Sum Patterns Research Articles

Two axis direction finding antenna system using sum–difference patterns in X band

ABSTRACTThis work proposes the direction finding antenna system in two axis (θ1, θ2) in X band using sum (Σ) and difference (Δ) patterns of received signal. Direction finding system is constructed by implementing the microstrip patch antenna array and 180° hybrid rat race ring coupler which generates Σ and Δ patterns of received RF signal. Initially, direction of arrival (DOA) is obtained in one axis, (θ1), vertical direction, using the Σ–Δ patterns of antenna array of two elements. Using the equations of Σ and Δ of two input signals, radiation patterns at different θ values have been observed in simulation and compared with measured pattern values of constructed circuit. By taking the ratio of Δ to Σ patterns, DOA has been estimated of designed circuit. Another circuit similar to first circuit, oriented at 90° (horizontal direction) has been implemented to estimate the DOA (θ2) in other axis. By taking the 3D radiation patterns of each circuit in anechoic chamber, both circuits are measured for performance; and from 0 to ±40°, DOA has been observed with rms error of less than 5° in both axis. At 10 GHz operating frequency, experimental results, using material RT Duroid 5880, show that satisfactory performance can be achieved with proposed setup. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2085–2092, 2015

An Epsilon-Near-Zero Total-Internal-Reflection Metamaterial Antenna

The total-internal-reflection (TIR) principle and the concept of an epsilon-near-zero (ENZ) material are combined to form an antenna exhibiting sum and difference patterns with good impedance properties. The ENZ material has been realized using a uniaxial wire medium (WM) metamaterial, and the departure from the behavior of an ideal ENZ material is discussed. The radiation pattern of the fabricated antennas has been measured and compared with simulation results.

Full polarimetric sum and difference patterns synthesis for conformal array

A convex optimisation-based full polarimetric sum and difference patterns synthesis method for a conformal array is proposed. The method adopts a manifold separation technique and a co-polarisation and cross-polarisation basis to model the conformal array response in a closed-form expression from array calibration measurements, and then formulates the full polarisation sum and difference patterns synthesis as convex optimisation problems. The method is applied to a simulated conformal spherical conformal array composed of 176 antenna elements; the low sidelobe and low cross-polarisation level sum and difference patterns are presented.

Optimal Synthesis of Reconfigurable Planar Arrays With Simplified Architectures for Monopulse Radar Applications

A new approach to the power synthesis of fixed-geometry reconfigurable planar arrays radiating sum and difference patterns is presented. The proposed design technique allows to maximize the radiation performance (field slope, amplitude, or even directivity) of both beam patterns over assigned directions subject to completely arbitrary masks for sidelobe bounds. Whatever the elements disposal and the array boundary, the overall problem is solved through a convex (quadratic) programming procedure. Moreover, if centrosymmetric antenna layouts are adopted, the synthesis is reduced to an even more powerful linear programming routine which preserves the solution uniqueness and optimality guaranteed by quadratic programming codes while dramatically decreasing their computational weight (and hence enabling the design of much larger planar arrays). The proposed approach also takes into account the need of reducing the complexity of the beam forming network (BFN), which is fulfilled by sharing part of the excitation amplitudes between the two radiation modalities. A set of numerical examples is reported and discussed to show the versatility and effectiveness of the proposed approach.

Reducing the Number of Elements in Phase-Only Reconfigurable Arrays Generating Sum and Difference Patterns

A new strategy for the synthesis of one-dimensional reconfigurable sparse arrays generating sum and difference power patterns is presented. In order to reduce the weight and complexity of the beam forming network, the design procedure provides solutions in which only one set of amplitude coefficients is required and just a π phase shift is needed for half array to switch between the two radiation modes. The synthesis is cast as the solution of a Linear Programming problem plus a local optimization procedure where the sparseness of the array layout is achieved by properly exploiting the principles of Compressive Sensing. Examples concerning the design of monopulse antennas show relevant savings of array elements with respect to conventional architectures.

Design of a Compact Circularly Polarized Dual-Mode Monopulse Cavity-Backed Substrate Integrated Waveguide Antenna

A novel compact dual-mode monopulse cavity-backed substrate integrated waveguide (SIW) antenna is proposed. The antenna consists of an array of two circular-polarized cavity-backed SIW antennas, a dual-mode section, and two input ports. ${\rm TE}_{10}$ and ${\rm TE}_{20}$ modes are excited in the multimode section to produce sum and difference pattern, respectively. A prototype of the proposed monopulse antenna at the center frequency of 10 GHz is manufactured. Measured results show 10-dB return-loss bandwidth of 4.4%, axial-ratio bandwidth of 1.9%, 9.2 dBi gain, and 25 dB null depth. The proposed antenna has good monopulse radiation characteristics and can be easily integrated with planar circuits.

A High-Linearity 76–85-GHz 16-Element 8-Transmit/8-Receive Phased-Array Chip With High Isolation and Flip-Chip Packaging

<?Pub Dtl=""?> An SiGe transmit–receive phased-array chip has been developed for automotive radar applications at 76–84 GHz. The chip is based on an all-RF beamforming approach and contains 8-transmit channels, 8-receive channels, and a complete built-in-self-test system. Two high-linearity quadrature mixers with an input <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$P_{1\,{\rm dB}}$</tex></formula> of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${+}{\hbox{2.5}}$</tex> </formula> dBm are used and allow simultaneous sum and difference patterns in the receive mode. The chip operates in either a narrowband frequency-modulated continuous-wave (FMCW) mode or a wideband mode with <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${&gt;} {\hbox{2}}$</tex></formula> -GHz bandwidth. A high-linearity design results in an input <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$P_{1\,{\rm dB}}$</tex></formula> of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${-}{\hbox{10}}$</tex> </formula> dBm (per channel), a system noise figure of 16–18 dB, and a transmit power is 4–5 dBm (per channel). The chip uses a controlled collapse chip connection (C4) bumping process and is flip-chipped on a low-cost printed-circuit board, and results in <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${&gt;} {\hbox{50}}$</tex></formula> -dB isolation between the transmit and receive chains. To our knowledge, this work represents the state-of-the-art in terms of complexity at millimeter-wave frequencies and with simultaneous transmit and receive operation for high-performance FMCW radars.

Pattern Synthesis of Sub-Arrayed Monopulse Planar Arrays

Synthesis of sum and difference patterns of a planar array is introduced in this article by means of a clustering algorithm. The whole array aperture is divided into several sub-arrays, which will reduce the cost and complexity of manufacturing the array antenna. The sub-array configurations and the corresponding sub-array weights are defined to minimize the maximum level of the side-lobes of the corresponding sum and difference patterns. Two kinds of arrays are considered here: in the first, the whole aperture is divided into several sub-arrays to get sum and difference patterns; in the other, the compromise difference pattern is obtained. Some numerical experiments are given to assess the feasibility and effectiveness of the proposed method.

Cluster Analysis for the Synthesis of Subarrayed Monopulse Antennas

The design of monopulse radar systems requires the synthesis of both a sum pattern and a difference pattern, which is quite flexible and hard to be optimized for subarrayed antennas. In this study, innovative approaches to synthesize the optimal sum and difference patterns independently for subarrayed monopulse arrays are presented. By exploiting the relationship of the subarray partition and optimal excitations, the synthesis problem is formulated as the clustering of a set induced by the optimal excitations. Thus, the optimal subarray partition is transformed to a clustering problem. A clustering method is presented to solve the array synthesis with uniform excitation at element level. Furthermore, an improved approach is proposed to synthesize low sidelobe patterns. When compared with several classical approaches, various numerical experiments validate the effectiveness and potentiality of the proposed methods.

Studies on Difference Patterns from Cosecant Patterns

Array antennas are popular in radar and communication applications. It is possible to control the pattern characteristics from array antennas very effectively and easily. Array designers used different techniques to produce narrow beams. But it is essential to produce not only narrow beams but also other beam shapes like Square and Cosecant beams. These shaped beams are extremely useful in search, track radars and also for ground mapping. The difference patterns are often produced from sum patterns with additional phase, but in the case of marine radars either sum or difference patterns are asymmetrical in their sidelobe structure. In view of the above facts intensive investigations are carried out in the present work to generate asymmetrical difference patterns form Cosecant patterns with Fourier series, Fourier Transform and Woodward-Lawson methodologies.

Compact Low Weight High Gain Broadband Antenna by Polarization-Rotation Technique for X-Band Radar

Less efficiency and gain is achieved by existence of aperture blocking phenomena in cassegrain antenna caused by the presence of subreflector or antenna feed. Also, length of feed cables causes delay which is another undesirable problem in antennas, since errors and less precision of detecting targets are created. To overcome these problems, low weight and compact optimized polarization-rotation monopulse cassegrain antenna is designed in this paper. The goal of our proposed rotating antenna is achievement of sum and difference patterns for target tracking in monopulse radar. In our work, left part of hyperbolic subreflector instead of right one has been used for reducing size of the antenna. The antenna is fabricated by grid wires instead of solid sheet metal reflectors and with composite technology for decreasing its weight. Width and volume of the antenna reduce by about 50% in comparison to other reflector antennas. This antenna has been simulated and manufactured in X-band and simulation data are in good agreement with measured ones. The antenna has the average gain of 35 dB from 8.5 up to 9.5 GHz. Also the antenna feed bandwidth is more than 50% and the antenna has efficiency of about 50% from 8 up to 10 GHz.

Direction Finding Using Multiple Sum and Difference Patterns in 4D Antenna Arrays

Traditional monopulse systems used for direction finding usually face the contradiction between high angle precision and wide angle-searching field, and a compromise has to be made. In this paper, the time modulation technique in four-dimensional (4D) antenna array is introduced into the conventional phase-comparison monopulse to form a novel direction-finding system, in which both high angle resolution and wide field-of-view are realized. The full 4D array is divided into two subarrays and the differential evolution (DE) algorithm is used to optimize the time sequence of each subarray to generate multibeams at the center frequency and low sidebands. Then the multibeams of the two subarrays are phase-compared with each other and multiple pairs of sum-difference beams are formed at different sidebands and point to different spatial angles. The proposed direction-finding system covers a large field-of-view of up to ±60° and simultaneously maintains the advantages of monopulse systems, such as high angle precision and low computation complexity. Theoretical analysis and experimental results validate the effectiveness of the proposed system.

SIW-Fed Yagi Antenna and Its Application on Monopulse Antenna

Planar Yagi antennas are commonly hard to possess simple structure, high gain, and broad bandwidth at the same time. In this letter, a new substrate integrated waveguide (SIW)-fed Yagi antenna is proposed with nonplanar director element, and it achieves bandwidth of 25.7% and gain of 9.46 dBi at 10.0 GHz. Integrated of an SIW hybrid ring coupler, a Yagi monopulse antenna is designed. Measured gain of the sum pattern is higher than 13 dBi, whereas the maximum null depth of the difference pattern is lower than ${-}$ 20 dB in 9.4–10.05 GHz. This type of monopulse antenna presents an excellent candidate in directional-finding system.

Ka-Band Slot-Microstrip-Covered and Waveguide-Cavity-Backed Monopulse Antenna Array

A slot-microstrip-covered and waveguide-cavity-backed monopulse antenna array is proposed for high-resolution tracking applications at Ka-band. The monopulse antenna array is designed with a microstrip with2×32slots, a waveguide cavity, and a waveguide monopulse comparator, to make the structure simple, reduce the feeding network loss, and increase the frequency bandwidth. The2×32slot-microstrip elements are formed by a metal clad dielectric substrate and slots etched in the metal using the standard printed circuit board (PCB) process with dimensions of 230 mm × 10 mm. The proposed monopulse antenna array not only maintains the advantages of the traditional waveguide slot antenna array, but also has the characteristics of wide bandwidth, high consistence, easy of fabrication, and low cost. From the measured results, it exhibits good monopulse characteristics, including the following: the maximum gains of sum pattern are greater than 24 dB, the 3 dB beamwidth of sum pattern is about 2.2 degrees, the sidelobe levels of the sum pattern are less than −18 dB, and the null depths of the difference pattern are less than −25 dB within the operating bandwidth between 33.65 GHz and 34.35 GHz for VSWR ≤ 2.

Optimal polarised pattern synthesis of wideband arrays via convex optimisation

The digital wideband arrays with data converters and digital signal processing capability permit greater flexibility in the pattern synthesis than conventional time-delay steered wideband arrays, which provides an opportunity to solve the polarised pattern synthesis of wideband arrays by using numerical optimisation algorithms. A finite-impulse response (FIR) filter is placed at each element to directly optimise the synthesised polarisation and wideband power patterns. Both the optimisations of the sum and difference patterns are formulated as convex programming problems to obtain efficient solutions. The proposed synthesis method, which has no special requirement on the array geometry and element pattern, is flexible and applicable to arbitrary arrays. By optimising the complex coefficients of FIR filters, any state of polarisation can be synthesised in a given angle-frequency space with frequency-invariant main beams and arbitrary sidelobe upper bounds. Various design examples are presented to testify the potentiality of the proposed method.

Optimized hyper beamforming of receiving linear antenna arrays using Firefly algorithm

In this paper, an optimized hyper beamforming method is presented based on a hyper beam exponent parameter for receiving linear antenna arrays using a new meta-heuristic search method based on the Firefly algorithm (FFA). A hyper beam is derived from the sum and difference beam patterns of the array, each raised to the power of a hyper beam exponent parameter. As compared to the conventional hyper beamforming of the linear antenna array, FFA applied to the hyper beam of the same array can achieve much more reduction in sidelobe level (SLL) and improved first null beam width (FNBW), keeping the same value of the hyper beam exponent. As compared to the uniformly excited linear antenna array with inter-element spacing of λ/2, conventional non-optimized hyper beamforming and optimal hyper beamforming of the same obtained by real-coded genetic algorithm, particle swarm optimization and Differential evolution, FFA applied to the hyper beam of the same array can achieve much greater reduction in SLL and same or less FNBW, keeping the same value of the hyper beam exponent parameter. The whole experiment has been performed for 10-, 14-, and 20-element linear antenna arrays.

Reconfigurable sum–difference pattern by means of parasitic elements for forward‐looking monopulse radar

This study describes the design of forward-looking monopulse arrays able to reconfigure the radiation pattern from the sum mode to the difference one by electronically switching a set of parasitic dipoles placed in front of a driven array of radiating dipoles. The antenna architecture is synthesised by optimising the geometric parameters of the passive elements, namely their positions and lengths. The generation of the difference beam is yielded by imposing a phase displacement of π to the excitations of half active array and activating the parasitic array by turning-on the switches that partition their lengths. As for the sum pattern, the effect of the parasitic dipoles is made negligible by turning-off the switches. A set of representative results is reported and discussed to show the effectiveness of the proposed approach.

탐색레이더용 피아식별안테나 후방 방사 수준 개선에 관한 연구

In this paper, we described the study on back-radiation level improvement of IFF antenna after briefly describing a design of IFF antenna to distinguish the target as the sub-antenna of surveillance radar. The proposed IFF antenna was minimized a size with use all-in-one power divider as a two-channel IFF antenna forming sum and difference pattern. The method for back-radiation level reduction was studied, and the identified method through the simulation confirmed the decrement throught the measurement.

AN ALTERNATIVE METHOD FOR DIFFERENCE PATTERN FORMATION IN MONOPULSE ANTENNA

Difierence patterns are vital for the successful function of tracking radar employing monopulse techniques to estimate target direction. Traditional monopulse antenna pattern synthesis methods require the use of two independent distributions, e.g., Taylor and Bayliss distributions, for formation of sum and difierence patterns for one antenna. Hence, these approaches require a feed network of considerable complexity. In this letter, a method for forming difierence pattern in linear arrays using a very simple beamforming network and two additional elements is described. The sum pattern is determined by adding signals received by original radiating elements of the array whereas the difierence pattern is determined by subtracting the output of the sum pattern from signals received from two external edge elements. The proposed method used to generate these two patterns ofiers signiflcant hardware and software savings over current methods.

Synthesis of Optimized Asymmetrical Sum Patterns Using Conventional Method

Sum patterns find applications in Radar for searching and ranging of the targets. A sum pattern with low sidelobe level is a desirable feature in these applications, in order to reduce EMI problems. Sum patterns with Asymmetrical sidelobe topography are considered, in applications where only certain angular regions of pattern are required to have low sidelobe level. Asymmetrical pattern characteristics can have lower beam widths for given design specifications as compared to symmetrical patterns. In view of this, a conventional method of synthesis is carried out in this paper, to produce asymmetrical sidelobe level patterns using discrete arrays. The effect of beam scanning on the pattern behavior is also analyzed for the above synthesized patterns.