| Summary: | 碩士 === 國立中興大學 === 電機工程學系所 === 106 === In recent years, the measurement of distance and orientation of objects gradually draws people’s attentions. Radar will not be affected by weather or light, thereby influencing the accuracy. Therefore, radar is often used in our daily lives. The frequency modulated continuous wave (FMCW) radar can measure distances but it usually can’t obtain the directions of objects. Therefore, we utilized the concept of array antennas and single-band modulation technique to make it possible to detect multiple directions simultaneously.
In this thesis, eight antennas are aligned as a 1-D antenna array, so that the radar system can detect three directions at the same time. The beamforming technology is also applied to both the transmitter (Tx) and the receiver (Rx) to make the power of radar beams narrowed to the direction to be observed. The simulation results show the power to the objects to be observed is increased by about 20 dB, and the power to the objects in the other directions is suppressed by about 20 dB. In addition, the radio-frequency (RF) VCO providing the two orthogonal signals of the single sideband modulation induces the issues of IQ imbalance. However, in the conventional fixed RF-frequency communication systems, the correction of this effect is only applied to the receiver. In this radar system, it is necessary to correct this non-ideal effect at the transmitter in this radar architecture, because the original single sideband signals will become double sideband signals after modulation without correction. That will be almost impossible to identify the number of objects. Therefore, this paper refers to a document with corrections on both the transmitting end and the receiving end. Here, the correction processes are performed at the transmitter. The up-converted signals are fed back directly to the down conversion mixer to extract the quantity of IQ imbalance by considering the delay time of the feedback path. This calibration process can reduce the power of the imaging peaks at the receiver by 40 dB by simulation.
For hardware implementation, this thesis proposes the hardware design to process the digital signals at the Tx and the Rx. The key functional blocks include Tx/Rx beamforming, IQ calibration and integration of the fast Fourier transform provided by Xilinx. Because of the 8 antennas, the hardware may be increased by 8 times. Fortunately, owing to the moderate speed requirement, the calculation units may be shared sometimes. Finally, the hardware of this digital calibration/correction process was implemented using Virtex7 XCVX330T of Xilinx for verification. The APR tool of ISE Design Suite 14.5 version was used with the synthesized clock rate of 193.9MHz and APR clock rate of 176.1 MHz.
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