CN2762154Y - High frequency ground rada digital coherent receiver - Google Patents
High frequency ground rada digital coherent receiver Download PDFInfo
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- CN2762154Y CN2762154Y CN 200420057632 CN200420057632U CN2762154Y CN 2762154 Y CN2762154 Y CN 2762154Y CN 200420057632 CN200420057632 CN 200420057632 CN 200420057632 U CN200420057632 U CN 200420057632U CN 2762154 Y CN2762154 Y CN 2762154Y
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Abstract
The utility model relates to a high-frequency ground wave radar digital coherent receiver which comprises a radio frequency analog front end, an A/D sampling circuit, a frequency synthesizer, a synchronous control circuit and a digital signal processing chip, wherein the radio frequency analog front end, the A/D sampling circuit and the digital signal processing chip are orderly and electrically connected; the frequency synthesizer and the radio frequency analog front end are connected; the synchronous control circuit is connected with the frequency synthesizer and the radio frequency analog front end. The utility model is characterized in that the intermediate frequency is the nominal intermediate frequency 21.4MHz. The utility model has the advantages of stable performance, simplified structure, easily obtained parts, high system linearity degree and high dynamic range.
Description
Technical field
The utility model relates to a kind of high-frequency ground wave radar receiver, specifically, relates to a kind of relevant high-frequency ground wave radar digital receiver based on the linear frequency modulation system.
Background technology
HF receiver works in the skip band of 3～30MHz.In this frequency range, external disturbance is serious, in order to satisfy the sensitivity index requirement, and effectively suppresses mirror to interference, adopts the superhet of three frequency conversion structures usually.The high-frequency ground wave radar receiver that the sea is surveyed works in skip band, and its structure has also adopted and the similar structure of common HF receiver.Generally there are not problems such as passage consistency in communication system mostly with single-channel mode work.The receiver of high-frequency ground wave radar is usually with much channel communication work, and for multichannel receiver, complicated repeatedly frequency conversion structure requires to result in hand cramps for stability, the passage consistency of receiver.
For simplifying the stability of radar arrangement, raising receiver, the HF receiver (design of high-frequency digital receiver front end circuit based on a mixing of software radio thought has appearred, 02 phase of " Electronics Engineer " calendar year 2001), this class receiver adopt intermediate frequency be 40MHz with the structure frequently that is in high school, work in the shortwave full frequency band.
To the high-frequency ground wave over-the-horizon radar that the sea is surveyed, its frequency of operation is usually less than 14MHz, at the characteristics of high-frequency ground wave over-the-horizon radar, can suitably reduce intermediate frequency, further simplifies radar arrangement.
High-frequency ground wave radar receiver is coherent receiver.The local oscillation signal of coherent receiver, transmitting obtains by technology such as frequency division, frequency multiplication, mixing by a clock source, and its frequency synthesizer is very complicated.
Summary of the invention
The purpose of this utility model is the frequency range at the actual use of high-frequency ground wave radar, select for use than Low Medium Frequency, employing is different from the AFE (analog front end) structure of general HF receiver, adopt full DDS (Digital Direct Synthesis) technology to realize frequency synthesizer, provide a kind of reliable and stable, have high-frequency ground wave radar numeral coherent receiver than high performance-price ratio.
The technical solution of the utility model is: high-frequency ground wave radar numeral coherent receiver, it comprises rf analog front-end, A/D sample circuit, frequency synthesizer, synchronization control circuit and digital signal processing chip composition, rf analog front-end, A/D sample circuit, digital signal processing chip are electrically connected successively, frequency synthesizer is connected with rf analog front-end, synchronization control circuit is connected with frequency synthesizer and rf analog front-end, it is characterized in that IF-FRE is nominal intermediate frequency 21.4MHz.
Aforesaid high-frequency ground wave radar numeral coherent receiver is characterized in that described rf analog front-end by duplexer, bandpass filter, and frequency mixer, low noise amplifier, crystal filter, amplifier, crystal filter are electrically connected composition successively.
Aforesaid high-frequency ground wave radar numeral coherent receiver is characterized in that described frequency synthesizer is made up of the DDS chip of two identical models, exports the linear FM signal that two road slopes are identical, initial frequency differs 21.4MHz.
Aforesaid high-frequency ground wave radar numeral coherent receiver, the linear FM signal that it is characterized in that described frequency synthesizer output, launch identically with the repetition period of local oscillator linear FM signal, in the initial moment in each cycle, the initial phase that transmits with local oscillation signal makes zero.
Aforesaid high-frequency ground wave radar numeral coherent receiver, the sampling rate that it is characterized in that described A/D sample circuit is 160KHz.
Specifically, the utility model one is that the intermediate frequency with radar is set at nominal intermediate frequency 21.4MHz, can use under this intermediate frequency cheap, the finished product crystal filter of function admirable; The 2nd, designed the AFE (analog front end) structure that is different from general communication control processor, make it be more suitable for the characteristics that the high band external noise is higher, the high-frequency ground wave radar transmitting-receiving is stood altogether; The 3rd, the DDS frequency synthesis technique of the strict control of design initial phase, emission is directly exported by the DDS device with local oscillation signal, has simplified frequency synthesizer greatly; The 4th, adopt lower sampling rate, use a digital signal processing chip DSP can finish Digital Down Convert, FFT (fast fourier transform) and the work of other signal Processing.These measures all help improving the radar receiver performance index and reducing cost.
To achieve these goals, the utility model has adopted following technical measures:
1) adopts a mixing, the structure of the direct bandpass sampling of intermediate frequency;
2) IF-FRE is selected nominal intermediate frequency 21.4MHz for use, and it is the crystal filter of 21.4MHz that intermediate-frequency filter is selected the centre frequency nominal value for use;
3) adopt the high structure of putting of nothing, bandpass filter directly is connected with frequency mixer, does not have traditional radio-frequency amplifier therebetween;
4) use the system clock of the above clock of 100MHz as DDS, directly generation transmits and local oscillation signal.Two road signal chirp slopes are identical, and initial frequency differs 21.4MHz.In the initial moment in each linear frequency modulation cycle, it is identical with the initial phase of local oscillation signal to transmit;
5) adopt 14 ADC devices that the intermediate-freuqncy signal of each analog channel is carried out bandpass sampling, sampling rate is between 60～160KHz, and sampled signal is delivered to DSP;
7) dsp chip is finished filtering, Digital Down Convert and fft algorithm, and data are done aftertreatment through USB or other bus transfer to outer computer.
The utlity model has following advantage:
1. use nominal intermediate frequency 21.4MHz as IF-FRE, the one, can directly purchase the intermediate-frequency filter of function admirable from market, need not custom-made; The 2nd, under than the Low Medium Frequency condition, can adopt than low sampling rate, reduced the burden of Digital Down Convert, directly can finish Digital Down Convert work by DSP, do not need extra hardware Digital Down Convert circuit;
2. the mixing for once of this receiver, analog device is few, the corresponding minimizing of nonlinearity product, the system linear degree is improved;
3. no height is put before the frequency mixer, has improved the dynamic range of receiver;
4. adopt the system clock of the clock signal of 100MHz～160MHz as the DDS device, the DDS device can directly be exported the local frequency that meets the demands, and promptly frequency synthesizer does not need other frequency changer circuit;
5. utilize digital filter to guarantee the consistance of filter bandwidht and useful signal bandwidth, realize optimum filtering.
Description of drawings
Below in conjunction with accompanying drawing and system work process the utility model is further specified.
Fig. 1-the utility model system construction drawing;
Among Fig. 1, the block diagram that fine line is represented is the hardware components of receiver, and heavy line is the software section of receiver, wherein:
The A1-receiving antenna;
A2-is an emitting antenna;
The 1-duplexer, when radar transmitter and receiver were stood altogether, preventing to transmit directly entered receiver;
The 2-bandpass filter, bandwidth and radar frequency of operation adapt;
The 3-frequency mixer;
The 4-low noise amplifier;
The 5-crystal filter, nominal center frequency 21.4MHz;
The 6-amplifier;
The 7-crystal filter, nominal center frequency 21.4MHz;
The 8-A/D converter;
The 9-I/Q signal separation algorithm;
The 10-Digital Down Convert;
11--inferior FFT;
12-is FFT for the second time;
The 21-system clock;
The 22-isochronous controller;
The 23-DDS device is used to produce chirped local oscillation signal;
The 24-DDS device is used to produce chirped transmitting;
The 25-power amplifier.
Fig. 2 is the circuit diagram of AFE (analog front end) among Fig. 1.
Embodiment
Referring to Fig. 1, in the specific embodiment of the utility model, it comprises high-frequency ground wave radar numeral coherent receiver:
The rf analog front-end of forming by 1-7, A/D sample circuit 8, by 23 and 24 frequency synthesizers of forming, isochronous controller 22 and digital signal processing chip DSP (9-12 carries out therein), rf analog front-end, A/D sample circuit 8, digital signal processing chip DSP (carrying out the device of the work of 9-12) are electrically connected successively, frequency synthesizer is connected with rf analog front-end, and synchronization control circuit is connected with frequency synthesizer and rf analog front-end and it is characterized in that IF-FRE is nominal intermediate frequency 21.4MHz.
The system work process of Fig. 1 correspondence is described.
The 21st, system clock, frequency is between 100MHz～300MHz.23, the 24th, identical DDS chip.24 outputs transmit.23 output local oscillation signals.Local oscillation signal is identical with the chirp slope that transmits, but frequency differs 21.4MHz.24 produce transmit and be amplified to the intensity that needs through 25, by emitting antenna A2 to aerial emission.Behind the electromagnetic wave of being launched and interacting goals, will produce reflection or scattering.
After target echo enters receiving antenna A1, at first pass through duplexer 1.The effect of duplexer is to prevent that the direct wave that emitting antenna is launched from entering receiver and stopping up receiver.When therefore transmitter was worked, duplexer 1 should be in off-state.Contain echoed signal and external disturbance in the signal of duplexer 1 output, filter the interference in the past of part working band, to improve signal quality by bandpass filter 2.
Target echo acts on frequency mixer 3, two signals respectively simultaneously with local oscillation signal (by 23 outputs) thereupon and form two component of signals after mixing.The component of signal that frequency is lower is is carrier wave with 21.4MHz, eliminated the signal of chirp rate, is our needed signal.Another frequency is higher, will be by the subsequent filter filtering.
The signal of frequency mixer 3 output a little less than, after low noise amplifier 4 amplifies,, form baseband signal through first crystal filter 5 filtering.This baseband signal is further amplified through amplifier 6, delivers to second crystal filter 7 filtering.The baseband signal of crystal filter 7 outputs is generated digital signal and delivers to the DSP processing by A/D converter 8 bandpass samplings.
The place that the front-end architecture that the utility model adopted significantly is different from traditional short-wave receiver is that the utility model places the low noise amplifier before the frequency mixer in traditional receiver after the frequency mixer.Benefit is to improve the system linearity degree in a big way, increases the dynamic range of receiver, and cost is that sensitivity index slightly descends.Receiver is that sensitivity should be less than external noise to the requirement of sensitivity index.For microwave radar, external noise level is very low, and sensitivity index requires corresponding just high.For high-frequency ground wave radar, external noise is far above set noise, and too high receiver sensitivity index is nonsensical.In the utility model, though the rearmounted sensitivity that has influenced receiver of low noise amplifier, last sensitivity index is still low than external noise, can not influence the indicators of overall performance of receiver.
Frequency synthesizer of the present utility model mainly is made of two DDS devices, and two road signal chirp slopes are identical, and initial frequency differs 21.4MHz.In the initial moment in each linear frequency modulation cycle, transmit (by 24 outputs) are identical with the initial phase of local oscillation signal (by 23 outputs).This technology makes frequency synthesizer settle at one go, and structure is very simple, can guarantee the coherence of signal simultaneously again.
The digital receiver of this programme does not adopt hardware Digital Down Convert circuit, directly finishes Digital Down Convert work by DSP.The sampling rate of A/D converter is according to the requirement design of bandpass sampling.High-frequency ground wave radar belongs to coherent receiver, need obtain the phase information of echo, and promptly sampled signal must become mutually orthogonal baseband I road and Q road signal.By DSP the part of sampled signal by digital processing (for example multiphase filtering) realized separating of baseband I road and Q road signal.
Used reference clock source is the active crystal oscillator of 120MHz in this example, through behind the clock driver circuit, as the system clock of DDS device AD9854.Under 120MHz system clock condition, AD9854 output signal highest frequency can reach 48MHz.One road AD9854 output radiofrequency signal is to transmitter, and another road AD9854 exports local oscillation signal.Under the Linear Frequency Modulation working method, except that initial frequency control word difference (local oscillation signal differs 21.4MHz with the initial frequency that transmits), all other control words of this two-way DDS device should be identical, with assurance radar coherence, and the degree of purity of intermediate frequency output signal.The initial phase of Linear Frequency Modulation signal,, guarantee that the initial phase of the linear FM signal of two road DDS devices output is 0 by forced resetting.
Fig. 2 is the example circuit diagram of AFE (analog front end) of the high-frequency ground wave radar receiver of central task frequency a 11～15MHz.The numeral of module in the digital corresponding diagram 1 in the frame of broken lines upper left corner among the figure.
Transmit-receive switch is selected SA630D for use among Fig. 2, receive-transmit isolation＞70dB; Bandpass filter is SBP-13, and effect is to suppress image frequency and intermediate frequency interference.The three dB bandwidth of SBP-13 is 4MHz, and suppressing the 40dB frequency is 10.5MHz and 17.5MHz.Greater than 45dB, greater than 62dB, can satisfy the needs that suppress above-mentioned interference to the inhibition of intermediate frequency 21.4MHz to the inhibition of image frequency 55.8MHz.In order to improve dynamic range, in this example, adopted the frequency mixer HAS-3H of high local oscillator, the local oscillator operation level is 17dBm.By the local oscillation signal undercapacity of DDS output with direct driving frequency mixer HAS-3H, so after the local oscillation signal that DDS exports, add this vibration magnifier RF2137.
In order to guarantee certain system sensitivity, after frequency mixer, connect a low noise amplifier GALI-5 immediately.In order to keep passage stable, generally a plurality of amplifiers are not linked to each other, otherwise can be too high because of gain, cause instability.Therefore after first GALI-5, insert the crystal filter 21.4MB4F that centre frequency is 21.4M.Subsequently, signal AD603 and GALI-5 further amplify, and make it satisfy the requirement of follow-up A/D sampling.Amplifier is not desirable linear unit in addition, can produce harmonic wave and intermodulation distortion, in the end places a wave filter after the one-level amplifier, effectively the harmonic wave and the intermodulation distortion of rejective amplifier generation.Make the signal of A/D sampling purer.
Of particular note, the input and output impedance of crystal filter 21.4MB4F and 21.4C3 is 1.5K Ω/2pF, falls far short with 50 Ω, and the output impedance of AD603 has only 2 Ω.Crystal filter input and output impedance only just has optimum performance under matching condition, therefore, should carefully design match circuit between the devices at different levels.In this example, we adopt L network impedance conversion simple in structure to realize the coupling of crystal filter.
According to the bandpass sampling theory, under the 21.4MHz intermediate frequency, can adopt the sampling rate of 160KHz to carry out the A/D conversion.Utilize the way of multiphase filtering, form two road complete i/q signals, the data transfer rate of every road signal is 80kHz.Each road signal is carried out filtering and extraction, and total extraction yield is 256, makes data transfer rate reduce to 312Hz.To the I road signal during each linear frequency modulation as real part, Q road signal is as imaginary part, carry out Fourier transform, obtain during the different linear frequency modulation cycles apart from echoed signal, echoed signal in the specific range unit is arranged sequentially, as the input signal of Fourier transform, make Fourier transform processing, can obtain the doppler spectral of the last echoed signal of this distance.
Claims (5)
1, high-frequency ground wave radar numeral coherent receiver, it comprises rf analog front-end, A/D sample circuit, frequency synthesizer, synchronization control circuit and digital signal processing chip composition, rf analog front-end, A/D sample circuit, digital signal processing chip are electrically connected successively, frequency synthesizer is connected with rf analog front-end, synchronization control circuit is connected with frequency synthesizer and rf analog front-end, it is characterized in that IF-FRE is nominal intermediate frequency 21.4MHz.
2, high-frequency ground wave radar numeral coherent receiver as claimed in claim 1 is characterized in that described rf analog front-end by duplexer, bandpass filter, and frequency mixer, low noise amplifier, crystal filter, amplifier, crystal filter are electrically connected composition successively.
3, high-frequency ground wave radar numeral coherent receiver as claimed in claim 1 or 2, it is characterized in that described frequency synthesizer is made up of the DDS chip of two identical models, export the linear FM signal that two road slopes are identical, initial frequency differs 21.4MHz.
4, high-frequency ground wave radar numeral coherent receiver as claimed in claim 3, the linear FM signal that it is characterized in that described frequency synthesizer output, launch identical with the repetition period of local oscillator linear FM signal, in the initial moment in each cycle, the initial phase that transmits with local oscillation signal makes zero.
5, as claim 1 or 2 or 4 described high-frequency ground wave radar numeral coherent receivers, the sampling rate that it is characterized in that described A/D sample circuit is 160KHz.
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| CN 200420057632 CN2762154Y (en) | 2004-12-13 | 2004-12-13 | High frequency ground rada digital coherent receiver |
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| CN 200420057632 CN2762154Y (en) | 2004-12-13 | 2004-12-13 | High frequency ground rada digital coherent receiver |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101833083A (en) * | 2010-04-16 | 2010-09-15 | 武汉大学 | Radio-frequency front-end circuit of L-band radar receiver |
| CN102608421A (en) * | 2012-03-07 | 2012-07-25 | 北京无线电计量测试研究所 | Frequency range extender for Fourier analysis for phase noise |
| CN101484827B (en) * | 2006-07-13 | 2012-08-15 | 艾利森电话股份有限公司 | A method and radar system for coherent detection of moving objects |
| CN102841336A (en) * | 2012-09-04 | 2012-12-26 | 中船重工鹏力（南京）大气海洋信息系统有限公司 | High-frequency ground wave radar multi-frequency signal coherent receiver |
| CN103630894A (en) * | 2013-06-04 | 2014-03-12 | 中国科学院电子学研究所 | Broadband multichannel coherent radar imaging system and control method thereof |
| WO2015176250A1 (en) * | 2014-05-21 | 2015-11-26 | 武汉德威斯电子技术有限公司 | Portable high-frequency ground wave radar for surveying ocean dynamics parameters |
| CN105824020A (en) * | 2016-03-12 | 2016-08-03 | 浙江大学 | Subcarrier-modulation-based continuous wave Doppler radar sensor and motion demodulation method |
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2004
- 2004-12-13 CN CN 200420057632 patent/CN2762154Y/en not_active Expired - Fee Related
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101484827B (en) * | 2006-07-13 | 2012-08-15 | 艾利森电话股份有限公司 | A method and radar system for coherent detection of moving objects |
| CN101833083A (en) * | 2010-04-16 | 2010-09-15 | 武汉大学 | Radio-frequency front-end circuit of L-band radar receiver |
| CN102608421A (en) * | 2012-03-07 | 2012-07-25 | 北京无线电计量测试研究所 | Frequency range extender for Fourier analysis for phase noise |
| CN102841336A (en) * | 2012-09-04 | 2012-12-26 | 中船重工鹏力（南京）大气海洋信息系统有限公司 | High-frequency ground wave radar multi-frequency signal coherent receiver |
| CN103630894A (en) * | 2013-06-04 | 2014-03-12 | 中国科学院电子学研究所 | Broadband multichannel coherent radar imaging system and control method thereof |
| CN103630894B (en) * | 2013-06-04 | 2016-08-24 | 中国科学院电子学研究所 | The control method of broadband multi-channel coherent radar imaging system |
| WO2015176250A1 (en) * | 2014-05-21 | 2015-11-26 | 武汉德威斯电子技术有限公司 | Portable high-frequency ground wave radar for surveying ocean dynamics parameters |
| CN105824020A (en) * | 2016-03-12 | 2016-08-03 | 浙江大学 | Subcarrier-modulation-based continuous wave Doppler radar sensor and motion demodulation method |
| CN105824020B (en) * | 2016-03-12 | 2018-06-12 | 浙江大学 | The continuous wave Doppler radar sensor of subcarrier modulation and movement demodulation method |
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