The performance of smart antenna greatly relies on the efficient use of direction-of-arrival (DOA) estimation techniques for both coherent and non-coherent signals. In practice, DOA estimation problems and difficulties increase when the signals in multipath propagation environments are highly correlated or coherent. Therefore exploring an algorithm which is capable of estimating coherent signals is of great importance. To overcome this problem a new high-resolution modified virtual singular value decomposition (MVSVD) algorithm for DOA estimation of coherent signals is proposed. It is based on the hybrid combination of the virtual array extension singular value decomposition (SVD), and modified MUSIC algorithms. The proposed algorithm provides many features such as: decorrelation of the coherence between the signals without reducing the rank of the covariance matrix or losing the array aperture size; high-resolution and more stability especially at low SNR values; and an increase in the maximal number of detectable signals to M − 1, where M is the number of antenna elements.
In this paper, a new super-resolution and highly stable DOA estimation technique of coherent sources is introduced. Furthermore, the proposed technique is applied to the data collected from the AWR1243 mm-wave 76-81 GHz frequency modulated continuous wave (FMCW) radar to estimate the DOAs of real targets. A virtual antenna array is proposed to increase the array aperture size and the dimension of the data covariance matrix which effectively helps in de-correlating the received signals and in increasing the number of detectable sources and hence improving the detection resolution. Moreover, a significant improvement in the DOA estimation capability is achieved by handling the frequency domain of the received signals instead of their time-domain representations. That is because the signal to noise ratio (SNR) is increased by a multiplication factor when it is transformed using FFT which acts as a filter for the noise. The simulation results proved the superiority of the proposed technique compared to the state of the arts in this field, especially at low SNR that approaches −35 dB.
Abstract-Direction of arrival estimation has a noteworthy significance in numerous applications, such as radar systems, smart antennas, sonar, mobile communications, and space communications. The algorithms used to estimate the direction of arrival are to some degree complex and time consuming. Also, the number of antenna elements is a discriminating parameter for assessing the performance of the DoA technique. For real time systems, quick and savvy techniques are required. Along these lines, decreasing the estimation time and also reducing the system cost while keeping a generally high precision are crucial issues. In this paper, a new technique for linear antenna arrays synthesis using optimized number of antenna elements and its application to direction of arrival estimation is introduced. The synthesized arrays exhibit approximately the same radiation pattern as the original arrays. The optimized antenna arrays are synthesized using reduced number of antenna elements. In this case, the number of antenna elements reduction will minimize the system cost and decrease the number of picked samples from the different signal sources. As the number of samples decreases, the dimensions of the steering matrix and data correlation matrix are reduced. In this context, the computational burden, estimation time, and system cost are optimized. The proposed technique can be applied to single or multi-snapshot DoA estimation techniques.
Distributed antenna arrays are arbitrarily large groups of neighboring nodes which are controlled to form virtual antenna arrays for both transmission and reception. Distributed beamforming (DBF) is widely used in wireless sensor networks (WSNs) and distributed massive Multi-Input Multi-Output (MIMO) systems. The research in DBF has been divided into four major research trends: radiation pattern analysis, optimization of power and lifetime, nodes synchronization, and array design. In this paper, a new algorithm is introduced to synthesize the radiation pattern of an arbitrarily distributed array using reduced number of distributed nodes. In this context, the reduction in the number of nodes results in minimizing the synchronization complexity between the synthesized array nodes and in minimizing the number of RF front ends. Thus, the overall system cost is reduced. In this algorithm, the three antenna array parameters (number of nodes, nodes locations, and nodes excitation) are properly adjusted to construct a close copy of the original array pattern. Different nodes selection ways are utilized to select the nodes required to synthesize the array for a desired radiation pattern. Also, uniform feeding and non-uniform feeding scenarios are introduced. In simulations, the proposed algorithm is applied to the synthesis of pencil-beam patterns. The simulation results reveal that the synthesized radiation patterns highly agree with the ordinary distributed array pattern in the case of non-uniform feeding. Also, the proposed algorithm can be applied to the synthesis of shaped-beam patterns via controlling the three aforementioned antenna array parameters and taking the shaped-beam pattern as the desired pattern in the algorithm.
Abstract-Compact size microstrip low-pass filters with sharp cutoff characteristics, narrow passband, low insertion loss, high attenuation in stopband and low cost are highly required in modern wireless communication systems. They are used to suppress the unwanted harmonics and noise caused by Radio Frequency (RF) front ends. In this paper a new design for compact microstrip LPF is proposed. It is based on utilization of Stepped Impedance Resonators (SIR), Defected Microstrip Structure (DMS), Dumbbell-shaped Defected Ground Structure (DB-DGS), and surface mount capacitor. The filter is realized on an F4B-2 substrate with ε r = 2.65, thickness h = 0.5 mm and loss tangentδ = 0.0013. The design is carried out using CST-Microwave Studio software. The equivalent circuit of the filter is analyzed and presented using ADS2006A software. The filter exhibits sharp cutoff frequency f c = 1.7654 GHz, wide stopband from 1.7654 GHz to 7 GHz with |S 21 | less than −10 dB, insertion loss less than 0.15 dB in passband and reduced size compared to the traditional LPF.
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