Design of Vivaldi array antenna with low sidelobe for Monopulse tracking application

In this paper, the spoof surface plasmon polaritons (SSPPs) transmission line (TL) of periodical grooved bow-tie cells is proposed. The complex propagation constant and characteristic impedance of the SSPPs TLs and microstrip lines (MLs) are extracted using the analytical method of generalized lossy TL theory. The properties of the SSPPs TLs with different substrates and the same geometrical configuration are experimented. Then, for comparison, two ML counterparts are also experimented, which shows that the SSPPs TL is less sensitive to the thickness, dielectric constant and loss tangent of the chosen substrate below the cutoff frequency, compared with the ML ones. The single-conductor co-planar quasi-symmetry unequal power divider based on this SSPPs TL is presented in microwave frequencies. For experimental validation, the 0-dB, 2-dB, and 5-dB power dividers are designed, fabricated, and measured. Both simulated and measured results verify that the unequal power divider is a flexible option, which offers massive advantages including single-conductor co-planar quasi-symmetry structures, wide-band operation, and convenient implementations of different power-dividing ratios. Hence, it can be expected that the proposed unequal power dividers will inspire further researches on SSPPs for future design of novel planar passive and active microwave components, circuits and systems.

Abstrct A novel coupled-line impedance-transforming structure with two parallel short-circuit stubs is proposed to design a wideband branch-line coupler with arbitrary power division in this article. In order to design this modified wideband branch-line coupler, analytical synthesis equations are obtained. As typical examples, four wideband branch-line couplers with different power dividing ratios are presented. The widest 20-dB return loss and isolation fractional bandwidth in these four numerical examples is almost 38%. Finally, two microstrip branch-line couplers operating at 1 GHz are fabricated and measured. One of these couplers has equal power division and a measured 13.9-dB return loss and isolation fractional bandwidth of 32.8%. The other one has 3-dB unequal power division and a measured 12.7-dB return loss and isolation fractional bandwidth of 37.6%. Obviously, this proposed branch-line coupler has several advantages, including a wide band, a compact size, an unequal power division, easy implementation (simple structure), and an analytical design method.

Two sequentially rotated, four stage, wideband circularly polarized high gain microstrip patch array antennas at Ku-band are investigated and compared by incorporating both unequal and equal power division based feeding networks. Four stages of sequential rotation is used to create 16×16 patch array which provides wider common bandwidth between the impedance matching (S 11 < −10dB), 3dB axial ratio and 3dB gain of 12.3% for the equal power divider based feed array and 13.2% for the unequal power divider based feed array in addition to high polarization purity. The high peak gain of 28.5dBic is obtained for the unequal power division feed based array antennas compared to 26.8dBic peak gain in the case of the equal power division based feed array antennas. The additional comparison between two feed networks based arrays reveals that the unequal power divider based array antennas provide better array characteristics than the equal power divider based feed array antennas.

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.

In traditional aerospace telemetry receiving systems, parabolic directional antenna or flat array antenna is generally adopted in the ground telemetry receiving antenna. The antenna array is synthesized into a fixed beam, tracking the target by mechanical scanning. When tracking multi-target is required, it is necessary to deploy multiple ground telemetry antennas to track their respective targets, i.e. one set of antennas tracks one target. Phased arrays antenna is an antenna system and technology developed on the basis of array antenna. Its antenna elements are synthesized into multiple independent beams, which can track one target at the same time, or track each target separately with different beams, so as to achieve the multi-target telemetry and tracking receiving function with a set of phased array antenna. The antenna array element is synthesized into multiple independent beams. This paper mainly discusses an implementation method of multi-target telemetry receiving antenna based on phased arrays technology.

This study presents a hybrid electromagnetic isolation mechanism in a transceiver array antenna operating at 5.8 GHz. Maximum isolation between transmitting and receiving array antennas, at a very close spacing (3 mm = 0.058 λ 0 ), and minimum mutual coupling between each array elements is achieved without antenna radiation pattern degradation. The achieved separation is equivalent to 44% size reduction compared with conventional half wavelength spacing criterion. Each of the transmitting and receiving array antennas is a four-element linear microstrip patch array antenna. The employed hybrid isolation technique is composed of defected ground structure, to minimise coupling between array elements, and uniplanar electromagnetic bandgap, to minimise the coupling between the transmitting and receiving antennas. The resulting transceiver array antenna system fulfils -35 dB mutual coupling between array elements, and 60 dB isolation between opponent transmitting and receiving array antennas. The proposed design procedures are discussed and analysed using electromagnetic full wave simulations. Results were verified through experimental measurements for reflection coefficient, mutual coupling and radiation characteristics in which a good agreement with simulated results is granted.

In this letter, compact substrate integrated waveguide (SIW) power dividers are presented. Both equal and unequal power divisions are considered. A quarter-wavelength long wedge shape SIW structure is used for the power division. Direct coaxial feed is used for the input port and SIW-tomicrostrip transitions are used for the output ports. Four-way equal, unequal and an eight-way equal division power dividers are presented. The four-way and the eight-way power dividers provide -10 dB input matching bandwidth of 39.3% and 13%, respectively, at the design frequency f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 2.4 GHz. The main advantage of the power dividers is their compact sizes. Including the microstrip to SIW transitions, size is reduced by at least 46% compared to other reported miniaturized SIW power dividers.

A k-band microstrip array antenna with low sidelobe is proposed in this letter. The antenna array is designed for anticollision radar application. It is a planar series-fed antenna array which consists of eight identical linear series-fed arrays with low sidelobe. The linear series-fed arrays are fed by a microstrip line with impedance matching stubs. The characteristic of low sidelobe can be realized by changing the width of the antenna units and the impedance matching stubs. The shorted holes at both ends of the linear arrays are used to enhance the performance of the antenna array in both impedance matching and radiation pattern. The antenna array is simulated, manufactured, and measured. The measurement results agree with the simulation results. The experiment results demonstrate that the voltage standing wave ratio (VSWR) of the antenna is less than 2 in the working frequency band (24.3–24.7 GHz). The sidelobe levels in both E-plane and H-plane of the antenna are less than −23 dB and good cross polarization is also obtained in the working frequency band.

Partial discharge (PD) is a localized dielectric breakdown in high- voltage insulation systems that can lead to catastrophic equipment failure if undetected. Early and accurate detection of PD is critical in ensuring the reliability and longevity of high-voltage equipment such as transformers, GIS (Gas Insulated Switchgear), and cables. Traditional sensors and narrowband antenna systems have limited sensitivity and frequency range, making them less effective for detecting weak PD signals over wide spectra. The narrow operational bandwidth and low sensitivity of conventional PD detection systems impede accurate localization and characterization of PD phenomena, especially under noisy or variable frequency conditions. There is a pressing need for a robust detection mechanism that combines broad frequency response with high detection sensitivity. This study proposes a Broadband Antenna System specifically designed for PD signal acquisition. The system incorporates a log-periodic dipole array (LPDA) antenna integrated with a low-noise amplifier (LNA), coupled to a high-speed digitizer. The LPDA provides ultra-wideband coverage from 50 MHz to 1.5 GHz, enabling the capture of various PD signatures. Finite Element Method (FEM)-based simulations in CST Microwave Studio validate the antenna design. Real-time testing is performed in a controlled high-voltage laboratory environment using a 100 kV test transformer and calibrated PD sources. The proposed antenna system demonstrated a 25% improvement in sensitivity and a 40% increase in detection range compared to standard narrowband antennas. It accurately detected PD pulses with charge magnitudes as low as 5 pC under noisy environments.

The use of bandwidth for mobile and cellular networks has been increasing at an unprecedented rate, with applications in emergent areas such as smart vehicles and civil infrastructure, telemedicine, and remote education. The predicted increase of mobile network utilisation requires a high data rate capacity to transfer information through the network. The current limited capacity of the fourth generation (4G) mobile network is not expected to satisfy the predicted high data demand by 2020. To meet this requirement, a new fifth generation (5G) mobile network has been proposed. In order to reach the high capacity demands, the 5G requires a wide frequency bandwidth, which is not available in the sub-3 GHz frequency spectrum. Therefore, many international organisations have assigned the millimetre-wave band (mm-Wave), which includes 24, 28, 37, 39, and 60 GHz, as a frequency band for 5G. Using mm-Wave raises many challenges such as an increase in the path loss, radiation field absorbed by the human body, signal polarisation misalignment, and MIMO antenna footprint inside the mobile handset. Therefore, designing beam-steering, reconfigurable circular polarization, and compact MIMO antenna systems for 5G applications is important to cope with these challenges. Although there are some antenna systems were reported recently for mm-Wave 5G, they had limited steering angles, one polarization types or bulky antenna size. This thesis aims to solve the current challenges mentioned above by developing mm-Wave 5G antenna systems and in doing so makes three main contributions to the field of mm-Wave 5G antenna systems.As the path loss and radiated fields absorbed by surface layers of the human body increase at mm-Wave, emphasis is given into the development of the beam-steering antenna system, which is the first contribution of this thesis. The beam-steering technique aims at reducing the effects of electromagnetic field exposure on the human head, as well as maintain a consistent connection between the handset and the base station. A novel compact three-dimensional (3-D) beam-steering system of mobile handsets at 28GHz is proposed. It consists of dipole antenna arrays, power dividers and digital phase shifters. Nevertheless, a novel technique of connecting p-i-n diodes to build a phase shifter is proposed for better performance. The proposed design has the ability to steer the beam in a wide angle in 3-D. it relies on using both sides of a printed circuit board for a two-dimensional antenna array. Moreover, to further improve the performance of the beam-steering system, a tunable power divider for mm-Wave 5G is presented. It is used to tune the feeding amplitude of the beam-steering antenna array, and thus reduces the side-lobe level (SLL) of the antenna radiation pattern.n nThe second contribution is the development of two reconfigurable circular polarisation (CP) structures for 5G applications at mm-Wave. CP is an effective technique to mitigate signal polarisation misalignment, phase deviation and multipath effect problems. Electrical reconfigurable methods are used to switch the CP type by using p-i-n diodes. Firstly, an open-ended stub concept with a simple feed circuit is used to build a novel reconfigurable CP patch antenna. Then the same concept is developed to build a reconfigurable CP antenna array system using branch-line couplers, power divider, and 4 p-i-n diodes. The open-ended stub concept is found to be efficient in both designs by reducing the complexity and the number of the p-i-n diode switches compared to the reported existing CP antenna systems in the literature.MIMO is a major technology of 4G mobile antenna system and also has disruptive potential for mm-Wave 5G. Therefore, the third contribution is the development of new design approaches to integrate the current 4G with futurist 5G MIMO antenna systems. Integrating these two technologies in one structure leads to a reduction of the total MIMO antenna footprint significantly within handsets, where the available space is limited. To that end, two novel 5G/4G MIMO antenna systems are built. First, 5G/4G MIMO antenna system is proposed by using one structure; and it covers multiband mm-Wave spectrums (28, 37 and 39) GHz for 5G as well as sub 3 GHz for 4G.n Moreover, to further improve the gain especially at mm-Wave band, an antenna array structure is deployed to build another 5G/4G MIMO antenna system. This design integrates 5G and 4G operations into a single structure; and covers a wideband 23-29 GHz for 5G and frequency-tuning 2.05-2.70 GHz for 4G.The developed antenna systems reported in this thesis positively contribute to the antenna design domain and are expected to encourage safety, compactness, reliability, and a multiband antenna system for the mm-Wave 5G industry in near future.n

The results of modeling of transmission coefficient between two Yagi-Uda antennas in antenna array are discussed in this article. The transmission coefficient S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> versus wave like distance between antennas and directors number are analyzed by moment method (MoM). Both E-plane and H-plane interactions are analyzed. Tree methods for the calculation of the antenna array radiation pattern subject to interactions are discussed. The radiation pattern for full antenna array calculated by MoM. It is the first method. In the second method the radiation pattern of one active irradiator subject to other irradiator is passive, and MoM calculates it. In the third method the full antenna array is decomposed to three fragments per tree irradiators. MoM calculates the antenna pattern of one fragment subject to all (three) irradiators. The pattern of full array is calculated by theorem of antenna pattern multiplication, but system factor calculated for array consist of three fragments. One can see, that all proposed methods allow achieving the same results

Shared‐aperture antenna arrays are attractive for 5G base stations, owing to their compact size and multi‐band frequency coverage. Decoupling surfaces are effective for suppressing crossband mutual coupling. However, their designs typically rely on full‐wave simulations of scattering parameters, which may not ensure a good radiation performance and is time‐consuming. A systematic methodology based on the hybrid equivalent circuit model and plane wave spectrum method is proposed for decoupling surface designs. The decoupling surface is represented by its equivalent circuit and the spectral expression converts the electromagnetic field into a circuit problem. Both the scattering parameter and radiation pattern can be solved with the circuit, offering an efficient design method that ensures consistent radiation patterns between the model and full‐wave simulations. A double‐layer decoupling surface with wide stopbands, high transmission property, and sharp roll‐off transition was realised. Furthermore, to reduce the overall profile height, the reflection phase of the decoupling surface was tuned. A triple‐band shared‐aperture base station antenna array was developed. Simulated and measured results demonstrate the array works properly in the 0.69–0.96 GHz, 1.7–2.7 GHz, and 3.3–3.8 GHz frequency bands with stable radiation patterns, and crossband mutual coupling is well suppressed, validating the effectiveness of the proposed methodology.

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.

Radars remain the only all–weather location systems, which is especially important in difficult conditions of their use. Antenna array technologies remain critical for the development of dynamic areas of technology and, first of all, UAVs location systems. The development of location systems and antenna arrays for UAVs has been going on for a long time. Radars and antenna arrays installed on medium– and large–class UAVs differ little from airplane and helicopter systems. Among UAVs, the maximum number of UAVs used are UAVs of minimal size, weight and cost. Due to their high maneuverability, minimal visibility and a large number of tasks to be solved. Therefore, radars are subject to minimum size, weight, dimensions and consumption requirements at maximum range. The widespread use of small UAVs has led to the fact that their radars and antenna arrays are on a par with automotive ones, when the possibilities for their placement are significantly limited, even more so than in cars. For the latter, the problem of miniaturization appeared earlier, but not as severely as in UAVs. Antenna arrays are subject to requirements for minimizing dimensions, weight and consumption. Nanotechnology provides this. It's safe to say that the time has come for large–scale solutions to complex problems in antenna systems. Depending on the type of a UAV, it is possible to use a number of methods for constructing antenna arrays: known and proven – linear and fractal; the most modern – metastructures; widely used – tiled; new: flexible and three–dimensional printed; a combination of several methods. Currently, the most attractive areas for the development of antenna arrays for UAVs are: scaling – growing a large number of similar structures to create large apertures; spacing antenna arrays across the surface of the carrier for viewing both forward, sideways and backward, as well as down and up. The development of silicon tiled antenna arrays has led to the realization of very high operating frequencies (90–100 GHz) on the most affordable process technologies (130–180 nm), and the antenna array is fabricated as a chip. The optimal option for constructing antenna arrays is to ensure the reception, conversion and preprocessing of input signals directly in the antenna system in real time, unloading the radar for solving problems that require powerful processing. Post–processing allows you to obtain a more accurate solution to the problem. The combination of pre–processing and post–processing, supported by advanced software and powerful artificial intelligence, expands the capabilities and improves the parameters of the location system. It is important that artificial intelligence ensures the autonomous movement of a UAV, although its use requires large consumption and memory resources. The integrated location system absorbed for the most part the capabilities of a large stationary radar. At the same time, minimum dimensions, weight and consumption are ensured to solve the necessary modern problems. Several radars with their own antenna arrays can be installed on a UAV, which operate in the internal network, complementing each other.

Sensors such as phased array radars play a crucial role in public safety. They are unavoidable for surveillance, threat identification and post-disaster management. However, different scenarios impose immensely diverse requirements for these systems. Phased array systems occupy a large space. In addition, if different antenna systems are needed for each function, the space required can be considerably large. For transportable platforms, such as ships and aircrafts, space and weight are critical parameters. Therefore, reconfigurable multi-band antennas are very attractive solutions for future multi-function sensor systems. Within this research work three different approaches are investigated to realize antennas for reconfigurable phased arrays. Wideband antenna designs constitute the first approach. Integrating this type of antennas with frequency selective filters provide the opportunity for fine tuning within one radar band. The wideband operation of the antenna is achieved by the blind-via feeding section and the quasi electric-magnetic radiating structure. The second approach involves the design of an antenna element with p-I-n diode switches. The switches are used to alter the antenna structure and thereby the operating frequency. Measured results verified the frequency reconfigurable capability of the antenna within L/S radar bands with frequency ratio more than 2:1. The planar structure, the back feeding mechanism, the compact size and the simple bias network made the proposed antenna suitable for array applications. The large frequency ratio and its usability in phased array applications made the design novel. Furthermore, for these frequency reconfigurable elements, a unique multi-scale array structure is introduced which can assure wide angle scanning for both frequency bands. The advantage of this novel array configuration is twofold: reduce the mutual couplings in the lower band, and increase the scanning volume for the higher band. A planar array demonstrator validated the proposed concept. In the third approach the operational band of an antenna is tuned by variable-impedance matching. In this study, the standard 50 ? matching is avoided and many advantages of variable-impedance matching are demonstrated. First, the principle is verified by tuning the frequency band of a microstrip antenna by an input-impedance tuneable CMOS RF-frontend. In the second design a novel dual-band E-slot antenna, with 2.5:1 frequency ratio, was designed. By changing the input-impedance the operating frequency of the antenna can be switched from L- to S-band. Variable-impedance matching provides few other advantages to phased array antennas. A scan-angle dependent impedance matching will assure low reflection coefficients for the entire scanning volume. On the other hand, it will reduce interfering and jamming signals coming from adjacent angles. The outcomes of this research work have led to solid understanding of how we can realize frequency reconfigurable antennas for adaptive phased arrays. The results will be particularly valuable in developing future narrow or wide beam radar systems with frequency reconfiguration and angular filtering capabilities.