Low Sidelobe Research Articles

Clear imaging method based on far-field beamforming for substation noise source identification

The noise problem of substations has become increasingly prominent in recent years, and the accurate identification of noise sources has been the prerequisite for substation noise control. By virtue of the advantages of long measurement distance and panoramic acoustic imaging, far-field beamforming based on solid spherical microphone arrays has broad application prospects in large substation noise source identification. Spherical harmonics beamforming (SHB) is a classical algorithm matched with spherical microphone arrays. However, its sound source identification results suffer from problems such as wide mainlobes at low frequencies and abundant sidelobes at high frequencies, which lead to limited acoustic imaging clarity. In order to achieve clear acoustic imaging of noise sources in large substations, the output of far-field SHB is reconstructed and the method of clear SHB (C-SHB) is proposed. The simulations and experiment show that C-SHB can significantly reduce the mainlobe width and suppress the sidelobe contamination, thus effectively improving the imaging clarity of SHB and enhancing its weak source identification capability.

A split-ring resonator full/sparse planar array based on Chebyshev polynomial

A planar split-ring resonator (SRR) antenna full/sparse array, fed by a Chebyshev distribution, is proposed in this paper. Following the Yagi principle, the antenna element consists of SRRs and an I-shaped resonator. The inclusion of the I-shaped resonator enhances coupling, resulting in high gain. Additionally, a 14 × 13 Chebyshev planar antenna array, based on corporate feed, allows for a non-uniform amplitude distribution to suppress side lobes. The proposed Chebyshev planar array exhibits high gain characteristics and low side lobe levels (SLL) in both the E- and H-planes. For sidelobes suppression further, by utilizing a genetic algorithm, a planar sparse array is constructed based on the proposed Chebyshev array. The measured gain of the array at 10.1 GHz is 22.4 dBi, with SLL values of −20.4 dB and −17.5 dB in the E- and H-planes, respectively. These results meet the requirements for wireless communication.

Design of multiple‐input multiple‐output radar amplitude‐bounded waveforms with desired ambiguity function based on sequential quadratic programming

AbstractThe transmit waveform with ambiguity function specifications in the range‐Doppler plane has been of great interest in traditional single antenna radar systems in recent years. This paper considers the design of waveform sets with a desired slow‐time ambiguity function for multiple‐input multiple‐output radar. Specifically, it is desirable that the ambiguity function has low sidelobes where clutter occurs, as this reduces the impact of the clutter on target detection. Instead of unimodular waveforms, the authors consider amplitude modulation signals and introduce the bound constraint on signal amplitudes into the optimisation for the consideration of transmitter efficiency. The design problem is formulated as minimising the weighted integrated sidelobes level of the ambiguity function over the range‐Doppler plane under bound constraints. The resulting problem has a highly non‐linear objective function and is constrained by bound constraints and quadratic equality (constant energy) constraints, making it difficult to solve. The authors develop an efficient algorithm based on the sequential quadratic programming technique and non‐linear conjugate gradient method to solve it. Simulation results show that the proposed algorithm is superior to the existing methods.

A Wideband, High Gain and Low Sidelobe Array Antenna for Modern ETC Systems

Modern electronic toll collection (ETC) systems are currently moving towards a system design that is capable of fast and optimal payment handling for a single lane. Thus, the antenna of a roadside reader unit (RSU) needs to provide sufficient coverage over the vehicle lane during a payment cycle. In this paper, a left-hand circularly polarized (LHCP) 2×4 array antenna is proposed for European standard RSU readers at 5.8 GHz. The proposed array antenna consists of patch element antennas with parasitic elements to enhance gain and bandwidth. Sequential phase rotation feeding networks are applied to make the antenna low-profile. By using the optimized nut-shaped metasurface, the antenna can achieve higher gain due to concentrated radiation power in the boresight direction. The antenna has a wide impedance bandwidth of 2.34 GHz (37.73%), axis ratio bandwidth of 2.07 GHz (32.9%), high gain of 17 dBi, and sidelobe level (SLL) lower than -15 dB at 5.8 GHz. Especially, half-power beamwidths are 34∘ and 17∘ in horizontal and vertical planes, respectively, which covers sufficient space for a single lane while avoiding interference with other lanes. The performance of the proposed antenna is verified by measured results. It showed that the proposed antenna is a promising candidate for ETC applications.

Wide-Angle Scanning Microstrip Patch Antenna Array for mmWave Applications with High Gain

This paper presents a modified rectangular microstrip patch antenna (MRMPA) array conforming to the hemisphere for wide-angle beam scanning. Two different conformal antenna array designs are presented in this work. The first of these designs, a 13-element MRMPA array conformal to the surface of a circular arc, and the second one, a 9-element array conformal to the surface of a hemisphere, are designed and optimized. The geometrical approach of calculating the phase value is used to calculate the phase value of each antenna. The simulated results show that the 13-element conformal MRMPA array is achieving a beam scanning angle of ±84° with a gain of 13.89 dBi with low side lobe levels, and further, the gain of the array is enhanced by a dielectric superstrate that improved the gain by ∼2 dBi at all the scanning angles. Second, an MRMPA array conformal to a hemisphere with nine elements is designed with beam scanning ability from φ = 0°−360° and θ = ±30° with a gain of 15.69 dBi, and further, the gain is enhanced by ∼3 dBi with the dielectric superstrate. Full-wave simulations have proven both designs to be accurate and aligned with theoretical calculations.

Design of a Wideband, High Steering Angle and Low Side-Lobes Levels Matrix Antenna

This paper presents the use of pixel-type radiating elements in the context of broadband beam steering. The elements are composed of a resonant cavity topped by a frequency selective surface, fed via a patch antenna and filled with dielectric substrates. This pixel antenna has a wide -10 dB matching band from 1.22 to 1.61 GHz, which corresponds to a 27% fractional bandwidth. It has an angular aperture greater than 124° and a realized gain between 3.3 and 3.8 dBi over the whole matching band. An array composed of 5 elements has been simulated and allows a steering on a range of ±60° in the E plane while keeping the gain variation below 3 dB. A prototype has been manufactured and presents a steering capacity between -56 and 53° on the whole band with side-lobes levels lower than -8.1 dB whatever the angle.

Generation of modified Bessel-Gauss beam with low side-lobes and large depth of focus using multiphase plate

The high side-lobes of the Bessel-Gauss beam generated by refractive axicon or reflective axicon is a major factor that hinders its practical application. In this paper, multiphase plate is used to modify the Bessel-Gauss beam, which can suppress the side-lobes and retain the diffraction-free property over a certain length. The radii parameters and the phase in each ring are optimized using genetic algorithm. By changing the circular rings in the multiphase plate optimized for refractive axicon into the elliptical rings according to the off-axis angle of the reflective axicon, side-lobe suppression for the reflective axicon can also be achieved without redesigning the multiphase plate. Simulation results show that side-lobes of less than 2% and depth of focus of ∼ 15 mm can be obtained with proper choice of parameters.

Robust Adaptive Beamforming Algorithm Based on Complex Gauss–Legendre Integral

This study addresses the poor robustness of the current beamforming algorithm for covariance matrix reconstruction and the high computational complexity in the covariance matrix reconstruction process. A robust beamforming algorithm based on the Complex Gauss–Legendre integral is proposed. The method firstly partitions the neighborhood of the interference signal and constructs the interference signal space using the complex Gauss-Legendre integral, then projects the received signal into the interference signal space to filter out the desired signal and complete the reconstruction of the interference noise covariance matrix, before finally correcting the steering vector mismatch using the improved optimal steering vector estimation method. The simulation results show that the method has good robustness and a low sidelobe in the presence of the steering vector mismatch and the presence of array perturbation. Compared with the previous works, the proposed CGL-ISV method provides a better beamforming performance.

Direct printable X-band low profile broadband reflectarray antenna using copper foils

This work reports on a compact and broadband reflectarray antenna that can be directly applied to the exterior surface of a nanosatellite. The design is composed of an annular ring with a wheel-shaped concentric structure loaded with two circular stubs acting as delay lines for maximum phase angle coverage. The design offers a phase variation of 576° in the X-band along with a peak measured gain of 26.6 dBi and an aperture efficiency of 49.24%. The design also offers low side lobe levels of −13 dB and −18 dB in both E- and H-planes at 11 GHz, respectively. Cross-polarization discrimination is also sufficiently large and is better than −32 dB and −36 dB for E- and H-planes, respectively. Moreover, the proposed printable reflectarray exhibited a 1-dB gain Bandwidth (BW) of 31.5 %. The design is produced by applying copper foils on float glass with a thickness of 2 mm as a proof of concept.

A Single Plane Low profile Patch Antenna π-Shaped Slots and Low Side Lobe Level for Directive Wireless Communications

The patch antenna was used recently for ISM band (5.725 – 5.875) GHz, the patch antenna suffers of being an antenna with low gain as well as narrow operating bandwidth with high side lobe level (SSL) radiation pattern. A single plane with low profile and easy fabrication microstrip patch antenna has been proposed in this work was presented for directive communications and operates in Industrial, Scientific, and Medical (ISM) band 5.8 GHz with low SLL radiation pattern and gain of 5.20 dB for pint to point (directive). The gain of antenna has been increased while SLL decreased due to shifting the radiating patch and feeder of antenna with specific distance toward –ve side of the X-axis without any need for using techniques which would increase overall dimensions of antenna. The antenna has been printed on Arlon AD 250 substrate. The simulated results of antenna’s gain, operating frequency, bandwidth, return loss, and radiation pattern are presented. CST Microwave studio software was used in this design simulation.

Two-Bit Planar Coding Reconfigurable Array Antenna for Dual-Polarized Wide-Angle Beam Scanning

In this communication, a dual-polarized coding reconfigurable array antenna with the characteristics of being low-profile, low-cost, relatively low-sidelobe and wide-angle beam scanning is proposed. By exciting the array via different feeding ports, horizontal and vertical polarized scanning beams can be generated. By adjusting the PIN diodes integrated on the feeding lines, the element presents four different phase states of -270°, -180°, -90°, and 0°, labeled as “00”, “01”, “10”, and “11”. An eight elements array antenna is designed based on the element. With the introduction of elaborately designed two groups of fixed phase delay, the sidelobe level at different scanning angles can be effectively reduced in two polarized directions and the gain are also improved. The simulated and measured results of the fabricated prototype indicate that dual-polarized ±60° wide-angle beam scanning, moderate array gain, relatively low sidelobe level, and low cross polarization level can be achieved. The proposed array antenna, which according to our best knowledge, is the first dual linear polarized wide angle beam scanning coding reconfigurable array without the feeding horn, might have good applications in base station and fully polarimetric radar.

Antenna Array with Low Side Lobe Levels for MIMO Applications

Abstract: To design a single element microstrip patch antenna at a frequency of 4 GHz. A uniform planar array with 4 patch elements is designed. A non uniform planar array is designed to overcome the mutual coupling effect. Simulation of the designed uniform planar array and non uniform planar array antenna array is performed on HFSS tools. A single microstrip feed patch antenna element is designed at a frequency of 4 GHz. The substrate material used is Rogers 6002. A 2*2 array is designed by using 4 similar patch elements. The proposed model has dimensions of the substrate as 58mm x 68mm, the dimensions of the patch is 20mm x 22mm. For the proposed model slots are added to each patch with the dimensions 5mm x 1mm. The substrate material used is FR4 epoxy. It is further improved by changing the dielectric material variations, slot arm length variations, slot arm thickness variations.

A dual-band dual-polarized low-side-lobe transmitarray using independent amplitude and phase controllable elements

In this paper, a novel transmitarray (TA) element with independent control capability of amplitude and phase under dual-band dual-polarized operation is proposed. By changing the physical size of the TA element, the phase variation of the element can cover 360° at two bands. Moreover, the phase change of the frequency band is less than 30° when the phase of the other band is changed. Meanwhile, a higher maximal transmission amplitude can be maintained when varying the phase. Amplitude modulation is achieved by rotating the TA element. Utilizing the proposed TA element, a dual-band dual-linear polarization (LP) TA with low side lobe level (SLL) operating at 12.5 GHz and 14.25 GHz is designed. The SLL can be decreased by amplitude modulation of the elements. The measured peak gains of the proposed TA are 25.96 dBi and 25.89 dBi at 12.5 GHz and 14.25 GHz. In addition, the measured SLLs of the yoz/xoz planes are −22.4 dB/−22.4 dB and −22.5dB/−22.3 dB at 12.5 GHz and 14.25 GHz, respectively. The proposed TA shows good SLL performances and great application potential in satellite communication systems.

A low sidelobe 77 GHz centre‐fed microstrip patch array antenna

AbstractA low sidelobe 77 GHz centre‐fed microstrip patch array antenna is proposed for automotive radar application. The proposed antenna comprises eight linear antenna arrays, each of which is centre‐fed by a coplanar waveguide with ground transmission line at the back of the microstrip patches. Each linear antenna array contains 10 patch antenna units, which are connected through a T‐type power divider network to achieve a −30 dB Taylor weighted distribution. The simulation results show that the designed phased array antenna has a good one‐dimensional phased scanning ability of ±45° with active voltage standing wave ratio less than 2 at 75–79 GHz, along with −20 dB low sidelobe symmetrical radiation patterns in the H plane. An antenna sample fed by a WR12 waveguide is fabricated and measured to verify its performance. The measured VSWR is less than 2 at 73.6–85 GHz. This design provides a new idea for millimetre wave automotive radar antenna design.

All-plasmonic optical leaky-wave antenna with a low sidelobe level

Optical antennas have received considerable attention in recent years due to their unique ability to convert localized energy to freely propagating radiation and vice versa. Sidelobe level (SLL) is one of the most crucial parameters in antenna design. A low SLL is beneficial to minimize the antenna interference with other optical components. Here a plasmonic optical leaky-wave antenna with low SLL is reported. Shifting spatial frequency by periodically modulating the electric-field amplitude in a plasmonic gap waveguide enables a free-space coupled wave out of the antenna. At the same time, precise control of the aperture fields by the modulation depth allows for reducing SLL. Simulation results indicate that the proposed design can achieve a high directivity of 15.8 dB and a low SLL of −20 dB at the wavelength of 1550 nm. A low SLL below −15 dB is experimentally demonstrated within the wavelength range from 1527 to 1570 nm. In addition, the low-SLL property is further verified by comparing it with a uniformly modulated antenna. By modulating the guided waves in the plasmonic gap waveguide in different forms, the aperture fields can be flexibly arranged to achieve arbitrary wavefront shaping. It bridges the gap between guided and free-space waves and empowers plasmonic integrated devices to control free-space light, thus enabling various free-space functions.

Low-Sidelobe Microstrip Patch Filtenna Array Fed by Higher Order Mode SIW Cavity

In this letter, a 1 × 3 microstrip patch (MP) filtenna array with low sidelobe level fed by TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">410</sub> -mode substrate integrated waveguide (SIW) cavity is investigated. Benefiting from the fact that the magnetic field amplitude at the adjacent region of the two central quasi-TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">110</sub> modes of the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">410</sub> -mode SIW cavity is twice that of the single quasi-TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">110</sub> mode on either side of the edge, it enables the filtenna array to obtain a binomial power distribution and then achieve low sidelobe level. In the fusion design of filtering power divider (FPD), the SIW cavity and the patch radiators are regarded as first and second resonators of filter respectively, meanwhile, the power dividing function is fulfilled by the coupling process between them. For demonstration, a filtenna array prototype centered at 13.2 GHz is designed, fabricated and measured. The measured results show that a peak gain of 11.6 dBi and a maximum efficiency of 85%. The measured sidelobe levels in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">E</i> -planes are both below than -19.1 dB at 13.06 GHz and 13.32 GHz. Good agreement between the simulation and measurement can be observed.

Pattern Reshaping of the Third Resonant Mode of Dipole and Slot Using Parasitic Elements

A simple approach for radiation pattern reshaping of the 3rd mode of dipole and slot antennas is proposed. Short parasitic strips or slots are added to both sides of the dipole or slot antenna. In the 3rd mode, the reversed current or E-field will destroy the omnidirectivity or bidirectivity of these two antennas. But, the induced current or E-field on the parasitic elements is opposite to that on the original antenna canceling the effect of the reversed current or E-field. As a result, the radiation patterns of the dipole and slot in the 3rd mode are reshaped to be omnidirectional or bidirectional, respectively. The effects of parasitic element length, spacing and position on radiation pattern have also been studied. Besides, it is proved that parasitic loops have the same effect. For simplifying impedance matching, a novel feeding method for slot antenna is designed specially without using lumped element. Two prototypes, dipole and slot antennas with parasitic elements, were fabricated and tested to validate the concept. The measured results are in good agreement with the simulated ones. The measured patterns of the 3rd mode are shaped with lower sidelobes and high realized gains. In both the 1st and 3rd modes, the dipole and slot antennas realize omnidirectional and bidirectional radiations, respectively.

Suppression of Sidelobes Directed to the Underlying Surface for Phase-Only-Controlled Phased Arrays

The method of phase synthesis is used to suppress the lower sidelobes (SLs) of he radiation pattern (RP) of phased arrays (PAs). The dependences of variations in the RP parameters on the level of the lower SLs are derived, and the limiting possibilities of the method for suppression of the SLs are determined. A scenario in which lower SLs are suppressed only starting from a certain arbitrary SL is also considered. It is shown that, in this case, it is possible to achieve a lower level of SL and less worsening of the remaining RP parameters.

Efficient binary sequence set designs for MIMO PMCW radar

Multiple-input multiple-output (MIMO) phase-modulated continuous wave (PMCW) radar systems have major advantages for mutual-interference mitigation over their linear frequency-modulated continuous wave (LFMCW) counterparts. To attain a virtual array length of M×M̃ with M transmit and M̃ receive antennas, a probing sequence set with both low auto-correlation sidelobes and low cross-correlations is needed for MIMO PMCW radar. To reduce the hardware cost of sequence generation, binary probing sequence (BPS) sets are desirable. We present herein four efficient computational algorithms to generate BPS sets with desirable properties, and arbitrary sequence lengths and arbitrary number of sequences in the set are allowed. When initialized by random BPS sets, they can be used to obtain many different BPS sets with similar properties, i.e., with large diversity. Moreover, fast Fourier transform (FFT) are exploited, making the algorithms computationally efficient. They can be used to design long BPS sets that are hardly possible using existing methods in the literature. The convergence properties and the relationships among the proposed algorithms are also analyzed under a unified framework. Numerical examples are included to illustrate the effectiveness of our designs.

Dual-Polarized Wideband Low-Sidelobe Slot Array Antenna for V-Band Wireless Communications

A dual-polarized wideband low sidelobe slot array antenna for wireless communication systems in the V-band is proposed in this work. Taylor distribution is applied with each radiating slot as a tapering unit in both polarizations. A compact 2 × 2 elements subarray is designed to achieve stable amplitude and phase distribution among elements with two sets of integrated compact wideband unequal power dividers for the E- and H-planes inside the subarray. Then, two layers of orthogonally polarized feeding networks with unequal E-plane T-junction power dividers are used to connect the subarrays to two standard waveguides WR-15 as input ports. The prototype of 8 × 8 elements is fabricated and measured in an anechoic chamber. The maximum measured gain is 25.3 dBi and 25.4 dBi for V- and H-polarization, respectively. The overlapped impedance bandwidth is from 57 to 66.4 GHz with reflection coefficiencies below -10 dB, and the isolation between two input ports is around 35 dB. Sidelobe levels of both polarizations are below -22 dB with good agreement with the simulations.