Log-periodic Dipole Array Research Articles

Surface Micromachined Millimeter-Wave Log-Periodic Dipole Array Antennas

Two wideband millimeter-wave end-fire log-periodic dipole array (LPDA) antennas are designed and fabricated using a sequential surface micromachining. The antennas are excited by monolithically integrating a micro-coaxial line feed in the antenna's lower boom designed to provide band rejection at 60 GHz. Antennas 1 and 2 are designed to operate in 18-110 GHz and 18 GHz-50 GHz bands, and measured up to 40 GHz and 50 GHz, respectively. VSWR <; 2.5 is obtained for both antennas throughout the measured bandwidth. Measured directivity around 10 dBi and consistent E and H-plane 3 dB beamwidths around 56° and 72°, respectively, are obtained for Antenna 2 throughout its bandwidth. Good pattern correlation between measured and simulated results is also achieved. This paper clearly demonstrates that the wideband high-quality millimeter-wave end-fire LPDAs are now possible.

Inkjet Printing of Novel Wideband and High Gain Antennas on Low-Cost Paper Substrate

A complete characterization of the inkjet printing process using metallic nanoparticle inks on a paper substrate for microwave frequencies up to 12.5 GHz as well as its application to low-cost, high gain and wideband antenna design are demonstrated in this work. Laser and heat sintering of metallic nanoparticles are compared on paper substrate for the first time which demonstrate immense cost and time benefits of laser sintering. The antennas fabricated using the characterized process include a Vivaldi for the UWB band which exhibits a significantly higher gain of up to 8 dBi as compared to the currently published inkjet printed antennas, and a novel slow-wave log periodic dipole array which employs a new miniaturization technique to show 20% width reduction.

A novel method for RCS reduction of the printed log-periodic dipole array

This paper devises a printed log-periodic Koch-dipole array (LPKDA) with low radar cross section (RCS) and proposes a novel wideband radar absorbing materials (RAM) with frequency selective surfaces. A wideband RAM is used as a ground plane of the LPKDA for in-band RCS reduction. The measurement result shows that the operating band is 6–12 GHz with a return loss higher than 10 dB and that the performance of radiation pattern of the antenna in the whole band is preserved. The RCS of the LPKDA with RAM can be reduced more than 28 dB at operating band by this method.

Miniaturized LPDA Antenna for Portable Direction Finding Applications

In this letter, a miniaturized log-periodic dipole array (LPDA) antenna operating from 1 GHz to 6 GHz is proposed for portable direction finding applications. To reduce the lateral size of an LPDA antenna, bow-tie elements and a top-loading technique are utilized and spacing factor is decreased to reduce the spacing between the LPDA elements. The proposed miniaturized LPDA antenna has the measured gain and front-to-back ratio ranging from 1.2 dBi to 3 dBi and from 7 dB to 22 dB, respectively.

Application of bacteria foraging algorithm in designing log periodic dipole array for entire UHF TV spectrum

In this article, an attempt has been made to revisit the design of well-established log periodic dipole array (LPDA) in light of recent optimization technique, the bacteria foraging algorithm (BFA). Although there are many works published in the literatures based on various optimization techniques, this article deals with the optimization of the LPDA for the entire ultra high frequency (UHF) television (TV) spectrum (470–870 MHz) covering 400 MHz bandwidth and accommodating 49 channels. The challenges of this design lie in selecting suitable values of τ and σ for 134 frequency points for which different sets of all the output parameters such as gain, input impedance (Zin), front-to-back ratio (FTBR), first side lobe level (FSLL), voltage standing wave ratio (VSWR), and so forth are obtained and then averaged over to get Gainav, ZinAav, FTBRav, FSLLav, and VSWRav close to the desired values. These average values are used to design suitable fitness function. Another important aspect of this article is to provide exhaustive design details for LPDA using network theory that would couple to the BFA for getting the optimized number of elements to satisfy the desired values of Zinav, Gainav, FTBRav, FSLLav, and VSWRav, set as 50 Ω, 9 dBi, 40 dB, 40 dB, and 1.1, respectively. Moreover, this LPDA design considers the standard wire gauge dipole elements, which is just a very practical approach in the design procedure. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.

Standoff Acoustic Modulation of Radio Frequency Signals in a Log-Periodic Dipole Array Antenna

An acoustic tone isonifying an antenna is shown to produce radio frequency (RF) distortion in a log-periodic dipole array. This distortion is capable of interfering with a sensitive receiver. The passive distortion produces two sidebands, the powers of which have a 1:1 relationship with both the RF and acoustic tone, but have nonmonotonic behavior with respect to RF and acoustic frequency.

UWB 통신용 대수 주기 보우타이 다이폴 배열 안테나

In this paper, a log periodic bow-tie dipole array (LPBDA) antenna for UWB communications is investigated. Bow-tie shaped dipole elements are used instead of general dipole elements for LPDA antennas and the input reflection coefficient and realized gain characteristics of the LPBDA as a function of a flare angle are analyzed. It turns out that as the flare angle of the bow-tie dipole elements is increased, the lowest operating frequency is shifted toward lower frequency and the operating frequency band is increased, but the average gain is decreased. However, the gain variation of the LPBDA is much decreased and the front-back ratio is improved compared to the LPDA. Standard LPDA and LPBDA with a flare angle of 13 degrees are fabricated on an FR4 substrate with a dielectric constant of 4.4 and a thickness of 1.6 mm. Measured gain for the LPDA ranges from 4 to 6.5 dBi at 3.1 to 10.6 GHz band, while that for the LPBDA is in the range of 4.2 to 5 dBi.

Measurement and Computational Analysis of the Radiation Patterns of EMC Antennas Used in Radiated-Emissions Measurements [Measurements Corner

Recently, several standards related to measurements of unintentional radiated emissions of electrical and electronic devices have introduced the need to have a knowledge of the half-power beamwidths (HPBW) of the antennas used during the measurements. Since above 1 GHz most antennas are very directive, information on the pattern has become very important, especially when it comes to understanding how much area the main beam is covering. The standards are extending the need to understand the radiation parameters of the antennas to frequencies in the 30 MHz to 1 GHz range. The present paper is intended as a reference to give information to the EMC engineer and technician on the radiation patterns of the most common EMC antennas used for radiated immunity. The paper also looks at simple methods of measuring the patterns of these antennas. The goal is to propose a simple approach to measure the patterns that will provide results that will be adequate for the EMC community at a low cost. The antennas covered are biconical antennas, log-periodic dipole arrays, hybrid antennas, and dual-ridge horns. As a quick check of the validity of the measured data, computational results are presented for the antennas measured. The Numerical Electromagnetics Code (NEG) and CST Studio Suite™ were used to generate data to compare with the measured results. These experiments give the EMC engineer the information needed to understand the radiation patterns and the half-power beamwidths of the antennas used to perform EMC measurements.

Inverted-L 형태의 다이폴 소자를 이용한 소형 LPDA 안테나 설계

본 논문에서는 1~6GHz 대역에서 동작하는 소형 대수 주기 다이폴 배열 (LPDA: Log-periodic Dipole Array) 안테나에 관해 연구하였다. LPDA 안테나의 폭을 소형화하기 위해 역(inverted)-L 형태의 다이폴 소자를 사용하였고, 전체 길이를 줄이기 위해 각 다이폴 소자 간의 간격을 줄였다. 역-L 형태의 다이폴 소자의 top-loading 길이를 증가시킬수록 LPDA 안테나의 폭을 더 줄일 수 있으나, 대역폭과 이득은 상대적으로 감소함을 알 수 있었다. 최종 제작된 소형 LPDA 안테나는 FR4(비유전율 4.4, 두께 1.6 mm) 기판 상에 제작되었고, 표준 LPDA 안테나와 비교하여 폭이 32%, 길이가 49% 줄어들었다. 측정한 이득은 1~6GHz 대역에서 1~3.1 dBi 범위에 있다. In this paper, a compact log periodic dipole array (LPDA) antenna operating from 1 to 6 GHz is studied. Inverted-L shaped dipole elements are used to miniaturize the lateral size of an LPDA antenna and the spacing factor is also decreased to reduce the total length of the LPDA antenna. As the top-loading length of the inverted-L shaped dipole elements is increased, the width of the LPDA antenna is decreased but the bandwidth and the gain of the antenna are decreased. The fabricated compact LPDA antenna is printed on FR4 substrate With a dielectric constant of 4.4 and a thickness of 1.6 mm, and its size is reduced to 32% in width and 49% in length compared to a standard LPDA antenna.

An Improved Method for Free-Space Antenna-Factor Measurement by Using the MUSIC Algorithm

This paper proposes a simple, fast, and accurate method for calibrating the free-space antenna factors of broadband electromagnetic compatibility (EMC) antennas. This method adopts a fixed-height calibration configuration and a multiple-signal-classification-based (MUSIC) data processing algorithm. Because this configuration does not require height scans, it significantly shortens measurement time and removes height-dependent calibration errors. In addition, the MUSIC-based data processing algorithm can remove unexpected reflections from the ground plane or any other reflecting objects, and transfer calibration into the free-space transmission model, from which the free-space antenna factors are obtained. The algorithm of this method can also automatically compensate for the phase center shift, which makes measurement easier and more convenient. To verify this method, numerical simulations for half-wave dipoles and experimental measurements for log-periodic dipole array (LPDA) and horn antennas are conducted. The simulated results for the half-wave dipoles indicate that the error from the theoretical AF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">FS</sub> can be within ±0.5 dB. In the case of the experimental measurements, the calibrated results are compared with other published standard methods: the mean differences can be as low as 0.25 dB for the LPDA, and as low as 0.36 dB for the horn antennas. The good agreement between results confirms that the proposed method can yield accurate estimations of free-space antenna factors for broadband EMC antennas. This method also provides a new alternative for obtaining fast and accurate antenna calibration.

Impulse Radiating Log-Periodic Dipole Array Antenna Using Time-Reversal Technique

A novel concept based on time-reversal technique is presented to achieve a nondispersive log-periodic dipole array (LPDA) antenna targeting in an impulse radiating antenna (IRA). The idea is to use a passive interface circuit module at the feeding line of the antenna, which works as the time-reversal prefiltering. The proposed method results in a nondispersive (high-fidelity) antenna by keeping the same LPDA structure that has the features of the LPDA antenna in terms of radiation pattern, VSWR, gain, and efficiency. The results show 40% improvement in the fidelity factor of the antenna.

Reduced log-periodic dipole antenna using a cylindrical-hat cover

A technique to decrease the size of log-periodic dipole array (LPDA) antennas employing inductive loads on its elements is introduced. This technique consists of adding a short-circuited cylindrical hat cover at the end of each arm of the antenna. Simulation and measurement results show that the total area, if considered as a trapezoid, of a fabricated LPDA antenna, based on the proposed technique, is approximately 50% smaller than the size area of a reference antenna using a conventional technique. The parameters of the reduced antenna are slightly modified, preserving the bandwidth, impedance, polarisation and radiation pattern shape. The drawback of this technique is the small reduction of gain, from 7.5 dB for the conventional antenna to 6.4 dB for the reduced prototype in the middle operation band.

A PRINTED LOG-PERIODIC TREE-DIPOLE ANTENNA (PLPTDA)

A miniaturized printed log-periodic fractal dipole antenna is proposed. Tree fractal structure is introduced in an antenna design and evolves the traditional Euclidean log-periodic dipole array into the log-periodic second-iteration tree-dipole array (LPT 2 DA) for the flrst time. Main parameters and characteristics of the proposed antenna are discussed. A fabricated proof-of-concept prototype of the proposed antenna is etched on a FR4 substrate with a relative permittivity of 4.4 and volume of 490mm £ 245mm £ 1:5mm. The impedance bandwidth (measured VSWR < 2) of the fabricated antenna with approximate 40% reduction of traditional log-periodic dipole antenna is from 0.37 to 3.55GHz with a ratio of about 9.59 : 1. Both numerical and experimental results show that the proposed antenna has stable directional radiation patterns and apparently miniaturized efiect, which are suitable for various ultra-wideband applications.

Wideband frequency reconfiguration of a printed log periodic dipole array

AbstractA reconfigurable printed log periodic dipole array (LPDA) is presented.It is shown that several frequency bands across a wide frequency range can be selected by switching the printed dipoles of the LPDA. In comparison with the reconfigurable printed dipole antenna introduced by the present authors before, the significant advantage of the reconfigurable LPDA lies in its flexibility in selecting the frequency bands with different bandwidths. The measurement results show that the reconfigurable LPDA operates over a frequency range of 3:1. The characteristics of the wideband reconfigurable LPDA is suitable for frequency switching in FCC ultra wideband allocation. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:861–864, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25040

Intellectual Property and Patent Abstracts

A collection of six patents along with abstracts and diagrams where applicable. Also listed are inventors, assignees, and dates filed. Covers some of the following technologies, theories, and schemes: a configurable and orientable antenna and corresponding base station; an ultra wideband loop antenna; and an ultra-wideband log-periodic dipole array with linear phase characteristics.

Wideband substrate integrated printed log-periodic dipole array antenna

This study presents a novel approach for designing broadband single layer printed log-periodic dipole array (PLPDA) antenna fed by substrate integrated waveguide (SIW). 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 SIW, provides a balun with a considerably wide bandwidth with low profile, broad dominant mode bandwidth, low insertion loss and so on. Prototype of the proposed substrate integrated printed log-periodic dipole array (SIPLPDA) antenna and 1×4 antenna array at Ka band are designed and fabricated; the measured data are in good agreement with the simulated results.

Accurate gain determination of LPDA by considering the phase center

A numerical simulation of gain measurement performed using the three-antenna method for a log-periodic dipole array antenna (LPDA) is presented. The electromagnetic simulation is based on the finite integration method. The gain variation attributable to measurement distance is estimated when using the conventional method in which the reference point of LPDA is considered. We propose a technique for estimating the phase center by exploiting this gain variation. The simulated results demonstrate the efficacy of considering the phase center for accurate antenna calibration.

Analysis, Design and Realization of a Novel Directive Ultrawideband Antenna

In this paper, we present a simple log-periodic-dipole-array (LPDA) solution that allows us to achieve good ultrawideband (UWB) performances. The antenna has been manufactured and the measurements agree well with the theoretical predictions. The antenna presents an average gain of 8 dB and a return loss better than -10 dB over the band from 4.2 to 10.6 GHz. Both the measured antenna transfer function and the computed effect on pulse transmission show good performances in comparison with already known UWB antennas.

Experiential Learning of Electromagnetic Concepts through Designing, Building and Calibrating a Broad-Spectrum Suite of Sensors in a Capstone Course

An electromagnetics-based design project was offered to a group of students as their final year (capstone) design project. Their objective was to create a suite of sensors to measure electromagnetic fields over a large range of frequencies. The project resulted in the design, fabrication and calibration of a field mill, fluxgate magnetometer, tuned search coils and a log-periodic dipole array antenna. The open-ended, experiential learning process exposed the students to numerous electromagnetic concepts, skills and learning methods not commonly found in traditional electromagnetic classroom settings. This paper provides an overview of the theory, design and output of the sensors.

Metamaterial-Based Dispersion Engineering to Achieve High Fidelity Output Pulses From a Log-Periodic Dipole Array

A metamaterial-enabled approach is presented that allows one to engineer the dispersion of a log-periodic dipole array antenna (LPDA) to make it more suitable for wide bandwidth pulse transmission. By modifying the LPDA with electrically small transmission line metamaterial-based negative and positive phase shifters, the phase of each element of the LPDA are adjusted such that in the main beam direction, the phase shifts between each element approximates a linear phase variation. The performance characteristics of the resulting dispersion-engineered LPDA are obtained numerically with HFSS and MATLAB simulations. By measuring in the far field the fidelity between the actual transmitted pulse and the idealized output waveform, the required component values of the phase shifters are optimized. Significant improvements in the fidelity of the pulses transmitted are demonstrated with eight and ten element LPDAs.