New Pattern Synthesis Methods For Leaky-wave Antennas And Their Applications

Today we are surrounded by electromagnetic wave.Electromagnetic interference makes the quality of communication deteriorated.That needs antennas with low side lobe or null in the radiation pattern using pattern synthesis,in order to decrease interference.The existing references for pattern synthesis are mainly about array antennas,but less about single leaky-wave antennas.The traditional pattern synthesis for leaky-wave antennas is generally adopted tapering structure,but this method needs complex calculation and high fabrication accuracy.According to theory of effective radiation sections(ERSs),the far fields of antennas are decided by ERSs.A null will be introduced in radiation pattern if there are some methods could restrain the radiation strength.According to the theory of field superposition,two antennas namely main antenna and slave antenna are designed,try to make the main beam of salve antenna's radiation pattern and the side lobe of main antenna's radiation pattern are destroyed,then a null in the radiation pattern can be generated.The main works and innovations of this paper are summarized as follow:1.A leaky-wave antenna based on HMSIW structure is proposed,and then restrain the radiation of ERSs by changing the positions of vias and extending the width of substrate,so as to introduce a null in the radiation pattern,the depth of null reaches-36,2 dB.Feeding structure is designed,which makes it possible to introduce null and keep a good impedance matching at the same time.At last,the designed antennas are fabricated and measured.2.A periodic leaky-wave antenna based on SSPPs structure with a null in the radiation pattern is proposed.Main and slave waveguides and its feeding structures based on uniform SSPPs are designed firstly,and the slave waveguide just follows behind the main waveguide.Then main and salve SSPPs waveguides are modulated to radiate,these namely are SSPPs leaky-wave antennas.Based on the theory of field superposition,by adjusting the amplitude,initial phase and main beam direction of slave antenna to make the main beam of slave antenna cancelled with some side lobe of main antenna,so as to introduce a null in the radiation pattern,and the depth of null is-23.8 dB.3.A SSPPs bended connector and leaky-wave antenna composed of main and slave antennas is proposed,to generate a null in the radiation pattern and enhance the radiation strength of main beam respectively.The factors influenced on transmission characteristic of bended connector are studied.Based on the theory of field superposition,adjusting the amplitude,initial phase and main beam direction of slave antenna,when the phase is opposite with the main antenna's one,the main beam of slave antenna cancelled with some side lobe of main antenna so as to produce a null,and the depth of null is-23.8 dB;when the phase is same as the main antenna's one,the main beams of slave antenna and main antenna coincide with each other,and their phases are same,so the gain of antenna is enhanced,about 1.5dB is improved,and the side-lobes of antenna is reduced at the same time.The advantages of this structure are the size of antenna reduces and the energy is used sufficiently.