Research Of Ultra-wideband Pulsed Anteena And Its Applications In Bioengineering

With the development of pulse power technology in recent years, sub-nanosecondand picosecond pulses have been realized, which made ultra-wideband (UWB)technology a wide range of applicantions in defense military and national economicfields. UWB antenna technology gets involved in the radtion of short pulses with verywide bandwidth as traditional antennas are not suited for it. To radiate short pulses,UWB antennas have to get flat frequency response, high withstand voltage and gooddirectivity with low side lobe and back lobe in the wide bandwidth. The performance ofUWB antenna reflects the performance of the UWB system critically as it is the corecompoment of UWB system. So, the researches on UWB antennas are of extremelyvital significance.The existing research shows that with high intensity picosecond pulse beingfocused on the tumor tissue on the base of the safety of the patients, the targeted tumorcells could be induced to apoptosis to realize noninvasive treatment. Noninvasivetreatment which can deal with the tumor cells effectively is selective and targetedcompared with traditional cancer treatments, and the key of realizing it is reasonabledesign and implementation of impulse radiated antennas. Based on the theories ofUWB antenna，we designed an Impulse Radiating Antenna by which picosecond pulsescan be radiated and some preliminary optimizations of the antenna were made. The gainand field pattern of the antenna are stable, and the voltage standing wave ratio is lessthan2. On the bases of it, we make some researches on the focusing properties of thepicosecond electric pulse focusing in the biological tissue. Whether picosecond electricpulse radiated in the air could focus in the biological tissue is the problem that we haveto deal with for promoting noninvasive treatment to clinic applications. According totheoretical and numerical analysis it is concluded that the difference of the dielectricconstant between the air and the biological tissue is disadvantageous for focusingpicosecond pulsesat targeted point in the biological tissue. The way of changing themedium inside the IRA by the medium of the dielectric constant similar with fat isproposed to solve it, and some simulations have been carried out to prove it.Imaging technology is also a hot topic of the UWB technology research inbiomedical engineering. It could show the human body structure or function directly insome ways, which can be used in disease prevention, clinical diagnosis and medical researches. Compared with traditional imaging technologies, microwave imagingtechnology is of high precision and low cost, and it could be used for times. And theperformance of the imaging technology depends on the performance of radiatedantennas partly. Therefore, we designed a new type of UWB radiated antennas of simplestructure, low cost and excellent performance called Valentine antenna by simualtions.The size of Valentine antenna is950mm×1136mm×52mm, and it works at the frequency band0.3-3GHz. And the gain and field pattern of the antenna are stable, and the voltagestanding wave ratio is less than2. We also designed a kind of transition considering ofthe practical applicantions of Valentine antenna. And the performance of Valentineantenna matched by the transition was researched by simulations, which is proved tomeet the design demands.