| Combined with the researched projects,the ultra-large aperture transmitting phased array for solar power station application and specific low-profile antennas are mainly studied in this thesis.Firstly,the dissertation illustrates the research station and existent problems at home and abroad,and then shows the topic significance and main results.Secondly,the research work can be divided into two parts.The first part designs the ultra-large aperture transmitting phased array used in space solar power station system,and then processes an 8×8 array to verify the feasibility of this design scheme.The second part studies on the feasibility of specific low-profile antennas,including missile-borne and low-profile composite multi-band antenna,low profile directional antennas?low profile wideband circularly polarized double-sided printed dipole antenna and its array,low profile wideband circularly polarized radial line slot array antenna?and low profile omnidirectional antennas?low profile wideband horizontally polarized omnidirectional antenna and its array,low profile dual frequency circularly polarized omnidirectional antenna?.Finally,the further study on these issues is also discussed.The research work in this dissertation is mainly concluded as follows:1.Research on the ultra-large aperture transmitting phased array for space solar power station applicationsAccording to the function requirement of space solar power station system,specific technical indicators are put forward for the ultra-large aperture transmitting antenna array.In this section,we design a new type of antenna element with high-power and phase-adjustable characteristics.With this array element,the entire transmitting antenna array is constructed to be a 1.2km×1.2km array?about 640 million array elements?.And it is optimized to achieve the small scanning angle range of 0.0003°and the high-precision pointing of 0.0001°for the array beam.On the basis of this study,an 8×8 antenna arrays and a set of unequal amplitude feeding network are processed.Experiments show that the simulation results agree well with the measured results.Therefore,the effectiveness and feasibility of the overall design scheme of the transmitting phased array are verified,which provides a good technical foundation for engineering realization.2.Research on the specific low profile antennasThe second part researches on the specific low profile antennas,which includes five antenna designs in specific application environments.The research works are demonstrated as follows:?1?Missile-borne and low profile composite multi-band array antennaAccording to the requirements of missile-borne systems,this section studies on the low-profile composite multi-band array antenna.With the given carrier platform and location,each of five antenna elements are designed with low profile,ultra-wideband,dual polarization and wide beam characteristics.First,the Vivaldi antenna is selected to achieve wideband coverage.To design the low-profile feature,a matching load is placed at the end of the antenna.Meanwhile,periodic slots of the antenna are introduced to improve the low frequency gain.Finally,all simulation designs consisting of the antenna array and radome are completed.Based on the simulated results,experimental prototypes are processed and tested.And the measured results meet the requirements of the technical indicators and engineering application.?2?Low profile wideband circularly polarized double-sided printed dipole antenna and its arrayThis section presents a low profile wideband circularly polarized double-sided printed dipole antenna and its array.The designed antenna element consists of a double-sided printed cross-dipole,four parasitic rings,and an AMC?Artificial Magnetic Conductor?reflector.The antenna element has the low-profile characteristic with an impedance bandwidth of 50.0%?1.29-2.15 GHz?and an axial ratio bandwidth of 27.7%?1.4-1.85GHz?.In addition,to further broaden the axial ratio bandwidth,a 2×2 antenna array is designed with continuous rotation feeding technology.The impedance bandwidth and axial ratio bandwidth are 59.5%?1.3-2.4 GHz?and 56.3%?1.15-2.05 GHz?,respectively.The measured results are in good agreement with the simulated results.Within the circularly polarized bandwidth,the measured maximum array gain is 15.0 dBic and the maximum radiation efficiency is 63%.Therefore,the proposed broadband circularly polarized antenna elements and its array can be applied in wireless communication systems.?3?Low profile wideband circularly polarized radial line slot array antennaThis section studies on a low profile wideband circularly polarized radial slot array antenna.The proposed antenna consists of two parallel plates,a monopole probe and a spiral slot array.First,the TEM mode fed by the coaxial probe is transformed into a radial mode within the cavity,thereby exciting the spiral slot array at the top of the cavity,and finally radiating the directional circularly polarized beam.By opening and cutting the radial cavity to reduce its quality factor,the bandwidth of the antenna is enhanced.In addition,the antenna has a low profile?0.23?0,where?0 represents the free-space wavelength at 15 GHz?,with an impedance bandwidth of 37.2%,an axial ratio bandwidth of 31.0%,and a maximum measured gain of 26.7 dBic at 17.5 GHz respectively.Therefore,the proposed antenna is suitable for high gain and circularly polarized applications at the Ku band.?4?Low profile wideband horizontally polarized omnidirectional antenna and its arrayA low profile wideband horizontally polarized omnidirectional antenna and its array are proposed in this section.The designed antenna element consists of a feeding network,four slotted arc dipoles,four parasitic strips and four directors.By introducing parasitic strips,the bandwidth can be widened.And the directors are loaded here to improve the antenna omnidirectional performance.The antenna has a low profile?0.01?L,where?L denotes the free-space wavelength at the lowest cut-off frequency?.The bandwidths of the element and its array are 84.2%?1.58-3.88 GHz?and 100.5%?1.39-4.20 GHz?,which cover 2G/3G/LTE and specific Wi-Fi/WiMAX bands.The measured results agree well with the simulated results.In addition,the gain variation in the horizontal plane is less than2.2 dB and the cross-polarization is less than-23 dB.The gain variation of the array in the horizontal plane is less than 2.0 dB,and the measured average gain is 6.7 dBi.Therefore,the proposed antenna elements and its array can be applied in wireless communication systems.?5?Low profile dual frequency circularly polarized omnidirectional antennaThis section investigates a low-profile dual-frequency circularly polarized omnidirectional antenna.The designed antenna consists of a square loop with four inclined slots,a square ground with four L-shaped slots,four shorting posts,and a coaxial probe.The vertical polarization component is provided by the top loaded monopole patch antenna while the horizontal polarization component is generated by the four inclined slots on the patch and the four L-slots on the ground.The antenna has a low profile?0.052?0,where?0is the free-space wavelength at 2.4 GHz?.The measured results show that the antenna meets the 2.4 GHz WLAN and 3.5 GHz WiMAX bands and agrees well with the simulated results.The left-hand and right-hand gain in the azimuth planes are-0.8 and 4.9 dBic at the center frequencies of the two bands.Based on the above characteristics,the proposed antenna can be applied in the wireless communication systems. |
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