Compact transmit receive hybrid electromagnetic isolation in antenna array transceiver system for full duplex applications

When array antennas are used for wide-frequency operation a difficulty with grating lobes is encountered at the upper frequency end of the operating band. This paper points out that the use of arrays for transmission and reception with different interelement spacings can be used to extend the operating frequency band in a radar system. The principle of transmitting-receiving arrays with different illuminations was used by Mattingly [2] to lower the sidelobe level of a radar array antenna. Birge [3] used it to reduce the number of elements in an array while preserving the resolution. The same principle is used in this paper to extend the operating frequency bandwidth of a radar antenna system. Relationships for an optimized radar array antenna system are derived. The criterion for optimization is the maximum bandwidth with a given total number of elements. It is shown that in an optimized system the number of elements in one array antenna is one greater than in the other, and the ratio of interelement spacings is inversely proportional to the square of the number of elements in the respective arrays. Based on these conditions, a function k is computed and tabulated. This function determines the number of grating lobes permissible in the specified angular sector, without overlap, as a function of the number of elements in the two arrays. An application to a high frequency (HF) ionospheric radar antenna system, now under construction, is used as an illustration of the principles outlined in the paper.

This paper deals with the synthesis of monopulse antenna patterns, sum and difference ones, for planar phased array antennas with an elliptical aperture boundary featuring unequal ultra-low peak sidelobe levels (PSLLs) for the two principal planes of its far field. The used synthesis method is the iterative Fourier transform (IFT) approach. The elliptical planar phased array antenna involved in this synthesis contains 3656 open-ended waveguide radiating elements arranged in a triangular element grid and has an aperture width and height of 50λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> and 25λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , respectively, where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength at X-band center frequency 1.0f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . The simulated monopulse pattern results will be compared with those of a 4680-element rectangular planar phased array antenna having the same width, height, radiator type and triangular grid as the elliptical array antenna. The monopulse patterns of the rectangular array antenna meet the same unequal ultra-low PSLL requirements as those of the elliptical array antenna. It will be shown that the elliptical array antenna with a slightly enlarged aperture containing 4170 elements features on receive comparable or even better far-field performance characteristics as that of the rectangular array antenna. All reported far-field pattern simulations take mutual coupling between the array elements into account.

This paper proposes EM mechanism to improve the isolation between transmitting and receiving array antennas using metamaterial EM band gap (MTM-EBG). The proposed mechanism can be applied to full-duplex array antenna system with very closely spaced arrays (0.33λ 0 ) with no degradation in radiation pattern. Using the proposed technique the isolation is shown to improve by >30 dB in an antenna array consisting of three-element microstrip patches designed to operate across 9.7 to 12.3 GHz. Parametric analysis was used to optimise the decoupling arrays performances. The proposed antenna array has physical dimensions of 65×22.5×1.6 mm3 and an electrical size of 2.16λ 0 ×0.75λ 0 ×0.053λ 0 , where λ 0 is free space-wavelength at mid-band of 10 GHz.

This paper presents rotational circularly polarized array antenna at 12 GHz. Array antenna degraded radiation performance because of mutual coupling between adjacent elements. General array antenna has same direction port each single elements. However, proposed rotational array antenna has different direction port to reduce the mutual coupling. As a results, mutual coupling of 2 by 2 rotational array reduce the about 10 dB compare with conventional array antenna. So proposed array antenna is better radiation performance than conventional; improve the realized gain, axial ratio, sidelobe level and efficiency.

In this paper, the novel hybrid enhanced particle swarm optimization and differential evolution (EPSO/DE) optimization technique [1–2] is used in designing different configurations of concentric circular arrays (CCAA) and concentric hexagonal arrays (CHAA). Many advantages were achieved by the rearrangement of the circular arrays (CA) and hexagonal arrays (HA) elements into CCAA and CHAA multi-ring geometries. Different configurations with two-rings, three-rings and four-rings are designed with the same number of elements and the same main beamwidth of the initial circular and helical geometries. The objective of this paper is to design optimum multi-ring antenna arrays that achieve minimum sidelobe level (SLL), high directivity and reduced mutual coupling in compare to traditional circular and helical arrays. Hybrid EPSO/DE algorithm is applied to optimize the complex weights (amplitude and phase) of the elements current. The objective is to minimize the SLL of the concentric configuration arrays while achieving the highest possible directivity and minimum mutual coupling.

Meteor radars have become common and important tools in the study of the climate and dynamics of the mesosphere/lower thermosphere (MLT) region. These systems depend on accurate angle‐of‐arrival measurements to locate the positions of meteor trails in the atmosphere. Mutual coupling between antennas, although small, produces a measurable error in the antenna pair phase differences used to deduce the angle of arrival of incident radiation. Measurements of the scattering parameter matrix for antennas in an interferometric meteor radar array have been made and applied to the existing angle‐of‐arrival calculation algorithm. The results indicate that mutual coupling of antennas in the array produces errors in the zenith angle estimate of less than ± 0.5°. This error is primarily in the form of a gradient across the field of view of the radar, which can be removed using existing phase calibration methods. The remaining error is small but will produce small systematic variations in the height estimates for detected meteors.

We propose an algorithm for creating a 3-D image of a planar interface with an array-type directional borehole radar. In this paper, we focus on the situation when the radar probe is close to the planar interface. In such circumstances, the reflected wave from the planar interface may be incident on the receiving array antenna at very steep elevation angles. This causes unusual arrival times of the wave at the array elements, and consequently some errors in imaging the planar interface. In our numerical simulation, the proposed algorithm generated a 3-D image of an interface around an exact position whereas a conventional method produced some spurious images opposite the correct position (i.e., off by 180 deg.). We then applied the proposed method to analyze reflected waves from a real-world fault in a rock. Using the proposed algorithm, we could successfully create a 3-D image of the fault, although this was not possible with the conventional method.

The synthesis of array antennas mounted on ships, or any other vehicular platform, is addressed here. Both the mutual coupling between the array elements, and their interaction with the mounting platform, are considered and introduced into the synthesis procedure. This is done by using a three-dimensional formulation of the method of moments, which models the currents induced on the platform and the antennas, combined with an optimization procedure. Some results are presented, illustrating the capability of the proposed synthesis method.

In this paper, we designed a rectangular patch single and array antenna by using CST software version 18.0. First, we used a copper as radiating patch and then the nanomaterial conductor like carbon nanotube (CNT) to improve the antenna performance. In both cases, the operating frequency is 2.4 GHz, which is used for many communication applications including Wi-Fi and Bluetooth. We have designed the four-element patch array antenna in two forms of arrangement (series and corporate feed). We used the substrate FR4 (its height=1.6 mm, Єr=4.3) and copper as the ground in all our designs. The return loss (s parameter) Always less than 10 dB the value of voltage standing wave ratio (VSWR) was close to the one in the designs. The highest directivity obtained from a patch array (1×4) antenna was 13.5 dBi when using carbon nanotube. Finally, we made a comparison of the analyzed results after simulation in a detailed table of the basic antenna properties, Including Return loss, VSWR, gain and directivity at the resonant frequency.

The principle of phased array microwave antennas can be applied at optical frequencies. The far-field antenna pattern is found by spatial Fourier transform of the optical field distribution across the subaperture plane. Inertia-free antenna pattern steering can be accomplished by proper phasing of the subaperture waves. A tolerance analysis shows that the required accuracy of phase relationship and subantenna alignment can be obtained in practice when implementing control loops. We develop schemes for both transmit and receive array antennas. Experiments carried out at (lambda) equals 1.06 micrometers demonstrated both modes of operation. Optical array antennas may be applied advantageously for fine pointing in intersatellite data links and in space lidar systems.

In this paper, a new array antenna configuration based on Electromagnetic Band Gap (EBG) structures has been proposed for 3.5GHz wireless communication systems. The proposed slotted EBG structure, high impedance surface (SHI), consists of three squares and a square ring deposited on a substrate (Rogers RO4350) which has a relative permittivity of 10.2 and a thickness of 1.27mm. Initially a matrix of 3×7 unit cells of EBG structures is introduced between two patches of an array and then a matrix of 3×14 unit cell of EBG structures is integrated between eight patches, which resonate around 3.5GHz (Wi MAX). The insertion of these structures between the radiating elements of an array antenna reduces the mutual coupling and antenna dimensions by approximately (8dB, 11%) and (12 dB, 5%) respectively for two, eight elements array antenna. In addition, the directivity has been slightly improved in the presence of EBG structures, from 4.52dB to 6.09dB for a two-element array antenna, and from 8.18dB to 8.4dB for an eight-element antenna.

In this paper we compare radiation patterns and mutual coupling in finite and infinite square lattice arrays of dielectric resonator antenna (DRA) elements. The array elements are cavity backed, slot fed cylindrical DRAs that utilizes the HE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11δ</sub> mode. It is observed that the degree of the mutual coupling for non-edge elements is very close to the mutual coupling between the corresponding elements in the infinite array. However, a large difference is observed in the mutual coupling between the center element and the two corner elements in the finite array with respect to the corresponding elements in the infinite array. The coupling is strongest in the E-plane and it is shown how it changes the embedded element patterns in the array.

A compact, low profile four-element helical array antenna is proposed and investigated in this article. This antenna comprises 4 turn helices. The single helical antenna and four-element array antenna are designed and simulated using ANSYS HFSS. A binary tree corporate feed network is used to distribute power equally among the antennas. The resonating frequency of the proposed antenna is 12GHz and can be used for high bandwidth and high gain applications. The results stipulate its advantages of high efficiency, high directivity, and a favorable axial ratio. The number of elements in the array was increased from 4 to 16 employing the sub-array technique and a comparison was done between this antenna and dish antenna which is generally used for satellite communication purposes.

Far-field pattern synthesis of small antenna arrays is a nontrivial problem. Typically radiation patterns are required to exhibit low sidelobe levels, whilst maintaining the ability to scan the main beam in space. Mutual coupling is a pertinent problem when the number of antenna elements is small, often precluding the use of conventional tapering algorithms. In this paper a technique previously employed to compensate for mutual coupling in linear arrays is extended to include small planar antenna arrays. The method consists of the calculation of the coupling coefficients between the array elements, which are then formed into a matrix and used to compensate for the effects of mutual coupling. It is then shown that this method is not suitable for all planar array configurations and a new technique is developed which allows the calculation of coupling matrices for these element configurations. Measured data from a small planar antenna array is presented, with the outlined methods employed to produce low sidelobe sum and difference beams.

To effectively find the direction of non-circular signals received by a uniform linear array (ULA) in the presence of non-negligible perturbations between array elements, i.e., mutual coupling, in colored noise, a direction of arrival (DOA) estimation approach in the context of high order statistics is proposed in this correspondence. Exploiting the non-circularity hidden behind a certain class of wireless communication signals to build up an augmented cumulant matrix, and carrying out a reformulation of the distorted steering vector to extract the angular information from the unknown mutual coupling, by exploiting the characteristic of mutual coupling, i.e., a limited operating range and an inverse relation of coupling effects to interspace, we develop a MUSIC-like estimator based on the rank-reduction (RARE) technique to directly determine directions of incident signals without mutual coupling compensation. Besides, we provide a solution to the problem of coherency between signals and mutual coupling between sensors co-existing, by selecting a middle sub-array to mitigate the undesirable effects and exploiting the rotation-invariant property to blindly separate the coherent signals into different groups to enhance the degrees of freedom. Compared with the existing robust DOA methods to the unknown mutual coupling under the framework of fourth-order cumulants (FOC), our work takes advantage of the larger virtual array and is able to resolve more signals due to greater degrees of freedom. Additionally, as the effective aperture is virtually extended, the developed estimator can achieve better performance under scenarios with high degree of mutual coupling between two sensors. Simulation results demonstrate the validity and efficiency of the proposed method.