TW201101720A - Joint circular array antenna and MFS-MC-DSSS technologies to estimate the DOA of a very low signal-to-noise ratio air target for bistatic radar - Google Patents

Abstract

Traditional phased-array radars, which employ direct sequence spreading (DSSS) technology to estimate the range, speed and direction of arrival (DOA) of an air target, can satisfy the requirements of long distance and high range resolution. This invention uses multi mode digital beamformer of a circular array antenna and the multiple carrier-DSSS (MC-DSSS) combined with multiple frequency spreader (MFS) modulation waveform to design the structure, algorithm and device of the very low signal-to-noise ratio (S/N) DOA estimation receiver for the bistatic phased-array radar. Specifically, the multi mode digital beamformer of the circular array antenna can receive both the line-of-sight (LOS) signal in direct path and the reflect signal generated from the air target, simultaneously. The MFS can provide the spreading gain for the cross correlation processing of the weak signals. In addition, the cross correlation processing for direct LOS signal and the very low S/N reflect signal is used to estimate the DOA of the air target. Finally, the formula of the correlation processing output is derived to simulate and verify the structure and device performance of the DOA estimation receiver for the bistatic phased-array radar operated under very low S/N condition.

Description

201101720 VI. Description of the Invention: [Technical Field of the Invention] The present invention relates to a target-oriented receiver architecture and apparatus for a two-state phased radar, and in particular to a circular array antenna and a multi-carrier direct spread spectrum sequence. The low-to-noise ratio target of the frequency spread spectrum technology is used to estimate the receiver architecture method and device. [Prior Art] The two-state radar system means that the radar transmitting end is not in the same geographical position as the radar receiving end. Therefore, the radar receiving end cannot directly know the waveform transmitted by the transmitting end. At the receiving end of the radar, the direct path from the transmitting end (1 ine-of-sight, L0S) and the reflected echo signal of the flying target are simultaneously received, and the direct reference power of the towel is far greater than the power of the target echo signal. Traditionally, two sets of high-directionality antennas are used to receive the different arrival directions of the UireetiQn Qf town _, _ road (four) test signal and the target echo signal, and separate the target echo signal from the test #. The hair switch is a set of ring-column antennas that can be used to make a wide beam. In the horizontal domain, the multi-mode digital ^ < rational = target echo signal is separated from the reference signal, and the specific direction is eliminated, and the interference is 。 „ 。. Therefore, compared with the conventional two sets of high directional antennas, the 阵列-shaped array antenna The multi-mode digital beamforming process can simultaneously receive reflection echoes in 15^ directions and improve the anti-jamming performance of the two-state radar system. Coherent 1 〇cat ion 201101720 The practice is to use a group The target echo signal and the reference signal arrival time difference (TD0A) estimate the target position. However, the error of the target echo signal TD0A of the low signal ratio is much larger than that of the high signal ratio direct path reference signal TD0A. The error amount is therefore large in implementation, mostly by using the target echo signal TD0A received by multiple different geographical locations, or by using the direct path reference signal TD0A from multiple different geographical locations to reduce the error of the estimated target position. The traditional TD0A approach does not use the high signal ratio direct path reference signal to improve the target echo of the low signal to noise ratio. The error amount of the TD0A, therefore, the present invention discloses the estimation of the target by the intersection processing of the direct path reference signal of the high signal-to-noise ratio and the target echo signal of the low signal-to-noise ratio. The present invention also discloses the application of the frequency spread spectrum ( Multiple frequency spreader (MFS) is used to adjust the waveform of the multi-carrier direct spread spectrum (MC-DSSS) to further improve the pulse compression gain of the cross-correlation processing. In view of the shortcomings of the prior art, the main object of the present invention is to provide a low-signal-to-phase ratio radar target for the two-state phased radar to the estimation frame, and the device uses a high-channel ratio direct path reference signal and low The cross-correlation processing of the target echo signals of the aperture-to-noise ratio estimates the direction of the target reflected echo signals. Another object of the present invention is to provide a method for constructing a two-state phased radar low-frequency t-target-to-estimated receiver and The device uses a set of %, array antennas, using a uniform beam to cover the horizontal domain of 360. The target echo signal and the reference are processed by the evening mode digital beamforming process. Signal 5 201101720 Knife open 'Asia to eliminate interference signals in specific directions, improve the anti-interference performance and signal-to-noise ratio of the two-state radar system. Another object of the present invention is to provide (4) phase-arrival radar low-signal ratio target estimation The architecture method and device, the application frequency multiplication, and the direct spread spectrum sequence (MFS_MC_DSSS) modulated waveform, further improve the pulse compression gain of the correlation processing, and reduce the false detection rate of the target detection. The purpose of the invention is to provide a method and a device for estimating the low-to-noise ratio target of the two-state phase-matching radar, and at least comprising: (1) transmitting-multi-carrier direct spread spectrum multiple frequency spread spectrum modulation waveform, improving cross-phase, processing Pulse compression gain, reducing target detection false positive rate; (2) a set of circular array antennas; (3) multi-mode digital beamforming processing using circular array antennas to separate target echo signals from reference signals and eliminate interference in specific directions Money, improve the anti-interference performance of the two-state radar system; (4) use the direct path reference signal and the target echo signal intersection (four) processing to estimate the reflected echo No. goals to. It is through the following diagram that the review committee has further clarified the description of the invention, the description of the figure and the detailed description of the invention, which can be helpful for the review work. [Embodiment] The detailed structure and relationship of the present invention will be described in conjunction with the following drawings to facilitate an understanding of the audit committee. First, the following is a detailed description of the eight-ring array antenna of the present invention and the multi-carrier direct spread frequency multiplying frequency spread spectrum technique = low signal-to-noise ratio target to estimate the receiver architecture method and The implementation of the device 201101720 example. The invention also deduces the correlation expression of the direct path receiver signal and the reflected echo signal of the low-signal phase ratio radar of the two-state phased radar, and verifies the estimation architecture and device performance of the invention in an analog manner. The implementation method is divided into five major items: Ring array antenna low signal-to-noise ratio target direction (Directi〇n 〇f arrival, doa) estimation architecture Ring array antenna low signal-to-noise ratio target to estimate receiver architecture

FIG. 10 and FIG. 14 show the low-to-noise ratio target-to-estimation receiving device of the combined ring array antenna and multi-carrier direct spread spectrum sequence frequency spreading technology of the present invention, which includes: - multi-carrier direct exhibition The frequency sequence transmitter, the multi-carrier direct spread spectrum sequence transmitter, further includes: - a multi-f skin directly exhibiting the county to develop the ship shape to generate the HU, the pulse wave is continued through the direct sequence spreader wheel directly = frequency a signal, the multi-carrier direct spread spectrum sequence frequency spreading, the generation further includes a pulse generator Lu Yang 2 von, a four-phase phase shift keying signal modulator 113, a frequency sweeper 114, a 641 leaf conversion) 115 and a digit/analog conversion; Γ-liter = 12' is used to amplify the multi-carrier direct spread spectrum frequency to the carrier frequency, and convert to radio frequency::; and the base frequency " Up-going. Loop antenna receiver 2, the loop antenna receiver further includes: a ring array (4) having a plurality of antenna elements, and the plurality of days 201101720 line elements can be at least two groups of sub-array antennas. Several sub-array antennas are available to receive 3 6 A signal in the direction of 0 degrees; a linear compensation pre-processor 22' accepts the trivial land-based rider, and the J-shaped array antenna 21 is not evenly distributed, and the antenna is received by the number μ, the symptom a sighs 1〇诡, The linear delay compensation is performed on the delay line to make it equivalent to a non-笙Μ. The non-specific spacing linear array antenna; a down-conversion 1 23 'receives the mis-compensation pre-processing n 22 signal conversion For a fundamental frequency signal, the down converter 23 further includes a Chebyshev window processor 23, a downconverter 232 and an analog/digital converter 233; - the zeroing processor 24' removes the direction of interference (4) And generating a fundamental frequency reflected echo signal and a fundamental frequency reference signal. The zeroing processor 24 is formed by a multi-mode digital beamformer 241, and the multi-mode digital beamformer further comprises: a multi-beam forming module The group 241 is an amplitude comparison target to the estimation module 2412 and the zero-pointing beamforming module 2413; a moving target indication processor 25 is configured to remove the fundamental frequency of the low signal-to-noise ratio generated by the zeroing processor μ Reflecting the echo signal, the fundamental frequency is reflected back The signal refers to the reflected clutter generated by the scatterer; the frequency doubling frequency sweeping circuit 26 is used to gain a few times the frequency spread spectrum increase ϋ 'The frequency doubling frequency spread circuit includes a frequency spread thief 262, a 64-FFT 261 and a four-phase phase shift keying signal adjuster 263; a parent correlation processor 27' estimates the target of the low signal to noise target reflected echo signal to the 'intersection related processor 27 The system includes a 201101720 64-FFT 271, a vibration; a Japanese-style towel field related processor 272, a 64-point Identical ring shifter 273, a multiple frequency 鲑 although the de-embellizer 274, a four-phase phase shift keying

No. 275, a pile η 切 R direct sequence despreader 276 and a digital frequency synthesizer 277; 1 U 贞 28' is used to determine a number of the loop antenna receiver 2, which is the output of the column antenna The maximum power, in the direction of the preliminary determination of the target of the flying target, the target detector 28 is constituted by the maximum value determiner 281 of the target detection;

The illuminator 29 determines the direction of the flight target from the target of the multi-mode digital beamforming processing device to the estimated mode detail. With the above structure, the circular array antenna multi-mode digital beamforming process generates the /beam ( Beam y.) Receives the received signal of the direct path (iine-of_sight;, L〇S) as the reference signal of the two-state radar, and generates the reflected echo signal of the first female beam (Beam々) to receive the flying target ^^ and reference The signal 5V(i) performs a cross correlation process to estimate the target direction of the low-to-noise ratio flight vehicle reflected echo signal. The actual antenna element arrangement of the ring array antenna is not in the straight line of the same space. The antenna element receiving signal must first undergo linear compensation pre-processing through the delay line to make it equivalent to a non-equidistant linear array antenna. Beam々 and Beam output reflected echo signals & U) and direct path reference signals & (〇after down-converting to baseband signals are respectively zeroed to remove interfering signals in a specific direction, resulting in fundamental frequency target reflection The echo signal 仏 (〇 and the fundamental frequency direct path reference signal 仏 (ί). The low signal-to-noise ratio of £/, ( ί) can be processed by 9 201101720 moving target indicati (MTI) The reflected clutter generated by the scatter is removed, and the output is "'r(t). Finally, the correlation process with the mountain (t) is performed and the target is estimated. 2. Before the linear array antenna is linearly compensated The architecture for processing the low signal-to-noise ratio target to the estimated receiver using a ring-shaped beamwidth array antenna is shown in Figure 2. The 16 antenna elements cover 360. The horizontal orientation. To meet the requirements of equal beamwidth, 4 antennas are selected. The array of elements is a sub-array antenna, as shown in Figure 3. The actual antenna element arrangement is not on the straight line of the same space. The distance between the two antenna elements in the middle is ^, and the distance between the antenna elements on both sides is shortened to the heart _/8). Alignment The distance from the antenna_axis is JSin(;r/8). For the antenna field type analysis, the phase compensation of the sub-array antenna is performed ^ _/2; r^sin(^/8) Jsin〇/8) [ 0 e ~ e 7 〇] (1) Make it equivalent to a non-equidistant linear array antenna, as shown in Figure 4. The antenna element spacing of the compensated equivalent sub-antenna array will become [0.71-〇〇8(-)·^, 0.71·^, 0.71 ·〇〇8(-).^](2) 8 antenna element weights 4 respectively Is [0.48, 1,1, 〇.48]. The 16 antenna elements produce 16 beam widths of 23. The equal width beam covers 36 inches. The horizontal domain, and then assume that the antenna gain of each antenna element is equal to 丨, then the corresponding field pattern of each equal-width beam is shown in Figure 5. This paper will approximate the original nonlinear array with this linear array model. Subsequent signal processing. The implementation architecture is shown in Figure 6. 4~ is the received signal of the adjacent four antenna elements 201101720 in the equal-width multi-beam array antenna. 3. Multi-mode digital beamforming processing The present invention utilizes 16 beams plus the vibration-forcing comparison method to find the direction of the target, and firstly uses the condition of the two beams to explain the homing principle of the amplitude comparison because different two phases The adjacent beam, which is responsible for different azimuth range estimates, is based on the same homing principle. Therefore, the two beams can be used to represent the generality. The antenna pattern of adjacent two beams in a monospaced multi-beam array antenna can be expressed as

Do 1 = Σ V muscle) (3) m=\ (4) AP2 = hJ'9^ m~2 Since the beam pointing adjustment is not performed, the above two methods do not use the beam pointing factor %. From the above-mentioned field equation, the antenna array pattern of the specific two beams obtained is as shown in Fig. 7. The output value of the db value of the two beams of the coffee and the handle is subtracted (but the division between 1 and the shank) is compared with the relationship between the difference field pattern of the two beam patterns of Fig. 8 to obtain the direction of the target signal. . The principle of tracking in the difference 疋 selects the ratio of the beam-forming of two different directions to the output power of the received target to the signal, because the difference between the two beam-formed field types on the fairy axis is therefore called the difference field type. . Since the output power of the difference field type is independent of the magnitude of the received signal power, the channel attenuation causes the change in the received signal power to not affect the differential field type. The range of azimuth between the two = peaks can be regarded as a negatively expensive range of homing, and the so-called instantaneous field of view (1) eld 〇f. When the beam is wide, the field of view is wider at 201101720. Instantaneous field of view has a considerable impact on the design of homing accuracy. In general, the wider the instantaneous field of view, the worse the accuracy of homing. The homing system block of the two-beam beam amplitude comparison is shown in Fig. 9. 〆

The hardware architecture of the multi-mode digital beamforming processor is shown in FIG. 10, and the functions are divided into three modules: a multi-beam forming module 2411, a differential field-based estimation module 2412, and a zero-direction pointing beam forming module 2413. . The purpose of the nulling of the beam antenna is to eliminate the special energy signal of the multi-beam antenna. The method is to use the multi-beam antenna as the auxiliary antenna group and direct the main beam of the auxiliary antenna group. Antenna 2 and the source direction, then multiply the signals received by the auxiliary antenna group by the signals received by the weighted antenna group, as shown in FIG. In order to reconcile the main circuit module 'multi-mode digital beamformer's specific direction zero = the same energy, directly use the private beam pointing beam among the 16 beams generated by multi-beamforming (respectively with you > with you ^ Linear combination yield = one, the linear combination of the directed beam of the ortho-zero beam BFnuu = BFM + w(On) BFs (5) produces a directed beam pattern of the specific nulling direction a, where w{0n) = -^M^n) code (3⁄4) zeroing weight

(6) It is known from (6) that the linear combination of adjacent pointing field types is used—the most important advantage of the zero-field type is that only a complex multiplication is required to add the zero-field to the specific- The square-scoring signal is zeroed, and the calculation of the zeroing weight only needs to use the strong dry method. With the equal-width array division model and the 12 201101720 system parameters set in the second item of the embodiment, the field patterns of (θ) and /2 (θ) can be obtained as shown in Fig. 11 and Fig. 2 . Fig. 13 is a simplified example showing that when the coffee is 15°, w di-0.5997 - Ο. Ι 8 ΟΙ 7· can be calculated, and the field pattern of Fig. 13 is synthesized, and the zero-suppression ▲ value is -80 dBc. • Mul tip array speading-multi carrier direct sequence spread spectrum (MFS-MC-DSSS) bimorphal phase The radar system block diagram is shown in Figure 14. Multi-carrier direct spread spectrum sequence frequency spread spectrum radar transmitter pulse generator output first thought pulse wave direct sequence spread spectrum signal output through direct sequence spreader (^={4 Cl K c127}. direct sequence spread spectrum signal G is subjected to four-phase phase shift keying (qps κ) modulation to generate 64 subcarrier complex signals of multi-carrier direct spread spectrum multiple frequency spread spectrum waveform = uniform } heart}, input 64-point inverse fast Fourier transform (Inverse Fast Fourier Transform) , IFFT) , 64-IFFT generates MFS MC DSSSj § number 仏 through digital to analog converter (d / a) ◎ transmission good carrier direct spread spectrum sequence frequency spread frequency baseband signal ^ (7). Then (four) financial device up Λ 'Current carrier direct frequency reduction frequency county frequency spread spectrum radar transmitting microwave signal can be expressed as =, 〇 < t < Tsym (7) where ^ is the carrier frequency, I is the time width of the fundamental frequency signal. The multipath environment of the system is shown in Figure 1. If the direct path k is incident on Beam j and the Beam / pointing angle is , the received reference signal can be expressed as 13 201101720 ^ (〇= (0j )[a (^ )^~pts(t -rt) + I(t)] + nt (〇, Tt =^- (8) c where eight The reference signal power 'π is the direct path distance, c is the speed of light / (ί) is the interference signal, /?, (() is the receiver noise. It is assumed that the transmitted signal 〆Θ is isotropic and non-dispersive (non- Dispersive narrow-band signal. In the far field condition, the incident element is 'array'. The signal wavefront is a plane wave.

The subarray antenna array is composed of four antenna elements whose array manif〇ld vector a (6〇 can be expressed as S_) f (9) where wavelength; L = c/Λ. The indirect path (Non-1 ine-of_sight, NL〇s) generated by the stationary scatterer can be expressed as 7 (〇 = ~ τΐ\τ( = Ml (10)

, = 1 C where is the path attenuation. Assume that there is only a single-target, if the signal is transmitted as a reference point (1 e· ί = 0), the distance between the target and the transmitting end is mandatory, and the distance between the target and the ring-shaped array antenna at the receiving end is 汜, and the relative speed is Κ . If the angle of the incident beam (Beam) 仏 of the target reflection signal is 仏, and the angle of the beam 曰 is 汍, the target reflected echo signal = WH {0n)[^9r)ifrs(t - m) + I (t) + lDpit)] + nr{t) (11) ^7(7)=a(A) is the direct coherent interference, y is (0 is the time delay of the time-varying. The relative target speed r, when the target is farther than the transmitting end, is far greater than 14 (12) 201101720 fT; ", 7" is the radar pulse repetition period, then D(t) = C + ν and / see (1) In order to transmit coherent interference from the transmitting end to the direct path of the incident beam, the eighth is to receive the echo signal power. Because the direct path coherent interference power is much larger than the indirect path receiving echo signal (the corpse X<A ) 'Even if the same person with the horror shoots Xiao Xiao in the second

Pointing to the beam, the Libian lobes, as shown in Figure 5, still do not remove the coherent interference. r(4) is a multi-mode digital beamforming zero-transformed-directed wave weight' that can generate over-represented zero-point repression, zeroing the "strong coherent interfering signal of the shot and maintaining the pointing 汍. The MTI filter can eliminate the interference generated by the stationary scatterer Signal / (〇. When 认=民,仏=队, then month st(f)= ·\ί^αι^(β -Tt, + nt(t) (t) = ^P^ars{t ~ D( t)) + nr {t) 〇3) where & is the antenna gain, if the received signal is referenced by the direct path s (the receiving time of the 为 is the reference point and the noise is ignored, the echo of the target reflection is said Sr ( 〇 can not be ^ (0

(14) where relative to 5V (the phase delay of 〇 is τ =

Rr R〇 C + ν angular frequency function is 15 (15) 201101720 Φ(ν)=

C +V (16) From (14), it can be seen that the two-state radar is old and the echo signal & (7) is "down to the fundamental frequency, and then the analog/digital converter outputs the base frequency coffee.

π ΐ ^ 〇# MFS-MC-DSSS MFS-MC-DSSS Fundamental Reference (4) 2: 4: The frequency is calculated relative to the displacement of 玄/4^丨& 〒1〇唬仏(/?) Le frequency Du Bu: Bu Er 2 to the Doppler frequency "compensated echo signal "heart) to obtain a wide 64 subcarrier complex number: Βτη(τ^)~ψ0(τ,ν) bx(T,v ) KL^Tv)] ° # ffl ^ 4- / ^ (Maxi coffee n Likelih00d Mn6t )} Use the big likelihood rule. Read two: 'KML Π obtains the spread spectrum signal A , . ^ ^ 1 ') Κ ~-1 (Γ, ν)}. Will solve the spread frequency as

: 疋, amber and echo signal noise M

^c;ΓΛ;(^ "U)f^ ML Off "A W(7'V) - Cw is irrelevant" Despreading self-phase

Turn off the processing output to eliminate the noise and meaning. In other words, when the correct Doppler frequency estimation and compensation is completed, the despreading frequency derivative == shrink processing still produces the maximum output power, and the target direction is estimated through the multi-mode; beam shaping process. Μ八波ΓΟ as shown in the figure ''The Quadrature Phase Shift Keying, οΡδΚ) ^ code), the output of the nebula encoder is § QPSK)_(星云编bk =—ppingic2k CM]yk,,K63 ((7) 201101720 The function in the expression represents the mapping function of the nebula encoder. When the QPSK is modified, it is a two-bit length of 1〇g24:2; the mapping: to a complex number, The code length of the directly stored signal is 6=. The MFS-MC-DSSS discrete fundamental frequency signal is umc{n)-~Yjbke 64-jlnn± (18) The reference signal and back are known by (7) and (13) The wave signal is passed through the mixer to reduce the Q frequency to the fundamental frequency and can be expressed as .U(〇= sr{t)e~^ = -Dit)Y^ = ^ΡΜ- rr)en^r^ ^ where the target radial velocity ! / is much smaller than the speed of light c, so c / (c + 〇 three i and + F) Ξ Ξ a is the Doppler frequency. If the analog-to-digital device samples the reference signal ... (wide) and the echo signal 仏U with the sampling rate A, then ~M = 4^t arUmdn - \jtfs J] exp(- j^7tfcTt) ^ urM = 4^arumc[n-[Trfsj]Qxp -j2n^n exp(-y2^crr) ^2〇) VJ s ) where Lx" denotes the integer closest to x. If the receiving time of the received direct path reference I-frequency signal 仏 ") is used as a reference point, then (2〇) can be expressed as ut[n] = ^arumc[n] ur [η] = ^[Frar umc [η - [fs J] exp - jin L·. n ) exp(_ β^τ)(2))

L v Λ J Using the variable expansion and time delay properties of the discrete-time Fourjer transform (17 201101720 DFT), (13) can obtain 1 63 Ά-~ ]=k εχρ(/2;ζΦ - ~ V64),~ = b/i"(22)

k=Q Substituting (22) into (21), we can get ur[n\ .ar exp(-j2^;r) « ^^ Lh exp -j2mdk\J jlnjk-k^n^ 64 64 (23) where h Two Ι Λ / Δ / ", △ / = / s / 64 is the interval frequency of adjacent subcarriers. It can be seen from (23) that the subcarrier 会 has a phase difference of the valence point and a frequency shift of the point at the receiving end. The value of the 'Machine Carrier Function' of the 64-FFT output can be expressed as bk> \nd, kD ] q 63 63 :"—ΣΣ^ «=〇^=〇64 j2mdk j2n{k-kD~k')n ~ 64-e - 64 (24) Since Tfc = Lr/J and bath = LiVA / "= Lr / c / (cA /)", in order to substitute (24) with the function of F, bk'(r, v) can be obtained. A^e -j^cx 63 63 -J2n\jfs\kj^{k-\yfr l^f\-k'^t 64 ΣΣν n-0k~0 64 e 64 (25) then the fth subcarrier function value The output sequence of the QPSK demodulator of &(r,v) is {c2k'(T^v) c2^+i(^v)} = deMapping^kl(T,v)l\/k' = 〇, lsK , 63 (26) where the function c/e#app//^{ } represents the mapping function of the QPSK demodulator, which maps a complex number to a sequence of length Z, then the nebula decoding output sequence of 64 subcarrier function values The spread spectrum code sequence 201101720 that reconstitutes the echo signal is summed with the sequence 4 (0, 0) of the training signal to produce a spread pulse output power value. P~\ xds(j^)= Σ^(0^)^(Γ,ν) (2 7)

/>=〇 J The aliasing function of the MFS-MC-DSSS radar waveform can be generated using equations (25), (26), and (9). Since the reflected echo signal used to estimate the distance is a low signal-to-noise ratio, the recovered direct sequence code (^(〇, 0) has a high bit error rate (in the case of 卯邠❹, in -l The bit error rate of the 〇dB signal-to-noise ratio is 〇·2738), and sufficient pulse compression power cannot be generated. Therefore, the present invention proposes to reduce the bit of the recovered direct sequence code 4 (〇, 〇) by the frequency spreading method. The error rate is 汾^ times the frequency spread spectrum processing is to transmit the same QpsK signal to the adjacent 5^ subcarriers ^ bi+o, NfSF=bMxN/SF =Λ = , ^-l (28) c>F y in the reception Do the frequency to spread the frequency A = go black / x na, ν, · = 0, 1, Κ, 荟 -1 (29) / =0 or

Therefore, it is known that the frequency gain gain is obtained. The _16dB signal-to-noise ratio (4) is changed to the example. After eight times the frequency spread spectrum, the hand-to-noise ratio can be improved, and the bit error can be reduced to 〇·229. Since four antenna elements are used, the maximum antenna gain produced by multimode beamforming is 6 dB, and the bit error rate can be further reduced to 〇.9838. Therefore, the target detection probability A will be greater than 1-0. 09838 = 0. 9016. 5. Numerical estimation and simulation results Multi-carrier direct sequence frequency spread spectrum (MFS-MC-DSSS) two-state radar 201101720 System simulation parameter table, as shown in Table 1. Figures 15 to 18 show the MFS-MC-DSSS cross-correlation function for different frequency spread ratios (shape = work ' 4, 8) under SNR t = 4 dB signal-to-noise ratio. It can be seen from Fig. 15~18 that the performance of the frequency spread spectrum eight times anti-noise is best - 16 dB # low noise ratio can still achieve 1.6dB pulse compression gain, and the spread frequency can reach the pulse compression gain of four times. And less than twice the spread frequency will not produce enough pulse compression gain. The multi-beam digital beamforming processing specification of the circular array antenna determines its resolution as the beam width (22.5), and then the target of the multi-mode number=beamforming process is used to estimate the target mode. The difference field of the amplitude comparison output has the same angular slope of 1. degrees. Table 1 Multi-carrier direct sequence double frequency spread spectrum two-state radar system simulation parameter table

Antenna gain (6dB modulation) QPSK (L = l〇g24 = 2) carrier frequency 1GHz signal interval 500//s number of sub-carriers (Number of sub-carriers, N) 64 frequency spread frequency (spread frequency, 1, 2, 4, 8 spread code length (DS code length, corpse) P = NxL / SF = 128, 64, 32, 16 bits signal-to-noise ratio (Signal-to- Noise ratio) SNRt = 4dB, SNRr = -16dB 20 201101720 In summary, the structural features and embodiments of the present invention have been disclosed in detail, and it can be fully demonstrated that the present invention is fully implemented in terms of purpose and efficacy. Progressive, extremely industrial use value, and for the current use in the market, according to the spirit of the patent law, the invention is fully in line with the requirements of the invention patent. Only the above, only this The preferred embodiments of the invention are not intended to limit the scope of the invention, and the equivalent variations and modifications made by the invention in the scope of the invention are still within the scope of the invention. Please review the examination committee and pray for it. Prayer. 〇21 201101720 [Simple diagram of the diagram] Figure 1 shows the low-to-noise ratio target to the estimated receiver architecture. Figure 2 shows the beam-wide array antenna structure such as the ring 16 antenna elements. Figure 3 shows the antenna element. Figure 4 is a schematic diagram of the path compensation of the array antenna. Figure 5 is a field diagram of the equal-width beam. Figure 6 shows the architecture of the digital beamforming.

Figure 7 is the adjacent two beam field pattern of multi-beamforming. Figure 8 is the difference field pattern of the adjacent two beams. Figure 9 is the multi-mode digital beamformer architecture. Figure 10 is the multi-mode digital beamformer. The hardware architecture diagram is shown in Figure 11 for the main array antenna pattern. Figure 12 is the auxiliary array antenna pattern. Figure 13 is the composite array antenna pattern. Figure 14 shows the multi-carrier direct spread spectrum multiple frequency spread spectrum dual state. Phase column lightning relay device block diagram

Multi-carrier direct spread spectrum sequence frequency spread spectrum cross correlation function graph (mf multi-carrier direct spread spectrum sequence frequency spread spectrum correlation function graph π map is multi-carrier direct spread frequency ship frequency spread frequency cross correlation function graph yor = 2) Figure 18 is the township "direct spread frequency phase doubled exhibition county function map (Μ = 1) 22 201101720 [main component symbol description] 1 ~ multi-carrier direct spread spectrum sequence transmitter

11~Multi-carrier direct spread spectrum multiple frequency spread spectrum waveform generator 111~pulse generator 112~direct sequence spreader 113~quad phase shift keying signal modulator 114~multiplier frequency spreader 115~64 -IFFT 〇 116 ~ digital / analog converter 12 ~ upconverter 2 ~ loop antenna receiver 21 ~ ring array antenna 22 ~ linear compensation pre-processor 23 ~ down converter 231 ~ Chebyshev window processor 232 ~ Frequency reducer q 233 ~ analog / digital converter 24 ~ zeroing processor 241 ~ multi-mode digital beamformer 2411 ~ multi-beam forming module 2412 ~ amplitude comparison target to estimate module 2413 ~ zero directed beamforming mode Group 25~moving target indication processor 26~multiple frequency despreading circuit 261~multiplier frequency spreader 23 201101720

262~64-FFT 263~quad phase shift keying signal conditioner 2 7~parent related processing patriarchal 271~64-FFT 272~amplitude correlation processor 273~64 point cyclic shifter 274~time frequency despreader 275~ Four-phase phase shift keying signal conditioner 276~direct sequence de-spreader 277~digital frequency synthesizer 28~target detector 281~target detection maximum value determiner 29~target to estimator 24

Claims (1)

201101720 VII. Patent application scope: 1. A low-sfl-ratio target estimation method combining circular array antenna and multi-carrier direct spread spectrum sequence frequency spreading technology includes the following steps: a. Using a multi-carrier directly The sequence multiplier spread spectrum transmitter transmits a multi-carrier direct spread spectrum sequence frequency spread spectrum modulation waveform; b. uses a set of loop antenna receivers to receive signals; c. multi-mode digital beamforming of loop array antenna receive signals What is the processing? Beam pointing mode, target-directed and zero-pointing mode; and d· utilizing the intersection of the direct path reference signal and the target echo signal. The processor estimates the target of the reflected echo signal. 2. The method of estimating the low signal-to-noise ratio of the combination of the ring array antenna and the multi-carrier direct spread spectrum multiple frequency spread spectrum technique as described in the scope of the patent application, the step b. The multi-mode digital beamforming processing device of the column antenna splits the target echo signal and the reference signal and eliminates the interference signal in a specific direction, thereby improving the anti-interference performance and the signal-to-noise ratio of the two-state radar system. 3. The multi-mode digital beamforming method of the multi-mode direct-frequency array spread spectrum technique combined with the circular array antenna and the multi-carrier direct spread spectrum multiple frequency spread spectrum technique as described in claim 2 The processing device's circuit includes a digital beam constituting group, a differential field type target, an estimation module, and a nulling pointing beamforming module. 4. For the application of full-time (4) (4) combined loop antenna array and multi-carrier direct spread spectrum phase frequency spread spectrum technology low signal-to-noise ratio target to 25 201101720 estimation method 'where the step d. In order to utilize a multi-carrier direct spread spectrum sequence frequency spread spectrum modulation technology to improve the direct path reference (4) and the target echo signal cross-correlation processing pulse wave compression selection, reduce the target detection false positive rate. </ RTI> </ RTI> </ RTI> </ RTI> </ RTI> </ RTI> </ RTI> </ RTI> </ RTI> </ RTI> </ RTI> </ RTI> </ RTI> </ RTI> </ RTI> <RTIgt; The sequencer, the multi-carrier direct spread spectrum sequence transmitter further includes: a multi-carrier direct spread spectrum sequence frequency spread spectrum waveform generator, and the pulse generator output π pulse wave directly through the direct sequence spreader output a sequence spread spectrum signal; and an up-frequency benefit for amplifying the output baseband signal of the multi-carrier direct spread spectrum multiple frequency spread spectrum waveform generator and up-converting the baseband signal to a carrier frequency' into a radio frequency signal; The antenna receiver further includes: a J-shaped array antenna having a plurality of antenna elements, wherein the plurality of antenna elements can be at least one of a group of sub-array antennas, and the plurality of sub-array antennas can be used for receiving 36-degree signal; a linear compensation pre-processor that accepts the circular array antenna signal and causes the antenna element to receive the signal through the delay line for linear compensation front To make it equivalent to a non-equal-spaced linear array antenna; a down-converter 'receives the linear compensation pre-processor signal into a baseband signal; and a zero-processor eliminates interference signals in a specific direction And generating a base 26 201101720 frequency reflected echo signal and a fundamental frequency reference signal; - a moving target indicating processor for removing a fundamental frequency reflected echo signal generated by the zeroing processor, the fundamental frequency reflection The echo nickname refers to the reflected clutter generated by the scatterer; the multiplier frequency despreading frequency circuit is used to make several times the frequency gain; the cross correlation processor 'estimates the low signal to noise ratio flight target reflection echo number The target is directed to; &quot; Ο ❾ a target (four) H 'used to determine _ loop antenna receiver several sub-array antennas which are the maximum power for the round to determine the direction of the flight target; and 6. the target &amp; The multi-mode digital beamforming process is used to determine the direction of the flight target to the estimated mode details: = the combination of the ring array antenna and the multi-load f directly in the range 5 Spread spectrum sequence frequency spread spectrum technology's low signal-to-noise ratio target to directly display the frequency spreader, a four-phase phase shift keying, and a four-phase phase shift keying. The spread spectrum... job-digit...multiplier frequency spread spectrum , - 彳天_Loading and measuring the receiving ratio of the residual ratio target to the = household 4 processor,: lower two more: subcontracting = circular array antenna and multi-cutting frequency spread spectrum technology low signal ratio target 27 201101720 Estimating a receiving device, wherein the zero processor is comprised of a multi-mode digital beamformer. 9. The low-noise-to-noise ratio target combined with the circular array antenna and the multi-carrier direct spread spectrum multiple frequency spread spectrum technique according to claim 8 of the patent application scope, wherein the multi-mode digital beamformer is further Including: a multi-beamforming module, an amplitude comparison target to the estimation module and a zero-pointing beamforming module. 10. The low-noise-to-noise ratio target combined with the circular array antenna and the multi-carrier direct spread spectrum multiple frequency spread spectrum technique described in claim 5, wherein the multiple frequency despreading circuit is further It includes a frequency spreader, a 64-FFT and a four-phase phase shift keying signal conditioner. 11. The low-noise-and-noise ratio target combining the ring array antenna and the multi-carrier direct spread spectrum multiple frequency spread spectrum technique according to claim 5, wherein the cross-correlation processor includes one 64-FFT, an amplitude correlation processor, a 64-point cyclic shifter, a double frequency despreader, a four-phase phase shift keying signal conditioner, a direct sequence despreader, and a digital frequency synthesizer. 12. Estimating a receiving device according to the low-to-noise ratio target of the circular array antenna and the multi-carrier direct spread spectrum multiple frequency spread spectrum technique described in claim 5, wherein the target detector is controlled by a target The maximum value of the detector is determined by the detector. 28