The Design Of FMCW Ranging Radar Based On Zero-IF Technology

The most basic function of radar is distance measurement.Ranging radar is widely used in the measurement of the object distance.With the development of science and technology,the level of ranging accuracy,size,power consumption and other requirements are getting higher and higher.The FMCW radar transmits a continuous signal with a wide bandwidth,and the transmit power is smaller relative to the pulse radar.In summary,this paper designs a miniaturized short-range zero-IF FMCW ranging radar system.The superheterodyne receiver as the commonly used receive by FMCW radar,it's hard to be highly integrated,this paper designed a FMCW range radar system worked in the 5.8GHz band using the zero-IF receiver as the radar receiver.In addition,radar data usually used DSP,SCM and other method to collecting and processing,and they're unflexiable enough.This paper use the computer sound card as an A/D converter in order to make the processing more convenient and flexible.The whole design is divided into transceiver part,antenna part and data acquisition and processing part.The transceiver section is divided into a transmitting part and a receiving part.Firstly,the transmitter part for the problem of the VCO's linearity,designed a sawtooth wave generator which has a adjustable range and period.Secondly,the zero frequency has the problem of LO leakage,DC bias and I/Q imbalance.The solution is to chose a Mixer that it's isolation is 50dB and on-chip integrated a 90 °phase shifter.Then,for the radar frequency band,transmission bandwidth and other parameters,use the HFSS design a directional miniature logarithmic antenna.This antenna is small in size and easy to process with respect to wideband array antennas and stacked antennas.Finally,a 16-bit sound card with a sampling frequency of 22.050KHz is used as the A/D converter to design a signal acquisition system in order to improve the convenience and flexibility of signal acquisition and processing.Using FFT to processing the signal by Matlab after acquisition,so as to get the target's distance information.The segmented processing method is proposed to process the signals at different distances,and the correction factor is introduced to correct the distance information to improve the accuracy.After processing,the radar system's parameters as follows:The size is 5.6cm'*7.6cm Transmit sweep bandwidth is 702.5MHz Transmit power is +7dBm Noise figure is 2.79 Sensitivity is-83dBmLogarithmic antenna's parameters as follows:The size is 2.6cma*3.1cm Working frequency is 5.155GHz-6.455GHz Gain is +7dB.