Fig. 1. Sidelobe characteristics of various window functions. (a) Blackman Harris window; (b) four-term Nuttall window; (c) four-term RV window; (d) five-term MSD windows
Fig. 2. Sidelobe characteristics of hybrid convolution window functions
Fig. 3. Spectral lines. (a) Frequency point is close to the spectral line k3; (b) frequency point is close to the spectral line k4; (c) frequency point corresponds to the spectral line; (d) frequency point is in the middle of the two spectral lines
Fig. 4. Ideal signals of LDV. (a) Components of the signal; (b) signal time domain waveform
Fig. 5. Relative error comparison of frequency detection in low frequency range
Fig. 6. Relative error comparison of frequency detection in high frequency range
Fig. 7. Signal spectrograms with different signal-to-noise ratios in the low frequency domain. (a) RSN=+5 dB; (b) RSN= -5 dB; (c) RSN=-10 dB; (d) RSN=-15 dB
Fig. 8. Comparison of absolute errors of signal frequency detection with different signal-to-noise ratios in low frequency domain
Fig. 9. Signal spectrograms with different signal-to-noise ratios in the high frequency domain. (a) RSN=+5 dB; (b) RSN= -5 dB;(c) RSN= -10 dB; (d) RSN= -15 dB
Fig. 10. Comparison of absolute errors of signal frequency detection with different signal-to-noise ratios in low frequency domain
Fig. 11. Comparison of relative errors in low frequency range
Fig. 12. Comparison of relative errors in high frequency range
Fig. 13. Optical structure of LDV adopted
Fig. 14. Experimental setup of LDV
Fig. 15. Measured signal sequence
Fig. 16. Comparison of relative error of speed
No. | Frequency /kHz | Arithmetic mean error of frequency detection /Hz |
---|
Method 1 | Method 2 | Method 3 | Method 4 |
---|
1 | 60 | 0.14612 | 0.03394 | 0.00311 | 0.00043 | 2 | 120 | 0.21278 | 0.05835 | 0.00570 | 0.00044 | 3 | 180 | 0.28677 | 0.06641 | 0.00946 | 0.00089 | 4 | 240 | 0.51563 | 0.11426 | 0.00709 | 0.00043 | 5 | 300 | 0.28149 | 0.06543 | 0.00928 | 0.00071 | 6 | 360 | 0.51563 | 0.11182 | 0.00803 | 0.00083 | 7 | 420 | 0.27638 | 0.06445 | 0.01013 | 0.00148 | 8 | 480 | 0.55653 | 0.10938 | 0.00791 | 0.00074 | 9 | 540 | 0.50886 | 0.06299 | 0.01247 | 0.00198 | 10 | 600 | 0.70963 | 0.10742 | 0.01038 | 0.00099 | 11 | 660 | 0.89343 | 0.06377 | 0.01201 | 0.00132 | 12 | 720 | 0.80304 | 0.06096 | 0.00916 | 0.00116 | 13 | 780 | 0.85076 | 0.06128 | 0.00707 | 0.00109 | 14 | 840 | 0.59613 | 0.05695 | 0.00713 | 0.00197 | 15 | 900 | 0.59272 | 0.06997 | 0.01402 | 0.00198 |
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Table 1. Accuracy comparison of frequency detection in low frequency range
No. | Frequency /MHz | Arithmetic mean error of frequency detection /Hz |
---|
Method 1 | Method 2 | Method 3 | Method 4 |
---|
1 | 60 | 352.58333 | 85.10400 | 5.24102 | 0.56917 | 2 | 120 | 501.79167 | 101.60000 | 11.12227 | 0.63840 | 3 | 180 | 750.15000 | 111.82080 | 11.27520 | 0.64300 | 4 | 240 | 537.40350 | 118.33333 | 12.72240 | 1.21042 | 5 | 300 | 884.41500 | 236.29760 | 28.78092 | 1.35044 | 6 | 360 | 597.87011 | 178.52800 | 18.16214 | 1.72480 | 7 | 420 | 898.27500 | 194.54400 | 29.65572 | 1.23250 | 8 | 480 | 630.36000 | 108.39600 | 15.76973 | 1.46664 | 9 | 540 | 973.89021 | 268.07760 | 28.61121 | 1.02708 | 10 | 600 | 602.56000 | 208.08000 | 16.52556 | 2.00390 | 11 | 660 | 917.64000 | 266.31360 | 31.96869 | 1.38240 | 12 | 720 | 811.15043 | 157.22100 | 19.10038 | 3.52998 | 13 | 780 | 1289.40000 | 219.13920 | 21.50608 | 2.37312 | 14 | 840 | 805.75000 | 177.69600 | 27.56436 | 2.48270 | 15 | 900 | 902.55010 | 247.39200 | 27.11180 | 3.56040 |
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Table 2. Accuracy comparison of frequency detection in high frequency range
No. | Frequency /kHz | Arithmetical mean of error /Hz |
---|
RSN=+5 dB | RSN=-5 dB | RSN=-10 dB | RSN=-15 dB |
---|
1 | 60 | 0.00010 | 0.19175 | 1.91040 | 311.33200 | 2 | 120 | 0.00013 | 0.35768 | 1.55472 | 307.64800 | 3 | 180 | 0.00017 | 0.41007 | 2.97344 | 1847.73040 | 4 | 240 | 0.00027 | 0.74996 | 2.01240 | 1923.08880 | 5 | 300 | 0.00017 | 0.56809 | 1.59552 | 1815.69040 | 6 | 360 | 0.00028 | 0.41415 | 4.99992 | 1938.87440 | 7 | 420 | 0.00020 | 0.73958 | 11.77808 | 861.35548 | 8 | 480 | 0.00025 | 0.90391 | 9.94064 | 870.19822 | 9 | 540 | 0.00035 | 1.19215 | 19.06470 | 745.90264 | 10 | 600 | 0.00029 | 0.93306 | 10.10534 | 731.23548 | 11 | 660 | 0.00043 | 1.18215 | 30.13222 | 583.45921 | 12 | 720 | 0.00035 | 0.93405 | 26.01698 | 472.77065 | 13 | 780 | 0.00038 | 1.12902 | 21.44346 | 588.97846 | 14 | 840 | 0.00042 | 1.11308 | 26.87693 | 950.60786 | 15 | 900 | 0.00045 | 1.05872 | 30.75494 | 882.29743 |
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Table 3. Comparison of absolute errors of signal frequency detection with different signal-to-noise ratios in low frequency domain
No. | Frequency /MHz | Arithmetical mean of error /Hz |
---|
RSN =+5 dB | RSN=-5 dB | RSN=-10 dB | RSN=-15 dB |
---|
1 | 60 | 0.41691 | 300.48639 | 1509.27371 | 454325.23911 | 2 | 120 | 0.49814 | 338.76866 | 1228.59782 | 1768065.17692 | 3 | 180 | 0.92389 | 526.98932 | 1369.85067 | 2385840.38721 | 4 | 240 | 0.97161 | 405.18828 | 9136.98548 | 558740.56227 | 5 | 300 | 0.63717 | 422.34939 | 9411.28992 | 521070.28999 | 6 | 360 | 1.06819 | 516.84130 | 9580.61613 | 446435.45613 | 7 | 420 | 0.79913 | 786.61318 | 6553.47962 | 1287100.12932 | 8 | 480 | 1.04420 | 531.24111 | 3526.26674 | 1313235.31676 | 9 | 540 | 0.97155 | 574.56118 | 3147.99428 | 935988.91351 | 10 | 600 | 0.58315 | 607.62123 | 6279.61570 | 558740.60196 | 11 | 660 | 0.89542 | 622.92420 | 9411.28991 | 521070.30481 | 12 | 720 | 1.10816 | 796.86612 | 9580.67975 | 446435.60156 | 13 | 780 | 0.84019 | 814.86427 | 8419.41077 | 2101635.54417 | 14 | 840 | 1.06821 | 612.24224 | 2350.84414 | 1313235.31558 | 15 | 900 | 0.99453 | 612.24617 | 2098.62523 | 2385350.23874 |
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Table 4. Comparison of absolute errors of signal frequency detection with different signal-to-noise ratios in high frequency domain
No. | Frequency /kHz | Arithmetical mean of error /Hz |
---|
FFT | Method 1 | Method 2 | Method 3 | Method4 |
---|
1 | 64.5264 | 4194.14941 | 4.70772 | 1.93381 | 0.32256 | 0.14568 | 2 | 123.1934 | 4152.20793 | 7.81245 | 3.47223 | 0.56742 | 0.27769 | 3 | 181.8604 | 4110.68583 | 8.14860 | 3.98346 | 0.84420 | 0.30182 | 4 | 240.5273 | 4069.57892 | 11.63889 | 6.20820 | 1.20541 | 0.50791 | 5 | 299.1943 | 4028.88316 | 15.33006 | 7.31160 | 1.59180 | 0.71136 | 6 | 357.8613 | 3988.59433 | 13.71006 | 8.38440 | 1.42384 | 0.84032 | 7 | 416.5283 | 3948.70831 | 17.15013 | 8.40424 | 1.77663 | 0.76533 | 8 | 475.1953 | 3909.22123 | 18.90783 | 10.10342 | 1.96140 | 1.00400 | 9 | 528.9795 | 3870.12924 | 20.66472 | 12.84120 | 2.15043 | 0.99814 | 10 | 587.6465 | 3831.42774 | 24.07887 | 12.97624 | 2.49912 | 0.95342 | 11 | 646.3135 | 3793.11352 | 22.45887 | 13.73043 | 2.33120 | 1.42140 | 12 | 704.9805 | 3755.18236 | 25.74423 | 13.40101 | 2.67124 | 1.36353 | 13 | 763.6475 | 3717.63057 | 29.05551 | 14.20563 | 2.84346 | 1.29140 | 14 | 822.3145 | 3680.45421 | 32.28012 | 17.21520 | 3.17943 | 1.43463 | 15 | 880.9814 | 3643.64973 | 33.88392 | 19.57682 | 3.51544 | 1.75682 |
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Table 5. Precision comparisons in low frequency range
No. | Frequency /MHz | Arithmetical mean of error /Hz |
---|
FFT | Method 1 | Method2 | Method3 | Method4 |
---|
1 | 54.7852 | 3808593.75686 | 3997.02938 | 2036.72159 | 343.86209 | 176.33953 | 2 | 113.4277 | 3759765.63471 | 6352.98234 | 3237.21821 | 546.54333 | 280.27863 | 3 | 172.0703 | 3710937.53730 | 11860.12172 | 5385.60410 | 1020.31929 | 523.24066 | 4 | 230.7129 | 3662109.38275 | 17203.43953 | 6876.16441 | 1480.00178 | 641.10807 | 5 | 289.3555 | 3613281.25344 | 14531.78766 | 7404.80062 | 1250.16114 | 717.94732 | 6 | 347.9980 | 3564453.13781 | 19756.84712 | 10067.27940 | 1699.66994 | 871.62561 | 7 | 416.4063 | 3515625.69218 | 24762.72983 | 12618.06748 | 2130.32308 | 1092.47338 | 8 | 475.0488 | 3466796.88477 | 22310.24485 | 11368.38211 | 2949.41357 | 984.27551 | 9 | 528.8086 | 3417968.75109 | 27215.20969 | 13867.75023 | 2750.42503 | 1200.67102 | 10 | 587.4512 | 3369140.63511 | 29592.98431 | 15079.36627 | 2279.33724 | 1305.57284 | 11 | 646.0938 | 3320312.51726 | 34283.78167 | 17469.60345 | 2341.30848 | 1512.51978 | 12 | 704.7363 | 3271484.38414 | 31970.75250 | 16290.97903 | 2545.86703 | 1410.47438 | 13 | 763.3789 | 3222656.25844 | 36596.80313 | 18648.22394 | 3148.40145 | 1614.56484 | 14 | 822.0215 | 3173828.13282 | 38856.96480 | 19799.90684 | 3342.84141 | 1714.27765 | 15 | 880.6641 | 3125000.11710 | 41117.10844 | 20951.58540 | 3537.28065 | 1813.99008 |
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Table 6. Precision comparisons in high frequency range
Item | Method 1 | Method 2 | Method 3 | Method 4 |
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Low frequency | 0.0044 | 0.00229 | 0.00043 | 0.00020 | High frequency | 0.0055 | 0.00273 | 0.00048 | 0.00024 |
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Table 7. Relative error averages in the low and high frequency ranges
Wavelength range /nm | Output bandwidth /MHz | Active area diameter /mm | Input optical power range / |
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400‒1000 | 400 | 0.5 | 8‒80 |
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Table 8. Main parameters of APD 430A/M
No. | Reference speed /(m·s-1) | Arithmetical mean of error /(m·s-1) |
---|
Method 1 | Method 2 | Method 3 | Method 4 |
---|
1 | 0.5415 | 1.58518×10-4 | 8.67780×10-5 | 1.88374×10-5 | 1.15203×10-5 | 2 | 0.5898 | 1.79469×10-4 | 9.70299×10-5 | 1.93083×10-5 | 1.18081×10-5 | 3 | 0.6377 | 2.15047×10-4 | 9.78912×10-5 | 1.91513×10-5 | 1.17123×10-5 | 4 | 0.7056 | 2.60572×10-4 | 9.86931×10-5 | 1.93083×10-5 | 1.18080×10-5 | 5 | 0.7683 | 3.14231×10-4 | 1.03356×10-4 | 2.15460×10-5 | 1.19047×10-5 | 6 | 0.8675 | 3.67119×10-4 | 1.12973×10-4 | 2.58036×10-5 | 1.26724×10-5 | 7 | 0.9369 | 3.10047×10-4 | 1.25720×10-4 | 2.78561×10-5 | 1.36800×10-5 | 8 | 0.9897 | 3.36604×10-4 | 1.31654×10-4 | 2.89313×10-5 | 1.77600×10-5 | 9 | 1.0425 | 2.69283×10-4 | 1.17746×10-4 | 3.56754×10-5 | 1.96536×10-5 | 10 | 1.0832 | 2.67506×10-4 | 1.04587×10-4 | 3.69357×10-5 | 2.15417×10-5 | 11 | 1.1238 | 2.56270×10-4 | 1.07916×10-4 | 4.29600×10-5 | 2.21475×10-5 | 12 | 1.1605 | 2.71244×10-4 | 1.36797×10-4 | 4.76400×10-5 | 2.38255×10-5 | 13 | 1.1972 | 2.48648×10-4 | 1.43981×10-4 | 4.76400×10-5 | 2.38213×10-5 | 14 | 1.2492 | 2.39082×10-4 | 1.57070×10-4 | 4.77600×10-5 | 2.38846×10-5 | 15 | 1.2971 | 2.51415×10-4 | 1.70160×10-4 | 4.81200×10-5 | 2.40676×10-5 |
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Table 9. Processing results of measured signals