In this paper, a method based on PGSA for the pattern synthesis of **linear** **antenna** **arrays** with the prescribed nulls is presented. Nulling of the pattern is achieved by controlling only the element amplitudes. Numerical results show that the PGSA is capable of accurately determining the element amplitudes which yield the array patterns with single, multiple and broad nulls imposed at the directions of interference while the main beam and the sidelobes are quite close to the initial pattern. Although only **linear** **antenna** **arrays** have been considered here, the PGSA can easily be used for **arrays** with complex geometries as well as nonisotropic-elements. As an optimization algorithm, the PGSA will most likely be an increasingly attractive alternative, in the electromagnetics and antennas community, to other optimization algorithms.

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Abstract: The gain or directivity of single **antenna** is less. To increase the gain and directivity the solution is **antenna** array. It is one of the common methods for combining the radiation from a group of similar antennas in which the phenomenon of wave interference is involved. In this paper analysis of **Linear** Broadside, Binomial, Dolph-Tchebyscheff **antenna** **arrays** is done. And results are compared. The Binomial Array is found best among these three types of **antenna** **arrays** in terms of directivity and sidelobes.

Here we do not consider the **antenna** beam steering. In fact, beam steering is an important issue in TMLAs and some methods for beam steering have been proposed [14, 15]. The eﬀect of beam steering on signal transmission will be our future studies. Without loss of generality, let α k = 0 for all elements and the signal is from θ = 0 ◦ ,

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specific radiation pattern in TMAA, electronically, a predetermined sequence of the relative on-time durations of the switches connected to the array elements is controlled easily, rapidly, and accurately during a fixed interval of time period. Recently, as investigated in [14]. TMAA architecture with a suitable control strategy can be applied to adaptive nulling in time-varying scenarios. However, inherent sideband radiations in TMAA reduces **antenna** efficiency and directivity [15, 16] when the desired pattern is synthesized at the operating frequency only. Accordingly, during the last decade, a number of contributions with different time-modulation approaches based on different optimization tools have been successfully applied to realize different patterns at the operating frequency by suppressing SBLs to sufficiently low values [10–13, 17–24].

[3] Y. Liu, Z. Nie, Q. H. Liu, "A new method for the synthesis of non-uniform **linear** **arrays** with shaped power patterns," Progress In Electromagnetics Research, vol. 107, pp. 349-363, Aug. 2010. [4] B. P. Kumar and G. R. Branner, “Design of unequally spaced **arrays** for performance improvement,” IEEE Trans. Antennas Propag., vol. 47, no.3 , pp. 511–523, Mar. 1999.

with good results. Most of the times, one technique is used mainly as a pre-optimizer for the initial population of the other technique. In [21], for example, the authors test two diﬀerent combinations of GA and PSO, using the results of one algorithm as a starting point for the other (in both the orders) to optimize a proﬁled corrugated horn **antenna**. Another hybridization strategy is proposed in [22], where the upper-half of the best-performing individuals in a population is regarded as elite and, before using GA operators, it is ﬁrst enhanced by means of PSO, instead of being reproduced directly to the next generation. The hybrid technique here proposed, called Genetical Swarm Optimization (GSO), and consists in a strong cooperation of GA and PSO, since it maintains the integration of the two techniques for the entire run. In fact, this kind of updating technique yields a particular evolutionary process where individuals not only improve their score for natural selection of the ﬁtness or for good- knowledge sharing, but for both of them at the same time. In each iteration the population is divided into two parts and they are evolved with the two techniques respectively. They are then recombined in the updated population, that is again divided randomly into two parts in the next iteration for another run of genetic or particle swarm operators. Fig. 2 shows the idea that stands behind the algorithm and the way to mixing the two main techniques.

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Optimization methods have drawn a lot of attention because of their wide applications, and most of them can be divided into two categories: global and local techniques. A global optimization method, Taguchi’s method (TM), was developed based on an orthogonal array (OA) and a reduced function (RF) for the syntheses of **linear** **antenna** **arrays** [1]. The main role of RF is reducing the optimization ranges to coverage to the best design parameters after several iterations. Two RFs, the exponential reduced function (ERF) and Gaussian reduced function (GRF), were proposed in [2] simultaneously.

Abstract—Circularly polarized millimeter-wave travelling-wave antennas, using substrate integrated circuits (SICs) technology, are designed, fabricated and tested. By using the SICs technology, compact antennas with low losses in the feeding structure and with good design accuracy are obtained. The elementary **antenna** which is composed of two inclined slots is characterized by full-wave simulations. This characterization is used for the design and development of **linear** **antenna** **arrays** with above 16 dB gain and low side lobe level (< −25 dB), using different power aperture distributions, namely uniform, Tchebychev and Taylor. Experimental results are presented at 77 GHz showing that the proposed antennas present good performances in terms of impedance matching, gain and axial ratio. These antennas have potential applications in integrated transceivers for communication and radar systems at millimeter-wave frequencies.

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is studied for **linear** **antenna** **arrays** using Bees Algorithm (BA). BA adjusts the amplitude of each radiating element to minimise the total output power in the direction of the interfering signals. Then the null steering algorithm is loaded with MATLAB using amplitude-only in order to facilitate the realization. Numerical examples of Chebyshev pattern with the single and multiple nulls imposed at the directions of interference are given to show the remarkable robustness, accuracy and flexibility of the BA.

**Linear** **antenna** **arrays** synthesis using reduced number of **antenna** elements has gained great research attention. Recently, the matrix pencil method (MPM) [1], forward-backward matrix pencil method (FBMPM) [2], and hybrid technique between the method of moments and the genetic algorithm (MoM/GA) [3] have been successfully applied to synthesizing **linear** **antenna** **arrays**. A new iterative technique for pencil beam pattern synthesis of **linear** and planar **antenna** **arrays** using minimized number of **antenna** elements is presented in [4]. The technique is based on a hybrid combination between the Nonuniform Fourier Transform (NUFFT) and a global optimization method. The NUFFT is utilized to determine excitation coeﬃcients for a ﬁxed positions nonuniform array. On the other hand, the simulated annealing (SA) is used alternatively to determine the optimal positions. The number of elements reduction is achieved by iteratively removing the elements that contribute the least to the array factor. Generally, the excitation coeﬃcients and elements locations are iteratively recalculated until the SLL is unchanged, or the maximum iteration number is reached. A hybrid technique for nonuniform planar **antenna** **arrays** synthesis considering the coupling between the array elements is presented in [5]. The deterministic array factor is used for the preliminary evaluation of the array excitation coeﬃcients and element positions for a desired radiation pattern. Afterwards, the obtained array structure is optimized using PSO in combination with the Multiport Network Model algorithm for fast modeling of spurious mutual coupling processes. In the same context, a modiﬁed diﬀerential

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scanning rate is considered a critical factor. The mechanical steering appears to be impractical for its slow rate and space consumption so the need for electronics scanning appears clearly. But unfortunately, the electronic scanning suffer from beamwidth broadening and gain variations with steering angles. In this paper, a fixed beamwidth electronic scanning algorithm is proposed. The proposed algorithm is based on synthesizing sets of excitation coefficients to direct the main beam at some scanning angles. The synthesis takes into consideration the fixation of the beamwidth at these angles. The main concept is to enlarge the **antenna** array aperture size to a predefined optimum value to get a fixed beam in all the scanning angles. The synthesis of the excitation coefficients is done using a scheme based on the method of moments due to its accuracy in solving such problems. The optimum spacing between elements is determined using the genetic algorithm. One of the main advantages of the proposed algorithm is the applicability of synthesizing multibeam **antenna** array of fixed beamwidths using the superposition principle. The system is already built and tested with conventional microstrip **antenna** array elements where good tracking results are observed.

Prataban Mookiah (2007) developed a reconfigurable multiport circular patch **antenna**. Here, the main objective of the design is to reduce the spatial correlation and subsequently maximize the link capacity. The dimension of the **antenna** is modified using microstrip line switches. The system is made to operate at 2.46GHz and SNR taken at 10dB. Joshua D. Boerman and Jennifer T. Bernhard (2008) have examined and analyzed the potential improvements in MIMO system capacity attainable through use of a small number of pattern reconfigurable antennas. The simulation and experimental results presented here in various multipath propagation scenarios indicates that large performance enhancements are possible compared to systems that use either fixed or randomly directed pattern reconfigurable antennas. The advantages are specifically significant when the **antenna** patterns can be directed optimally to not only possess a high degree of diversity but also to provide enhanced SNR through increased **antenna** gain. Future scope in this area includes to determine that, what kind of **antenna** pattern reconfigurability will be most advantageous and responsive in a particular environment, leading to the development of new kinds of reconfigurable antennas. Additionally, for all of these cases, an overall system performance analysis will be conducted that includes the effects of receiver noise.

Taylor’s method of distribution [3] is used as the basis. Different **arrays** are considered and the method of thinning and thickening are employed. Comparative studies are made on the radiation patterns. In fact patterns are generated by many methods. Schelkunoff polynomial method [4] generates a pattern with the nulls in specified directions. For the design of the array, the number of nulls and their locations are specified. The number of radiating elements and their excitation levels can be obtained as the nulls and their locations are known. Using Fourier transform method the excitation distribution of either a continuous line source or a discrete array for a specified radiation pattern can be designed.

Wong [44] investigated the “vector-cross product” for direction finding with spatially spaced dipole and loop triad but ignored the effect of spatial phase-factor, which can improve the accuracy of direction finding. In order to get the finer estimate for the DOA, at least two finer direction-cosines’ estimates should be obtained. The dipole-loop triad pair can present three coarse direction-cosines ’ estimates from the “ vector-cross pro- duct ” result and one finer direction-cosine ’ s estimate from the inter-triad spacing phase. Thus, another **antenna** is employed to provide the other finer direc- tion-cosine ’ s estimates from the inter-sensor spacing phase factor and at the same time to increase the array aperture. Figure 1 depicts the array geometry used in this work.

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spacing increases, both variances reach their maximum value more quickly. For the T RAs this can be easily explained since a larger aperture corrisponds to a narrower ﬁrst-null beam-width (see Eq. (3)). A similar reasoning also applies for the GBAs since the larger the array aperture the larger the bin extensions and hence the ﬁrst-null beam-width of each terms in the summation of Eq. (14). In any case, even by increasing the average spacing between **antenna** elements the growth of variance of GBAs becomes faster, and the relative advantage over the T RAs is maintained, because the bins are always smaller than the whole aperture, although for both array types the region of randomness † , within the visible space, becomes larger.

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This paper presents the analysis of bent ground plane antennas for multiple-input-multiple-output (MIMO). Here, **antenna** array with three elements are proposed to evaluate the diversity performance of MIMO antennas systems. Then a three-element suspended plate **antenna** array with a bent ground plane is analyzed. The diversity performance of the design is analysed with the simulation results. At suspended angle α = 0 o , the reflection coefficient of **antenna** is found to be - 26.58 dB with an isolation of -47.53dB at resonance frequency 5 GHz. While At suspended angle α = 45 o , the reflection coefficient of **antenna** is found up to -29.69 dB with a maximum isolation of - 56.65dB.

The focus of this chapter is to introduce a smaller form factor high gain pattern reconfigurable MIMO **antenna** array for handheld terminals. The array is designed and developed using the concept of parasitic **arrays** [96–103] where a driven and one or more closely coupled parasitic elements work in tandem to allow pattern reconfig- uration. Since the parasitic elements can be brought very close to the driven **antenna** element the form factor of the array will be much smaller compared to a traditional phased array making them more suitable for handheld device applications. Although many articles have been published in the literature on parasitic **arrays** that address dipole or monopole antennas for base stations [97, 98], patch **antenna** **arrays** [99, 100], and dipole **antenna** **arrays** for wearable wireless applications [31-33], this is the first ever reported detailed work on a high gain pattern reconfigurable collinear parasitic array for the handheld to our knowledge. Very preliminary results of this work were presented at a conference recently [62]. This chapter presents more significant design, analysis, and experimental results and system level simulation results.

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There is an increasing demand of super high frequency, low profile, low cost, beam scanning[1]-[5] and low volume antennas. Therefore the array and slot antennas are used to achieve these performances. Based on the concept of array and slot **antenna** parameters are compared with the substrates like FR_4 and RT_Duroid 5880. These elements are properly coupled and fed by the Microstrip feed[8]. The input electromagnetic power can be efficiently transferred between the feed port and the space. The parameters like return loss and gain are compared with the substrates such as FR-4 [7] and RT_Duroid 5880 [6] for array and slot **antenna**. To realize an effective transform from 50 to 377 ohm, some novel patch **arrays**[3] were developed.

It is clear that the sampling approach as sketched above is formally questionable. Indeed, the side-lobe maxima of |φ ( u ) | does not in general correspond to the side-lobe maxima of the array factor magnitude. Moreover, the **linear** Lagrange interpolation hardly matches the side-lobe behaviour between two sampling points. Nonetheless, the sampling approach is very simple and shows that it returns results in good agreement with some numerical experiments [3]. Also, SLL estimation can be a little bit reﬁned by removing the independence hypothesis and considering only adjacent samples to be correlated [6].

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two input ports while increasing the internal ﬂares, which delays the occurrence of side lobes and keeping the return loss intact, i.e., below − 10 dB [7]. The authors [8] employed CSRR (Complementary Split Ring Resonator) which creates the interferometer pattern to reduce side lobes. The parasitic patches can also be used for reducing side lobes [9]. The authors in [10] have designed an omnidirectional **antenna** which has low side lobes. The authors in [11] have used a cylindrical patch for omnidirectional characteristics. Use of triangular **antenna** [12, 13] elements in an array leads to the reduction of side lobe level, i.e., side lobe suppression. Also triangular **antenna** elements have smaller dimensions than a rectangular structure, so it is widely used in the applications where compact **antenna** is required or by using evolutionary algorithms such as Fireﬂy algorithm, self adaptive diﬀerential evolution method and biogeography based optimization method [14]. The authors in [15] have fed a patch **antenna** array with corporate feed with appropriate amplitude tapers. Each **antenna** element is fed with individual separate feedline for low side lobes. In this paper, a triangular nonuniform **antenna** array is used with Dolph- Chebyshev amplitude excitation with corporate feed and is applied to uniform spaced triangular patch **antenna** elements. The designed **antenna** array operates in C-band [16], i.e., 4 GHz–8 GHz. Amplitude excitations to all the patches are diﬀerent according to Dolph-Chebyshev polynomials so as to reduce the side lobes. The impedances to top patches, bottom patches and middle patch are diﬀerent. The orientation of the paper is such that in the second section the design of **antenna** element is discussed such as length and width of **antenna** element as well as substrate used. In the third section, the design of the **antenna** array is discussed. In the fourth section, simulated and measured results and comparison between them are presented. The last section of the paper concludes the proposed work.

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