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Venkata Kishore Kothapudi,Vijay Kumar 한국전자파학회JEES 2018 Journal of Electromagnetic Engineering and Science Vol.18 No.2
In this paper, compact linear dual polarized series-fed 1 × 2 linear and 2 × 2 planar arrays antennas for airborne SAR applications are proposed. The proposed antenna design consists of a square radiating patch that is placed on top of the substrate, a quarter wave transformer and 50-Ω matched transformer. Matching between a radiating patch and the 50-Ω microstrip line is accomplished through a direct coupled-feed technique with the help of an impedance inverter (λ/4 impedance transformer) placed at both horizontal and vertical planes, in the case of the 2 × 2 planar array. The overall size for the prototype-1 and prototype-2 fabricated antennas are 1.9305 × 0.9652 × 0.05106 λ0<SUP>3</SUP> and 1.9305 × 1.9305 × 0.05106 λ0<SUP>3</SUP>, respectively. The fabricated structure has been tested, and the experimental results are similar to the simulated ones. The CST MWS simulated and vector network analyzer measured reflection coefficient (S11) results were compared, and they indicate that the proposed antenna prototype-1 yields the impedance bandwidth > 140 MHz (9.56–9.72 GHz) defined by S11 < −10 dB with 1.43%, and S21 < −25 dB in the case of prototype-2 (9.58–9.74 GHz, S11 < −10 dB) > 140 MHz for all the individual ports. The surface currents and the E- and H-field distributions were studied for a better understanding of the polarization mechanism. The measured results of the proposed dual polarized antenna were in accordance with the simulated analysis and showed good performance of the S-parameters and radiation patterns (co-pol and cross-pol), gain, efficiency, front-to-back ratio, half-power beam width) at the resonant frequency. With these features and its compact size, the proposed antenna will be suitable for X-band airborne synthetic aperture radar applications.
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SFCFOS Uniform and Chebyshev Amplitude Distribution Linear Array Antenna for K-Band Applications
Venkata Kishore Kothapudi,Vijay Kumar 한국전자파학회JEES 2019 Journal of Electromagnetic Engineering and Science Vol.19 No.1
In this study, a compact series-fed center-fed open-stub (SFCFOS) linear array antenna for K-band applications is presented. The antenna is composed of a single-line 10-element linear array. A symmetrical Chebyshev amplitude distribution (CAD) is used to obtain a low sidelobe characteristic against a uniform amplitude distribution (UAD). The amplitude is controlled by varying the width of the microstrip patch elements, and open-ended stubs are arranged next to the last antenna element to use the energy of the radiating signal more effectively. We insert a series-fed stub between two patches and obtain a low mutual coupling for a 4.28-㎜ center-to-center spacing (0.7λ at 21 ㎓). A prototype of the antenna is fabricated and tested. The overall size of the uniform linear array is 7.04 × 1.05 × 0.0563 λg³ and that of the Chebyshev linear array is 9.92 × 1.48 × 0.0793 λg³. The UAD array yields a |S11| < –10 ㏈ bandwidth of 1.33% (20.912–21.192 ㎓) and 1.45% (20.89–21.196 ㎓) for the CAD. The uniform array design gives a −23 ㏈ return loss, and the Chebyshev array achieves a −30.68 ㏈ return loss at the center frequency with gains of 15.3 ㏈i and 17 ㏈i, respectively. The simulated and measured results are in good agreement.
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