Design Of Low Cost Miniaturized Ultra-wideband Feed Antennas

Antenna feeds supply energy to(or receive energy from)a secondary antenna,which includes a reflector,lens,or beam waveguide.At present,antenna feeds are mainly applied to satellite communication,radar,radio telescope,deep space detector and ground microwave and millimeter wave radio links,whose performances will affect the behaviors of the whole system directly.In recent years,people have put forward higher performance requirements for the next generation of antenna feeds,mainly including a broad working frequency band,an ability to receive signals of various polarization,a low reflection loss,a low level of cross-polarization and side-lobe,and a narrow beamwidth.Therefore,it is of great significance and value to study the ultra-wideband antenna feeds.In this thesis,when the spatial envelope of the feed system is limited,the multi-feed system is too large and costs high,it is necessary to replace multiple antennas with a single antenna to realize broadband signal reception,low cost and miniaturization.The completed tasks are as follows:A 5-40 GHz four-ridged horn antenna is designed and main parameters affecting the performance of four-ridged horn antenna are simulated and optimized.In the design of a ridged waveguide,in order to reduce the cutoff frequency,the influence of ridge spacing and width on the cutoff frequency is analyzed.In the design of the reflection chamber,to improve the energy transmission in the working frequency,the influence of the shape of the reflection cavity on the antenna return loss is analyzed.In the design of four-ridged horn section,in order to achieve good impedance matching and antenna far-field radiation characteristics,the influence of horn aperture size and ridge curvature parameter k on antenna impedance matching and radiation pattern is analyzed.The final four-ridged horn antenna designed can provide a voltage standing-wave ratio of less than 3,an octave ratio of 8,and a gain range of 8.1d B-16 d B in the whole 5-40 GHz frequency band.Another antenna designed in this paper is a 3-30 GHz logarithmic periodic antenna array.An exponential metallic reflection chamber is designed at the low frequency end,which can suppress the antenna's back lobe,and improve the antenna's front and rear ratio,so that the bandwidth of the antenna is expanded about 500 MHz and up to 10 x frequency.To meet the requirement that the radiation patterns in two main planes should be symmetric,a pyramidal array form is set up with four antenna elements.The beamwidths of the antenna array in the two main planes are almost identical.The gain of the antenna array is also increased by about 2.5d B compared with the antenna element,making the gain range from 10.3d B to 15.4d B.At last,the prototypes of the two kinds of antennas are fabricated and measured,and the measured results are in good agreement with the simulated results.It meets the design requirements.The two kinds of antennas proposed in this thesis have some value in practical application and certain guiding significance to the development and design of the similar antennas.