Quadrifilar Helix Research Articles

Shared-radiator design of broadband and dual-mode antenna for personal role radio applications

Abstract Shared-radiator design of a broadband and dual-mode antenna that simultaneously covers the VHF/UHF band and satellite navigation band is presented for personal role radio (PRR) applications. Quadrifilar helix antenna (QHA) is devised to be a circularly polarized radiator which as well acts as a part of the upper half radiation arm of the dipole antenna and be equivalent to a linearly polarized radiation current carrier at VHF/UHF band, forming a symmetrical dipole antenna with a sinusoidal current distribution. A 5th-order balanced matching network comprised of five cascade L-sections is adopted to obtain the maximum possible working band-width and a 3.76:1 band-width (116 %) at VHF/UHF band is achieved. Strong mutual coupling effect of the two operating modes is observed near 1.5 GHz originated from QHA shared-radiator design, and a new balun structure is applied to achieve high isolation and self-decoupling, subsequently |S21| of the two operating modes is significantly reduced from about −18 dB to below −32 dB at satellite navigation band without affecting the reflection coefficient and radiation efficiency. The measured results show that radiation patterns of the manufactured prototype is basically consistent with corresponding simulation counterparts.

A multi-stable deployable quadrifilar helix antenna with radiation reconfigurability for disaster-prone areas

In disaster-prone areas, damaged infrastructure requires impromptu communications leveraging lightweight and adaptive antennas. Accordingly, we introduce a bi-stable deployable quadrifilar helix antenna that passively reconfigures its radiation characteristics in terms of pattern and polarization. The proposed structure is composed of counter-rotating helical strips, connected by rotational joints to allow a simultaneous change in the helix height and radius. Each helical strip is composed of a fiber-reinforced composite material to achieve two stable deployed states that are self-locking. The reconfiguration between an almost omnidirectional pattern and a circularly polarized directive pattern enables the antenna to be suitable for both terrestrial and satellite communication within the L-band. More specifically, the presented design in infrastructure-less areas achieves satellite localization with directive circularly polarized waves and point-to-point terrestrial connectivity with an almost omnidirectional state. Hence, we present a portable, agile, and passively reconfigured antenna solution for low-infrastructure areas.

Design of Miniaturized Dual-Mode Antenna for Handset Terminal Communication

This paper presents a miniaturized dual-mode handset antenna design. A quadrifilar helix antenna (QHA) is utilized to work at higher band (1980-2010 MHz and 2170-2200 MHz) with circular polarization. By cutting off a circular slot on the outer conductor of the QHA feedline and introducing four quarter-wavelength short-circuited stubs, the QHA radiator and its feedline can also work as a monopole antenna at lower band (440-560 MHz) with linear polarization. With this radiator-sharing technique, the dual-mode characteristics can be achieved utilizing only a QHA; therefore, the antenna dimension can be reduced remarkably since it is unnecessary to design an additional monopole antenna. Moreover, the short-circuited stubs are designed with stripline and integrated with the one-to-four power divider and phase shifter for further miniaturization. The measured S11 is less than -8 dB. The typical gain is higher than 0.5 dBi at lower band and 2.5 dBi at higher band. The AR of the QHA is better than 1.3 dB, and the head SAR values are much lower than the international standard at both lower and higher bands. The proposed miniaturized dual-mode antenna can be applied to portable handsets to realize the intercom and satellite communications.

Integrated Design of Multimode and Multifrequency Miniaturized Handset Antenna at VHF/UHF Bands

This paper presents an integrated design of a multimode and multifrequency miniaturized handset antenna working at the lower band (0.24–0.7 GHz) with linear polarization and higher band (1.98–2.01 GHz and 2.17–2.20 GHz) with circular polarization simultaneously. At the higher band, the quadrifilar helix antenna (QHA) is utilized with each arm developed into two arms of different lengths and linearly tapered widths to realize double resonance and increase the bandwidth. Moreover, a helical stub behaving as a director is introduced to improve the antenna gain. At the lower band, the outer conductor of the QHA feedline and four QHA arms are designed to constitute a monopole antenna through proper feeding and introducing four quarter-wavelength short-circuit stubs. With this radiator-sharing technique, the QHA not only works at the higher band with a circular polarization pattern but can act as a monopole antenna working at the lower band with a linear polarization pattern simultaneously. As a result, the size of the antenna can be reduced remarkably. Finally, the proposed antenna is fabricated with a total length of 228 mm and a diameter of 15 mm. At the lower band, the measured S11 is below −8 dB, and the gain is larger than 0.5 dBi. At the higher band, the measured S11 and AR are better than −13 dB and 3 dB, respectively, and the gain within the zenith angle range of 0°−35° is greater than 2.5 dBi, which demonstrates better performance.

A Polarization Reconfigurable 3D Printed Dual Integrated Quadrifilar Helix Antenna Array Embedded Within a Cylindrical Dielectric Mesh

This article presents a polarization reconfigurable dual integrated quadrifilar helix antenna array that is embedded within a cylindrical-shaped mesh of dielectric material. The entire structure is 3-D-printed and equipped with grooves to support the eight radiating elements and accordingly enforce the helical pitch and orientation. The dual antenna array, acting as one, features double fractional bandwidth (i.e., 30%) while exhibiting polarization reconfigurability by switching between left-handed and right-handed circular polarization states. More specifically, the proposed structure operates over the span of frequencies between 1.7 and 2.3 GHz while ensuring a circularly polarized behavior. The polarization reconfigurability is obtained by changing the phase excitation of the eight helical arms. Accordingly, a dedicated feeding network is proposed to achieve the required phase reconfiguration. A prototype is fabricated and tested as a proof of concept, where the measured results agree well with the simulated data. The 3-D-printed fabricated prototype reconfigures its circularly polarized behavior over the entire operating bandwidth with a maximum measured realized gain of 6.4 dBic, an axial ratio that varies between 0.5 and 2.5 dB, and cross-polarization levels of at least 20 dB along the direction of maximum radiation.

New Antenna Designs to Boost the Plasma Density in Helicon Sources

Plasma can be generated using radio frequency (RF) electromagnetic waves for a large variety of applications, such as energy and propulsion generation. Often, the desire is to achieve higher densities for given input power and helicon sources have demonstrated a high efficiency. The design of the antenna that couples the wave plays a major role in the efficiency of generating the plasma particles. Many geometries were studied and compared, but the relationship between the antenna characteristics and the plasma production is still missing. In this article, we identify the power-law dependence between the plasma density and the Gain of an antenna. The latter is determined using numerical simulations in a vacuum, whereas the former is acquired experimentally. The power-law dependence is obtained using four different antenna elements operating under the same experimental conditions on the Polaris linear plasma device. The design a posteriori of a new inductive antenna with a modified quadrifilar helix topology, exhibits not only a higher gain but also confirms the power law. The confirmation of this law will significantly impact the future of many technologies that leverage helicon plasmas.

A Pattern Reconfigurable Circularly Polarized Quadrifilar Helix Antenna Through Phase Control

We have proved in theory and simulation that the circularly polarized (CP) radiation from a resonant quadrifilar helix antenna (QHA) is independent of the phase between two composed bifilar helices, while the CP radiation pattern can be reconfigured by controlling this phase. It is demonstrated that the QHA is capable of generating a wide range of CP radiation patterns, including two cardioid patterns toward both ends, two vertical toroid patterns in two different orientations, and the mixed patterns of cardioid and toroid. A wideband and multilayer feeding network was developed to excite the four basic modes of the proposed QHA through phase control in the experiment. The simulated and measured right-handed circular polarization (RHCP) radiation patterns agree quite well. The proposed QHA was also designed to cover several global navigation satellite system (GNSS) bands. The measured impedance bandwidth is 1.26–1.65 GHz (26.8%) and the 3 dB axial ratio bandwidth is 1.1–1.8 GHz (41.4%) in the endfire mode. It is shown that the proposed QHA can be easily operated in two endfire modes to have an equivalent isotropic pattern for flying objects. When the antenna is operating in the endfire mode, the gain is in the range of 2.1–3.5 dBi, and the radiation efficiency is 70%–85% in the operating band.

Garmin GPSMAP 66sr: Assessment of Its GNSS Observations and Centimeter-Accurate Positioning.

In 2020, Garmin released one of the first consumer devices with a dual-frequency GNSS chip and a quadrifilar helix antenna: GPSMAP 66sr. The device is intended to serve as a positioning and navigation device for outdoor recreation purposes with positioning accuracies on the few meter level. However, due to its highly accurate GNSS dual-frequency carrier-phase observations, the equipment can also be used for centimeter-accurate positioning. We performed extensive test measurements and analyzed the quality of its code and carrier-phase observations. We calibrated the Garmin GPSMAP 66sr antenna with respect to its phase-center offset and phase-center variations. We also performed dual-frequency GPS/Galileo precise point positioning (PPP) and precise relative positioning in baselines to virtual reference stations (VRS). We demonstrate and explain how centimeter-accurate positioning can be achieved with this novel kind of equipment.

A Shape Generation Method for 3D Printed Antennas With Unintuitive Geometries

Additive manufacturing used in combination with versatile shape generation methods can enable designers to realize unintuitive antenna designs with bespoke electromagnetic behaviors that would normally be extremely difficult or even impossible to manufacture using conventional techniques. In this paper, we present a new custom algorithm that produces arbitrary three-dimensional (3D) meander line antennas. This algorithm is used in conjunction with multi-objective optimization to create two quadrifilar helix antennas (QHAs) and one monopole antenna, all with unique electromagnetic performances. One QHA has a wide bandwidth, high broadside gain, and compact size, while the other has a dual-band nature with different radiation patterns in each band. Similarly, the monopole example is a dual-wideband design which targets Wi-Fi applications. These structures possess a meander radius that varies with height as well as conductor thickness that varies along the meander path which allows for improved antenna performance over conventional meander line antennas. An example design was fabricated and tested in order to validate the performance of the optimized virtual antenna model.

Design of a Highly Miniaturized, Inherently Matched, Spherical Folded Dipole Antenna and Evaluation of Its Quality Factor

A highly miniaturized 3-D spherical folded dipole antenna has been reported, for which inherent impedance matching is achieved with respect to a practical source impedance by employing a simple series– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$LC$ </tex-math></inline-formula> loading combination, thereby engineering its input impedance. In order to maximize its bandwidth, the miniaturized antenna employs a spherical helix structure as the folded arm that occupies the full volume of the corresponding Chu sphere. A bifilar (two folded arms) and a quadrifilar (four folded arms) helix loaded folded dipole antenna are designed, and full-wave simulations show that both the resulting antennas demonstrate excellent impedance matching when miniaturized by 85% in comparison to a resonant dipole operating at the same frequency. Despite the high degree of miniaturization, the resulting radiation efficiencies for the bifilar and quadrifilar antennas are found to be 87.1% and 90.6%, respectively. Furthermore, various quality-factor definitions are explored for the quadrifilar antenna, and it is observed that the resulting quality factor is around 1.83 (1.22) times that predicted by the Chu (Thal) lower bound.

Design of miniaturised printed quadrifilar helix antenna with isoflux coverage and wide‐angle circular polarisation

In the study, a miniaturised printed quadrifilar helix antenna (PQHA) with isoflux coverage and wide-angle circular polarisation is presented. It is composed of a three-stage stepped impedance spiral arm and open stubs. Each of the three-stage spiral arms has different pitches and number of turns. For the last-stage spiral arm, meander lines are used. The proposed PQHA features the characteristics of wide bandwidth, isoflux radiation, small size, and wide-angle circular polarisation. Moreover, in order to feed the proposed PQHA, a miniaturised quad-feed network is designed to provide equal amplitude signals with sequential orthogonal phases. For demonstration, a prototype is designed, fabricated, and measured. The overall size of the proposed antenna is 88 × 88 × 132 mm (0.44 λ0 × 0.44 λ0 × 0.66 λ0). The results show that isoflux radiation with a coverage of about ±60° is realised from 1.40 to 1.62 GHz (14.6%) while maintaining more than 10 dB return loss and larger than 200° 3-dB axial ratio beamwidth.

Multi-frequency quadrifilar helix antennas for cm-accurate GNSS positioning

Abstract For a few years now, GNSS multi-frequency quadrifilar helix antennas (QHA) are available to be used for precise GNSS applications. We performed test measurements with two types of multi-frequency QHA and compared them with a geodetic patch antenna. Although code and carrier phase noise and high-frequent multipath was determined to be larger as compared to the geodetic antenna, the fast-static horizontal coordinate accuracies are on the same level and demonstrate cm-accuracy capability. One of the QHA types exhibited an increased susceptibility to near-field multipath effects which resulted in a degraded accuracy of the vertical coordinate component.

Co-Circularly Polarized Van Atta Array Enabled by Quasi-Monostatic STAR Antennas

A true in-band full-duplex (IBFD) co-circularly polarized (CP) Van Atta array with the active enhancement of the radar cross section (RCS) at 2.45 GHz is demonstrated for the first time. This operation is enabled by a quasi-monostatic simultaneous transmit and receive (STAR) element consisting of two quadrifilar helix antennas (QHAs) counter wound with respect to each other and placed coaxially. Co-CP operation is realized by operating one helix in the forward mode and the other in the backward mode, which increases the isolation between the transmit (Tx) and receive (Rx) layers at the antenna level. To further enhance the isolation, the Van Atta array beamforming network (BFN) is formed from a reduced complexity CP configuration featuring only 90° hybrids and amplification. The concept of operation is verified through measurement of a two-element array and simulated eight-element array with aid from a novel method for the synthesis of Van Atta array performance from conventional range and bench measurements. The effect of mutual coupling in the array is examined along with the role of the phase delay in the BFN.

Spaceborne miniaturized UHF dual band helix antenna with a small frequency ratio

AbstractThis study proposes a novel miniaturized circularly polarized (CP) ultrahigh frequency (UHF) quadrifilar helix antenna for spaceborne applications. The dual‐band operation is realized using four inverted‐U shaped helical strips (IUSHSs) that are rotated and alternately arranged on the four faces of a hollow polyimide cuboid in a sequential rotation manner, which effectively reduces the size of the antenna. Furthermore, the four IUSHSs are connected by a cross‐shape strip at the top of the antenna to control the dual resonant frequencies, resulting in a small dual‐band frequency ratio. The proposed antenna is both lightweight and robust when compared with the conventional miniaturized CP antennas operating at similar bands with similar performance. In particular, its compact radiator provides effective miniaturized spaceborne solution without the need of high‐dielectric coefficient materials. A device for spaceborne application that operates at 402/505 MHz is designed, fabricated, measured, and in‐orbit tested with a weight of 651 g and an effective size of 0.161 × 0.161 × 0.228 λ3402MHz (λ402MHz is the wavelength at 402 MHz). The measured gain and axial ratio of the proposed antenna are better than 5.32 dBi and 2.18 dB, respectively, within 2 and 12 MHz bandwidth for the two bands. The test results proved that the methods used to design the proposed antenna are effective.

A Wide Beam Printed Quadrifilar Helix based Circularly Polarised Radiating Element for Electronically Steered Antenna

Wide beam and low axial ratio performance of printed quadrifilar antennas result in very attractive circularly polarised radiating element for wide scanned Electronically Steered Antenna. A compact printed quadrifilar Helix antenna (PQHA) has been designed and realised at S-Band frequency. Simulation and optimisation of designed antenna has been performed using ANSYS’s high frequency structure simulation (HFSS) software for its impedance, axial ratio (AR) performance and radiation characteristics. The developed circularly polarised antenna has 3-dB beam width of 130° and peak gain of 3.4dBic at 2.6 GHz. The developed antenna shows excellent AR performance over the frequency band as well as over the radiated beam. Half power axial ratio bandwidth of developed antenna is 27.4% (2.2 GHz - 2.9 GHz) while the impedance bandwidth is 32% (2.1 GHz - 2.9 GHz). Design has been validated through measured results. Designed wide band PQHA can be used as radiating element for electronically steered antenna for large beam steering application.

A low‐profile dual‐band circularly polarized antenna based on artificial magnetic conductor

A low-profile dual-band circularly polarized (CP) antenna with wide beamwidth is proposed in this article. The proposed antenna is composed of three layers of spiral patches, an artificial magnetic conductor (AMC) reflector and a four-feed network. The three-layer spiral patches as a quadrifilar helix antenna are employed to achieve dual-band CP radiation. Then, a metal ground is replaced by one square-shaped AMC surface to improve the antenna performance. With these antenna structures, the antenna size is only 0.36λ0 × 0.36λ0 × 0.106λ0 at 1.268 GHz. The antenna exhibits the impedance bandwidth ranging from 1.17 to 1.39 GHz and 1.49 to 1.58 GHz (|S11| < −10 dB). Furthermore, the proposed antenna has excellent axial ratio beamwidths of 171° at 1.268 GHz and 201° at 1.561 GHz. With these excellent characteristics, the designed antenna can be well applied to global navigation satellite systems.

Miniaturized wideband quadrifilar helix antenna for satellite navigation application

AbstractIn this article, we present a method for designing miniaturized and broadband quadrifilar helix antenna, which has better bandwidth than other smaller antennas and more compact than larger bandwidth antennas. The antennae in this design have same size with axial lengths of 24 mm and diameters of 18 mm. The antennae are miniaturized by folded arms and dielectric loading. In both cases, a short pin is added to adjust the impedance matching and broaden the bandwidth. Inside and outside diameters of the loading dielectric cylinder are the parameters used for controlling the center frequency, which can be shifted between 1.2 and 1.8 GHz. An antenna with a central frequency of 1.5 GHz was simulated and measured to verify the design. In addition, this design could provide bandwidth of 100 MHz for satellite navigation application. Two antennae, operating at 1.227 and 1.575 GHz with 100 MHz bandwidth, are simulated. The 1.227 GHz antenna covers GPS L2, BEIDOU B2 and B3, GLONASS G2, and Galileo E5b bands. The 1.57 GHz antenna covers GPS L1, BEIDOU B1, B1C, B1I, and Galileo E1 bands.

Desain dan Implementasi Antena Quadrifilar Helix untuk Komunikasi Antarpulau pada Pita UHF

Riau Islands, which consists of thousands of islands and is located in the border area of Indonesia, has its own challenges. Based on this strategic geographical location, there are threats and opportunities to develop inter-island information systems. Wireless long-range communication is considered the most suitable for these conditions. Antennas are an important part of wireless communication. Research and fabrication of the Helix Quadrifilar antenna by utilizing the advantages and consideration of simple, lightweight and inexpensive materials, as the receiver antenna in inter-island communication systems. In this research, the design was carried out with the assist of the Antenna Magus software, measurements were using a Vector Network Analyzer instrument, and testing accomplished under the LOS conditions. The results are fabricated antenna optimum frequency shift of 433 MHz to 452.5 MHz, within 5.88% error percentage. The antenna fabrication, which is measured at a frequency of 433 MHz, obtained return loss -13.06 dB and VSWR 1.5, that meets the criteria of 1 ≤ VSWR ≤ 2. Quadrifilar Helix Antenna fabricated results can receive data from GPS sensors, temperature, humidity, air pressure, wind speed and wind direction of up to 9 kilometers. So that this antenna is suitable to be used as an antenna for inter-island UHF communication.

Compact dual‐band printed quadrifilar helix antenna for practical hand‐held devices

Compact dual‐band printed quadrifilar helix antenna for practical hand‐held devices

QUADRIFILAR HELIX ANTENNA FOR WEATHER SATELLITE RECEPTION

The study designed and implemented quadrifilar helix antenna (QHA) for weather satellite signal reception. The antenna design and optimization were done by varying the element diameter, the radial lengths, the axial lengths, and element materials on adopted model. The simulated QHA has far-field radiation pattern in the upper hemisphere with maximum gain of 4.14dBi at 0o and omnidirectional coverage, half-power beamwidth of 140o, bandwidth of 6.5MHz, and VSWR of 1.13. The implemented QHA has major lobe in conformity with the simulated QHA with maximum gain of 10.75dB at 0o, and half-power beamwidth of 104o.