CN1804656B - Method for calibrating high-frequency radar antenna array channel by using ionosphere echo - Google Patents
Method for calibrating high-frequency radar antenna array channel by using ionosphere echo Download PDFInfo
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- CN1804656B CN1804656B CN 200610018271 CN200610018271A CN1804656B CN 1804656 B CN1804656 B CN 1804656B CN 200610018271 CN200610018271 CN 200610018271 CN 200610018271 A CN200610018271 A CN 200610018271A CN 1804656 B CN1804656 B CN 1804656B
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Abstract
The invention relates to an adjusting method for using ionospheric echo to do high frequency wire array channel, which is characterized in that it detects the ion layer reflecting signal in high frequency radar ionospheric echo and uses the statistical analysis on array each channel ionospheric echo to do the channel amplitude and phase adjusting. It is a truly non-channel adjusting method without any limit to the wire array type.
Description
Technical field
The present invention relates to a kind of method of utilizing the Ionospheric Echo signal higher-frequency radar to be carried out array channel calibration.
Background technology
High frequency (3-30MHz) radar realizes that with sky wave or the propagation of ground wave mode over-the-horizon detection, wavelength and maneuvering target (as aircraft, naval vessel etc.) yardstick quite obtains advantages such as bigger scattering area and data transfer rate are lower because of it, is used widely at aspects such as maneuvering target detection and tracking, marine environmental monitorings.
Higher-frequency radar adopts aerial array, and the application space wave beam forms or directional technology comes the target azimuth is estimated moving targets such as the naval vessel of over-the-horizon detection in real time, aircraft and guided missile.In addition, utilize the scattering mechanism of frequency electromagnetic waves, can realize ocean surface flow field, wind field and wave field on a large scale, high precision and round-the-clock real-time monitoring at ocean surface.
Because the effect of multiple factors such as difference of each receiving cable hardware itself and surrounding enviroment influence, the amplitude of each passage of aerial array and phase propetry are inconsistent in the reality, this causes amplitude and phase gain after echoed signal receives through different passages inconsistent, promptly produces the passage mismatch.The passage mismatch causes that beam scanning and orientation error increase, even complete mistake, thereby is one of key issue that influences the higher-frequency radar detection performance.In order to guarantee that radar can effectively work, must take measures to make the passage mismatch to be limited in certain scope: on the one hand, when hardware is made, to improve the consistance that technology guarantees each passage as far as possible; On the other hand, adopt signal processing means estimating channel mismatch parameter, carry out the receiving cable amplitude and phase correction.
Existing channel correcting method can be divided into active correction and passive correction two classes.In the active correction method, artificial auxiliary source is positioned over the enough transmitted reference signal at a distance in aerial array the place ahead, come estimating channel amplitude and phase mismatch parameter by measuring this known signal in the amplitude and the phase place of each receiving cable output signal.In passive bearing calibration, need not to be provided with auxiliary source, and directly utilize the echo information estimating channel mismatch parameter that receives.In high-frequency ground wave radar, utilization once is positioned over the signal of array the place ahead transponder receiving radar emission at a distance and launches after amplification and go back, and extracts passage width of cloth phase mismatch parameter by this answer signal.Though this method principle is simple, yet has been subjected to considerable restraint in the application of practical matter: in high-frequency ground wave radar, array the place ahead is the ocean, and afloat placement of transponder and maintenance are very difficult, and are difficult to long-term work.Therefore, in high-frequency ground wave radar, be more suitable for adopting passive bearing calibration.In existing passive bearing calibration, need carry out repeatedly complicated interative computation to the echoed signal of a plurality of the unknowns, calculated amount is very big, requirement of real time surely differs, and the optimal treatment that is adopted might converge on local optimum, but not therefore global optimum may obtain wrong result.And the difference between actual radar system and passive bearing calibration assumed condition also makes the practicality of general passive bearing calibration reduce greatly.Wuhan University's wave propagation laboratory once adopted marine single arrival direction target echo signal (as island, beacon, drilling platform, ocean wave scattering echo etc.) to realize passive correction as correction signal, and the separation of wherein single arrival direction echo is that translation invariant array element idol group realizes by the array that adopts particular form.Its concrete implementation detail can be with reference to No. 03128238.5 Chinese invention patent application " a kind of method of utilizing marine echo to carry out array channel calibration " and No. 200510018438.3 Chinese invention patent applications " a kind of method for correcting passive channels based on non-linear antenna array ".There is not the placement and the maintenance issues of auxiliary source in foregoing invention, realized receiving cable in real time from normal moveout correction.But, it is the marine echo that translation invariant array element idol group is separated single arrival direction that foregoing invention must depend on specific array format, thereby be disadvantageous to the miniaturization and the portability of high-frequency ground wave radar, and when adopting linear array, can't solve the nonuniqueness problem of front direction.Simultaneously, in above-mentioned bearing calibration, still adopt multidimensional search algorithm, had bigger calculated amount, and still existed search to converge on the risk of local optimum.
Summary of the invention
Limitation at existing method, the purpose of this invention is to provide a kind of method of utilizing Ionospheric Echo to carry out higher-frequency radar aerial array channel correcting, the Ionospheric Echo signal that utilizes higher-frequency radar to receive, for higher-frequency radar provides a kind of cheapness, accurately and can be applicable to the method for correcting passive channels of arbitrary form aerial array, to improve the radar system performance.
Technical scheme of the present invention is: a kind of method of utilizing Ionospheric Echo to carry out higher-frequency radar aerial array channel correcting, it is characterized in that: in the higher-frequency radar echo, detect the ionospheric reflection echoed signal, utilize the statistical study of each passage upper ionized layer echoed signal of array to carry out the correction of channel amplitude and phase place.
Aforesaid method is characterized in that: detect the Ionospheric Echo signal by default signal-noise ratio threshold on the distance spectrum of each frame sampling signal of each radar; Utilize on each receiving cable the statistical average estimating channel amplitude mismatch parameter of spectrum value amplitude ratio on the same distance, promptly
Realize amplitude correction, wherein
Be the relative amplitude parameter of i passage, i=1 ..., M, M are the passage number, X
I, lBe l Ionospheric Echo spectrum value on the passage i, l=1 ..., L, L are Ionospheric Echo spectrum point sum; Utilize on each receiving cable the statistical average estimating channel phase mismatch parameter of spectrum value phase differential on the same distance, promptly
Realize phase correction, wherein
It is the phase mismatch parameter of i passage.
Advantage of the present invention is: need not to be provided with any artificial auxiliary source, make channel correcting more cheap; Do not adopt complicated iteration optimization computing, avoided the optimizing result to converge on local extremum, and calculated amount is very little; Because Ionospheric Echo is direct reflection wave, its intensity is far above sea backscattering echo signal, thereby can guarantee the accuracy of proofreading and correct; The Ionospheric Echo signal satisfies far field condition, and arrival direction always Array Method to, it is used for proofreading and correct more simple and efficient, need not to carry out single arrival direction echo spectrum point search, thereby greatly reduces computation complexity; China is located in middle low latitudes, the ionosphere long-term existence, thereby channel correcting can long-term stability carry out reliably; Bearing calibration to the aerial array form without any restriction, thereby improved the dirigibility that the radar array form is selected, strengthened the possibility of Radar Miniaturization and portability.
Description of drawings
Fig. 1, the higher-frequency radar fundamental diagram of the embodiment of the invention.Wherein, 1 receiving antenna, 2 local oscillation signals, 3 separate range conversion, 4 channel correctings, 5 Doppler-shifts, 6 azimuth discriminations.
Fig. 2, the wave path synoptic diagram.
Fig. 3, receiving antenna array element synoptic diagram.
Fig. 4 typically contains the distance spectrum of Ionospheric Echo signal.
Fig. 5, the Ionospheric Echo signal relative amplitude curve of the 2nd, 3 passages and the amplitude correction value that estimates.
Fig. 6, the Ionospheric Echo signal relative phase curve of the 2nd, 3 passages and the phase correcting value that estimates.
Embodiment
Below in conjunction with drawings and Examples, the present invention is done more detailed explanation.
The principle of work and the working environment of higher-frequency radar are described below:
High-frequency ground wave radar is made up of emitting antenna, receiving antenna array, transmitter, receiver, signal processor etc. usually, for reducining the construction costs and maintenance cost generally adopts altogether location of transmitting-receiving.Radar sea emission forwards frequency electromagnetic waves receives ocean backscattering echo signal to extract flow field, sea, wind and wave field information and sea moving target information.Radar adopts the linear frequency modulation system usually, in each frequency sweep cycle to demodulation after signal carry out low-pass filtering, the discrete Fourier transform (DFT) of sampling and fast time domain obtains the distance spectrum of this frequency sweep cycle, wherein each spectrum is o'clock corresponding to a spectrum value sample on the distance element, in time a plurality of distance spectrum sequences are carried out slow time domain discrete Fourier transform at the coherent accumulation of being made up of a plurality of frequency sweep cycles and obtain distance-Doppler's two-dimensional spectrum (as shown in Figure 1, wherein 1 is receiving antenna, 2 is local oscillation signal, 3 for separating range conversion, 4 is channel correcting, 5 is Doppler-shift, and 6 is azimuth discrimination).Distance-doppler spectral by signal on a plurality of receiving antenna passages just can extract extra large attitude information and moving target information.
Because the imperfection of emitting antenna directional diagram, be not all electromagnetic wave energy all along radiation from sea surface, the part electromagnetic wave is always arranged towards the overhead Vertical Launch of antenna.And the side exists ionosphere more than 100 kilometers on the ground, for frequency electromagnetic waves, has good electric conductivity, therefore can be with the transmit reflected back ground and by radar receive (as shown in Figure 2 of radar in vertical direction, wherein 7 is ocean surface, 8 is sea-surface target, 9 is ionosphere), thus form " ionosphere interference ", and what radar received is the marine echo that is superimposed with " ionosphere interference ".
Key of the present invention is to detect in the echo distance spectrum in each frequency sweep cycle Ionospheric Echo spectrum point, estimates corrected value by the amplitude of each passage spectrum point and the statistical average of phase place then.
Supposing that radar adopts M unit aerial array to receive, serves as with reference to unit with antenna 1, antenna i (i=1 ..., three-dimensional coordinate M) is (x
i, y
i, z
i), (x wherein
1, y
1, z
1)=(0,0,0), its amplitude and phase mismatch parameter are respectively g
iWith
Far field echo signal source s (t) is so that (θ, α) (wherein θ and α are respectively the horizontal azimuth and the angle of pitch, incide as shown in Figure 3) antenna array, and then target to antenna i with respect to the wave path-difference to antenna 1 is in the space
Δ
i＝-x
isinθ+y
icosθ-z
isinα (1)
Received signal on the antenna i is
Wherein
K=2 π/λ, λ are the radar operation wavelengths, and w (t) is orientation (θ, the α) external noise on, v
i(t) be the internal thermal noise of antenna i, satisfy E[|w (t) usually |
2The E[|v of]＞＞
i(t) |
2].Radar carry out that wave beam forms or orientation before, must estimate and proofreaied and correct amplitude and phase mismatch parameter, to obtain correct target Bearing Estimation.
Ionospheric Echo is generally produced by the ionosphere vertical reflection, and the scatter echo on other directions (α ≠ 90 °) very a little less than.Therefore for the Ionospheric Echo signal, formula (1) wave path-difference is reduced to Δ
i=z
i, formula (2) then is reduced to
Because Ionospheric Echo is much better than than marine echo usually, and direction is always vertically greatly direction α=90 °, therefore becomes a kind of good array channel calibration signal source.
Determine between the common distance regions that occurs of Ionospheric Echo the distance spectrum signal to noise ratio (S/N ratio) that the every frame sampling of radar on this interval obtains to be compared with default Ionospheric Echo snr threshold according to priori, detect an Ionospheric Echo spectrum point X
I, lFig. 4 is the distance spectrum that a width of cloth typically contains the Ionospheric Echo signal, and wherein 10 is distance spectrum substrate level values, the 11st, and Ionospheric Echo intensity threshold (this routine snr threshold is 10dB), the 12nd, detected Ionospheric Echo spectrum peak.
The amplitude ratio of passage i being gone up all Ionospheric Echo spectrum points on all Ionospheric Echo spectrum points and the passage 1 carries out statistical average, obtains the amplitude correction value of passage i
Fig. 5 is each passage with respect to the Ionospheric Echo signal amplitude of passage 1 than curve and the amplitude correction value that estimates.
The phase differential of passage i being gone up all Ionospheric Echo spectrums on all Ionospheric Echo spectrum points and the passage 1 carries out statistical average, obtains the phase correcting value of passage i
Fig. 6 is that each passage is with respect to the Ionospheric Echo signal phase difference curve of passage 1 and the phase correcting value that estimates.
With the correction of the received signal on the passage i be
Claims (1)
1. method of utilizing Ionospheric Echo to carry out higher-frequency radar aerial array channel correcting, it is characterized in that in the higher-frequency radar echo, detecting the ionospheric reflection echoed signal, utilize the assembly average of each passage upper ionized layer echo signal amplitude of array and phase place to carry out the correction of channel amplitude and phase place; Utilize of the statistical average of each passage upper ionized layer echoed signal, promptly to the amplitude ratio of reference channel
Come estimating channel amplitude correction parameter, wherein
Be the relative amplitude parameter of i passage, i=1 ..., M, M are the passage number, X
I, lBe l Ionospheric Echo spectrum value on the passage i, l=1 ..., L, L are Ionospheric Echo spectrum point sum; Utilize of the statistical average of each passage upper ionized layer echoed signal, promptly to the phase difference value of reference channel
Come estimating channel amplitude correction parameter, wherein
It is the phase mismatch parameter of i passage.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1924607B (en) * | 2006-09-14 | 2010-05-12 | 武汉大学 | Method for controlling multiple working conditions high frequency radar receiver |
| CN101581782B (en) * | 2009-06-15 | 2012-05-23 | 武汉大学 | Method for inhibiting ionospheric clutter in portable high frequency groundwave radar |
| CN102812594B (en) | 2010-09-08 | 2015-08-19 | 华为技术有限公司 | A kind of channel calibration method, Apparatus and system |
| CN102707270B (en) * | 2012-06-18 | 2013-07-24 | 武汉大学 | Automatic estimation method for antenna pattern relative to high-frequency ground wave radar |
| CN103869293B (en) * | 2014-03-31 | 2016-03-02 | 武汉大学 | A kind of method realizing reception sky wave and ground wave OTHR signal simultaneously |
| CN109375182A (en) * | 2018-10-30 | 2019-02-22 | 浙江大学 | Radar receiver amplitude-phase consistency corrects system |
Citations (3)
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|---|---|---|---|---|
| CN1407348A (en) * | 2001-09-04 | 2003-04-02 | 刘凤才 | Extending range of radar by artificial ionosphere and target detection by radar refraction |
| CN1566983A (en) * | 2003-06-30 | 2005-01-19 | 武汉大学 | Method for array channel calibration by utilizing ocean echo wave |
| CN1664611A (en) * | 2005-03-24 | 2005-09-07 | 武汉大学 | Method for correcting passive channels based on non-linear antenna array |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1407348A (en) * | 2001-09-04 | 2003-04-02 | 刘凤才 | Extending range of radar by artificial ionosphere and target detection by radar refraction |
| CN1566983A (en) * | 2003-06-30 | 2005-01-19 | 武汉大学 | Method for array channel calibration by utilizing ocean echo wave |
| CN1664611A (en) * | 2005-03-24 | 2005-09-07 | 武汉大学 | Method for correcting passive channels based on non-linear antenna array |
Non-Patent Citations (4)
| Title |
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| 万显荣，杨子杰，文必洋，柯亨玉.高频海态雷达软件无线电接收机的设计.数据采集与处理19 4.2004,19(4),470-474. |
| 万显荣，杨子杰，文必洋，柯亨玉.高频海态雷达软件无线电接收机的设计.数据采集与处理19 4.2004,19(4),470-474. * |
| 杨绍麟，柯亨玉，田建生，吴世才，杨子杰.高频地波雷达基于海洋回波的通道幅度自校准方法.电子与信息学报24 9.2002,24(9),1233-1237. * |
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