Srivastava, "A smart antenna for wireless communication systems using spatial signal processing," Journal of Communications, vol. 90 Figure 5.3 Interelement distance and polar radiation 93 Figure 5.4 Simulation of the number of elements and polar radiation.
Research Objectives 4
This means that the radiation from a smart antenna can be directed over the best signal path, reducing the power consumption of the wireless devices.
Smart Antenna Technologies 4
Smart antenna arrays processing procedures 5
The marginal factor can be determined using equation (3.4), and the value remains the same for all operating frequencies. Weighting simulation (a) Array factor simulation, radiation pattern versus azimuth angle, (b) Radiation pattern simulation for N = 64, and (c) Simulation
Benefits of smart antenna arrays 6
Research Contributions 8
Note that in the general case the array factor must include another (multiplicative) term, the field pattern of each array element (i.e. the above assumes that each array element pattern is isotropic). In this chapter, some of the antenna elements used in the analysis are discussed in subsections below. The RHC/LHC for the intended circular polarization depends on the excitation of the antenna.
4.31) where dsincos , |cos(φ/2)| The term is known as the array factor because it describes the interference pattern for two antennas, regardless of what antenna is used. At the adaptation index k, according to the mean square error (MSE) function 𝜀{|𝑒(𝑘)|2} = 𝜀{|𝑑(𝑘) − 𝒘𝐻𝒙(𝑘)|2}, the LMS algorithm updates the weight vector according to do. Akhtar, “Fully Automatic Gain Control Beamformer for Smart Antenna Array System,” International Journal of Computer Science and Mathematics in Electrical and Electronic Engineering, vol.
Gupta, “The effect of mutual coupling on the null performance of adaptive antennas,” IEEE Antennas and Propagation, vol.
![Figure 2.1. Omni-directional Radiation Pattern and Directional [9].](https://thumb-ap.123doks.com/thumbv2/pubpdfnet/10643346.0/38.892.133.762.111.392/figure-2-omni-directional-radiation-pattern-and-directional.webp)
Organization of the Thesis 9
RESEARCH BACKGROUND 13
Introduction 13
Antenna arrays increase the gain and directivity of a single antenna, thus improving the transmission and reception patterns of antennas used in communication systems [78]. In the space-time domain, the array can be used to filter signals by exploiting their spatial characteristics.
Parameters of Antenna 14
- Radiation Intensity 14
- Antenna’s Gain 15
- Antenna’s Directivity 16
- Radiation pattern 16
For our research work, this antenna parameter has been useful for deriving the proposed gain model for this work in Chapter 4, Section 4.2. In order for an antenna to have a good reception of the signal, the polarization of the signal and the polarization of the antenna must match.
Types of Antenna and their Applications 18
The three basic types of antennas that exist are (a) wire antennas, (b) aperture type antennas, and (c) antenna arrays. Antenna arrays are a combination of individual antenna elements of a wire antenna or a diaphragm antenna.
Antenna Arrays 19
- Adaptive antenna arrays beamforming and beam steering 20
- Antenna arrays factor and pattern multiplication theorem 21
Adaptive beamforming is a method that can dynamically adjust the array pattern to optimize the parameters of the signals received by the antenna elements. Assume that the signal from the first element of the array has zero phase at an observation point very far from the array.
Effects of Mutual Coupling in Antenna Arrays 23
Interconnection is usually characterized using parameters such as mutual impedance, s-parameters, a coupling matrix or an integrated element. The strong mutual bond is strongly experienced whenever groups are able to scan its beam closely towards the direction of the bottom fire [102].
Brief History of Smart Antennas 24
This has a tremendous influence on the BER for the switched beam approach, thus reducing the system performance [29, 104]. It is the automatic change in radiation pattern and its response to the available environmental signals with the help of the accompanying digital signal processor (DSP) and the series of antennas that make the system called smart antennas.
Types of Smart Antennas 25
- Switched beam approach 25
- Adaptive array (or optimum combining) approach 29
- Dynamically phased array (or direction findings) approach 32
This is done in order to increase the gain of the antenna in the desired direction, while decreasing it in the direction of unwanted signals. Frequent intra-cell handovers are reduced due to continuous monitoring of the mobile user.
Basic Operation of Smart Antenna Systems 35
35 Electronically controlled phased arrays are known for their ability to generate a targeting beam based on a given control signal and may be a potential multipath mitigation solution [120]. There are different algorithms based on different criteria for updating and calculating the optimal weights. This is the most important novelty in smart antenna systems.
Novelty and Performance Improvements on Smart Antennas 36
The digital signal processor accepts the intermediate frequency signal in digital format and the processing of the digital data is driven by software. The optimization is based on a specific criterion, which minimizes the contribution of noise and interference, while producing the maximum beam gain in the desired direction.
Modelling of RF Security Systems using Smart Antennas 37
- Smart antennas as a transceiver 38
- The RF security antenna design 38
Here in this research work (Oluwole and Srivastava [65]), smart antenna is used for security purpose against any hacking in RF transmission signals. When there is an RF attack, there will be signal alarm at the receiver for remote transmission of alarm information about the mobile station.
Open Problems in Smart Antenna Arrays 42
Conclusions 42
This chapter discusses the various antenna elements used in the analysis of smart antenna arrays. In this chapter, a smart antenna using a circular fed linear patch antenna and a waveguide fed pyramid antenna was analyzed.
Introduction 43
- Design parameters for circular pin-fed linearly patch antenna 45
- Simulation results for circular pin-fed linearly patch antenna 46
This is the area contained by 3 dB of the peak of the main beam in Figure 3.2 (a). The angular separation at which the size of the radiation pattern decreases from the top of the main beam, which is half the power beam width, is 00. The side loop level (Sll), which is the maximum level of the side loops away from the main beam pattern, is 7.1 dBi.
Waveguide-Fed Pyramidal Horn Antenna 49
- Modeling of the antenna element 50
- Design equations of horn antenna 51
- Estimated performance of the smart antenna element 54
There is a phase difference in the aperture direction due to the wave tracing different distances from apex to aperture. A further advantage of the horn antenna is that it can be operated over a wide high frequency range, as there is no resonant element in the antenna. 54 From these tables we can conclude that the directivity of the waveguide pyramidal horn antenna is increasing and the bandwidth decreases with increased frequency.
Antenna Arrays Analysis and Synthesis 57
- Mathematical model of uniform linear array synthesis 58
- Uniform circular array radiation pattern synthesis 62
- Phase-tapered weights 67
- Dolph-Chebyshev arrays method for the proposed model 68
d is the inter-element spacing between neighboring elements of the array and properly fed of equal size. This last step is approximate and the group model function is significantly different from Es(u). Finally, the brightness coefficients of the array element are determined by a harmonic analysis of the model function samples.
Determination of Directivity and Gain for Improved Performance
- Far-field of the adaptive array antenna 77
- Radiation intensity function of the antenna element 83
Antenna directivity D(θ, ϕ) can be described as a quantity that refers to the directional transmitting characteristic quality of the antenna element. To calculate the gain and directivity of the array, its far field must be found. It specifies that the effective length of the antenna is a function of the direction of angle θ, and has a maximum value when θ = 900.
Signal Quality Improvement and Performance Analysis of
The synthesis of antenna arrays is crucial in smart antennas as it shapes the radiation pattern of the antenna array. In the case of wide-sided array, the field is maximum in the direction perpendicular to the axis of the array. The plot shown indicates that the beam former can be steered in the desired direction by the main beam.
Adaptive array beamforming algorithms adjust current amplitudes with complex weights. Sun, “Performance of a large-scale adaptive antenna array in the presence of mutual coupling,” IEEE Transactions on Antennas and Propagation, vol.
Requirements and Specifications for the Proposed Model Phased
Broadside Linear Antenna Arrays for the Proposed Model 99
- Properties of broadside array 101
- Directivity control 106
This antenna produces a highly directional radiation pattern that is perpendicular to the plane of the array. The output power of the array at any time t can be expressed as the square of the magnitude of the array output, i.e. In practice, X is usually used as the optimal beamformer above to estimate the optimal array weights [90, 152].
Conclusions 107
- Introduction of smart antenna 108
- Preliminaries of the mathematical signal processing array
Wideband Beamforming 117
One of the advantages of the frequency domain approach over the time domain for large bandwidth signals is the computational approach. Some advantages of frequency-invariant broadband beamforming are: (i) higher convergence speed and (ii) lower computational complexity. The effective approach to solve the blind broadband beamforming problem is the frequency invariant beamforming technique.
Spatial Techniques of Antenna Arrays 120
- Spatial smoothing technique 120
- Spatial filtering 120
Delay-Sum-Beamforming Technique 122
From equation (3.18), which uses the array factor, it can be applied to the delay-and-sum beamformer. Assuming we have an M with equal spacing of linear antenna array units of an omnidirectional antenna, and the distance between the elements along the x direction is d. If the plane wave for a uniform linear array is changed from the plane wave considered previously to a monochromatic plane, the response delay-and-sum beamformer tuned to r can be expressed as:
Direction of Arrival (DOA) Approximation 128
Equation (6.40) provides the derivation for the estimation of some optimal beamformers that need the Direction of Arrival (DOA) information to control the optimal weight vector. The performance and optimization depends on the idea that the DOA of the desired signal is recognized to the system.
Deterministic Beamformer 129
Uncorrelated Signal Sources Estimation 130
Adaptive Beamforming: An Excellent Performance for Smart
Adaptive beamforming is a process by which adaptive spatial signal processing is performed on an array of antennas. By adding the signals constructively weights in the preferred signal direction, adaptive beamforming technique creates radiation pattern on the antenna array thereby nulling the pattern in the unwanted direction which is interference [25]. It has the capacity to operate in either the block mode or the recursive mode approach.
Least Mean Square (LMS) Algorithm Formulation 135
The updated weights are moved in the negative direction of the gradient by the step size parameter [10, 91]. Consider the output of the beamformer at time u, y(u) is specified by a linear addition of the numbers M antennas [X1, (u) as weight vector. Therefore, a prerequisite for a satisfactory convergence of the Wiener solution of the mean of the LMS weight vector is [10].
Recursive Least Square (RLS) Algorithm for the proposed model 140
Loh, "Electrically small and low-cost smart antenna for wireless communication," IEEE Transactions on Antennas and Propagation, vol. Ksienski, "Effect of mutual coupling on the performance of adaptive arrays," IEEE Transactions on Antennas and Propagation, vol. Ismail, "A microstrip antenna array for indoor wireless dynamic environments," IEEE Transactions on Antennas and Propagation, vol.
Conventional and Optimum Adaptive Beamforming Schemes 142
Conclusions 146
The closed expression of the smart antennas adaptive beamforming algorithms has been derived in this chapter. The adaptive beamforming is used as a technique to create the radiation pattern on the antenna array by adding the signals weights constructively in the preferred signal direction and zeroing pattern in the interference direction. It is also observed that there is no grating lobe when d/λ = 0.5, which we considered as the optimal design spacing for the array antenna elements in the smart antenna.
Conclusions 147
Volakis, “Excitation characteristic taper for wideband closely coupled antenna arrays,” IEEE Transactions on Antennas and Propagation, vol. Vegni, “A new design method for Blass matrix beamforming networks,” IEEE Transactions on Antennas and Propagation, vol. Xue, “Circularly polarized planar aperture antenna for millimeter wave applications,” IEEE Transactions on Antennas and Propagation, vol.
