Design and Optimization of Conformal Slot Array Antennas for X-band Applications
In 1st part of this thesis, the design of the waveguide fed slot array antenna is presented with Bayliss and Taylor P pattern to meet the requirements of a tracking radar system, as well as the high power eciency. The standard X-band waveguide is used for the design purpose at a center frequency of 9.375 GHz. The proposed design is simulated in full-wave EM simulator with opposite excitation to realize the pattern. It is observed that the simulated results are well in agreement with theoretical data. For both arrays, VSWR 2, while SLLs for and P patterns are -20 dB and -8 dB, respectively.
In 2nd part, the design of the slot array antenna is presented for tracking radar applications. To meet the requirements, P pattern array of 36 is optimized using PSO, while the pattern array of 25 is synthesis using Bayliss current distribution technique. The P pattern array has a feeding structure based on three inclined slot elements, while pattern array has opposite excitation. From full-wave simulation, the gain for P pattern is noted to be 16.84 dBi with an SLL of -18.59 dB. The depth of principal null for pattern is equal to -27.2 dB. It is also observed from simulations that for both the cases, VSWR 2. Furthermore, the overall dierence between P and patterns is 43.9 dB at = 0.
In 3rd part, the design of an X-band conformal slot array antenna is presented for cube satellites. The proposed antenna array consists of 16 elements, which are center inclined on the surface of a dielectric substrate. A dumbbell-shaped slot is etched from the bottom side of the radiating structure, and a SIW feeding structure is utilized to feed the proposed array. The feeding structure is also has a dumbbell-shaped broadband feeding slot on its upper part to couple the energy to the radiating structure. The simulations of the proposed design are done in Ansys HFSS and it is observed that the proposed antenna array oers a gain of 11.15 dBi with SLL of -19.62 dB at a center frequency of 10 GHz.
In 4th part, the design of an X-band cylindrical conformal SIW slot array antenna is presented. The wave propagation characteristics on the cylinder are investigated to verify fundamental propagation mode and the MLS algorithm is used to synthesize the array. To avoid spurious radiations, RWG to SIW feeding structure is utilized to feed the array elements. A exible substrate is used for the design of 16 slot elements array. From simulation results, SLL of -21.72 dB and gain of 9.8 dBi have been achieved with VSWR 2 at a center frequency of 10 GHz.
In 5th part, the design of the nose-cone conformal SIW slot array antenna is presented for modern radar applications. Firstly, the wave propagation characteristics are investigated in doubly curved SIW, and it is observed that they are non-uniform along the longitudinal direction of nose-cone conformal SIW. To ensure the constant wave propagation along the length of conformal SIW, the conventional design of SIW is reformulated for nose-cone conformal SIW and circuit model modication is demonstrated. Secondly, the procedure for designing a SIW-based array on curved surfaces has been developed. In the proposed design, RWG to SIW feeding structure has been used to avoid spurious radiations. Finally, 16 element-based nose-cone conformal slotted array has been designed and compared with planar and cylindrical conformal arrays. It has been observed from the results that the nose-cone conformal slot array oers low SLLs and high gain. For the validation of the proposed design, the conformal slotted array has been fabricated and measured, which exhibited a reasonable agreement between the measured and the simulated data.
Finally, the last part of the thesis presents the design of SIW based dual-beam conical conformal slot array antenna for X-band applications. The proposed design consists of two SIW arrays of 16 slot radiators located at = 0 and 180. The sub-arrays are fed using an RWG to SIW 12 balanced T-junction power divider. The arrays are projected in the longitudinal direction on a conical surface having a lower and upper radius of 1.660 and 1.330, respectively. The power divider and SIW arrays are designed and simulated in full-wave EM simulation software. It is observed from the results that the proposed array has two main beams in H-plane located at = 90, and have SLLs of -22.80 dB and -20.12 dB, respectively. For the validation of simulation results, the proposed antenna system is fabricated and measured, and a reasonable agreement is observed between both results.