CN106645949A (en) Heterodyne sweep-frequency type spectrum analyzer based on low frequency detection
CN201145721Y (en) Multifunctional cable fault tester
CN108983174B (en) Meteorological radar integrated test equipment
CN211348423U (en) High-frequency signal measuring device
CN208597083U (en) A kind of simple X-band Network Analyzer
CN201477162U (en) Capacitive device medium loss angle online monitoring device
CN102364348A (en) Frequency spectrum automatic monitoring analyzer for satellite ground station intermediate-frequency signal
CN109490624B (en) Pulse signal frequency measurer
CN209606513U (en) One kind being based on AD9361 multichannel spectrum analysis Embedded Hardware Platform
CN109581272A (en) A kind of direct current energy meter detection system
CN112730985A (en) Special spectrum analyzer for surface wave marine environment surveying equipment
CN100584278C (en) Device for testing the compatibility of front end amplification channel of ultrasonic diagnostic device
CN202393829U (en) Satellite earth station intermediate frequency signal frequency spectrum automatic monitoring analyzer
CN205786849U (en) Time and frequency measurement equipment
CN207718222U (en) A kind of performance comprehensive test device of Distributed Control System
US9188617B2 (en) Using a shared local oscillator to make low-noise vector measurements
CN207799062U (en) Reconnaissance radar simulated target detection device
CN204086550U (en) Big Dipper detector
CN201115674Y (en) Device for testing the compatibility of front end amplification channel of ultrasonic diagnostic device

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
WW01 Invention patent application withdrawn after publication

Application publication date: 20210430

WW01 Invention patent application withdrawn after publication