Log-periodic Array Research Articles

Mathematical analysis for resonant frequencies of a novel 3-element log periodic patch array

Mathematical analysis for resonant frequencies of a novel 3-element log periodic patch array

DOA Estimation Method for Ultra-Wide-Band Insect Radar Based on Variable Conical Conformal Array: Adjustable MUSIC Algorithm

Insect radar is an important tool for studying the ecological behaviors of insects. Due to the harsh environment, radar is susceptible to interference from ground echoes, which makes it difficult to monitor insects in low altitude. To study the flying insects at low altitude in radar entomology, the research of ultra-wideband (UWB) insect radar based on log-periodic antenna array was proposed. This method uses a conical conformal array to receive signals and an improved multiple signal classification (MUSIC) algorithm to process the signals. This array is capable of monitoring insects of different sizes in the ultra-wideband range, adjusting the angle of the cone tip to change the position and polarization information, and obtaining information on various insects flying at low altitude. The problem of two-dimensional angle of arrival estimation of insect cone conformal array was analyzed by computer simulation, which are low-altitude flying targets with different cone apex angles. In addition, a modified multiple signal classification algorithm was implemented to make the radar search and catch multiple targets faster and more accurate. The algorithm greatly reduces computational complexity while maintaining the accuracy of estimation. There is a linear relationship between the time calculation and the accuracy with the modified algorithm, compared with the relationship between exponential growth and the generalized MUSIC algorithm. Finally, the experimental simulation has proved the superiority of the proposed algorithm.

A high gain multiband offset MIMO antenna based on a planar log-periodic array for Ku/K-band applications

An offset quad-element, two-port, high-gain, and multiband multiple-input multiple-output (MIMO) planar antenna based on a log-periodic dipole array (LPDA) for Ku/K-band wireless communications is proposed, in this paper. A single element antenna has been designed starting from Carrel’s theory and then optimized with a 50-Ω microstrip feed-line with two orthogonal branches that results mainly in a broadside radiation pattern and improves diversity parameters. For experimental confirmation, the designed structure is printed on an RT-5880 substrate with a thickness of 1.57 mm. The total substrate dimensions of the MIMO antenna are 55 × 45 mm2. According to the measured results, the designed structure is capable of working at 1.3% (12.82–12.98 GHz), 3.1% (13.54–13.96 GHz), 2.3% (14.81–15.15 GHz), 4.5% (17.7–18.52 GHz), and 4.6% (21.1–22.1 GHz) frequency bands. Additionally, the proposed MIMO antenna attains a peak gain of 4.2–10.7 dBi with maximum element isolation of 23.5 dB, without the use of any decoupling structure. Furthermore, the analysis of MIMO performance metrics such as the envelope correlation coefficient (ECC) and mean effective gain (MEG) validates good characteristics, and field correlation performance over the operating band. The proposed design is an appropriate option for multiband MIMO applications for various wireless systems in Ku/K-bands.

A Compact Log Periodic Planar Dipole UHF Array Sensor for Partial Discharge Measurements

A compact log periodic planar dipole UHF array antenna from 500 MHz to 2.2 GHz for partial discharge measurement in power transformers is presented in this paper. The compactness of the designed antenna is achieved by shaping the arms and tuning selected dipole elements of the array to fill the unoccupied areas. Shaped dipole arrangement results in additional capacitance between the antenna elements enhancing the bandwidth. The designed antenna achieves a fractional bandwidth of 126% and the size is ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.495\lambda _{0} \times 0.63\lambda _{0} \times 0.0144\lambda _{0}$ </tex-math></inline-formula> ) at center frequency of 1.35 GHz. The proposed antenna is experimentally validated on FR4 3.2 mm thickness substrate. The measured gain of antenna is 4 ± 0.5 dBi over 800 MHz to 2.2 GHz which provides lower variation in measured partial discharges. The effective antenna height of the proposed antenna is measured to be over 15 mm. The measured return loss is better than 10 dB over the frequency range. Moreover, partial discharge measurements with oil filled test objects demonstrate that the designed antenna can receive partial discharge signals effectively.

A miniaturized three‐dimensional log periodic Koch‐dipole array antenna using T‐shaped top loading

A log periodic dipole array antenna (LPDA) is miniaturized by using top loading. The Koch dipole further helps to shrink the antenna size. Different from the traditional LPDA that features a planar structure, the proposed log periodic Koch-dipole array (LPKDA) adopts two identical pairs of top-loaded Koch-dipoles that deploy orthogonally along the feed line. This results in a tree-like three-dimensional antenna geometry, which introduces one extra dimension of freedom for antenna designers. The influence of the top-loading on antenna's impedance bandwidth is studied under the Wheeler and Chu's limit. The characteristic of the Koch-dipole is analyzed. Taking the advantage of 3D printing technology to fabricate complex models, the proposed LPKDA is printed by selective laser melting using aluminum alloy. The simulated −10-dB bandwidth is 117.4% (0.91-3.54 GHz) The LPKDA has the average gain of 5.3 dBi over the 1 to 3.5 GHz impedance bandwidth in measurement. Radiation patterns agree well in simulation and measurement. Compared with conventional LPDA of the same impedance bandwidth, the proposed LPKDA features 42%-dimensional reduction. This letter proves the feasibility of antenna optimization by using both innovative design method and advanced fabrication process.

T‐fed for end‐fire pattern of log‐periodic microstrip array

This article considers feeding techniques for Log Periodic Microstrip-Antenna Array (LPMA). It proposes simple design equations of LPMA for each feed configuration. For an operating band of 4 to 6 GHz, we use a scaling factor of 1.05. EM simulation studies and measurements on prototypes show that the T Fed LPMA gives 2 to 5 dBi gain improvement over other configurations. Unlike many other LPMA configurations, the proposed configuration follows proper Log-Periodic principle with almost an end-fire radiation pattern. These design principles will be useful in LPMA synthesis and the prototype-based designs can find applications in various areas including Wi-Fi, C band, and others.

Log-periodic temporal apertures for grating lobe suppression in k-space tomography.

Millimeter-wave (mmW) imaging receivers have demonstrated the ability to sense radio-frequency (RF) waves using traditional phased antenna array techniques, and, through a coherent photonic up-conversion process, image these waves using free-space optical systems. Building upon the idea of coherent up-conversion, k-space tomography extends the functionality of the millimeter-wave imaging receiver as a two-dimensional spatial processing unit to three-dimensional sensing with the addition of frequency detection. In this configuration, an arrayed waveguide grating, or temporal aperture, is implemented following the photonic up-conversion of RF signals received by the phased array. These waveguides of varying length add a spectral beam-forming network to the existing spatial beam-forming of the mmW-imaging receiver. The introduction of three-dimensional phase information to the imaging system disrupts the ability to directly image the RF signal distribution on a photo-detector array, requiring the application of tomographic algorithms to reconstruct the power distribution of the received signals. In order to receive and properly recover the spatial-spectral distribution of RF sources, the antenna array and temporal array must be sampled adequately to avoid introduction of grating artifacts into the system response. Grating lobes, an artifact of regular spacing of elements within a grating, restrict the alias-free field of regard for antenna arrays, or the free spectral range for time-delay based arrays, thus limiting the spatial-spectral monitoring of RF sources via the k-space imaging modality. To alleviate this constraint, we present a non-uniform log-periodic array sampling for the k-space tomographic time-delay based aperture, greatly increasing the free spectral range of the system while maintaining the number of existing channels.

Design and Performance Analysis of Printed Square Log Periodic Array Microstrip Patch Antenna at 2.5 and 3.5 GHz

Design and Performance Analysis of Printed Square Log Periodic Array Microstrip Patch Antenna at 2.5 and 3.5 GHz

Novel low profile ultra‐wideband capacitance loaded log‐periodic monopole array with reduced transverse dimension

A novel low profile log-periodic array with vertically polarised end-fire radiation patterns is proposed in this study. It totally consists of 22 antenna elements with three different types of monopole antennas. Specifically, conventional monopoles were utilised at the high end band, while monopoles with different types of top-hat loadings were designed for lower frequency band operation. Shorting posts are strategically introduced to maintain a good impedance matching at the lower band. A folded microstrip line is printed on the back side of the ground plane to feed the array. The log-periodic monopole array achieves a very low profile of 0.063 λ l, where λ l is the wavelength at the lowest operating frequency in free space. Moreover, the array also exhibits an extremely narrow width of 0.075 λ l in the transverse dimension, which makes the array an attractive candidate for phased array development along the transverse direction. A prototype of the array is fabricated. Measured results show that the array achieves a minimum realised gain of 4.5 dBi across a wide frequency band of 1.19–11.7 GHz (9.83:1).

2–18 GHz Conformal Low-Profile Log-Periodic Array on a Cylindrical Conductor

This paper presents a conformal log-periodic array covering an ultra-wideband of 2–18 GHz. It employs monopoles of different heights for the high band, top-hat monopoles for the middle band, and folded top-hat monopoles for the low band. The top hats help to achieve a low profile of the monopoles while the folding is to maintain a good input resistance at the low band. A meandering microstrip line on the bottom is used to feed the array. The proposed antenna is mounted on a conducting cylindrical surface with all the top hats conformal and aligned to the outline of the cylinder. A prototype is fabricated and tested. Measured results show that an impedance bandwidth from 2 to 18.3 GHz (9.15:1) for VSWR $0.053~\lambda _{L}$ at the lowest operating frequency, which should be useful in many communication systems such as missile and airborne applications.

Printed Log-Periodic Monopole Array Antenna With a Simple Feeding Structure

A novel printed log-periodic monopole array (PLPMA) antenna is proposed and investigated. The antenna has advantages of easy design, wide bandwidth, and high gain. Compared with conventional printed log-periodic dipole array antennas, the antenna has a simpler feeding structure, and its monopole elements have smaller size and can be printed on a single side of the substrate. A PLPMA with 12 printed monopole elements is designed. A prototype of the antenna is fabricated using the standard printed circuit board process, and measured results are consistent with theoretical and simulated results. Measured results show that the design has a broad operation band from 8.4 to 14.6 GHz, in which the voltage standing-wave ratio is lower than 2.0 and the gain is high and stable with a variation from 6.5 to 9.5 dBi.

Lens Antenna for Wide Angle Beam Scanning at 79 GHz for Automotive Short Range Radar Applications

This communication presents the design and experimental verification of a substrate integrated waveguide fed lens antenna for 79 GHz automotive radar applications. The proposed integrated lens antenna consists of a six layer cylindrical Luneburg lens illuminated by 17 source elements of substrate integrated waveguide fed by a planar log periodic dipole antenna array. The Luneburg lens is developed by using a unique foam material AirexR82 ( $\varepsilon _{r} = 1.12$ ), which is drilled and pressed to achieve the different dielectric constant needed to follow the index law inside the lens. The return loss and the radiation characteristics of the proposed integrated lens antenna are investigated and validated by measurements. A good agreement between the measured and simulated results is observed. The measured results confirm the beam scanning capability of the proposed integrated lens antenna for a wide scan angle of ±85° in azimuth plane having a maximum antenna gain of 15 dBi at 82.5 GHz and gain drop of less than 2.75 dB for the edge feeds. The estimated radiation efficiency of the antenna is found to be 67% at 82.5 GHz.

Design of Substrate Integrated Waveguide (SIW) Fed Log Periodic Microstrip Array Antennas

A substrate integrated waveguide fed microstrip array antenna structure using the log-periodic principle has been designed. The antenna elements and the feeding networks have been designed and simulated using Ansoft HFSS software. Three element and six element log periodic microstrip array antennas have been fabricated and tested. The simulated and experimental results are in good agreement. The bandwidth achieved increases from 5 GHz for a three element antenna to 10.1 GHz for a six element antenna, exhibiting a good frequency independent behavior which is also justified by the radiation patterns and values of gain at different frequencies.

SKALA, a log-periodic array antenna for the SKA-low instrument: design, simulations, tests and system considerations

The very demanding requirements of the SKA-low instrument call for a challenging antenna design capable of delivering excellence performance in radiation patterns, impedance matching, polarization purity, cost, longevity, etc. This paper is devoted to the development (design and test of first prototypes) of an active ultra-wideband antenna element for the low-frequency instrument of the SKA radio telescope. The antenna element and differential low noise amplifier described here were originally designed to cover the former SKA-low band (70-450MHz) but it is now aimed to cover the re-defined SKA-low band (50-350MHz) and furthermore the antenna is capable of performing up to 650MHz with the current design. The design is focused on maximum sensitivity in a wide field of view (+/- 45deg from zenith) and low cross-polarization ratios. Furthermore, the size and cost of the element has to be kept to a minimum as millions of these antennas will need to be deployed for the full SKA in very compact configurations. The primary focus of this paper is therefore to discuss various design implications for the SKA-low telescope.

A Novel Planar Log-Periodic Array Based on the Wideband Complementary Strip-Slot Element

A novel microstrip log-periodic array based on the broadly-matched complementary strip-slot radiating element is proposed. The array consists of microstrip-fed log-periodically-scaled slots on the ground plane and their complementary stubs on the microstrip layer. Since the radiating element is not resonant, the analysis differs from the previously reported log-periodic arrays. Low scale factor (τ) with high radiation efficiency is possible, since the element radiation efficiency is not resonant and the relative spacing (σ) does not have to be selected for good matching, because the element is intrinsically matched. A design example with τ = 0.909, σ = 0.17 and 15 elements has been analyzed. The achieved bandwidth goes from 2.7 to 8.7 GHz, with a radiation efficiency and a gain of better than 85% and 5 dB, respectively. Moreover, the antenna can be terminated in an open circuit without affecting its performance. Simulated and experimental results show that the radiation pattern is stable over frequency. A method for computing the radiation pattern using equivalent circuits as well as results with a reflector plane for cancelling the beam in one half-space are also included. Due to the good performance, simplicity and low cost, this antenna can be suitable for broadband applications.

Design of log periodic dielectric resonator array for NATO-K band applications

This paper presents the performance of a Log Periodic Dielectric Resonator Array (LPDRA) for NATO–K band (18–40 GHz) applications. In this paper, a new wide bandwidth antenna with flat conformal characteristics is formed by application of log periodic technique to the series fed electromagnetically coupled rectangular overlaid dielectric resonator array. This LPDRA has been simulated using a CST microwave studio suite 2010. The simulated results show the wider impedance bandwidth, covering the frequency range of 18–40 GHz with a Voltage Standing Wave Ratio (VSWR) less than 2 and radiation efficiency greater than 95%. Its maximum gain is 9.9 dBi at centre frequency 28 GHz. Parametric studies of the antenna with CST microwave studio based design data and simulated results are presented here. The scaling factor of 1.05 has been chosen for this design.

Investigation on Log-Periodic Dielectric Resonator Antenna Array for Ku-Band Applications

A log-periodic dielectric resonator antenna array for Ku-band (12 to 18 GHz) applications is investigated. The resonators of a seven-element rectangular-shaped dielectric resonator antenna array are arranged in a log-periodic fashion. The proposed antenna is excited by a log-periodic microstrip series feed line. It provides broadband with 46% of wider impedance bandwidth covering a frequency range of 11.4 to 18 GHz with |S 11| less than −10 dB. The proposed array achieved a maximum gain of 11.4 dBi at a frequency of 14.5 GHz. The measured S-parameter, gain, and radiation patterns are presented for different frequencies. The scaling factor of 1.05 has been chosen for this design. Simulated results are compared favorably with physically measured values.

Design of a compact triangular ring antenna and its array using log periodic property

ABSTRACTA microstrip triangular‐ring antenna structure designed using the log‐periodic principle has been proposed. The antenna elements and the feeding networks have been designed and the antenna simulations are done using Ansoft HFSS software. Shorting posts have been used at the center of the edges of the ring to adjust the shift in the resonant frequency. The simulated and tested results show that the ring antenna with three posts resonated at the same frequency as the triangular patch giving an enhanced gain and a size reduction of 81%. A log periodic array of three triangular rings is also designed and analyzed which gives a good frequency independent behavior in the frequency range of 6.6–11.6 GHz. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:41–46, 2014

Wideband simplified feed for printed log‐periodic dipole array antenna

A novel simple approach is presented for designing a broadband single layer substrate printed log-periodic dipole array (PLPDA) antenna by using microstrip technology. The PLPDA antenna has the merits of wide bandwidth, low profile and light weight, which should be fed by the balanced line. The balanced line, created by the geometric features of the microstrip, provides a balun with a considerably wide bandwidth with low profile, broad bandwidth and low insertion loss etc. The prototype of the proposed microstrip printed log-periodic array at Ka band is designed and fabricated; the measured data are in good agreement with the simulated results.

Simplified Printed Log-Periodic Dipole Array Antenna Fed by CBCPW

A novel simple approach for designing single-layer printed log-periodic dipole array (PLPDA) antenna fed by conductor-backed coplanar waveguide (CBCPW) is presented. The PLPDA antenna has the merits of wide bandwidth, low profile, and stable radiation pattern, which should be fed by the balanced line. The balanced line, created by the geometric features of the CBCPW, provides a balun with a considerably wide bandwidth with low profile, broad bandwidth, low insertion loss, and so forth. The prototype of the proposed CBCPW-fed printed log-periodic array at Ka band is designed and fabricated; the measured data are in good agreement with the simulated results.