Time Modulation-Based Enhanced Sum-Difference Monopulse Beamforming Pattern Generation Using SPDT Harmonic Switching Networks

A flexible approach based on a hybrid differential evolution strategy (HDES) is developed for adaptive pattern nulling with time modulated linear antenna arrays. The HDES adjusts the least significant bits of the digital phase shifters and the on-off time sequence to minimize the total output power, deep nulls can then be placed in the direction of the interferences. Thanks to the new design freedom introduced in time modulated antenna arrays, this adaptive nulling approach exhibits better performance over the traditional phase-only, amplitude-only, and phase-amplitude adaptive nulling methods, in terms of the practical implementation, nulling depth, and pattern deterioration. Several representative examples are presented to show the effectiveness of the proposed adaptive nulling approach.

In time-modulated antenna arrays (TMAAs), as a result of periodical switch-on and switch- ofi of the antenna elements, including operating frequency (termed as center frequency) signal, sideband signals are appeared at either sides of the center frequency in integer multiples of the modulation frequency. In this paper, it is shown that without using phase shifters, just by suitably controlling the on-time instants (OTIs) and on-time durations (OTDs) of a time-modulated linear antenna array (TMLAA) elements, simultaneously, along with a pencil beam pattern at the operating frequency, a shaped beam pattern can be obtained at both the flrst positive and negative harmonics of the time- modulation frequency. The important advantage of such a technique is that realization of multi-beam pattern in conventional antenna array (CAA) system generally requires complex feed network, whereas by using simple radio frequency (RF) switching circuit in the feed network of TMLAA, by virtue of the properties of harmonic radiations, synthesis of a shaped pattern at either (positive or negative) harmonic results in generating the same pattern in its opposite harmonic, and the synthesized patterns at difierent harmonics can be simultaneously used as independent communication channels. By employing a difierential evolution (DE) based optimization method, numerical results for a 16-element TMLAA with uniform excitation show that in conjunction with a pencil beam pattern at the center frequency, a ∞at-top or a cosec square pattern at flrst positive and negative sidebands of side-lobe levels (SLL) i20dB can be synthesized by suppressing the higher sideband level (SBL) to below i10dB.

This paper proposes a trapezoidal pulse-based ON-OFF switching approach for the optimum beamforming performance in a time-modulated linear antenna array (TMLAA). The Fourier series property is used to adjust the transient behaviour trapezoidal switching function (τn1) and constant slope (τn2) of the trapezoidal pulse to obtain the highest steering main beam of the fundamental and harmonic components of the radiation pattern. Also, the sidelobe level (SLL) and sideband level (SBL) are simultaneously lowered. Despite the fact that harmonic beams are typically thought of as an interfering radiated pattern in time-modulated antenna arrays, the shifted harmonic frequency can also be useful in a variety of contexts. The beam steering of the harmonic is made possible by the optimal adjustment of the switch time instant τn1 and τn2 of the trapezoidal pulse signal without any optimization of the excitation amplitude weights. The optimal switching ON and OFF duration is evaluated by utilizing an evolutionary algorithm called Cultural Algorithm (CA). The antenna radiation characteristics are changed by using a series of Radio Frequency (RF) switches to modulate the static excitations using a trapezoidal pulse sequence to alter the time-modulation. Toward this approach, unique cost functions are designed and simulated for the simultaneous reduction of SLL, SBL and harmonic beam steering in TMLAA. The proposed cost function-based CA algorithm is able to get beam steering as arbitrary beam steering, multi-beam steering and beam steering in a user-defined direction.

A novel optimization method for multiple beamforming with null steering is proposed. Firstly, an invasive weed optimization method is improved in order to optimize the search depth. In the process of the seed diffusion, the crossover operation of genetic algorithm is introduced to modify the seed individuals, which can meliorate the searching ability and convergence speed of the algorithm. Then, the harmonic beamforming technology based on time modulated antenna array is presented, and multiple objectives about peak power and null steering are built. Finally, the improved invasive weed optimization algorithm is used in null forming based on pattern synthesis of antenna array, and the element excitation amplitude of time modulated antenna array is set to the excitation value obtained by the improved optimization algorithm. The simulation results show that the improved invasive weed optimization algorithm is superior to the conventional algorithm in performance. The simulation results show that forming null in the specified direction can be achieved while generating multiple beams.

Reduction of Sidelobes of the power pattern of Antenna Array with time modulation technique called time modulated antenna array (TMAA). Amplitude and spacing is used as optimizing variables for the reduction of side lobe level (SLL) of TMLAAs. The switching time sequence of each element of array is predefined. The method is demonstrated in the course of 12, 16, 20 element TMLAAs. Different outcomes are offered to explain the reward of this method deeming optimal SLL reduction, as compared to non-optimized TMLAAs.

This research presents the design of time-modulated antenna arrays with UWB performance. The antenna arrays consider a linear topology with eight UWB disk-notch patch antennas. The technological problem is to find out the optimum antenna positions and/or time sequences to reduce the side lobes and the sidebands in all of the UWB frequency ranges. The design process is formulated as a bacterial foraging optimization. The results show that the uniform array generates a better SLL performance whereas the non-uniform array obtains a wider bandwidth. The uniform array obtains an SLL < -20 dB from 3.37 GHz to 4.8 GHz and the non-uniform array generates an SLL < -7 dB from 2.97 GHz to 5.26 GHz. The sideband levels are very similar for both cases with a value of around -17 dB.

An improved procedure to lessen side lobe levels (SLLs) and side band levels (SBLs) in time modulated linear antenna arrays (TMLAAs) by using the optimization process. In that optimization process we give the discrete values of static excitation amplitudes and phase of continuous values of on-time duration of the elements of antenna array. We used the particle swarm optimization (PSO) technique to reduce the maximum of SLLs and SBLs to a pre defined desired value of antenna element. This has been optimized in a way that the discrete values of input excitation amplitude are obtained by PSO algorithm. The simulation result of time-modulated linear antenna array (TMLAA) is presented by reducing SLL and SBLmax to below −40 dB and to −35 dB respectively by taking 30 elements.

A planar millimeter-wave 2-D beam-scanning multibeam array antenna fed by compact 16-way beamforming network (BFN) in multilayered substrate integrated waveguide (SIW) technology is addressed. The BFN is formed by connecting two stacks of sub-BFNs, the E-plane sub-BFN and the H-plane sub-BFN. The H-plane sub-BFN is realized by a traditional H-plane 4 x 4 Butler matrix (BM). The key point of this design is to propose an E-plane 4 x 4 BM which realizes a planar E-plane sub-BFN. These two sets of sub-BFNs can joint directly without resorting to any connectors or connecting networks to form such a compact 16-way BFN with a reduced area of merely 3λ x 12λ. After that, to be compatible with the proposed BFN, a ladder-type 4 x 4 slot antenna array is employed, which is comprised of four linear 1 x 4 slot antenna arrays. Different from traditional array, the four subarrays are distributed in separate layers for the purpose of jointing to the BFN more conveniently. Transition network are also required to connect the BFN with the antenna array. Finally, a compact 2-D scanning multibeam array antenna based on the planar SIW BFN are fabricated and measured, which would be an attractive candidate for 5G application.

Multi-core fiber (MCF) has been one of the main innovations in fiber optics in the last decade. Reported work on MCF has been focused on increasing the transmission capacity of optical communication links by exploiting space-division multiplexing. Additionally, MCF presents a strong potential in optical beamforming networks. The use of MCF can increase the compactness of the broadband antenna array controller. This is of utmost importance in platforms where size and weight are critical parameters such as communications satellites and airplanes. Here, an optical beamforming architecture that exploits the space-division capacity of MCF to implement compact optical beamforming networks is proposed, being a new application field for MCF. The experimental demonstration of this system using a 4-core MCF that controls a four-element antenna array is reported. An analysis of the impact of MCF on the performance of antenna arrays is presented. The analysis indicates that the main limitation comes from the relatively high insertion loss in the MCF fan-in and fan-out devices, which leads to angle dependent losses which can be mitigated by using fixed optical attenuators or a photonic lantern to reduce MCF insertion loss. The crosstalk requirements are also experimentally evaluated for the proposed MCF-based architecture. The potential signal impairment in the beamforming network is analytically evaluated, being of special importance when MCF with a large number of cores is considered. Finally, the optimization of the proposed MCF-based beamforming network is addressed targeting the scalability to large arrays.

This paper introduces an application of the dandelion optimization (DO) algorithm in antenna arrays. This is the first time that the DO algorithm has been used for optimizing antenna arrays. For antenna array optimization, sidelobe level (SLL) and deep nulls are key technical indicators. A lower SLL can improve the signal-to-noise ratio and reduce the impact of clutter signals outside the main beam. Deep nulls need to be aligned with the direction of interference to eliminate the influence of interference sources. The combination of the two can effectively improve the anti-interference ability of the entire system. Therefore, antenna arrays with ultra-low sidelobes and ultra-deep nulls are currently hot in the field of antenna array design and are also some of the key technologies needed to achieve modern high-performance radar systems. As a new type of evolutionary algorithm inspired by nature, the DO algorithm is inspired by the wind propagation behavior of dandelions in nature. This algorithm iteratively updates the population from three stages of ascent, descent, and landing, ultimately finding the optimal position. It has good optimization ability in solving complex problems such as those involving nonlinearity, discreteness, and non-convexity, and the antenna array pattern synthesis optimization problem belongs to multivariate nonlinear problems. Therefore, the DO algorithm can be effectively applied in the field of antenna array optimization. In this work, we use the following method to obtain an optimized pattern of a linear array with the lowest sidelobe level (SLL), null placement in particular directions, and a lower notch in particular directions: by controlling the antenna array’s element spacing and leaving the phase unchanged to optimize the current amplitudes and by controlling the excitation current and phase fixation of the antenna array and changing the element spacing. In the first and second examples, different algorithms are used to reduce the SLL of the antenna. In the first example, the DO algorithm reduces the SLL to −33.37 dB, which is 2.67 dB, 2.67 dB, 3.77 dB, 2.74 dB, and 2.52 dB lower than five other algorithms. In the second example, the SLL optimized by the DO algorithm is −42.56 dB, which is 5.04 dB and 1.48 dB lower than two other algorithms. In both examples, the DO algorithm reduces the SLL lower than other algorithms when the main lobe of the antenna is not significantly widened. Examples 3, 4, and 5 use the DO algorithm to optimize the amplitude of the current, generating deep nulls and deep notches in specific directions. In Example 3, the DO algorithm obtains a depth of nulls equal to −187.6 dB, which is 66.7 dB and 44.3 dB lower than that of the flower pollination algorithm (FPA) and the chaotic colony predation algorithm (CCPA), respectively. In Example 4, the deep null obtained by the DO algorithm is as low as −98.69 dB, which is 6.67 dB lower than the deep null obtained by the grey wolf optimization (GWO) algorithm. In Example 5, the deep notch obtained by the DO algorithm is as low as −63.1 dB, which is 6.4 dB and 1.9 dB lower than the spider monkey optimization (SMO) algorithm and the grasshopper optimization algorithm (GOA), respectively. The data prove that the DO algorithm produces deeper nulls and notches than other algorithms. The last two examples involve reducing sidelobe levels and generating deep nulls by optimizing the spacing between elements. In Example 5, the SLL obtained using the DO algorithm is −22.8766 dB, which is 0.1998 dB lower than the lowest SLL of −22.6768 dB among other algorithms. In Example 6, the SLL obtained using the DO algorithm is −20.1012 dB, and the null depth is −125.1 dB, which is 1.592 dB lower than the SLL obtained by the cat swarm optimization (CSO) algorithm and 19.1 dB lower than the deep null obtained by the GWO algorithm, respectively. In summary, the results of six simulation experiments indicate that the DO algorithm has better optimization ability in linear array optimization than other evolutionary algorithms.

This paper proposes a high isolation of single pole double throw (SPDT) PIN diode switch using switchable dumbbell-shaped defected ground structure (DGS). The proposed SPDT switch was designed for radio frequency (RF) front-end transceiver of antenna array multiple input multiple output (MIMO) in millimeter wave 28 GHz band. The switchable dumbbell-shaped DGS can be switched between allpass and bandstop responses where the bandstop response of the DGS can be utilized as a high isolation in the SPDT PIN diode switch circuit. A simple mathematical analysis is explained in this paper for the bandstop and allpass responses of the switchable dumbbell-shaped DGS. The propose SPDT switch was designed based on Roger RT/Duroid 5880 with 0.254 mm thickness and relative dielectric constant of 2.2. The simulated result showed that the proposed SPDT PIN diode switch produced an isolation of 36.36 dB at 27.3 GHz (center of 28 GHz band), which was 63% higher than the conventional SPDT design.

This paper proposes a 2x4 microstrip antenna array for mono-pulse tracking radar in the S-Band. In the proposed design, a rat-race coupler is paired with a 2x4 patch antenna array at 3GHz. The feed is given to the sum and difference ports of the rat-race coupler to obtain the sum and difference patterns. The design aims to help in tracking. The tracking is done in one-dimensional space, and the design has limited elements with better efficiency. In the proposed design, the simulated and measured results have a return loss of at least - 10 dB at 3 GHz and the sum pattern has a main lobe and side lobe difference of at least 12 dB, while a null depth of at least 20 dB is achieved in the difference pattern. A gain of 17 dB has been noted. The simulation of this design was done on Ansys HFSS and MathWorks Antenna Toolbox softwares with an epsilon value of 2.2 of the Rogers RT 5880 substrate with a thickness of 1.6 mm. The design also contains chamfered elements to decrease the side lobe levels.

A beamforming network with flat-topped radiation patterns is proposed in this paper. The proposed network has two input ports and six output ports. It is designed based on matrix decomposition theory and combined with the optimization algorithm. The whole network consists of five directional couplers with unequal power division ratio and phase difference, which is orthogonal and lossless. When the proposed beamforming network is connected with a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1\times 6$</tex> antenna array, two flat-topped radiation patterns with symmetrical coverage can be obtained.

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.

In this article, a metasurface (MS) is placed as superstrate to counteract the effect of mutual coupling in linear antenna array in X-band. The metasurface is single layered and consist of single split ring resonator (SRR) and two I-shaped structures. The proposed metasurface can curb the interactions between adjacent antenna elements by collimating the electric field and reduce horizontal magnetic field interactions due to its negative refractive index and mu-near-zero property. The functioning of metasurface is tested by placing it above a 1×3 patch antenna. The experimental measurement shows an isolation below -25 dB in the 5.12% operational bandwidth with maximum isolation of -38.2 dB for an edge-to-edge distance of only 0.16λo. The active radiation pattern indicates an improved cross-polarization levels to below -30 dB, in both the orthogonal planes. The performance of MS is further tested for a 1×7 linear array where a 9.2 dB reduction in coupling value is observed. On placing the MS on the array there is no change in the operational bandwidth indicating that no modifications is needed in the antenna array geometry making it a preferable and easily transferrable solution to already existing antenna array.