| With the growing demand of exploration and tracking,wireless communication is flourishing.As a key component of wireless terminal device,the antenna is bound to become broad-banding and intelligent.Meanwhile,to enhance the flexibility of information transmission and the anti-polarisation mismatch ability of channels,circularly polarised antenna has become a research hotspot in recent years.Particularly,ultra-wideband circularly polarised antenna can receive radiant waves of arbitrary polarisation and its radiated waves can be received by antenna of arbitrary polarisation;additionally,it can also restrain rain and fog and resist multipath interference,which made it widely used in the fields of satellite communication,radar,etc.Thus,in this paper,the main contents are ultra-wideband dual circular polarised antenna,ultra-wideband circular-polarized dipole antennas,X-band ultra-wideband circularly polarised antenna and its array,according to the demand of the project requirements.Firstly,a design technique of ultra-wideband dual circularly polarised microstrip slot antenna was studied.The proposed antenna is fed by the coplanar waveguide(CPW).Then,insert a perturbation patch shaped as a reversal ‘L' into a square groove and connect another one to the feeder,which excites two kinds of orthogonal equal-amplitude resonant modes,obtaining the dual circularly polarised antenna with the property of broadband.Additionally,to optimise circular polarisation functionality and standing wave ratio bandwidth,we etched two rectangular grooves on the ground plate.It shows that,through simulation and actual measurement,antenna studied in this paper can respectively obtain an impedance relative bandwidth of 70.4%(2.3~4.8GHz)and a 3-dB axis ratio relative bandwidth of 48.6%(2.1~3.45 GHz.Within the operating frequency,the maximum gain can reach 3.95 dBi,which meets the requirements of the scientific research project for ultra-wideband and circular polarization performance.And it can be used for Bluetooth/WLAN(2400~2484MHz)and WiMAX(2.5~2.69 GHz,3.2~3.8GHz)and other low-power communication systems.Secondly,the ultra-wideband circularly polarized dipole antenna unit is studied.In this paper,we utilised coaxial feed of simple structure.Through the coaxial line,this antenna feeds a pair of centrally symmetric fan-shaped microstrip dipoles,which have opposite directions,making them produce a phase shift of 180°.When odd-mode fed,this antenna produces pattern null in the direction of the coaxial line,which reduces the drive current outside of the coaxial line.To increase gain,we set a hollow cylindrical cavity resonator outside of this antenna.Through simulation and analysis towards the size of the dipole pair,it obtained a relative bandwidth of voltage standing-wave ratio(VSWR?2)of 43.74%(2.45~3.81GHz)and an axis ratio(AR<3dB)relative bandwidth of 45.64%(2.4~3.75 GHz).Within the effective axial ratio band,the gain at the centre frequency(3.00GHz)is 8.84 dBi.The full coverage of Band38,Band41 and Beidou bands(2491MHz)and S-band(2330~3700 MHz)was achieved.However,when operating in actual scurviness,the microstrip circularly polarised antenna has low physical strength.Moreover,metallic materials can enhance physical strength of the whole antenna,sustaining longer under bad working conditions.Thus,in this paper,we conducted simulation and analysis on all-metal circularly polarised antenna,which obtained a relative bandwidth of voltage standing-wave ratio of 42.98%,an axis ratio relative bandwidth of 43.39% and the gain at centre frequency of 9.03 dBi.The simulation results show that the all-metal circularly polarized dipole antenna and the microstrip dipole antenna have similar performance,and the all-metal dipole circularly polarized antenna has the advantages of simple fabrication,good mechanical strength,and strong applicability,and the gain is high.It can be used in mid-range warning radar and tracking radar systems.Finally,the X-band ultra-wideband circular polarization units and arrays are studied.This subject adopts 0°,90°,180° and 270° rotation array technology to achieve ultrawideband and good circular polarization performance.Active VSWR<2 is 6.0~13.0 GHz,the relative bandwidth is 73.68 %.In this paper,the frequency range of antenna axis ratio AR<0.1dB is 6.0~13.0 GHz,and the relative bandwidth is 73.68%.In order to realize the high gain requirements of the project antenna,a 5×5 left-circular polarization array was modeled and simulated with a maximum gain of 16.6188 dB and a 3-dB beam width of 20.1546°.At phi=0°,the maximum gain is 10.2588 dB with a sweep of 25°.At phi = 45°,the maximum gain without scanning is 16.6188 dB,the 3-dB beam width is 22.6804°,and the maximum gain is 14.3096 dB with a sweep of 25°.The circularly polarized arrays studied have ultra-wideband and circular polarization properties,and can easily achieve the high-gain and narrow beam characteristics required by the project,which can meet the needs of X-band satellite array antennas. |
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