Low‐sidelobe marine radar microstrip array antenna based on hybrid algorithm and metamaterial

Array Antennas used in some applications such as RFID systems, WiMAX, and collision avoidance radar, must have very low side lobes. Antenna with higher beam efficiency (BE) and lower side lobe level (SLL) can increase the coverage area of RFID systems, transmission bit rate and at the same time decrease the energy consumption and interference levels. The application of RFID system at 860–960 MHz frequency band will likely be witnessed in different emerging wireless applications as well as associated increase in energy consumption will also be witnessed in the near future. It is possible to achieve higher BE and lower SLL by implementing different amplitude or phase distribution technique in the array antenna. This paper describes a new method of SLL reduction and increase of BE by adopting staircase concept of power distribution of array antenna. The new beam forming technique optimizes between SLLs and BE.

Multi-beam antenna is an important way to increase the channel capacity of cellular communications. It is available in two ways, one is based on optical methods, such as Luneberg lens and Rotman lens. However, the common problem with this method is that the lens size is too large or difficult to process. Another method is based on beam-forming network composed of coupler and phase shifter, such as Butler matrix. The Butler matrix has been studied for a long time, in the form of microstrip, stripline, or substrate-integrated waveguide. The substrate-integrated waveguide with low insertion loss is mainly used in the higher frequency such as millimeter wave band. The microstrip is mainly used in 4G/5G base stations, suitable for broadband design and process. Low side-lobe level, narrow beams are especially important for multi-beam base station antennas. The traditional Butler matrix is 4 × 4 Butler matrix for 4-beam base stations. However, the traditional Butler matrix can only output equal-amplitude power, with a side-lobe level higher than −13.4 dB. The beam width is too wide due to the few number of antenna. The 4 × 4 Butler Matrix with attenuator can reduce the side-lobe level, but it will increase the insertion loss of the beam-forming network. The 4 × 4 Butler matrix with phase shifter and power divider can form a 4 × 6 Butler matrix, which reduce the beam width beam and side-lobe level. However, for large-angle scanning, not only the side-lobe level, but also the grating-lobe problem caused by the wide-angle scanning and wide antenna spacing needs to be solved. The array with triangle arrangement can reduce the side-lobe and grating-lobe level. A wide-band 4-beam antenna array and beam-forming network for 4G base stations are presented in this paper. Adopting triangular arrangement, the number of antenna in sub-array is increased, and the antenna spacing is reduced, resulting in good side-lobe and grating-lobe level suppression. The output amplitude and phase errors are small over a wide band, with low insertion loss.

This paper proposes a novel high gain and low sidelobe level (SLL) linear microstrip array antenna for outdoor WLAN applications. The antenna consists of two main parts, which are a linear array and a reflector. The linear array comprises of 10 elements; those have been designed on Rogers RT/Duroid 5870tm with the dimensions of 422×100×10.15 mm3. To gain low SLLs, a series fed network was designed to have the output signals being proportional to the Chebyshev distributions (with preset SLL of -30 dB). Furthermore, Yagi antenna theory has been applied by adding directors above every single element to increase the directivity of the single element. The reflector has been constructed at the back of the proposed structure. Simulation results show that the array can provide high gain of 17.5 dBi and a low SLL of -26 dB. A prototype has been fabricated and measured. Good agreements between simulation and measurement data have been obtained.

The development of wideband antennas with low sidelobe level (SLL) is vital for many up-to-date special communication and air traffic control applications. As it has been reported earlier, array antennas have advantages in SLL but are inherently narrower band than reflector antennas. Another question, not easy for array antennas (if being compared with reflectors), is usually the cost. Researchers do their best to extend the bandwidth (BW) of low SLL arrays and reduce their cost. The task to achieve a good SLL is especially difficult in the case of small array aperture because amplitude and phase (A&/spl phi/) errors, the mutual coupling, and edge effects are more influential in this case than for large arrays. In this paper cost effective design approaches are considered for an S-band dipole antenna array with relatively small aperture and potential opportunities are investigated to improve SLL and BW. The cost reduction is provided by use of the printed circuit technology for all antenna components (radiators, beamforming networks, phase shifters) and by minimizing the number of components. The improving of SLL and BW is provided by A&/spl phi/ errors minimization, mutual coupling and edge effect suppression.

To meet the growing demand for Millimeter Wave antenna performance, we investigated the series-fed microstrip array antenna operating at 77 GHz and analyzed its admittance characteristics using the microstrip transmission line model. A two-dimensional low-sidelobe microstrip array antenna has been designed, which composed of $8 \times 8$-element rectangular patches by combining the form of serial feeding and the microstrip power divider. The simulation results show that the optimized serial feed antenna array can achieve a gain of more than 22.6dB at the center frequency of 77.5GHz. The half-power lobe widths of the E-plane and H-plane are about 14.7° and 11.7°, respectively. By using quarter-wavelength transformer and amplitude weighting, the side lobe level (SLL) of the series-fed array antenna is lower than −17dB. The bandwidth is about 810MHz (VSWR<1.5). This antenna is easy to manufacture, and has the characteristics of low sidelobe, high gain and narrow beam, which meets the design requirements.

In this paper, we simply analyzed the advantages of conformal antenna array, and proposed a method to realize conformal antenna array of airborne with high gain and low side-lobe level (SLL). We designed a Vivaldi antenna unit, which's work frequency is 400MHz~800MHz. Conducting the experiment with HFSS by choosing the Dolph-Chebyshev synthesis method and using its E surface to dispose, which showed that this method can reach the design target. Secondly, aiming at the limited application of uniform linear array (ULA) in the actual project application, studied the effect of non-uniform linear array (NULA), the experiments showed that due to the adoption of the sub-array, some of the SLL become large, and the SLL maximum value is inversely proportional to the number of units in sub-array, Finally, this paper put forward the cross array, it not only overcome the limit to disposal for antenna unit width, but also reduce the requirement for wing size to achieve large array, the experiment proves that it almost has no obvious influence on array performance by this method.

To achieve a high gain and low first side-lobe level, variants of linear and planar series fed circular and hexagonal microstrip antenna arrays using the binomial distribution, are proposed around 3000 MHz frequency band, on thinner Arlon substrate (h ~ 0.027λg). The linear 7 × 1 array of circular patches, yields first side-lobe level of −25 dB with a gain of 12.7 dBi, whereas using hexagonal patches, respective values are, −28 dB and 12.9 dBi. The planar 5 × 3 and 5 × 5 arrays using half wavelength and wavelength spacing are presented. An optimum response is obtained in 5 × 5 array for the wavelength inter-element spacing. Here, using circular patches, first side lobe level in the E and H-planes is −29 and −14 dB, respectively, with a peak gain of 17.6 dBi, whereas that using hexagonal patches, the respective first side lobe level in the E and H-planes is −26 and −17 dB, with a peak broadside gain of nearly 19 dBi. Thus using a thinner substrate, proposed series feed binomial planar arrays offer a gain of more than 15 dBi with a lower first side lobe level.

In this paper, a novel embedded helix dielectric rod antenna is presented for high gain radiation with circular polarization (CP) and low side lobe levels for IoT Applications. Different from the conventional dielectric rod antennas, this proposed antenna is an integrated structure that combines the advantages of the helix and dielectric rod antennas. The presented antenna mainly consists of three parts: a tapered helix as primary feeding for CP, a dielectric rod with printed loops embedded for higher directivity, and a dielectric rod end for improving the gain further. After studying and analyzing the working principles of each part, an optimum design operating at 8–9.7 GHz is carried out as an example. A prototype is also fabricated and tested. The measured results show that the prototype can provide 18.41 dB maximum gain within the length of 7.7 λ. The side lobe level is below −20 dB, and the axial ratio is better than 1.14 dB in the whole frequency band. Compared with the traditional helix antenna and dielectric rod antenna with the same electric length, the presented antenna has a higher gain with a lower side lobe level and with good polarization purity.

For the first time, the rectangular dielectric resonator (DR) operating in higher-order TE3δ1 mode is investigated and used as a magnetic-dipole driver to design quasi-Yagi antenna with high gain. For further enhancing the antenna gain, a near-zero-index (NZI) metamaterial (NZIM) is proposed instead of the traditional directors and put in the front of DR driver. It is a simple structure and composed of a set of the parallel metallic lines printed on a substrate along the end-fire direction. Benefiting from the higher-order mode operation of the DR and NZIM, the realized gain of the proposed antenna can reach 10.3 dBi, including the gain improvement of 2 dBi resulting from the employed NZIM. To verify the design concept, the prototype of quasi-Yagi DR antenna with NZIM is fabricated and characterized. The measured results agree very well with the simulated results.

Optimizing antenna arrays is essential for achieving efficient beamforming with very low sidelobe level (SLL) where adopting tapered window functions is one of the straightforward efficient techniques for achieving this goal. Recently, two-dimensional (2D) beamforming has been extensively required for many applications; therefore, this paper proposes two extrapolation techniques applied to one-dimensional (1D) tapered functions to efficiently feed 2D antenna arrays using cross-linear and adaptive radial tapering techniques. The first proposed 2D cross-linear tapering technique determines the 2D tapering coefficients by Hadamard multiplication of two right-angled grids of repeated 1D functions, while the second proposed adaptive radial tapering technique locates the antenna element in the 2D array in terms of its radial distance with respect to the array center, then converts this distance to an element index in a virtual 1D tapering window to determine the element weighting value. The adaptive radial tapering technique is optimized for achieving the minimum SLLs. The two proposed techniques are analyzed and discussed, where it is found that the adaptive radial tapering provides deeper SLLs compared to the cross-linear tapering technique. The two extrapolation techniques are examined for four window functions including triangular (Bartlett), Hamming, cosine-square, and Blackman windows, and the simulation results show that for extrapolating the Blackman window using adaptive radial tapering, a –50 dB SLL can be achieved which is independent on the array size, while cross-linear tapering provides –35 dB and –41 dB SLLs for and antenna arrays, respectively.

This article introduces an amplitude and phase independently adjustable transmitarray aperture with a thin profile and low cost to fabrication characteristics, and a transmitarray antenna (TA) featuring the high gain and low sidelobe level (SLL) is realized based on it. The TA is made up of a standard feed horn and a transmitarray aperture, each of which comprises a three-layer metasurface that is well-designed to tune the transmitted phase and amplitude on its own. As a result, the transmitarray aperture can cover the 360° phase range required for phase compensation while also realizing the amplitude distribution calculated by the Taylor design, contributing to the low SLLs. The advantage of independently controlling the amplitude and phase not only enables the proposed TA to be easy to realize and less cost on optimization but also improves the performance of high gain and low SLLs with a low profile and easy fabrication. Theoretical analyses and simulations are carried out, and a prototype is fabricated and measured. At 10 GHz, the measured peak gain is 21.16 dBi, with SLLs of −31.21 and −29.93 dB in the H- and E-planes, respectively. As a result, the tight agreements between measurement and simulation validate the design concept.

The ultra high frequency (UHF) band spectrum will likely be congested in near future since the next generation wireless as well as Radio Frequency Identification (RFID) system users will witness the use of UHF band technology with increased demand of bandwidth, bit rate, frequency spectrum and power consumption. The alternate solution is the use of millimeter-wave band technology. It is possible to improve data throughput, range resolution and multi-user capability in mm-wave band RFID system. ‘Higher power reception efficiency and lower side lobe level (SLL) of radiation pattern’ is required for RFID system that will increase the tag range and transmission bit rate. At the same time lower SLL will minimize the interference level. Beam pointing error is another problem of UHF band antenna which reduces the tag range and bit rate. These problems can be minimized by using large number of antenna elements. But with UHF band signal it is practically difficult to construct large array antenna; since the array size becomes tremendously larger with the increase of antenna elements. ‘Higher power reception efficiency and lower SLL’ can practically be obtained by using non-uniform power distribution of large number of antenna elements in millimeter wave band. A new and technically better method of beam forming by implementing the concept of staircase power distribution (SPD) of antenna elements at 60 GHz has been investigated and presented in the paper. The SPD method is compared with Gaussian edge tapering method. It was found that the maximum SLL (MSLL) is the lowest in case of SPD. The beam efficiency of SPD is also equivalent to that of Gaussian edge tapering method. It is easier to fabricate a larger number of antenna elements within smaller area with SPD at 60 GHz system; since the antenna size is smaller and the number of different power distribution in SPD case is less and stepwise uniform. Uniform and less number of different power distribution of SPD also minimizes other technical errors.

This paper presents a method for sidelobe level (SLL) reduction, return loss improvement, and bandwidth enhancement in notch-loaded TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> mode rectangular patch antennas. In this method, a fractal-slot is introduced in the center of notch-loaded patch to remove the unwanted out-of-phase current regions. It is shown that a combination of the fractal-slot and notch loading technique can achieve significant improvement in SLL, return loss, and bandwidth of notch-loaded TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> mode without compromising gain or symmetry of radiation patterns. Moreover, the method also gives an additional degree of freedom to improve the impedance matching without changing the feed location. A prototype of the antenna is fabricated to verify the proposed method. The proposed antenna shows a measured gain of 13 dBi with a low SLL of −16 dB. Furthermore, it shows symmetrical patterns in both planes with cross-polarization (X-pol) levels of less than 35 dB. An under-sampled <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times 4$ </tex-math></inline-formula> array of the proposed antenna is also presented by utilizing its low SLL property to simplify the complexity of feed networks in high gain array antennas. The array offers the same directivity and SLL as that of an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8\times 8$ </tex-math></inline-formula> array of fundamental mode rectangular patch elements in the same area.

In this communication, we introduce a novel design for mitigating the side-lobe level (SLL) of the half-mode substrate integrated waveguide (HMSIW)-based leaky-wave antenna (LWA). Applying a novel approach through modification of the side aperture of HMSIW, we achieved an SLL of -13.8 and -11.2 dB in the upper hemisphere and full space, respectively. The key novelty of this communication is the reduction of SLL in full space while the state-of-the-art antennas only mitigated the SLL in the upper hemisphere. Furthermore, tapering the open side aperture in a thin trapezoid shape led to a significant reduction of beam squint. The operating frequency band of the antenna matches the allocated 5G wireless network millimeter-wave bands from 26 to 30 GHz. The measured peak realized gain of the antenna is 10.6 dBi at 28.5 GHz. The length, width, and height of the HMSIW antenna are 70, 15, and 0.5 mm, respectively. The antenna was fabricated on a Rogers RT/Duroid 5880 substrate. Excellent agreement between the measurements and simulated results was observed. The discrepancies between the measured and simulated results were analyzed by a complete and thorough sensitivity analysis that included the effects of the fabrication tolerances, connectors' misalignment, and bending due to the mechanical stress. High gain, low SLL, and compactness are among the advantages of the proposed antenna making it a suitable candidate for the miniaturization of 5G communication systems.

In this paper, a deformed radiating element is proposed to design a comb-line array antenna for low sidelobe levels in the millimeter-wave band. To design the comb-line array antenna with a low sidelobe level, the use of the wide radiating elements for a relatively large radiation conductance is required. However, the conventional rectangular radiating element has transverse current flows on it, resulting in undesirable transverse radiation conductance for cross-polarization. On the contrary, in the proposed radiating element, which is implemented by cutting obliquely the connection part to the feeding line from a rectangular element, the radiations from the transverse currents cancel each other, and low radiation conductance for cross-polarization and dominant radiation conductance for co-polarization are achieved. A 17-element linear comb-line array antenna with the sidelobe below −20 dB is designed and measured at 79 GHz. Using the proposed radiating elements, we obtained the sidelobe level of −21.9 dB in the array, but the array using the conventional radiating elements shows the sidelobe level of −16.9 dB. This letter demonstrates the availability of the proposed element for the easy and accurate design of the comb-line array antenna with the low sidelobe level.