Folded Dipole Antenna Research Articles

Wideband and Miniaturization of Antenna Composed of Metal Case with a Slot and Inner Folded Dipole Antenna

Wideband and Miniaturization of Antenna Composed of Metal Case with a Slot and Inner Folded Dipole Antenna

Design and implementation of RF power levels measurement system from indoor to outdoor in Isparta province

This paper presents a novel, low-cost, and portable RF power measurement system, operating in GSM 900 and GSM 1800 frequency bands. This measurement model consists of four basic circuits; microstrip folded dipole antenna (MFDA) that received the ambient RF signals, a power meter that generates DC output voltage according to received RF signal power level, a microprocessor that converts the data's analog to digital, and a computer to record and screen the time-varying data. Seventeen measurements, each for six hours, were performed in nine locations in Isparta for the indoor-to-outdoor scenario. The range between the minimum and maximum power values of the average RF power levels obtained in time-dependent measurements was calculated as approximately 15 dB, 18 dB, and 33 dB for indoor, semi-indoor, and outdoor ambients, respectively. The indoor/semi-indoor/outdoor ambient RF power levels were respectively varied between −55.1 dBm to −4.13 dBm, −43.92 dBm to −6.12 dBm, −44.89 dBm to 0.1 dBm in all measurements.

Polycaprolactone‐Based Zinc Ink for High Conductivity Transient Printed Electronics and Antennas

AbstractDistributed sensors and electronics can be used in agriculture to optimize crop management and improve environmental outcomes. Electronic devices in these outdoor spaces require medium to long range (>1m) wireless communication of data over several weeks or months, which in turn requires high conductivity (1 × 105 Sm−1) antennas. Printed bioinert or ecoresorbable conductors, comprising carbon, magnesium, or zinc fillers, typically exhibit conductivity on the order of 10–1000 Sm−1 and lifetimes from a few hours to a few days. A print‐based fabrication process for chemically treated zinc traces, which achieves conductivity of up to 6 × 105 Sm−1 is reported here. The ink formulation uses a non‐water‐soluble soil biodegradable polycaprolactone binder. The ink and printing processes reported here led to stable conductive traces that are used in ultra high frequency radio frequency identification (UHF‐RFID) folded dipole antennas operating at 915 MHz. The conductivity of the printed traces is maintained for over 70 days in ambient environments when traces are protected by a biodegradable beeswax encapsulation layer.

Dual-Broadband Dual-Polarized Folded Dipole Antenna with Stable Radiation Pattern

Dual-Broadband Dual-Polarized Folded Dipole Antenna with Stable Radiation Pattern

One hundred fifty GHz folded dipole antenna‐on‐chip based on artificial magnetic conductor structure

AbstractA folded dipole antenna using an artificial magnetic conductor (AMC) structure is proposed to improve the frequency bandwidth and reduce the size of the antenna on a chip. To change the distribution of the electromagnetic (EM) field, the proposed AMC structure shaped with square‐in‐square rings (SSRs) is arranged along the radiating metal of the folded dipole antenna and implemented on the lowermost metal layer of the backend oxide layers (BEOLs) between the radiating metal of the top layer of the BEOL and the ground plane of the bottom of the substrate. The SSR of the proposed antenna‐on‐chip (AoC) widens the frequency bandwidth by varying the electrical length to the ground and reduces the physical size of the radiating metal by increasing the effective permittivity. The 3D EM‐wave simulation shows that the proposed AMC structure changes the distribution of EM‐wave in the BEOL and Si substrate such that more EM fields are condensed around the radiating metal and the electrical length to the ground is nonuniform and longer. The AoC with the proposed AMC structure was fabricated using a 65‐nm standard complementary metal‐oxide semiconductor process with one‐poly and nine‐metal. Compared with the conventional 150‐GHz antenna that was implemented on the same die, the proposed differential antenna was measured to be a −10 dB bandwidth of 46 GHz, with a 1.12‐times improvement, and a size reduction of 20.4%. The measured gain of the proposed antenna was −5.99 dBi including the passive balun with an insertion loss of −1.36 dB in simulation.

A Parallel Folded Dipole Antenna With an Enhanced Bandwidth for 5G Millimeter-Wave Applications

In this communication, a planar folded dipole antenna array with wide operating bandwidth and compact size is proposed for 5G millimeter-wave (mmWave) applications. The basic antenna element is a pair of parallel folded dipoles (PFDs) connected at the terminals. Compared with a single half-wavelength dipole, the PFD can achieve a flatter impedance curve in the working frequency band, and it is easier to achieve broadband impedance matching with 50Ω feeding line. Moreover, a coupling slot feeding method is adopted to feed the proposed antenna element. The capacitance provided by the coupling slot can counteract the inductance caused by the PFD, thus improving the impedance matching at the low frequency band. Benefiting from the innovative design, the proposed antenna element can achieve an ultra-wide impedance bandwidth of 64% and a compact size of 0.26λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.28λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . Furthermore, a wide scanning angle with ±50° over wide bandwidth is testified by a 1×8 array using active simulation. For verification, a 4×4 full corporate-fed array is designed based on the proposed element. The measured results prove that the proposed 4×4 array has a -10 dB impedance bandwidth of 65% covering 17 to 33.75 GHz and a peak gain of 17.5 dBi. The measured total efficiency is from 69% to 82% over the working frequency band. With the merits of compact size, wide working bandwidth, and wide beam scanning angle, the proposed antenna is a good candidate for mmWave wireless communications.

Miniaturized Broadband Dual-Polarized MIMO Antenna Array With Stable Radiation Pattern for Base-Station Application

A wideband dual-polarized MIMO antenna array having small size and stable radiation performance for base station applications is introduced. The antenna element, which is formed by four folded dipole antennas arranged in a small square aperture, is introduced to obtain excellent impedance matching and steady radiation pattern within a broad bandwidth of 36.7% (0.69-1 GHz) with low profile. Based on the high-performance element, a compact broadband dual-polarized MIMO array for mobile communications is then designed. To stabilize the radiation pattern of the MIMO array, a new method of element-shared scheme and 90° phase compensation are introduced to design the MIMO array to obtain stable half power beamwidth (HPBW) of around 64° for desired 120° sector coverage of cellular mobile communications. A special feed network with good performance is designed to excite the MIMO array. The MIMO array introduces a broad bandwidth of 43.7% (0.68-1.06 GHz) for reflection coefficient < -15 dB, as well as good isolation of more than 25 dB between all the ports. Steady radiation pattern with HPBW of 64±7° as well as low sidelobe level of below -15 dB are observed, which is desirable for modern mobile communications.

A Semi-Elliptical UWB Folded Dipole Antenna

In this paper, a novel structure of a semi-elliptical folded dipole for ultra-wideband (UWB) receiving applications is discussed. This proposed antenna has a directive radiation pattern resulting in a high gain over the bandwidth. The design uses a planar technology including a microstrip line to slot line transition and optimized curves to obtain a measured impedance bandwidth of 2.3–26 GHz with the condition of S11 &lt; −6 dB (level accepted for receiving antenna) and meets S11 &lt; −10 dB in several bands. Additionally, the simulated gain ranges from 5 dBi to 9.5 dBi across the entire bandwidth with an efficiency of at least 75%. This antenna model offers a reconfiguration capability. The symmetrical feeding used in this antenna creates the directive behavior. Characteristics of this semi-elliptical folded dipole antenna make it suitable for modern wireless communications, such as 5 G around 3.5 GHz, and easy to integrate in antenna arrays (MIMO systems). The four ports of the antenna also make it a candidate for radiation pattern reconfigurability applications reducing in this way the number of elements in network antennas.

Bidirectional Gain Enhancement of Folded Dipole Antenna Using Midstrips Array

A novel low-profile method to improve the bidirectional gain of a dual-element folded dipole antenna (DFDA) is presented. The proposed technique employs surface current distribution conditioning using integrated parasitic elements while preserving the radiators. We introduce a middle layer consisting of a 1-D array of metal strips embedded between the upper and lower surfaces of the dipole, called midstrips. The midstrips are designed as parallel resonators and play the key role of current polarizing of the dipole currents. At the presence of the midstrips, the cross currents on the dipole surface are polarized out of phase and cancel each other, improving radiation-polarization purity consequently. The co- components are changed from a distributed form to a triple current form, which leads to the excitation of a new resonance. The geometric-progression-based array factor is extracted to model the gain enhancement mathematically. Two DFDA prototypes with and without midstrips are fabricated with identical thickness ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.014\lambda _{0}$ </tex-math></inline-formula> at 2.7 GHz) and 10 dB-S11 bandwidth of over 18.5%, which shows a bidirectional-gain enhancement of more than 2.9 dB and an efficiency of over 84% at the presence of the midstrips.

High-Gain Millimeter-Wave Antenna-in-Display Using Non-Optical Space for 5G Smartphones

This article presents a high-gain display-integrated antenna topology, for the first time, embedding radiating traces into a nonoptical space, referred to as the dead space (DS), which is the edge part of the display panel; however, it does not perturb the optical illumination of the display. Thus, the proposed antenna topology is denoted as antenna-in-display (AiD). To fit the extremely narrow embedding conditions of the given DS (= <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.03 \lambda _{0}$ </tex-math></inline-formula> at 28 GHz), a new-shape coplanar waveguide (CPW)-fed folded dipole antenna was devised and efficiently tailored in the DS area. The bottom side of the panel was modified to render the effect of a coplanar defected ground structure (CDGS) for antenna minimization, and a new asymmetrical antenna geometry was proposed for wideband impedance matching and broadside radiation pattern. Compared with conventional studies, the proposed antenna concept provides an improved gain resulting from the good conductive metal in DS, the complete display visibility, and touch sensor compatibility, whereas the previous antenna-on-display (AoD) approaches inherently suffer from the limited gain obtained at the expense of lower conductivity of the optically invisible antenna electrodes. Because the proposed AiD concept enables the direct fabrication of antenna traces into the DS area of the display panel, eliminating need for an additional film, a lower package profile, and cost reduction can be achieved. The proposed prototype was fabricated and verified using an actual smartphone. The measured data confirm 12.32 dBi gain, 54.3% radiation efficiency, and 3 dB gain bandwidth larger than 3 at 28 GHz.

Systematic design and prototyping of a low‐cost passive UHF‐RFID transponder

AbstractThis paper presents a methodical design and prototyping of a passive European ultra‐high frequency (UHF) band radio frequency identification (RFID) transponder. The transponder has a 70 × 17 × 0.3 mm3 copper antenna whose design is based on the folded dipole architecture and utilizes techniques such as meandering and end loading to match a Texas Instruments (TI) UHF‐RFID chip through a T‐match feeding network. The tag's simulated and measured performances indicate good coverage of the entire UHF band with a return loss better than 10 dB. The transponder was then fabricated using inexpensive off‐the‐shelf materials and its performance was tested. The proposed tag achieved good gain, read range, and cost efficiency when compared with current folded dipole antennas and can be easily adapted for various applications such as supply chain, access or security, and vehicle identification.

Broadband dual‐polarized folded dipole antenna with simple feed structure

AbstractA broadband folded dipole antenna for dual‐polarized radiation is presented. It comprises two couples of folded dipoles and a planar reflector. To enhance the impedance matching over broadband, each couple of folded dipoles is parallelly connected by stepped coplanar striplines and then excited by a simple feed structure consisting of a 50‐Ω coaxial cable and a rectangular strip. To stabilize the radiation and further improve the impedance matching during an extremely broadband, a rectangular director is utilized and loaded upon each folded dipole. This antenna provides an extremely broad bandwidth of 77.6% (1.68–3.81 GHz) with return loss &gt;15 dB, and good isolation of larger than 25 dB. It also obtains a steady half‐power beamwidth of 66° ± 4° and a gain of 8.6 ± 0.8 dBi during the broadband. This makes it attractive for mobile communication.

Folded-Dipole Antenna Geometrical Analysis for THz Microbolometer

To improve the responsivity of terahertz (THz) antenna-coupled bolometer, heater (load) resistance has to be increased to suppress the thermal conduction and realize larger temperature rise of the thermistor. Proper design of antenna is therefore essential to assure the impedance matching between antenna and heater. From this viewpoint, a high-impedance folded-dipole antenna (FDA) has been studied numerically by the finite element simulation. The effect of FDA structural parameters such as number of arms, antenna width, and arm spacing are discussed with the lumped port and resistive heater coupled to the antenna gap for the cases of radiating and receiving modes, respectively. The product of resonant resistance and area efficiency is used to predict the improvement made by FDA as a figure of merit (FOM) correlated to the bolometer responsivity. This study revealed that the optimum FOM in FDA-coupled bolometer operating at 1 THz was obtained with three arms, 1-μm antenna width and 4-μm arm spacing. A comparison was made with the result from a half-wave dipole antenna and revealed that FDA could enhance the bolometer responsivity by a factor of 15. This research demonstrated the effectiveness of the FDA to improve the performance of THz antenna-coupled bolometer for applications such as imaging for non-destructive inspection.

Wideband and Efficient 256-GHz Subharmonic- Based FMCW Radar Transceiver in 130-nm SiGe BiCMOS Technology

This article proposes a fully integrated single-channel bistatic frequency-modulated continuous-wave (FMCW) radar transceiver (TRX) that operates at a center frequency of 256 GHz. The main focus of this work is to realize a wideband and efficient radar TRX that offers high resolution of target detection in the short-range FMCW radar sensing application. The radar TRX chip is designed and manufactured using the 130 nm silicon–germanium (SiGe) bipolar complementary metal-oxide-semiconductor (BiCMOS) technology which offers heterojunction bipolar transistors (HBTs) with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{\mathbf {T}}/f_{\mathbf {MAX}}$ </tex-math></inline-formula> of 300/500 GHz. The transmitter (TX) of the radar TRX is based on a fundamentally operated multiplier-by-8 chain architecture that offers a 3-dB bandwidth of around 65 GHz with a saturated output power of −5.4 dBm. On the other hand, the receiver (RX) is based on a subharmonic architecture that provides a conversion gain (CG) of 10.4 dB with an average noise figure (NF) of 23.5 dB. This TRX is realized with two integrated on-chip folded dipole antennas. The antenna offers high antenna gain and radiation efficiency due to the use of the selective localized backside etching (LBE) technique. This chip consumes 305 mW of power from a 3.3-V supply and occupies a silicon area of 3.3 mm2. The radar range measurement is performed in an anechoic chamber, and it shows the maximum dynamic range (DR) of around 34 dB at 1-m range of the target.

A Mutual-Coupling-Suppressed Dual-Band Dual-Polarized Base Station Antenna Using Multiple Folded-Dipole Antenna

An interleaved shared-aperture dual-band dual-polarized base station array antenna is proposed in this article. The lower-band (LB) element is realized by using a multiple folded-dipole antenna (MFDA) and four parasitic loops. To interpret the working principle of the MFDA, a double folded-dipole antenna (DFDA) is firstly analyzed by using the transmission line (TL) model. Then, by combining two bended DFDAs and introducing four parasitic loops, a low cross-band scattering LB element with a high out-of-band rejection level of 16 dB is obtained to cover 2.3–2.7 GHz. The higher-band (HB) element with a wide impedance bandwidth of 42.5% (3.0–4.6 GHz), a high roll-off rate (RoR) of 249.2 dB/GHz, and a high out-of-band rejection level of 17 dB is obtained by introducing a meander line loop (MLL), a rectangular loop (RL), and V-shaped strips (VSS) near the dipole arms. By combining the proposed low-scattering low-pass LB element and the high- RoR high-pass HB element, a novel interleaved shared-aperture dual-band dual-polarized array antenna with a small frequency ratio of 1.46 and a high cross-band isolation level of 25 dB is realized. Due to the low-scattering characteristic and filtering response of the LB element, the radiation patterns of the wideband HB sub-arrays are almost unaffected.

A Wideband Folded Dipole Antenna with an Improved Cross-Polarization Level for Millimeter-Wave Applications

A low-profile planar millimeter-wave (MMW) folded dipole antenna fed by substrate integrated waveguide (SIW) is proposed in this letter. By etching the gaps at the proper position of 1.5λ dipole, an additional resonant mode is generated. Accordingly, the working bandwidth is greatly broadened. In addition, by appropriately adjusting the length of the dual-side parallel strip line (DSPSL), the radiated electric fields generated by the aperture of the feeding SIW and the connecting metallic vias of the folded dipole are designed with an out-of-phase potential. Hence, the cross-polarization of the presented folded dipole antenna is improved as well. As a demonstration, a prototype is fabricated and measured. The experimental results exhibit that the proposed folded dipole has a −10 dB impedance bandwidth of 58.5% (from 30.3 GHz to 53.7 GHz), a gain of around 5 dBi with more than 120 degrees beamwidth in H-plane, and a cross-polarization levels below −15 dB, covering the working frequency band. Compared with the up-to-date planar dipole antenna, the proposed folded dipole achieves the widest working bandwidth and low cross-polarization level. The proposed antenna can be used as the terminal antenna of the MMW communication system.

A Wideband Folded Dipole Antenna With Stable Radiation Patterns Under Multiresonant Modes

A novel wideband folded dipole antenna (FDA) with stable radiation patterns under multiresonant modes is proposed in this communication. First, by lengthening and widening the driven strip of an FDA, the input resistance of its 1st- and 3rd-order modes declines significantly. Second, the driven and non-driven strips are further widened at a fixed ratio to achieve better impedance matching. Third, a pair of open-slot loops (OSLs) is advisably added to compress the resonant frequency of the 5th-order mode close to that of the 3rd-order mode for bandwidth improvement. Finally, a prototype is fabricated to provide experimental verification of the idea, and measured results show that the proposed FDA has a bandwidth of about 82% from 1.72 to 4.10 GHz, which exhibits a good agreement between measurement and simulation. In particular, the proposed FDA obtains stable radiation patterns in the entire operating band.

Analysis and Implementation of Harmonic Injection Locking in Cross-Coupled Oscillators Exploiting Inter-Harmonic Translations

This paper proposes a new approach to above- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{max}$ </tex-math></inline-formula> power detection, using harmonic injection locking of a cross-coupled oscillator and the resulting change in oscillation amplitude. The paper starts with the development of a theoretical framework for this receiver. Two previous methodologies are combined: analyzing an injection-locked oscillator as an active device in a positive feedback loop with a frequency selective network; and the more recently proposed way of modeling non-linearities by using inter-harmonic translation coefficients. Using this framework, a compact equation for the expected voltage response of the receiver is derived. Finally, the design of a receiver consisting of a 200 GHz cross-coupled oscillator with a 600 GHz folded dipole antenna as its tank inductor is discussed. A Noise Equivalent Power (NEP) of 2.3 pW/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sqrt {\text {Hz}}$ </tex-math></inline-formula> is achieved with the proposed receiver.

Responsivity and NEP Improvement of Terahertz Microbolometer by High-Impedance Antenna.

The antenna-coupled microbolometer with suspended titanium heater and thermistor was attractive as a terahertz (THz) detector due to its structural simplicity and low noise levels. In this study, we attempted to improve the responsivity and noise-equivalent power (NEP) of the THz detector by using high-resistance heater stacked on the meander thermistor. A wide range of heater resistances were prepared by changing the heater width and thickness. It was revealed that the electrical responsivity and NEP could be improved by increasing the heater’s resistance. To make the best use of this improvement, a high-impedance folded dipole antenna was introduced, and the optical performance at 1 THz was found to be better than that of the conventional halfwave dipole antenna combined with a low-resistance heater. Both the electrical and optical measurement results indicated that the increase in heater resistance could reduce the thermal conductance in the detector, thus improved the responsivity and NEP even if the thermistor resistance was kept the same.

Compact Wideband and Variable Impedance Transformation Ratio Balun for Folded Dipole

Aiming at dipoles with different impedances, a wideband balun with adjustable impedance for the balanced port is proposed in this communication. The balun is directly connected to the dipole to form an antenna element, so it also needs to meet: no connection line is required; the overall size is less than a quarter of the wavelength. The proposed balun realizes balanced–unbalanced conversion through aperture coupling, and dual slot ensures its wide-band characteristics. Due to the high-impedance characteristics of the folded dipole (FD), the balun has achieved impedance conversion ratios of 6:1, 8:1, 10:1, and 12:1, and the corresponding bandwidths are 82.1%, 67.1%, 53.7%, and 44.4%, respectively. Finally, three types of wideband dipoles with different characteristic impedances are fabricated to verify the versatility of the balun.