The Design Of Frequency Scan Antenna Based On Stripline Feed Networks

With the development of space and missile technology, modern radar and communication technology are increasingly demanded, among which radar antenna’s beam are specially asked for the quick scan with the change of frequency. Frequency scan antenna, as the name implies, is a kind of antennas whose beam-pointing is changing with operating frequency. This paper mainly designed a frequency scan antenna array which works in X-band. The main research work is as follows:Theoretical analysis: firstly, I did some research on the basic theory of frequency scan antenna array and carried out 4 basic structural parameters(d, m, L, m?) which have a strong influence on antenna’s scanning. Then, I analyzed the pattern of the frequency scan antenna array combining Taylor synthesis and triangular lattice configuration, as well as determining the spacing between the antenna array elements; Finally, I emphatically analyzed the structure of low loss slow wave line which plays a decisive role in frequency scanning antenna. By comparing the property of different slow wave line, I finally chose serpentine, which characterized by small size, light quality and simple structure. Besides, I made a loss comparison among suspended microstrip line, microstrip line and stripline when working in X-band. Finally, stripline structure characterized by low loss was adopted as the slow wave line of frequency scan antenna array.Simulation design: firstly, using HFSS electromagnetic simulation software simulated doublet antenna, which is the element of frequency scan array. After the optimization, the antenna model I obtained has good performance parameters on VSWR, gain, lobe width and so on. Then, according to the antenna’s aperture distribution, I determined the topological structure of one-to eighteen power divider network. Meanwhile, I simulated 17 power dividers which are realized by four branches stripline directional coupler. Because of the phase deviation between two output ports, low pass filter was used to reduce the phase deviation. Concerned with the computer resource of the lab, I divided the one-to eighteen power divider network into 4 parts: one-to-five power divider, one-to-four power divider, one-to-three power divider and one-to-six power divider. After separately simulated and optimized these four small power divider networks, I matched them together and simulated the whole networks. The final results of the one-to-eighteen power divider network show that the optimized model meet the required specifications on standing wave, amplitude, phase and so on. Besides, I simulated and optimized one-to-four wilkinson power divider for line feed. At last, I simulated and optimized 4 ? 18 frequency scan antenna array and the obtained antenna pattern shows that the antenna array meets the desired scan angle, beam width, sidelobe level and gain.Processing and testing: according to the simulation model, I manufactured and tested the physical antenna array. The measurement results show that the physical antenna array meets the specifications of frequency scan antenna array on scan angle, beam width, sidelobe level and gain, which proves that the designed antenna array is feasible in practical applications.