Sidelobe Level Of Array Research Articles

Design of 77 GHz automotive angular radar array antenna with wide beamwidth and flat gain

A wide beam, flat gain planar array antenna based on beamforming technology is designed for automotive angular radar systems. The array antenna consists of three 1×10 series feed line arrays, which are designed by Dolph-Chebyshev antenna synthesis method with unequal spacing distribution to reduce the side lobes. In order to satisfy the needs of the automotive angle radar wide field of view (FOV), the beamforming techniques are used for the planar array antenna to broaden the beamwidth of the azimuth plane and improve the flatness of the gain. The simulation and the measured results agree well. The measured results show that the 1×10 line array sidelobe level is −19.7 dB; the 3×10 planar array antenna has a 3 dB beamwidth of 106.4°, and the azimuth gain flatness range can reach ± 45°, the maximum gain is 11.3 dBi.

Modelling and Simulation of Vertical Fin Style Aluminium Heat Sink for Controlled Thermal Compensation in Absorber Loaded Antenna Array

Enhanced array performance can be achieved by increasing number of array elements but at the cost of increased side lobe levels. These sidelobes can be supressed by integrating graphene oxide based electromagnetic absorbers along with antenna array on a single substrate. Absorbers can effectively reduce the side lobe levels of array by absorbing their interelement coupling waves, the ambient temperature of array however increases as the absorbed side lobes dissipate into heat which is not desirable. Temperature compensation technique is hence proposed whereby the temperature shift is controlled by utilizing heat sink mounted absorber for improving the performance of antenna array.

Investigation of substrate materials for graphene oxide absorber loaded antenna array increased ambient temperature

Integration of electromagnetic (EM) wave absorber with patch antenna array on single substrate provides a very efficient way to improve the radiation pattern of array by reducing mutual coupling effect. The placing of absorber on array assembly may however affect the radiation characteristics due to the heat generated from absorbed power. As the microwave absorber dissipates the inter-element waves in terms of heat via absorption, the ambient temperature of array increases which consequently varies the patch dimensions and dielectric properties of the substrate thus shifting the resonant frequency of array. These effects have been investigated for graphene oxide-based absorber loaded rectangular patch array designed on different substrates such as silicon, gallium arsenide, aluminium oxide and Roger RO3210. On the basis of percentage variation in return loss and effective bandwidth an optimum substrate is proposed which undergoes minimize temperature effect without deteriorating the gain and directivity of the antenna array. The results show that for Graphene oxide-based absorber with Roger RO3210 substrate having high melting temperature of 4236.85 °C, side lobe level of array is reduced from 3.737 dB to 2.551 dB with increased major lobe gain. Due to absorbed power, ambient temperature of array increased from room temperature (27 °C) to 187 °C significantly shifting the resonant frequency from 10.4 GHz to 8.9 GHz. Further the comparison results show that with aluminium oxide substrate the array exhibits minimum temperature sensitivity hence proving to be a better choice for design of microwave absorber loaded antenna array.

Numerical Optimization of Compressive Array Feed Networks

Compressive antenna arrays reduce the number of beamforming controls by taking a limited number of weighted combinations of the element signals. A compressive array sidelobe level (SLL)-minimization algorithm, inspired by coherence-optimization algorithms, is presented. Optimized compressive arrays are shown to obtain better SLLs than existing weighted thinned arrays and completely overlapped subarrays. The design of a compressive array with arbitrary sidelobe requirements shows that increasing the number of elements for a given number of beamforming controls improves the array performance over a conventional array. A compressive array with a hard null is proposed to suppress the interference before sampling. Where beamforming controls are the main cost drivers, the proposed approach promises to increase the array performance without a significant increase in cost.

An Antenna Array Sidelobe Level Reduction Approach through Invasive Weed Optimization

The problems of synthesizing the beam patterns of the linear antenna array (LAA) and the circular antenna array (CAA) are addressed. First, an optimization problem is formulated for reducing the maximum sidelobe level (SLL) of the beam patterns. Then, the formulated problem is solved by using the invasive weed optimization (IWO) algorithm. Various simulations are performed to evaluate the effectiveness of the IWO algorithm for the synthesis of the beam patterns of the LAA and the CAA. The results show that IWO has a better performance in terms of the accuracy, the convergence rate, and the stability compared with other algorithms for the SLL reductions. Moreover, the electromagnetic simulation results also show that IWO achieves the best performance for the beam pattern synthesis of the antenna arrays in practical conditions.

IMPROVED DIFFERENTIAL EVOLUTION STRATEGY FOR ANTENNA ARRAY PATTERN SYNTHESIS PROBLEMS

An Improved Difierential Evolution (IDE) algorithm is proposed for optimization problems. With the novel mutant operation adopting sub-optimal individual, the convergence of Difierential Evolution (DE) algorithm is accelerated without increasing the risk of premature. Five typical test functions are minimized using DE and IDE algorithms, and the results show the superior performance of IDE algorithm. Furthermore, the algorithm is applied to pattern synthesis of two antenna arrays. Broad nulls are formed in radiation pattern of a linear array to suppress broad-band interferences. In a microstrip patch array, the sidelobe level of array is decreased about 12.9dB and the mainlobe can scan to the desired angle.

Sidelobe Level and Wideband Behavior of Arrays of Random Subarrays

We propose an extension to the concept of random antenna arrays. Three new array geometries are introduced which are intended to incorporate the wide bandwidth capability of a random array while having simplified geometry to increase their suitability for lower-cost applications. The behaviors of the periodic array of random subarrays, array of periodically rotated random subarrays, and array of randomly rotated random subarrays are each characterized probabilistically. Results indicate that subarray rotation can lower the sidelobe level of the array factor. An example of the design process is presented with calculated array factors