Sum Patterns Research Articles

Neural networks for rapid phase quantification of cultural heritage X-ray powder diffraction data

Recent developments in synchrotron radiation facilities have increased the amount of data generated during acquisitions considerably, requiring fast and efficient data processing techniques. Here, the application of dense neural networks (DNNs) to data treatment of X-ray diffraction computed tomography (XRD-CT) experiments is presented. Processing involves mapping the phases in a tomographic slice by predicting the phase fraction in each individual pixel. DNNs were trained on sets of calculated XRD patterns generated using a Python algorithm developed in-house. An initial Rietveld refinement of the tomographic slice sum pattern provides additional information (peak widths and integrated intensities for each phase) to improve the generation of simulated patterns and make them closer to real data. A grid search was used to optimize the network architecture and demonstrated that a single fully connected dense layer was sufficient to accurately determine phase proportions. This DNN was used on the XRD-CT acquisition of a mock-up and a historical sample of highly heterogeneous multi-layered decoration of a late medieval statue, called `applied brocade'. The phase maps predicted by the DNN were in good agreement with other methods, such as non-negative matrix factorization and serial Rietveld refinements performed with TOPAS, and outperformed them in terms of speed and efficiency. The method was evaluated by regenerating experimental patterns from predictions and using the R-weighted profile as the agreement factor. This assessment allowed us to confirm the accuracy of the results.

On Difference Pattern Synthesis for Spherical Sensor Arrays.

An innovative method for synthesizing optimum difference patterns of the spherical sensor array is introduced, along with a sidelobe tapering technique. Firstly, we suggest employing the spherical harmonics of degree ±1 to synthesize the spherical array difference pattern; secondly, we study the mapping relationship between the difference pattern of the spherical sensor array and the difference pattern of the uniformly spaced linear array (ULA) with odd-numbered elements; finally, we enhance the Zolotarev difference pattern, which is a counterpart to the Dolph-Chebyshev sum pattern that traditionally allows synthesis only for ULA with even-numbered elements. Our modification extends its applicability to synthesize difference patterns for ULA with odd-numbered elements. Leveraging the optimal difference pattern, a generalized Bayliss difference pattern synthesis method designed for the ULA with odd-numbered elements is further proposed. To illustrate the effectiveness of our approach, we present several design examples through experimental simulation.

High‐gain tapered monopulse antenna based on octuple excitation method in diffusion bonding technology at W‐band

AbstractThe authors present the design, fabrication and testing of a W‐band monopulse antenna. This antenna consists of three main building blocks: an array with 48 × 48 slots, a tapered corporate‐feed network and a comparator. The comparator has four input ports to generate sum and difference patterns in orthogonal cardinal planes for monopulse operation. A novel octuple excitation is adopted for the corporate network to achieve a side lobe level lower than −20 dB for the sum patterns and simultaneously reduce drastically the manufacturing complexity. Diffusion bonding technology is used for fabrication. Twenty‐four etched copper sheets with a thickness of 0.2 mm are stacked to realise the prototype. The total size of the antenna is , with λ0 being the wavelength at the centre frequency (94 GHz). The antenna presents an isolation better than 12 dB among the input ports in the 84–100 GHz band. The realised measured gain is 40.7 dBi at 94 GHz. The measured 3‐dB gain bandwidth is 17.4%. The difference patterns at 94.0 GHz present null depths of −24.0, −18.0, −17.5, and −17.4 dB, in the E‐, H‐, 45°‐, and 135°‐planes, respectively.

W‐band multimode monopulse horn feed for reflector antenna

AbstractThis letter proposes a W‐band multimode monopulse horn (MMH) feed to improve the total efficiency (TE) of the reflector antenna. The feed consists of a MMH and a single‐layer comparator. The MMH utilizes one pyramidal horn and four rectangular waveguides (RWGs) for feeding. The eight electric modes required in the MMH yield excellent sum and difference patterns. The impact of unwanted modes is suppressed using a 90° phase difference approach. The comparator contains four novel 3 dB couplers and E‐plane RWGs, providing low loss and high multiport transmission performance. The MMH feed has been fabricated, tested, and applied to a Cassegrain antenna. The measured maximal TE for the Cassegrain antenna between 90 and 97 GHz is 54.9%. The realized gain of the sum beam is 40.3 dBi at 93.5 GHz. The null depths of difference beams in the azimuth and elevation planes are about −37.7 and −29.1 dB, respectively.

A Study of Direction-of-Arrival Estimation with an Improved Monopulse Ratio Curve Using Beamforming for an Active Phased Array Antenna System

When constructing a wireless communication network, the line of sight of radio waves is limited by the terrain features in a ground communication network. Also, satellite communication networks face capacity limitations and are vulnerable to jamming. Aviation communication networks can solve the above-mentioned problems. To construct seamless aviation communication networks, fast counterpart location estimation and efficient beam steering performance are essential. Among various techniques used for searching the counterpart’s location, the monopulse technique has the advantage of quickly estimating the location through a simplified procedure. However, the nonlinear characteristics of the monopulse ratio curve, which are inevitably caused by the general antenna beam shape, both limit the location estimation range and reduce the estimated location accuracy. To overcome these limitations, a method that improves the estimation accuracy and extends the range by correcting the sum and difference patterns using the beamforming technique of active phased array antennas was proposed. An antenna system model suitable for aviation communication networks was presented, and the proposed model was experimentally proven to be effective. An average angle error of 0.021° was observed in the estimation of the accuracy of the antenna location.

Synthesis of Annular Sum and Difference Patterns Produced by Array-Fed Ring-Focus Reflector

Synthesis of Annular Sum and Difference Patterns Produced by Array-Fed Ring-Focus Reflector

Sum and difference patterns synthesis with common excitation amplitude

This paper focuses on the joint optimization problem of sum and difference patterns with common excitation amplitudes and separate excitation phases. The objective is to reduce the complexity of the antenna system while still maintaining a certain degree-of-freedom (DoF) in synthesizing dual-patterns. The problem is formulated with angular response and common excitation amplitude constraints, making it a nonconvex optimization problem. To address this, we introduce two groups of auxiliary variables to decouple the excitation vector from the complex nonconvex constraints. This allows the original problem to be effectively solved via alternately determining the closed-form solutions for several single-variable optimization subproblems. Additionally, our approach is extended to scenarios involving dynamic range ratio (DRR) reduction, aiming to lower the cost and difficulty of hardware implementation. Theoretical analysis and simulation results are provided to demonstrate that the proposed algorithm can converge to the Karush-Kuhn-Tucker points of the original problem. It is also observed that our approach is capable of generating desired dual-patterns with common excitation amplitudes, regardless of the presence or absence of DRR control.

Dual-Mode Conical Horn Antenna with 2-D Azimuthal Monopulse Pattern for Millimeter-Wave Applications.

In this paper, a novel concept of a three-dimensional full metal system including a Dual-Mode Converter (DMC) network integrated with a high-gain Conical Horn Antenna (CHA) is presented. This system is designed for 5G millimeter wave applications requiring monopulse operation at K-band (37.5-39 GHz). The DMC integrates two mode converters. They excite either the TE11cir or the TE01cir modes of the circular waveguide of the CHA. The input of the mode converters is the TE10rec mode of two independent WR-28 standard rectangular waveguide ports. By integrating the DMC with the CHA, the whole system, called a Dual-Mode Conical Horn Antenna (DM-CHA), is formed, radiating the sum (Σ) and difference (Δ) patterns associated to the monopulse operation. To adequately prevent the propagation of higher order modes and mode mutual coupling, this integration procedure is carefully designed and fabricated. To prove the performance of the design, the DMC network was fabricated using subtractive manufacturing by Computer Numerical Control (CNC) technology. The CHA was fabricated using additive manufacturing by Direct Metal Laser Sintering (DLMS) technology. Finally, the simulation and measurement results were exhaustively compared, including return loss, isolation, radiation pattern, and gain of the full DM-CHA structure. It is noteworthy that this system provided up to ±11° per beam in the angular of arrival detection to support the high data rate operation for 5G satellite communications in the millimeter-wave band.

Design of a Broadband Comparator Network at $X$-Band

This paper presents a novel broadband comparator network design operating at X-band. A multilayer aperture coupling scheme and shielding around the microstrip structures are utilized to achieve broadband performance. There are two main building blocks of the proposed comparator network. These are a quadrature hybrid coupler and a 90-degree phase shifter. These two main components are designed to have broadband performance so that the designed comparator would also have wideband performance. The proposed quadrature hybrid coupler achieves more than 19.7 dB return loss, a 0.75 dB amplitude imbalance, and 1.4 ° phase imbalance along the frequency band 5 GHz to 10 GHz. The 90-deg. phase shifter has less than -10 dB S11 in addition to having less than 1.6 °. phase error and 1.5 dB insertion loss within the frequency band 5 GHz to 9.9 GHz. The proposed comparator is acquired by combining the multiple quadrature hybrid couplers and phase shifters. The results of the manufactured and simulated comparator agree well with each other. The impedance bandwidth (VSWR<2) of the manufactured comparator is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> 61 and operates from 5.26 GHz to 9.9 GHz. An 8x8 microstrip patch antenna array is designed and manufactured to verify the comparator network's sum and diff pattern forming capability. The far-field measurements of the proposed comparator combined with the 8x8 antenna array indicate that 36 dB null depth is acquired at the azimuth plane, and 40 dB null depth is achieved at the elevation plane.

A Wideband 1-bit Reconfigurable Electromagnetic Surface for Monopulse Radar Applications

We present a wideband 1-bit reconfigurable electromagnetic surface (REMS) for monopulse radar applications at X-band. The proposed REMS element integrates a 1-bit reflection-type phase shifter controlled by a PIN diode. By altering the working states of the PIN diode, well-defined beam scanning is obtained. Furthermore, selecting different feeding states can realize the sum (Σ) and difference (Δ) patterns. The key design issues, including element modeling, coding design, and feed optimization, are studied to obtain good Σ and Δ beam performance. Experimental results show that REMS achieves a high gain of 23.3 dBi, a low sidelobe level of -15 dB, and a low null depth of -30 dB. The wide-angle monopulse beam-scanning up to ±60° is obtained. The gain bandwidth of -3 dB ranges from 9.35 to 11.75 GHz, with a relative bandwidth of 22.75%. Thus, the proposed multi-feed REMS brings new freedom for the Σ and Δ beam scanning, which provides wide application prospects for the monopulse radar system.

Analysis of On-Antenna Power Combining for Realization of Pattern-Reconfigurable Multifeed Microstrip Antennas

This article explores an on-antenna power combining concept for multifeed microstrip antennas. We incorporated different radiation modes of multifeed antennas, thereby optimally exploiting the given space of a single radiator. The analytical cavity model is revisited to facilitate analysis of the on-antenna power combining mechanism in planar topologies. The analytical modeling is first aimed to apply to conventional patch structures and offers an in-depth design methodology. As the analytical method is facing limitations in irregular-shaped antennas we proposed a reliable and computationally cheap numerical method based on the eigenvalue analysis of the scattering matrix. The proposed method can be used to extract the optimum excitation and impedance of each port of resonant-type multifeed antennas. Due to the proposed numerical method, one can examine the excitation vector and the active impedance values for different radiation modes of multifeed antenna concurrently. Next, the reliability of the solutions of the proposed numerical method is evaluated against the analytical solutions through some examples. A multifeed structure not only can furnish on-antenna power combining but also assist with tailoring reconfigurable antennas. Finally, a practical planar radiator topology featuring multifeed excitations exhibiting a high-gain reconfigurable antenna with sum and difference patterns is devised.

Array Design Using Genetic Algorithm for the Generation of Sum and Difference Patterns

In the field of pattern synthesis, the design of arrays to synthesis optimized sum and difference patterns in a successive manner is an important problem in most of the radars. Although several researchers published many papers in the open literature, investigations are made by the authors to design arrays of discrete radiators using a well-formulated Genetic Algorithm (GA). The practical constraints are taken into account to design an amplitude distribution to produce the sum pattern with desired side lobe levels without broadening the main beam. Such sum patterns are found to be very useful in high-resolution radars where the EMI problems are also addressed. In IFF radars, both sum and difference patterns are extremely useful to distinguish between friendly aircraft and enemy aircraft. Such patterns are conventionally produced involving two antennas. One is a directional antenna and another is an omnidirectional antenna. However, in the present work, they are generated using only one directional antenna. The patterns with a deep null in the boresight direction and difference lobes with a high slope are produced with an antiphase excitation to one-half of the array.

Conceptual Design of a Semi-Dual Polarized Monopulse Antenna by Computer Simulation

Presented in this paper is a conceptual design by computer simulation of a monopulse reflector antenna with dual-circularly polarized sum patterns and linearly polarized azimuth and elevation difference patterns, which can be called a semi-dual polarized antenna. The proposed antenna consists of a five-element monopulse feed and a prime-focus parabolic reflector. The novelty of the proposed antenna is a monopulse feed consisting of a dual-circularly polarized square waveguide sum channel radiator and linearly polarized rectangular waveguide azimuth and elevation difference channel radiators. The separation of dual circular polarization is realized by a septum polarizer. The difference pattern is obtained by feeding two rectangular waveguides in opposite directions using a coaxial probe. The proposed monopulse feed geometry requires only two power combiners for a monopulse comparator network while providing dual-polarized performance comparable to the full dual-polarized sum and difference channel monopulse scheme. The concept of the proposed antenna is shown in a conceptual design by computer simulation. The monopulse feed is designed first, and then combined with a parabolic reflector. The designed monopulse reflector antenna operates at 14.5–16.0 GHz, and shows excellent sum and difference pattern characteristics: 36.1–36.7 dBc sum channel directivity with 0.65 dB boresight axial ratio and 32.6–32.9 dBi difference channel directivity with 1.56–1.66° crossover angle.

A monopulse array antenna based on SIW with circular polarization for using in tracking systems

In this paper, a monopulse slot array antenna with substrate integrated waveguide (SIW) has been designed and fabricated for application in tracking systems. This antenna has circular polarization and has a very simple design. For increasing the efficiency of the antenna and maintaining its one-layer structure, this design utilizes two modes (TE120, TE210) to excite the slots rather than the complex feed network commonly used in monopulse antennas. The feeding ports are well-isolated due to the orthogonality of the two modes. The feeding cavity is operated in these two modes to obtain the difference and sum patterns. The proposed antenna at the center frequency of 10 GHz has an impedance bandwidth of 200 MHz, and the reflection coefficient in this bandwidth is less than −10 dB. The zero depth of the difference pattern is less than −24 dBi, while the obtained gain of the sum pattern is 13.6 dBi. The polarization axial ratio is less than 3 dB in the range of 9.98–10.02 GHz. Also, the antenna aperture efficiency is 50 % at the desired frequency.

UWB full polarization single-plane monopulse reflector antenna

ABSTRACT UWB dual polarization azimuth plane monopulse feed-reflector antenna is presented. Quadridge ‎open ended waveguide working in frequency range from 6 to 12 GHz is proposed as feed for Cassegrain ‎reflector. The feed phase center distance is 0.65 and 1.3 at lowest and highest operating ‎frequency respectively. Sum (Σ) and Diff (Δ) radiation pattern of the feed array are measured in ‎anechoic chamber using same electrical length coaxial cable and 180°Coupler. The results are in good ‎agreement (vertical and horizontal polarizations) with numerical simulation especially for the main ‎beam. To enhance gain value, 50 cm reflector antenna has been used. A proper crossover is achieved ‎by controlling F/D ratio of the equivalent reflector. A compact Cassegrain reflector compatible to feed ‎array is designed and fabricated. The radiation characteristics measurements of the feed-reflector ‎system have been performed using outdoor measurement setup. By ignoring coupler insertion loss, ‎Sum (Diff) gain range is between 24.8 (17) dBi at 6 GHz and 31.7 (29.5) dBi at 12 GHz. Cross pol and null ‎depth better than −31.5 and −24 have been obtained. ‎

Polarization Diversity Controllable Monopulse Antenna Array Design

The design of a compact and wideband circularly polarized (CP) Monopulse antenna is presented. Firstly, the small-sized antenna element (13mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times13$ </tex-math></inline-formula> mm), with the impedance bandwidth (BW) of 80.5% (4.3-10.1 GHz) and axial ratio (AR) bandwidth of 48.1% (6-9.8 GHz), and the gain of 7.2 dBic is designed. The array structure consists of two rat-race couplers; two metalized via holes that generate sum and difference patterns, and four branch-line couplers for CP characteristic improvement. The proposed antenna is capable of controlling CP diversity in both sum and difference beams. Additionally, with 50% BW and 25% 3-dB AR results and also with null-depth of less than −48 dB, it is a convenient design for tracking purposes.

Wideband band-notched monopulse antenna design utilizing differential mode and common mode radiations

This letter proposes a dual-port wideband monopulse Vivaldi antenna based on a new perspective of common mode and differential mode radiations. To realize the sum and difference patterns utilizing the differential and common mode radiations, a metallic wedge is introduced in the center of the Vivaldi antenna, the effect of the virtual magnetic wall disappears, and the realistic electric wall plays the dominant role, fulfilling the boundary condition for difference beam under common mode excitation. Meanwhile, the sum beam is kept unchanged under differential mode excitation. The desired sum and difference radiation patterns are realized in a single Vivaldi antenna under differential mode and common mode excitations, respectively. Moreover, a notched band is introduced for interference suppression, and the notched frequency can be easily controlled by adjusting the microstrip feeding stub without loading an extra resonator. Measured results show that the proposed monopulse antenna exhibits 101 % fractional bandwidth from 2.2 GHz to 6.7 GHz, in which a notched band is from 3.75 GHz to 4.3 GHz. Across the operational band, the average gain of the sum pattern is 8 dBi, and the null depth of the difference pattern is below −15 dB. Measured results agree well with the simulated ones.

High Gain Monopulse Variable Inclination Continuous Transverse Stub Antenna for Satellite-Aided Vehicular Communications

This article presents a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> -band high gain monopulse variable inclination continuous transverse stub (VICTS) antenna for satellite-aided vehicular communications. The radiating part is divided into four regions and fed by an air-filled single-layer E-plane waveguide comparator cascaded with two groups of mirror-symmetric multiple-port excited linear source generators (LSGs). Two waveguide delay lines are carefully designed to compensate the phase difference between the adjacent radiating regions in the desired frequency band. Combined with the nonuniform slow-wave structure underneath the radiating slots, excitation signal with uniform phase distribution can be obtained, and then, the sum and difference patterns can be produced by using the comparator. For verification, a prototype operating at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K$ </tex-math></inline-formula> -band is designed and demonstrated. The experimental results show that the reflection coefficients for the sum and difference patterns are all lower than −10 dB within the frequency range of 19–21 GHz. The gain drop of the sum pattern is less than 5.7 dB within the beam scanning range of −1° to −62° at 21 GHz, while the amplitude imbalance and null depth of difference patterns are less than 4.5 and −20.6 dB, respectively. The proposed antenna can be a potential candidate for the future Internet of Vehicles.

Single-Layer 2-D SIW monopulse slot antenna array with dual-mode comparator

A single-layer 2-D substrate integrated waveguide (SIW) monopulse slot antenna is proposed in this paper. By adopting the dual-mode monopulse comparators (DMCs), the feeding network exhibited excellent amplitude-phase consistency and high isolations between input ports. Additionally, the structure of the proposed antenna is effectively simplified by integrating the feeding network with the radiation part on a single-layer substrate. Based on it, a monopulse antenna prototype is fabricated and measured. The measured results show that the −10 dB shared impedance bandwidth of 4 ports is 2.05 % (9.65–9.85 GHz) and the isolations between ports are better than 25 dB. The measured gain of the sum pattern is 13.93 dBi at 9.75 GHz, and the null depths of the difference patterns are lower than −30 dB.

Location Based Services for Remote Education and Health Institutes Using Sum-Difference Signal Patterns

This paper presents a simple approach to providing location-based services (LBSs) for the remotely located educational and health institutes on demand, particularly in emergency situations i.e., COVID-19, using an antenna array. The proposed approach consists of the sum and difference patterns of the signal obtained from the antenna array at the base station of a wireless network. It provides the location of the targeting institute i.e., education and health, in terms of the angle-of-arrival (AoA) which can be used to steer the radiation beam in the targeted direction in order to provide the desired services i.e., emergency wireless communication link. In this way, fast and high bandwidth-based communication and networking can be possible for the mentioned organizations. We show antenna array design and location finding results in this paper. The obtained results in terms of antenna parameters and AoA show that the proposed approach is efficient, less complicated, and can be implemented in the next-generation wireless networks i.e., AI-enabled IoT and 5G systems, particularly for the educational and health institutes.