Research And Design Of Wide-beam Antennas

The development of fuze systems and satellite navigation systems has also driven the development of terminal antennas.In fuze applications,the antenna is required to be able to detect and identify targets in a large range to accurately obtain target information.The wide beam antenna has a wide beam converage and can be better applied to fuze systems.In satellite navigation systems,wide beam circularly polarized antennas can enable the antenna to obtain a wide range of accurate information,thereby improving communication quality.The dissertation aims to study the following four wide beam antennas: a wide beam open-ended waveguide antenna operating at 10 GHz,a wide beam waveguide slot antenna at 8.1 GHz,a wide beam magnetoelectric(ME)dipole antenna operating at 8.1 GHz,and a low profile widebeam circularly polarized microstrip antenna operating at 2.492 GHz.These four antennas can achieve wide beam performance and have their own advantages: the waveguide antennas have simple structures and can be integrated for fabrication;the wide beam electromagnetic dipole antenna has a uniform pattern and wide bandwidth;the wide beam circularly polarized microstrip antenna is easy to achieve low profile and miniaturization.Details are as follows.1.A wide beam open-ended waveguide antenna operating at 10 GHz and a wide beam waveguide slot antenna operating at 8.1 GHz are proposed.These two antennas are based on the ordinary rectangular waveguide structure,chamfering along the wide sides of the waveguide at the waveguide opening to expand the beam.At this time,the beamwidth of the H-plane can only reach about 150°,and the ripple of the E-plane pattern is big.Further broadening the beamwidth of the antenna is necessary.For the wide beam open-ended waveguide antenna operating at 10 GHz,a pair of metal stubs are added along the chamfered position on both sides of the wide wall of the waveguide to achieve wide beam performance.The measured results show that the gain of 160 ° beamwidth coverage is above 0 d B.Excluding the fluctuations at individual declination angles(near + 33°)of the E-plane,the beamwidths of the E and H-planes are 208° and 158°,respectively.And the-10 d B impedance bandwidth reaches 8.4%.For the wide beam waveguide slot antenna operating at 8.1 GHz,two pairs of oblique slots at the narrow sides of the waveguide enable the antenna to achieve wide beam performance.The measured results show that the gain of 160 ° beamwidth coverage is above 0 d B.Excluding the fluctuations at individual deflection angles(near-37°)of the E-plane pattern,the beamwidths of the E and H-planes are 204° and 159°,respectively.And the-10 d B impedance bandwidth reaches 23%.2.A wide beam ME dipole antenna operating at 8.1 GHz is proposed.The ME dipole is composed of parallel short circuit plates perpendicular to the ground and two downward-tilted arms,which is coupling fed by the bent coaxial probe.Then reflector plates inclined along Eplane edge are added,the scattered electric field between the dipole and the side wall of reflector plates compensate the weak area of radiation to widen the beamwidth of E-plane.A pair of metal walls are employed to change the existing electric field phase of the antenna to widen the beamwidth of H-plane.The actual measurement results show that the-10 d B impedance bandwidth is 35.6%.Both of the half-power beamwidths of the E-plane and the H-plane are183.2°.The maximum gains of the E plane and the H plane are 2.52 d B and 2.64 d B,respectively.3.A wide-beam circularly polarized microstrip antenna operating at 2.492 GHz is proposed.The antenna is fed by a single point.Four circular patchs with different radius are loaded on the four corners of the square radiation patch to achieve circular polarization.Then four identical grounded metal pillars in the axial direction of the patch are loaded to widen the beamwidth of the antenna,and the metal discs are loaded above the metal pillars to reduce the profile of the antenna.The measured results show that the antenna has an impedance bandwidth of 17.6% at a center frequency of 2.492 GHz,the 3 d B axial ratio bandwidth is not less than5 %.The beamwidths of the phi = 0° and the phi = 90° are 156° and 157°,respectively.The 3d B axial ratio beamwidths of the two main planes are 192°and 199°,respectively.