Log-periodic Dipole Research Articles

Pattern reconfigurable antenna with specified main lobe deflection and stable bandwidth by using bistable composite laminates

Pattern reconfiguration of antennas has become a very important measure to improve the signal gain and working bandwidth by manipulating beam direction. Developing rational methods to find the reconfigurable structure is a key problem. In this paper, a collaborative optimization method is proposed to comprehensively consider both the geometric parameters of the bistable substrate and the size of the radiation patch. This method enables the design of a pattern reconfigurable antenna with specified main lobe deflection and stable bandwidth. Specifically, by using a two-step process, the log-periodic dipole antenna (LPDA) is conformally mapped from the planar substrate to the bistable substrate. Further investigation reveals that the main lobe deflection angle and bandwidth stability are influenced by the geometric parameters of the bistable substrate and the size of radiation dipoles, respectively. Thus, these parameters are selected as design variables for solving the proposed collaborative optimization model. The transformation between two stable configurations enables the proposed LPDA to deflect the main lobe of the H-plane pattern by 30° while maintaining consistency in the E-plane patterns. Importantly, the resonant frequencies remain unaffected and the bandwidth does not decrease during the pattern reconfiguration. Notably, the pattern reconfigurable mechanism is rooted in that the transformation between the two stable configurations alters the number and position of the dipoles in the radiation region and their current path, thereby changing the radiation direction of electromagnetic waves. The proposed collaborative optimization method has a potential application for other types of antennas and offers opportunities for various applications in the field of wireless communication.

Investigation of a Circularly Polarized Log-Periodic Dipole Antenna

Investigation of a Circularly Polarized Log-Periodic Dipole Antenna

A 1 bit Raw Voltage-recording System for Dedicated Observations of Transients at Low Radio Frequencies

Recently we had reported commissioning of a prototype for pulsar observations at low radio frequencies (<100 MHz) using log-periodic dipole antennas in the Gauribidanur Radio Observatory (≈77°E, 14°N) near Bangalore in India (https://www.iiap.res.in/?q=centers/radio). The aforementioned system (the Gauribidanur Pulsar System) is currently being augmented to directly digitize the radio-frequency signals from the individual antennas in the array. Our initial results using a 1 bit raw voltage-recording system indicate that such a back-end receiver offers distinct advantages like (i) simultaneous observations of any set of desired directions in the sky with multiple offline beams and smaller data rate/volume, and (ii) archival of the observed data with minimal resources for reanalysis in the future, either in the same or a different set of directions in the sky.

Spectral Smoothness of Ground Plane Backed Log-Periodic Dipole Antennas for Radioastronomical Applications

The spectral smoothness properties of the low-frequency array of the square kilometer array (SKA), namely, SKA-Low, are an important issue for its scientific objectives to be attainable. A large array of 256 log-periodic dipole antennas, installed on top of a 42 m circular ground plane, will work as an SKA-Low station in the frequency range of 50–350 MHz. In this article, the ground plane-induced effects are examined in terms of antenna beam spectral characteristics, while different antenna placements are considered. Results are produced both at the isolated antenna and at the array level in the band 50–100 MHz, by employing an approximate method for the speeding-up of array simulations. We attempt to distinguish the ground plane effect from that of mutual coupling among antennas, which appears to be more severe at specific frequencies, using 2 figures of merit. The discrete Fourier transform (DFT) components of gain pattern ratios identify the fundamental spatial components of the ripple, while the envelope correlation coefficient quantifies the penalty to considering an infinite ground plane.

Electromagnetic performance of generalized deployable log periodic dipole antenna with mechanical errors

The primary contribution of this paper is to investigate the effect of mechanical errors on the electromagnetic (EM) performance of the generalized deployable log-period dipole (GDLPDA) antenna. The concept of the “GDLPDA” is introduced first. Additionally, an electromechanical error analysis model is developed to assess the effects of dipole machining errors and deformations on the EM performance of GDLPDA. Based on this model, positional errors in two directions along the feedline are considered. Furthermore, an electromechanical error analysis model considering dipole rotational errors on cross-polarized electric fields is established. The actual positional and rotational errors are simulated to analyze the EM performance of GDLPDA. The simulation results show that the dipole positional and rotational errors can degrade the EM performance. Specifically, positional errors reduce gain and pointing accuracy, along with an increase in the 3 dB beamwidth. Rotational errors generate cross-polarization fields, decreasing the level of the co-polarization amplitude. This insight can help antenna design engineers to optimize GDLPDA to minimize the adverse effects of error on performance.

Solar Radio Spectro-polarimeter (50–500 MHz). I. Design, Development, and Characterization of a Cross-polarized, Log-periodic Dipole Antenna

The Zeeman effect has been routinely used to image and quantify the solar photospheric magnetic field (B). Such a direct measuring technique is not yet available for the corona (Lin et al. 2004). Since almost all transient nonthermal radio emissions from the corona are either partially or fully circularly polarized, observing their polarization signatures over broad frequency ranges would be of help to estimate B as a function of heliocentric height. This article aims to describe the design and development of a Cross-polarized Log-Periodic Dipole Antenna (CLPDA), an integral part of a radio spectro-polarimeter, which works in the 50–500 MHz frequency-range and to explain the tests that were carried out to characterize it. The above frequency range corresponds to a heliocentric height range ≈1.03 < r < 2.5 R ⊙ (R ⊙ = photospheric radius), wherein the numerous coronal nonthermal transients associated with space-weather effects are observed to originate. The CLPDA is used to determine the strength and sense of polarization of the received radio signal. The uncertainty involved in the determination depends on the polarization-isolation (PI) between the two orthogonal components of a CLPDA. Some of the recent advancements made in the antenna design concepts at high frequencies (∼GHz) were adopted to reduce the PI at low frequencies (∼MHz). Throughout the above frequency range, the CLPDA has a gain, return loss, and PI of ≈6.6 dBi, ≲−10 dB, and ≲−27 dB, respectively. The average PI of the CLPDA varies from −30 to −24 dB over an azimuthal angle range 0° to ±45° within which the observations are performed regularly.

LPDA-inspired Material-Geometry joint wide-angle broadband absorption based on metapyramid

The rapid development of metamaterials offers a new avenue to achieve exotic electromagnetic properties, such as perfect absorption for important stealth engineering applications. So far, there are few demonstrations of wide-angle broadband absorption, due to the stringent impedance matching requirement. Here, inspired by the concept of log-periodic dipole antenna (LPDA) for broadband emission, we propose a wide-angle broadband absorption based on both indium tin oxide (ITO) material and judiciously engineered metapyramid geometry. The strip ITO arrays on the sidewalls of metapyramid follow the quasi-LPDA strategy for gradient impedance and expands significantly both angular and spectral operating bandwidth by a cascading of multiple electric and magnetic resonances, as revealed by the rigorous characteristic mode analysis. Our experimental results show that the exotic absorption reaches above 0.9 at 45° tilted incidence for both transverse electric and transverse magnetic polarizations across the band of 8 ∼ 18 GHz. Our strategy circumvents the issues of limited-angle operation, high costs and high weight raised by metal structures, providing a new paradigm toward wide-angle broadband metadevices.

LPDA Calibration Using an UAV for Synthesizing UWB Impulses

In this letter, the possibility of synthesizing ultra-wideband (UWB) impulses with a conventional log-periodic dipole antenna (LPDA) mounted on a quadrotor unmanned aerial vehicle (UAV) was demonstrated. The formation of impulses using LPDA (bandwidth from 427 MHz to 1.01 GHz) with a duration of 1.9 ns, containing one period of field oscillations, became possible due to compensation of amplitude and phase-frequency distortions introduced by the antenna into radiated and received impulses. Compensation for these distortions was carried out by inverse filtering method after calibrating the antenna-feeder path at various heights UAV hovering above the reference reflector (brass mesh). The conductive carbon elements of UAV, located in the near field of the antenna, are indirectly taken into account during the calibration of antenna-feeder path parameters and do not introduce significant distortions into the generated impulses. The suggested method of synthesizing UWB impulses can find application in environmental remote sensing and can also be used to sharpen fronts of impulses radiated\received with LPDA.

Research on Near Field Signal Behaviour of Localizer Antenna System

Near-field (NF) signal distribution behavior with a radius of 150 meters was studied to compare with far-field (FF) distribution characteristics. It can be found more flexible and detailed in NF than the signal from an NF monitor with only a single location. The origin of the measured value and signal detection method on the equipment was introduced in detail. The three-dimensional model was established and optimized by phase analysis as well as the measured data on-site. There was little difference between a measured distribution and a theoretical calculation in space. The change of directional weakening of the Log Periodic Dipole Antenna (LPDA) was proposed. Unequal amplitude signal synthesis together with Fresnel loss was considered to research and explain the incredible power gain. The modified 3D model is in good agreement with the measured results.

MUSER and IPS telescopes for solar and space weather observations

This paper describes the recently built solar radio spectroscopy-imaging facilities, including near future developments and upgrades, as well as the IPS (Interplanetary Scintillation) telescopes under construction in China for solar and heliospheric studies. MUSER (Mingantu spectral radioheliograph), renamed from CSRH (Chinese spectral radioheliograph) after the construction, covers 400 MHz-15 GHz frequency range which was established during 2009–2016 in Mingantu Observing Station at Zhengxiangbaiqi, Inner Mongolia of China, under the National Major Scientific Research Facility Program of China. At moment MUSER is composed of two arrays with MUSER-I covering 400 MHz-2.0 GHz with 40 4.5 m mesh antennas and MUSER-II covering 2–15 GHz with 60 2 m dish antennas. MUSER will be extended to have its third array MUSER-L covering 30–400 MHz frequency regime with 224 LPDAs (log-periodic dipole antennas) under the Meridian-II Project, which is a National Science Infrastructure Project of China, to be constructed in the current two years. MUSER will provide solar radio images monitoring the solar eruptions from solar surface into interplanetary space. An IPS telescope array is going to be built in the current two years under the same National Science Infrastructure Project of China, with the main IPS telescope of three 140 m × 40 m cylinder antennas located in MUSER site and two 30 m antennas in two nearby counties each about 200 km away. The working frequency will be at 327 MHz and 654 MHz with dual linear polarizations. The cylinder antennas will have a sky zenith angle of 60 degrees and be able to observe thousands of radio sources. The IPS telescope will provide important information about solar wind and solar eruptions from the Sun to the Earth environment. The MUSER and IPS telescopes at Mingantu Observing Station, National Space Science Center of Chinese Academy of Sciences will play important role in solar and space weather studies.

Complete Design Procedure of a Size Constrained Printed Planar Log-periodic Dipole Antenna

Complete Design Procedure of a Size Constrained Printed Planar Log-periodic Dipole Antenna

A Novel Compact High Gain Wide-Band Log Periodic Dipole Array Antenna for Wireless Communication Systems

This paper implies a prototype for a broad-band log periodic dipole antenna (LPDA) with dimensions of 20 × 40 × 0.508 mm3 equipped with directors. The LPDA is based on Roger’s RT5880 with εr = 2.2. The 4-arms with alternative stubs constitute the LPDA, which is evenly spaced on both lines. At the substrate’s back, the 50Ω main feeder line is placed on partial ground. The directors are also incorporated and studied in a regular matrix at a predetermined distance to improve gain, further reduce side lobes, and widen the frequency band. The performance of the antenna covers a wide spectrum of millimeter waves ranging from 26 up to 44 GHz. The realized gain for the antenna is 8.97, 11.96, 13.96, and 14.29 dB at 28 GHz, 35 GHz, 38 GHz, and 43 GHz, respectively. The total gain is 14.29 dB as a peak gain. The antenna was designed and tested for 5G communication applications in autonomous vehicles, and the design cost for the antenna is low in comparison to dielectric lenses. The model exhibits symmetrical radiation patterns for the antenna range. The results of the simulations and the testing of the implemented antenna elements coincide quite well. The proposed design outperforms earlier work in this field.

Miniaturization design of log periodic dipole antenna based on dovetail structure

Aiming at the problems of large size and small gain of log periodic dipole antenna (LPDA) in high frequency (HF), this article introduces miniaturization technology to design a miniaturized HF broadband LPDA unit antenna with high gain. In this article, a dovetail structure is designed for LPDA to greatly reduces its transverse size, and adopts a larger scale factor and a smaller spacing factor to reduce its longitudinal size. The effects of scale factor, spacing factor, oscillator angle, parallel oscillator and erection height on the impedance characteristics and radiation performance of dovetail LPDA are studied. Finally, the feasibility of dovetail LPDA is verified by simulation and experiment, which shows that the proposed antenna size is only 7.92 × 15.52 m2, voltage standing wave ratio is less than 1.8, and gain is more than 11 dBi. The proposed dovetail LPDA has high gain, wide bandwidth, and small size, which can work independently and can also be used as the unit antenna of HF broadband antenna array.

Slot implementation on second iteration of fractal log periodic dipole antenna for UHF band application

Abstract In this paper, the design of the second iteration of Log Periodic Fractal Koch Antennas (LPFKA) with and without slot implementation is designed for Ultra High Frequency (UHF) band applications. The slot implementation is applied on each of the radiating elements to reduce the antenna’s size and to prevent the shifting of a lower frequency to a higher frequency. The antenna is operated at a frequency between 0.5 GHz and 9.0 GHz. The Computer Simulation Technology (CST) software was used to design and simulate the antenna. The performance of the antenna such as reflection coefficient, radiation pattern and gain have been analyzed. The antennas have been fabricated using an FR4 laminated board with a dielectric constant of 4.6, tangent loss of 0.019, and a thickness of 1.6mm. The results show a positive outcome, with a stable radiation pattern over the operational bandwidth and a reflection coefficient of less than -10 dB for the designed frequency.

Improved feeds for log-periodic microstrip antenna arrays

AbstractThis note proposes a log-periodic microstrip antenna (LPMA), particularly after developing possible feed structures. The process develops an appropriate feed such that the LPMA can exhibit almost end-fire characteristics such as a log-periodic dipole antenna. The study simulated two LPMAs, one with five elements and the other with seven elements, followed by measurements on a five-element prototype. The five-element prototype LPMA with such a feed exhibits a bandwidth of 2.2–3 GHz. Over this band, radiation patterns remain consistent with a gain of 9.8 dBi. Simulated results follow the measured ones closely.

A compact and high gain metalens antenna based on impedance matching mechanism

A compact wideband metalens antenna which is composed of a log-periodic dipole antenna (LPDA) and metalens is proposed operating over the band of 1.7–2.7 GHz. The metalens is designed by using anisotropic ABA structures (A: impedance matching layer (IML), B: phase gradient metasurface lens (PGMS lens)) to reduce the back-lobe level and achieve high-performance. The PGMS lens is used to achieve a considerable phase shift range, and two IMLs are introduced to eliminate unnecessary reflection caused by the impedance mismatch and further increase phase coverage. Hence, the metalens features a low profile with a thickness of 0.29 λ 0 , where λ 0 is the free-space wavelength at 2.2 GHz. The measured results demonstrate that the proposed metalens antenna has a wide impedance bandwidth of 45% (1.7–2.7 GHz) and −3 dB gain bandwidth of 40% (1.8–2.7 GHz), respectively. Moreover, the gain is averagely increased by 9.56 dB in the whole working band, and the maximum gain achieves 16.1 dBi at 2.2 GHz. These characters make the proposed metalens antenna suitable for microwave imaging systems and other applications.

Parameter-constrained DOA estimation for directional uniform circular arrays with plane-reflection effect

A new multi-parameter direction-of-arrival (DOA) estimation model with image pattern factor is proposed for directional uniform circular arrays (UCAs) in the presence of plane-reflection effect. Firstly, to accurately formulate the characteristics of the radiation pattern impacted by the plane-reflected effect, a modified multi-parameter 3D radiation pattern with image pattern factor is derived on the principle of sources reconstruction. This model is well verified in theory by comparing it with the pattern of the practical log-periodic dipole antenna (LPDA). Secondly, having introduced this radiation pattern into the response vectors, the DOA estimation method with the constrained height-to-wavelength ratio (HWR) is then formulated, which is aimed to improve the achievable estimated accuracy within the full spatial coverage. Unlike the most existing models, it is well suited to the situation when there are reflected signals impinge on the response array. Thirdly, in order to evaluate the DOA performance with the constrained parameters, the deterministic Cramer-Rao Bound (CRB) function is derived. The qualitative analysis on CRB is referenced in the design of the available parameters of antennas on the premise of the uniform DOA estimation performance. Finally, the relationships between the DOA performance and the various constrained parameters are demonstrated in the simulations. The simulation results indicate that the DOA method using the proposed model has a superior estimation performance comparing to the traditional models when reflected signals exist.

Optimization Design and Development of UHF Antenna for PD Detection in Substation

In this paper, a directional logarithmic periodic antenna is designed to meet the application requirements of local discharge detection in substation.The model of log-periodic dipole antenna was established by using high frequency electromagnetic wave simulation software, and the effects of dielectric substrate thickness, dielectric constant of dielectric substrate and patch size parameters on antenna return loss and standing wave ratio were analyzed.Finally, the dielectric substrate thickness of the antenna is 1.6mm, the material is TEflon, and the width of the assembly line is 4mm.According to the selected antenna type and size, the uHF signal receiving antenna is manufactured.

A vehicle‐mounted high power LPDA design for 8‐22 MHz applications

AbstractThe design of high‐power vehicle‐mounted log periodic dipole antenna for 8‐22 MHz use was discussed. It is shown that the antenna has a power endurance of 150 kW. With the application of the coefficients variation method, the total size of the proposal was shrunk to 12 × 18 m so that it can be mounted on a vehicle of 10 m long by an elevation tower. The voltage standing wave ratio over the entire frequency band is lower than 2.0 without utilizing any match network.

Wideband Gain Enhancement of High-Isolation and Quasi-Omnidirectional Metamaterial MIMO Antenna for Vehicular Radar

In this paper, a gain-enhanced wideband multiple-input-multiple-output (MIMO) antenna with high isolation and quasi-omnidirectional radiation is proposed. It is a hexagonal structure and includes six identical end-fire log-periodic dipole antenna (LPDA) elements. These antenna elements are distributed in the same plane and uniformly placed in a rotating arrangement with an angle difference of 60°, and then are suspended over a large metallic plate (LMP). To enhance the wideband gain, different metasurface (MS) lens with high refractive index is deployed around the end-fire log-periodic dipole. The uniform MS lens makes electromagnetic waves deflect toward the array axis of the LPDA, whereas the gradient MS lens could form focused plane electromagnetic waves in the end-fire direction. Furthermore, these antenna elements are isolated with a complementary split ring resonator (CSRR)-based electromagnetic band-gap (EBG) structure owing to its wide bandstop frequency and small-size characteristics. To validate the design concept, the prototype is fabricated and measured. The measured -10-dB impedance bandwidth covers 2.85-10.9 GHz (FBW 117.1%) and the gain varies from 10.37 to 14.82 dBi. Moreover, high isolation of better than 22.4 dB and low envelope correlation coefficient (ECC) of less than -62.3 dB are achieved between antenna elements. The proposed wideband MIMO antenna could be suitable for vehicular radar.