Antenna Element Research Of Wide-band And Wide-angle Active Electronically Scanned Array

To suffice the general-purpose demands of the forth generation combat aircraft, it is inevitable that the antenna technique of wide-band and wide-angle Active Electrically Scanned Array (AESA) is of concerned. The antenna of the wide-band and wide-angle AESA is the system of co-aperture and board airspace scanning, and is the pivotal technique of the forth generation airborne radar. Associated tightly to a "Wide-band and Wide-angle Active Electrically Scanned Array Antenna" Pre-research project, this dissertation presents a systematic investigation on the analysis and design of the antenna elements of the wide-band and wide-angle AESA, tapered slot antenna (TSA) is discussed emphatically, and a modified design of Linearly Tapered Slot Antenna (LTSA) is demonstrated with the character of wide-band and wide-angle radiation. The author's major contributions on the subject can be summarized as follows:1. Great back-radiation and low gain in the main-direction are shown in the routine form of vivaldi antenna. A modified vivaldi antenna possessing stable gain appearance, is proposed by optimizing the shape of the regular vivaldi antenna patch. An improved vivaldi antenna operating at the bandwidth of 6-18GHz is designed and fabricated, and the test on the electronical characters of modified antenna is presented. Contrast with routine vivaldi antenna, the gain of modified antenna has been promoted prominently at the whole bandwidth.2. Based on regular Linearly Tapered Slot Antenna (LTSA), a modified design of LTSA is demonstrated for miniaturization wide-band wide-angle radiation. The proposed antenna is optimized by wizardly grooves and notches on the patch for wide-band wide-angle radiation. Measured results show that the Voltage Standing Wave Ratio (VSWR) of proposed antenna is below 2 at the operation frequency (8.2～14.5GHz) and the half-power beamwidth (HPBW) of modified miniature antenna achieves 120°at the main frequency (10.5～12.6GHz).3. An indirect, fast and accurate method to induce the active element pattern is investigated by combining single antenna pattern and active reflective coefficient which shows the element scanning character in the array. Proposed method is capable of enhancing the efficiency and succeeds in the antenna design.4. The impedance and radiation characters in the AESA of Linearly Tapered Slot Antenna (LTSA) are deeply investigated, and a dielectric-cut, stripline step tapered slot antenna is proposed. Test results of 169 elements array demonstrate that proposed antenna possesses perfect wide-band and wide-angle radiation characters. Measured element VSWR in the array is less than 1.6 at the frequency of 8～12GHz, the HPBW is wider than 100 degrees at the frequency of 8～10GHz, and the cross-polarization is lower than -20dB. The Pre-project of "Wide-band and Wide-angle Active Electrically Scanned Array Antenna" is completed excellently.5. For the Electronical Antagonism demands of conformal antenna array, the radiation parameters of conformal antenna array are synthesized and optimized using a hybrid genetic algorithm (HGA), which combines the real-coded genetic algorithm (RCGA) and the simplified quadratic interpolation (SQI) method. By analyzing the mutual coupling effects on the individual element patterns and synthesizing amplitude weights of the elements, the perfect patterns are obtained which have appointed sidelobe level and "wave-null" zones.6. A useful model for analyzing mutual coupling (MC) of X-type polarization diversity system is propounded. Thus the analytical expressions for both the average received power for each antenna element and spatial correlation between elements are also derived, and the effects of both MC and the mean Direction of Arrival (DOA) on the average power and capacity of MIMO wireless channels are investigated. Analysis results show that MC decrease the average received power of each elements and channel capacity in the MIMO polarization diversity system.7. Mutual coupling (MC) analysis model of X-type polarization diversity system is proposed, the effects of MC both of antennas and circuit on performance of system are investigated. To consider MC, it is not only increasing the correlation for polarization diversity system, but decreasing the ratio of received average power and improving the system polarization diversity gain. The paper also presents that cross-polarization differentiated gradeτhas the great effects on the system performance.