| Frequency Modulated Continuous Wave(FMCW)Radar is widely used in automotive driving assistance and unmanned aerial vehicle(UAV)remote sensing due to its miniaturization and low cost.Meanwhile,it has the capability of high resolution(HR)imaging,exploiting a large frequency sweep bandwidth of the transmitted signal.In this thesis,we have designed and developed a 24 GHz FMCW HR imaging radar system for UAV application.The detailed achievements are listed as follows:1)A 2 × 6 array microstrip patch array antenna for FMCW radar was designed and implemented.The characteristical parameters are: the center frequency is 24.2GHz and the bandwidth reaches 1.4GHz with the return loss of the antenna less than-10 d B,antenna gain reaches 17 d B,E-plane(azimuth plane)half-power beam width is 14.5°,H-plane(elevation plane)half-power beam width is 37°,and antenna pattern direction gradually shifts from-1°to + 0.5° in the range of 24 GHz to 24.5GHz with 0° at 24.3GHz.The transmitting antenna and the two receiving antennas have the same structure,and the isolation between the transmitting and receiving antennas is greater than 50 d B.The antenna S-parameter and pattern measured results are consistent with the simulation results.2)A 24 GHz high-resolution FMCW radar front-end system is designed and implemented.The RF front-end transmitting link uses a hybrid mode of digital frequency synthesis and phase-locked loops(PLL),which avoids the shortcomings of integer boundary spurs for the swept signal and hardly fast implementation.The experiment results show that the transmitted signal sweep bandwidth can reach 700 MHz with the center frequency of 24.25 GHz,the maximum non-linear offset is 608 KHz,the maximum linear sweep time is 400 us,and the sweep period is 600 us.After the IF signal output by the RF front-end receiving link is amplified and filtered,the analog-to-digital signal conversion is performed by a dual-channel ADC with a sampling rate of 12.5MHz and the output signal is 16 bits for digital signals.Each scan period outputs 16 KB of data.3)After using the baseband acquisition board of the cooperative enterprise to realize the basic radar target detection function,the complete radar system test was completed.The size of the entire radar system is 170 mm × 90 mm × 28 mm,powered by a single 12 V power supply.The system can be triggered by a wireless switch to start working,through the Ethernet connection,the upper computer can store the echo signal data in real time.The baseband data uses the existing radar data acquisition scheme.The digital signal is transmitted from the RF front-end board to the baseband acquisition board through a 60-pin high-speed digital socket and transferred to the host computer.The experimental results in the dark room show that the radar can detect a static target with accurately measuring the distance.For the radar scanning mode,the experimental results show that the radar has a beam scanning range of 13 degrees on the azimuth plane,and has a coverage range of more than 30 degrees on the pitch plane. |
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