A simulation analysis of conventional array antenna and MMA loaded array antenna have been also made for Bistatic RCS and depicted in Figure 5.22. For horizontal polarization at ϕ = 00, the Bistatic RCS of the referenced antenna array and proposed antenna array have been
simulated and analyzed at 10 GHz. The Bistatic RCS of the MMA loaded antenna array reduced throughout the angle theta (θ) with a significant reduction in between -1100 to 960. The maximum reduction between the referenced antenna array and MMA loaded antenna array observed of 11.75 dBsm at -320 and 22.08 dBsm at 320 respectively as shown in Figure 5.22(a).
At ϕ = 900, the Bistatic RCS of the MMA loaded antenna array reduced significantly for angle θ in between -1540 to 1540. The maximum reduction between the referenced antenna
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(a) (b)
Figure 5.22 Comparisons of Bistatic RCS of the referenced array and proposed MMA antenna array for (a) horizontal and (b) vertical polarization at 10 GHz.
array and MMA loaded antenna array observed of 7.13 dBsm at -480 and 7.13 dBsm at 480, respectively.
For vertical polarization at ϕ = 00, the Bistatic RCS of the referenced antenna array and
proposed antenna array have been simulated and analyzed at 10 GHz. The Bistatic RCS of the
MMA loaded antenna array reduced throughout the angle θ with a significant reduction in
between -1570 to 1570. The maximum reduction between the referenced antenna array and
MMA loaded antenna array observed of 7.94 dBsm at -480 and 8.23 dBsm at 480, respectively as shown in Fig. 9(b). At ϕ = 900, the Bistatic RCS of the MMA loaded antenna array reduced significantly for angle θ in between -330 to 330. The maximum reduction between the referenced antenna array and MMA loaded antenna array observed of 16.51 dBsm at -320 and 16.51 dBsm at 320, respectively as shown in Figure 5.22(b).
5.4. Chapter Summary
In this chapter, a single-band low RCS rectangular patch antenna is presented, analyzed and is based on shorted stubs with rectangular bars MMA in Section 5.1. The reflection coefficient (S11) and the radiation pattern of the modified antenna are also studied and it almost
has a negligible effect on antenna performance. The co-polarization and cross-polarization patterns with respect to E-Plane and H-Plane of the proposed structure have been also analyzed. Effective isolation of 82.5 dBi and 24.65 dBi are observed for both planes and that indicated the suppression of cross-polar radiations. Further, Comparisons are made between the proposed antenna and the previously reported antennas that clearly justify the novelty of the proposed model. The results suggest that loading of shorted stubs MMA absorber plays an
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important role and modified the antenna properties along with efficiently enhance the RCS capabilities of the rectangular patch antenna. The result shows a maximum Monostatic RCS reduction of 21.22 dBsm achieved for the proposed structure operation at X-band. This MMA absorber structure finds its various applications in military and defense area for the enhancement of RCS capabilities in the antenna.
In Section 5.2, comparative design analyses of MMA loaded patch antenna have been proposed. Analyses have been also made to study the effect of MMA on patch antenna before and after loading it. The results indicate that the radiation performance of the patch antenna has been affected marginally. Design 1 shows unsatisfactory directivity and gains response. Whereas for Design 2 and Design 3, directivity is enhanced with gain is affected slightly. A single patch antenna design has some limitations and suffers from low radiation performance such as narrow bandwidth, lower directivity, gain, radiation efficiency and less power handling capability. So it cannot be suitable for long-distance communication, especially in military applications. One of the vital solutions is to combine a number of antennas to form a patch array. It has been found that its overall radiation performance enhances and this is covered in Section 5.3.
In Section 5.3, we have proposed a shorted stubs metamaterial absorber operating at 10 GHz of the resonant frequency in X-band. A comparison has been made between reference antenna array and MMA modified antenna array. It has been found that when MMAs are loaded in a rectangular 2 × 2 patch antenna array, it significantly reduces the RCS of the structure throughout the observation band. Henceforth increase the stealth capability of the structure.
However, maximum resonance peak reduction is observed in 10 GHz at which MMA has been designed. The Monostatic and Bistatic RCS analysis have been made for x-p as well as for y-p of incidence wave. The overall radiation performance of antenna array with and without
MMA remains preserved and unaffected. Even though, the gain, directivity, bandwidth and
radiation efficiency found marginally increased. Because of the limitation on size and some very common errors during the fabrication process, then measurement precision, a slight variation in measured results observed with respect to simulated one.
These structures find its applications in stealth technology for military planes, space aircraft, missiles, ships, and other sensitive vehicles for long distance wireless communication and meant for lower detectable objects.
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Chapter-6
RCS Reduction of Patch Antenna using Dual-Band
Shorted Stubs MMA
In this chapter, we are proposing a dual-band slotted patch antenna with thin dielectric for
Ku-band applications. A rectangular patch with a pair of bent slots at each side of the center
has been designed that resonant at 11.95 GHz and 14.25 GHz with respect to ITU standard. For the perspective of In-band RCS reduction application, a dual resonance ultrathin shorted stubs
MMA has been designed that operates at same frequency bands. Its behavior at an oblique angle
of incidence and polarization sensitivity has been analyzed. The radiation performances of dual-band slotted patch antenna for S11, -10 dB bandwidth, VSWR, and Z11 along with
co polarization and cross polarization polar plots patterns for directivity and gain have been analyzed and observed. The Monostatic and Bistatic RCS response have been examined carefully and methodically for the referenced and proposed antennas. Finally, comparison of results with previously proposed dual-band antennas has been made to validate and justify the novelty of this proposed structure.