A Study On Low-profile And Wideband Antennas With End-fire Radiation

Low-profile and wideband antennas with end-fire radiation are very promising in airborne,carrier-borne and vehicle communication and radar system.Based on this application background,some research is done on the principle of broaden the bandwidth and low the profile of the antenna.This dissertation focuses on the analysis of H-plane horn antenna and monocone antenna with low profile and wide bandwidth,the main work are summarized as follows:1.A low-profile and wideband H-plane horn antenna mounted on a large conducting ground plane is proposed with stable radiation patterns and gains.Introducing ridge structure can broaden the bandwidth and lower the impedance of the antenna,which makes the impedance matching easier.An arc-shaped horn aperture printed on the slab extending along the horn can smooth the transition from horn to the free space.Front-to-back ratio of the radiation pattern can be improved in the same time.As a result,a frequency bandwidth of 93%is achieved as the profile of the antenna is 0.13?0.The proposed H-plane horn antenna can be made into conformal form because of its low profile.Two slots along two sides of the flare part of the ridged waveguide are cut to solve the problem of poor impedance matching caused by the curvature.With the utilization of the slots,the matching between the feed line and the horn antenna is improved and the working frequency bandwidth is broadened simultaneously.2.A wideband linear array in H-plane and a monopulse antenna are designed based on the proposed H-horn antenna.In order to construct the linear array in the H-plane,the aperture size of the horn antenna in the H-plane should be less than one dielectric wavelength,which leads to a poor impedance matching especially in the lower frequency range.In order to reduce the deterioration of the VSWR of the H-plane horn antenna,the side walls of the flare part of the antennas are removed.Through using a wideband monopulse comparator to feed the H-plane horn array,a wideband monopulse antenna is realized.3.A low-profile and wideband monocone quasi-Yagi antenna is designed to generate end-fire radiation beams with an antenna height of 0.15?0.The antenna consists of one driven monocone with two slots cut on the loaded top hat,five identical grounded cones serving as a roll of reflectors and another two parasitic cones beside the driver to suppress the side-lobe level and improve the front-to-back ratio.The antenna can achieve a broad frequency bandwidth(98%)with a low profile.The antenna also exhibits stable nearly end-fire radiation beams over the same frequency range.It is observed that measured results agree well with simulated ones.4.A wideband H-plane horn antenna based on corrugated substrate integrated waveguide(CSIW)technology with a very low profile is presented.CSIW structures are realized by replacing the vias of traditional SIW structures with open-circuited microstrip stubs and exhibits good transmission characteristic.The CSIW H-plane horn antenna shows better performance and simpler structure compared with the SIW one.A horn aperture with a specified shape is utilized,so that the poor impedance matching because of the structure restriction can be smoothened.The antenna also brings out the stable radiation beam in the wide frequency band(113%).