The Use Of Subarrays In Sparse Phased Array Antenna For Wide-Angular Scanning Radar Applications

Akbar, Fannush Shofi (2021) The Use Of Subarrays In Sparse Phased Array Antenna For Wide-Angular Scanning Radar Applications. Doctoral thesis, Institut Teknologi Sepuluh Nopember.

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The use of element patterns with a narrow angular profile highly degrades the scanning efficiency of wide-angular scanning linear arrays. This type of element has a significant scan loss. Furthermore, a high sidelobe level (SLL) cannot be avoided when the antenna is scanned to large scan angles. Existing techniques can only mitigate one of the two critical parameters stated above. However, a wide-beam pattern element can overcome the significant scan-loss problem, but it has a complicated practical design. In addition, the high SLL may be lowered successfully by amplitude tapering, which on the other hand, reduces antenna efficiency.
This dissertation presents a novel method in compensating for such performance deterioration using subarrays. Our approach utilizes integrated subarrays in the full array. The subarrays used have controlled patterns, favoring some directions for appropriate scan-loss compensation (SLC) and suppressing others to reduce SLL. This method may be applied with any antenna element and has high efficiency because it uses uniform amplitude distribution. The scanning is limited to only one dimension due to the linear array design.
The first section of this dissertation covers the distinct setups and subarray pattern expressions for each of the four subarray types. Moreover, their functions, capabilities, and location in the full array arrangement are described. The first and second subarrays have two and three elements, respectively, located along the x-axis. Both are effective for correcting scan loss and reducing high SLL in the opposite ϑ directions. The three-element subarray is then expanded to five elements to reduce scan-loss and SLL. It is created by overlapping the right-side element of the left subarray with the left-side element of the right subarray of the three-element. The third subarray has three elements along the y-axis and can adjust the array pattern in the y-z plane (φ=90°) and increase the directive gain. The last subarray type has an arbitrary number of elements along the x-axis. Its purpose is to reduce the SLL by increasing progressively the inter-element spacing. All of the mentioned subarrays, combined with the non-uniform array, are discussed in the following section of this dissertation.
This dissertation presents several non-uniform array designs, such as Dynamic Programming (DynProg), Cyclic Difference Sets (CDS), Spatial Tapering with Stretching, and Moving Average (MA) Thinning, which aim to obtain array configurations with controlled SLL while the antenna is scanning, as well as to minimize the number of its components because there are fewer elements and more empty spaces for accommodating subarrays.
The validation of the proposed subarray designs is carried out analytically and experimentally in this research. For analysis, an exact mathematical formula for calculating the directive gain is employed. Meanwhile, microstrip-based antennas and feeding networks are built for testing. At 3 GHz, the experimental validations of the realized subarrays are exceptionally well-matched.
The validated subarrays are then combined to form the full array. There are two final array designs: a planar array with three elements width, and a linear array, both with 41 elements, 33 multi-bit phase shifters, 12 1-bit phase shifters, and four attenuators, for amplitude control. The final (linear) array design improves SLC by 0.9 dB, while SLL is 3.4 dB lower than the uniform linear array (ULA) at 60° scanning. Meanwhile, the final (planar) array design achieves scan-loss of -4.5 dB and PSLL of -19.5 dB, also at 60° scanning.
The proposed design's performance implies that it is suitable for radar applications that use active phased array antenna technology, such as surveillance (air and sea), Ground-Controlled Interception (GCI), and Early Warning (EW) radar in military defence. This concept can also be expanded into a full planar array with 3D scanning capabilities.

Item Type: Thesis (Doctoral)
Uncontrolled Keywords: Subarray, Phased Array, Wide-Angular Scanning
Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK7871.6 Antennas (Electronics)
Divisions: Faculty of Intelligent Electrical and Informatics Technology (ELECTICS) > Electrical Engineering
Depositing User: Fannush Shofi Akbar
Date Deposited: 14 Aug 2021 15:12
Last Modified: 14 Aug 2021 15:12

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