The Research And Design Of UWB Impulse Radar

Ultra-wide band(UWB) impulse radar is a new radar of target detection, localization and imaging with emitting narrow pulse. It has a lot of advantages such as good penetration properties, high resolution and low power consumption, It can be used in a variety of civilian and military fields,for instance, geological exploration, indoor positioning, anti-stealth technology, wall against terrorism, jungle exploration, life rescue, airport safety supervision system,etc. This thesis focuses on the key technologies of UWB impulse radar of transceiver system, and makes research mainly in the following aspects:(1) The history process, current development and technical advantages and significance of ultra-wideband impulse radar are introduced. The basic theory of UWB impulse radar including the basic structure and radar equation are explained.(2) The two new UWB narrow pulse source bases on avalanche transistor and the step recovery diode theory respectively, are designed and produced, in addition, the various factors that affect the pulse amplitude and width are analyzed. The produced avalanche pulse source has the maximum amplitude of about 3V and the minimum pulse width of about 1ns and the step pulse source acquires the maximum amplitude of about 950 mV and the minimum pulse width of 350 ps. these results show the technology of avalanche can obtain greater amplitude and step pulse has narrower pulse width.(3) An UWB low noise amplifier(LNA) based on the theory of negative feedback is designed and tested with bandwidth of 0.1-1GHz; gain more than 38 dB and noise-figure less than 2dB. It is designed by adding feedback capacitance in source pole of transistor to compensate for the high frequency gain and taking advantage of ADS to optimize the input and output port impedance rapidly, and also selecting the appropriate feedback resistor and additional optimization objectives to avoid the tedious steps of finding the best match point the circle on the Smith chart.(4) On the basis of equivalent sampling theory. We uses FPGA to produce 10 clocks signal of 200 MHz, the clock signal is sent to the ADC MAX1121 as the sampling clock after delayed 52ps(equivalent sampling rate of 20 GS / S)by chip CDCF5801. After delay sampling of 192 times, a complete echo signal data is collected into the FIFO buffer of FPGA. The collected data sequence is reorganized by BLOCKRAM so that getting the correct waveform, and then the data is programming into the internal storage unit of solid state memory AT45DB161 D through FPGA. When need to process and analyses the data, we can read them by the FPGA via a serial interface, and transmit the data to PC through MAX232. The echo wave data sampling circuit achieves the UWB impulse radar data acquisition on low cost four-layer board of FR-4 and avoids purchasing expensive high-speed ADC, and controls costs well while acquiring good system performance.