Planar Spiral Antenna Research Articles

High radiation efficiency and tunable resonance planar double-turn spiral antenna for manipulation of nitrogen-vacancy centers.

Nitrogen-vacancy (NV) centers in diamond are promising quantum sensors, where microwave antennas play a crucial role in manipulating the spin states accurately. Conventional microwave antennas often struggle to balance radiation efficiency and bandwidth. To address this challenge, we design a planar double-turn spiral antenna (PDTSA), based on the ring microstrip antenna (RMA). PDTSA demonstrates an ∼4.5-fold increase in radiation efficiency compared to RMA. In addition, the PDTSA allows linear tunability of the resonance frequency up to 500MHz by adjusting the spiral input length. This feature addresses the limitations of a narrow working frequency range, which are typically caused by the narrowband in high-radiation-efficiency antennas. The experimental results show that at an absolute input power of 1W, the PDTSA increases the Rabi frequency from 1.72 to 8.06MHz compared to the RMA. This enhancement accelerates quantum state manipulation and reduces phase accumulation errors. These characteristics make PDTSA suitable for applications in quantum sensing and precision measurements using NV centers.

A Compact Circularly Polarized Planar Spiral Antenna With Ultrawide Bandwidth and Directional Radiation Pattern

A compact circularly polarized (CP) planar spiral antenna with ultrawide bandwidth and directional radiation pattern is proposed for ultra‐wideband (UWB) positioning applications. The proposed antenna consists of a dual‐arm planar spiral with a tapered microstrip line, two L‐shaped metallic shorting stubs, and a square ground plane with four stepped slots. By connecting two L‐shaped metallic stubs to both the ends of the dual‐arm spiral through metal posts, the traveling wave current path is effectively extended, resulting in a significant improvement of the CP bandwidth. Additionally, both impedance bandwidth and circular polarization performance of the proposed antenna can be enhanced by adopting four stepped slots on the square ground plane. Measured results show that the planar spiral antenna features an impedance bandwidth from 3.23 GHz to 7.0 GHz (more than 73.7%), a 3‐dB axial ratio (AR) bandwidth of 62.1% (3.05 GHz–5.8 GHz), and finally achieves an overlapping bandwidth of 56.9% (3.23 GHz–5.8 GHz). On the overlapping bandwidth, this antenna maintains a gain consistently above 6 dBic while the peak gain reaches about 7.4 dBic. The overall size of the antenna is 0.59λg × 0.59λg × 0.17λg (λg is the free‐space wavelength at the lowest frequency, 3.23 GHz). Thanks to the ultrawide CP bandwidth and compact size, the proposed antenna can be a promising candidate for UWB positioning applications.

Coherent manipulation of nuclear spins in the strong driving regime

Spin-based quantum information processing makes extensive use of spin-state manipulation. This ranges from dynamical decoupling of nuclear spins in quantum sensing experiments to applying logical gates on qubits in a quantum processor. Fast manipulation of spin states is highly desirable for accelerating experiments, enhancing sensitivity, and applying elaborate pulse sequences. Strong driving using intense radio-frequency (RF) fields can, therefore, facilitate fast manipulation and enable broadband excitation of spin species. In this work, we present an antenna for strong driving in quantum sensing experiments and theoretically address challenges of the strong driving regime. First, we designed and implemented a micron-scale planar spiral RF antenna capable of delivering intense fields to a sample. The planar antenna is tailored for quantum sensing experiments using the diamond’s nitrogen-vacancy (NV) center and should be applicable to other solid-state defects. The antenna has a broad bandwidth of 22 MHz, is compatible with scanning probes, and is suitable for cryogenic and ultrahigh vacuum conditions. We measure the magnetic field induced by the antenna and estimate a field-to-current ratio of G/A, representing a six-fold increase in efficiency compared to the state-of-the-art, crucial for cryogenic experiments. We demonstrate the antenna by driving Rabi oscillations in 1H spins of an organic sample on the diamond surface and measure 1H Rabi frequencies of over 500 kHz, i.e. -pulses shorter than 1 —an order of magnitude faster than previously reported in NV-based nuclear magnetic resonance (NMR). Finally, we discuss the implications of driving spins with a field tilted from the transverse plane in a regime where the driving amplitude is comparable to the spin-state splitting, such that the rotating wave approximation does not describe the dynamics well. We present a simple recipe to optimize pulse fidelity in this regime based on a phase and offset-shifted sine drive, which may be optimized in situ without numerical optimization procedures or precise modeling of the experiment. We consider this approach in a range of driving amplitudes and show that it is particularly efficient in the case of a tilted driving field. The results presented here constitute a foundation for implementing fast nuclear spin control in various systems.

A compact radio-frequency ion source for high brightness and low energy spread negative oxygen ion beam production.

A high brightness and low energy spread (∆E) ion source is essential to the production of a high-quality primary ion beam applied in secondary ion mass spectrometry (SIMS). A compact 13.56MHz radio-frequency (RF) ion source with an external planar spiral antenna has been developed as a candidate ion source for the production of negative oxygen ion beams for SIMS application. This ion source is designed with a three-and-a-half-turn water-cooled planar antenna for RF power coupling, a multi-cusp magnetic field for effective plasma confinement, and a three-electrode extraction system. The experimental results show that more than 50 µA negative oxygen ion beams have been extracted, which consist of 56% O-, 25% O2-, and 19% O3-. The ion energy distribution of the negative oxygen ion beam exhibits a Gaussian distribution with a minimum ∆E of 6.3eV. The brightness of the O- beam is estimated to be 82.4Am-2 Sr-1V-1. The simulation, design, and experimental study results of this RF ion source will be presented in this paper.

Development of a fully planar logarithmic spiral antenna with integrated balun in UWB GPR systems for landmines detection

ABSTRACT In this paper, a compact cavity-backed logarithmic spiral antenna with an integrated broadband planar balun is presented. This fully planar antenna is used for detection of anti-personnel (AP) landmines in GPR systems. Unlike conventional spiral antennas, which are fed by unbalanced coaxial cable or vertical baluns, and these feed lines make them bulky and frail, in this design, a microstrip-to-parallel strip balun is integrated with the spiral antenna and makes the whole structure compact, planar, and robust. Moreover, a metal cavity is utilized at the back of the antenna to prevent backward radiation and enhance the forward penetration depth to the ground. In choosing the operational frequency bandwidth, a compromise is made between the penetration depth and detection resolution. A prototype of the antenna is fabricated and its performance in landmine detection is evaluated with measurements. The measured results show that the antenna works over the frequency range of 1.5 GHz−4.5 GHz (bandwidth = 100%) with |S11| < −10 dB, a penetration depth of 10 cm in the soil with good detection resolution, gain >8 dB and axial ratio <3 dB. These factors make the proposed antenna a suitable candidate for pulse radar applications, in which low pulse distortion and wide bandwidth are key factors.

A novel dual-port dual-layer planar spiral slot multiband antenna

In order to realize a dual-port multiband antenna, a novel planar spiral slot antenna is proposed and analyzed. The antenna adopts a dual-layer substrate structure. A spiral slot is etched on its bottom metal surface with a ring gap beside the slot to improve the isolation and lower the frequency. An elliptical metal ring radiation unit in the middle surface of the antenna plays the role of radiating and impedance matching. Two mutually perpendicular microstrips on the upper surface are used for feeding the radiation unit. The simulation and test results show that two ports of the antenna can work at multiple frequencies with the same radiator, and the isolation is more than 13.5 dB in the working bands (1.86-1.99 GHz, 2.47-2.5 GHz, 2.57-2.64 GHz, 2.90-5.7 GHz and 6.35-9.66 GHz). The antenna has the advantages of high gain, small volume, quasi omnidirectional radiation, and so on.

Wideband composite planar spiral antenna for generation of tunable angular momentum wave.

In this paper, a composite planar spiral antenna consisting of an eight-arm equiangular spiral antenna and eight Archimedean spiral antennas has been designed to radiate electromagnetic wave carrying tunable angular momenta in a wide band. A tunable eight-way Wilkinson power divider network is used to offer three kinds of feeding modes for the equiangular spiral antenna, and thus the composite antenna can radiate the electromagnetic waves with angular momenta of the modes l=1, 2, and 3, respectively. The Archimedean spiral is introduced to improve the gain of the composite antenna in the case of the angular momentum of l=3. By analyzing axis ratio (AR) of the proposed antenna, the generated angular momentum of l=1 is spin angular momentum (SAM), and the angular momenta of both l=2 and 3 include SAM and orbital angular momentum (OAM). Simulated and measured results are given to demonstrate good performance including tunable modes, good purity and wide band.

Present Situation and Development of Internal Sensors for Ultra-high Frequency Detection in Gas Insulated Switchgear

This paper discusses the application situation of the ultra-high frequency (UHF) method and optical method in the detection of partial discharge of gas insulated switchgear (GIS), and the differences between external and internal UHF sensors. The sensor is a key technology in the PD detection method, and its performance directly affects the validity of the monitoring results. Different partial discharge detection sensors have different characteristics and working environments. UHF sensor has the advantages of wide detection range and convenient layout. Optical sensors have the advantages of high sensitivity and fast response speed. Six main types of internal sensors are evaluated and the performance indicators of internal sensors are discussed which includes disc antenna, loop antenna, dipole antenna, planar spiral antenna, conical antenna, photoelectric composite sensor. Furthermore, some problems need to be solved are proposed for further research, which is of great significance to the safe and stable operation of power equipment.

Fully planar frequency independent square Archimedean spiral antenna with impedance transformer for ground penetrating radars

AbstractAn ultra‐wideband unidirectional circularly polarized planar self‐complementary and compact Archimedean square spiral antenna is proposed in this paper. Compared to the conventional center‐fed or vertically‐connected coaxial line spiral antennas, the proposed antenna has a completely planar feed structure. The traditional impedance transformer (balun) in the third dimension is moved to the planar plane based on a wideband microstrip line to coplanar stripline transition to realize a completely planar spiral antenna. This impedance transformer is integrated with the spiral antenna to achieve a planar structure and to adapt the impedance into a conventional 50 Ω coaxial cable. The performance of the proposed antenna is simulated and measured. The proposed antenna has a compact size of 90 × 90 × 1.6 mm3 on an FR4 substrate and can yield a large −10 dB impedance bandwidth ranging from 2.14 to 9.8 GHz which is equivalent to a fractional bandwidth of 102.13% with unidirectional radiation patterns. The VSWR is less than two in the operating bandwidth and the axial ratio (AR) is less than 3 dB in the frequency range of 1‐8 GHz. The simulated radiation efficiency ranges between 20% and 80%. The characteristics of the proposed antenna make it suitable for ground‐penetrating radar applications and many others.

Modeling and analysis of the spiral antenna properties for the research of the brain radiatio in the microwave range

This paper investigates a planar single-arm spiral antenna used to measure human brain radiation in the frequency range 3-5 GHz. The investigation is carried out using numerical modeling (finite elements method) by employing ANSYS Electromagnetics Suite 19.2. The model of human brain tissues and the antenna are built in this software. The optimization of antenna parameters is carried out to obtain the best matching and sensing depth. The frequency dependence of the antenna input impedance, reflection coefficient is computed, and the volume distribution of electromagnetic field in the head tissues is obtained. We investigate the influence of the matching layer to the antenna characteristics in the case of the deviation of the electrical parameters of the head tissue top layers. The matching layer is located between the spiral antenna plane and the surface of the head. The additional simulation is carried out by using WIPL-D Pro EM simulator to validate the obtained results. Shabashov E. P., Shabunin S.N., Mrdakovic B. Modeling and analysis of the spiral antenna properties for the research of the brain radiation in the microwave range. Ural Radio Engineering Journal . 2020;4(1):84–99. DOI: 10.15826/urej.2020.4.1.005

A Broadband Planar Spiral Antenna Design for Electromagnetic Signal Monitoring

In order to meet the wide-band full-space radio monitoring task, the design of a circular-polarized planar dual-arm composite spiral antenna is presented in this paper. The antenna operation covers the L-band and S-band frequencies ranging from 200 MHz to 6 GHz (relative bandwidth is 187.1%). The equiangular spiral is applied to the beginning of the Archimedean spiral, which reduces the input impedance of the antenna, thereby reducing the length of the cross-section of the feed balun and realizing the miniaturization of antenna. The antenna is designed to be simple in structure and small in size. The diameter of the radiating surface and the length of the section are only 1/5 and 1/50 of the working wavelength. The simulated and measured results show that the antenna has a very good impedance matching (standing wave ratio of less than 2.5), and the antenna has good symmetry, and has good circular polarization and wideband characteristics. Finally, the antenna is applied with an USRP (universal software radio peripheral) to carry out the electromagnetic signal monitoring experiment outdoors. The results show that the designed antenna can receive electromagnetic signals in the 200 MHz - 6 GHz band and can be used for full-space radio monitoring.

Compact multiple cut‐corners square spiral antenna for stepped‐frequency continuous wave radar system

AbstractStepped frequency continuous wave (SFCW) radar is a promising noncontact method to detection of human vital signs. Antenna as a key component of radar directly related to the performance of the radar. In this letter, we present a 0.5‐1.2 GHz compact multiple cut‐corners square spiral antenna for SFCW radar system. Compared with conventional planar spiral antennas, the improved antenna possesses the advantages of miniaturization and excellent axial ratio. The gradient‐change of the cut‐corners along the radiation determines its operation range: large cut‐corner corresponds to high frequency, while small cut‐corner affects low frequency. This design successfully leads to a small geometric size of 0.282 × 0.282 × 0.133 m. We measured this improved antenna in an anechoic chamber, and the results demonstrated that the circular polarization bandwidth for axial ratio ≤3 dB approached 100%, and a right‐hand circularly polarization (RHCP) gain of 4‐8.98 dBic in end‐fire direction is achieved in its operational range. Finally, we designed the experiment, experimental results show that the proposed antenna can work well with the SFCW radar in the detection of human vital sign (respiratory signals), indicating a great potential for detected life in practice.

Production of O- and O2 - beams with the negative ion source at Institute of Modern Physics.

A negative oxygen ion source is under development to produce O- and O2 - beams used for a secondary ion mass spectrometer at Institute of Modern Physics (IMP), and both filament and radio frequency (RF) schemes are tested. The filament driven ion source, which was initially designed for H- production, has a 10-pole multicusp plasma chamber, two sets of virtual magnetic filters, and a 3-electrode extraction system. The RF scheme, which is improved by changing a RF back plate from the filament ion source, has an external planar spiral RF antenna behind an AlN window. The RF power system consists of a continuous wave (CW) 13.56 MHz/2 kW power supply, a capacitive automatching network and a water-cooled flat RF antenna made from a 6-mm copper tube. Oxygen and carbon dioxide gases are used to produce O- and O2 - ion beams, and ion composition is analyzed by using a Wien filter. However, the lifetime of filaments sustains from several minutes to hours before fracture occurred while the RF one can work stably with no maintenance, and the experiment results will be given on O- ion production with two different technologies using our ion source test facility.

The Design of Planar Rectangular Spiral Antenna for Corona Discharge in Transmission Lines

With the increasing grade of high voltage transmission lines, the frequent occurrence of corona discharge has brought great potential safety risk and power losses to power system. Therefore, the detection of corona discharge in transmission lines is of great significance to power system. Rectangular spiral antenna is widely used because of its smooth impedance and better circular polarization characteristics. In this paper, a planar rectangular spiral antenna is designed for the detection of radio frequency electromagnetic waves given out corona discharge of transmission lines. The basic structure of the antenna is determined by optimizing the length, spacing and turns of coil. The feasibility of the antenna is verified by experiments.

Comparison of plasma-enhanced atomic layer deposition AlN films prepared with different plasma sources

A comparative study of thin aluminum nitride (AlN) films deposited by plasma-enhanced atomic layer deposition in the SENTECH SI ALD LL system applying either a direct inductively coupled plasma (ICP) or an indirect capacitively coupled plasma (CCP) source is presented. The films prepared with the ICP source (based on a planar triple spiral antenna) exhibit improved properties concerning the growth rate per cycle, total cycle duration, homogeneity, refractive index, fixed and mobile electrical charges, and residual oxygen content compared to the CCP source, where the comparison is based on the applied plasma power of 200 W. The increase of the plasma power to 600 W in the ICP process significantly reduces the residual oxygen content and enhances the electrical breakdown field. The AlN layers grown under these conditions, with a growth rate per cycle of 1.54 Å/cycle, contain residual oxygen and carbon concentrations of about 10% and 4%, respectively, and possess a refractive index of 2.07 (at 632.8 nm).

Dual CP Polarization Diversity and Space Diversity Antennas Enabled by a Compact T-Shaped Feed Structure

A compact T-shaped feed structure (TFS) is reported that enables the realization of two types of diversity antennas: a polarization diversity antenna (PDA) and a spatial diversity antenna (SDA). Both systems have a high potential for mobile wireless communication applications. The TFS includes four ports and two independent coaxial channels with effective isolation between them all. The PDA is a dual CP omnidirectional antenna. Its optimized prototype achieves measured impedance bandwidths of 16.4% and 15.28% in its LHCP and RHCP states, respectively, and realized gains in both between 4.8 and 6.46 dBic. The inner thin coaxial cable (ITCC) of the TFS directly drives its LHCP subsystem, facilitating its improved omnidirectional performance. This ITCC is also used to directly feed the SDA’s low-profile directional planar equiangular spiral antenna and its side port drives its omnidirectional RHCP antenna. Good hemispherical coverage is realized with a measured common impedance bandwidth larger than 14.35% with more than 40-dB isolation between its two ports. The corresponding measured realized gain of the SDA is between 4 and 7.8 dBic. The measured results for both optimized prototypes confirm their simulated performance characteristics.

A passive SPICE model for rectennas

PurposeThis paper aims to present a SPICE model to represent antennas in receiving mode. The model can be used to evaluate the performance of the antenna when it is coupled to several different nonlinear electric circuits. The proposed methodology is particularly suitable for rectenna applications, as it allows the analysis of different configurations for a rectenna more efficiently than using full-wave analysis simulators coupled directly to each rectifier circuit.Design/methodology/approachThe model presented uses reciprocity theory to calculate the ideal voltage source of the Thevenin-equivalent circuit for an antenna. Vector fitting is then used to approximate the model to rational functions that can be converted to Resistor, Inductor and Capacitor circuits. Additional components are added to the circuit to prevent numerical instability.FindingsTwo rectennas are used to illustrate the performance of the proposed model, one based on a 2.45-GHz rectangular patch antenna and another based on a planar spiral antenna. The second antenna has impedance with positive and negative real parts along the frequency range, which could lead to numerical instabilities. The proposed method is shown to be stable while working with these negative resistance values, which may appear during circuit parameterization.Research limitations/implicationsThe equivalent SPICE circuit model for the antenna makes it easy to simulate nonlinear circuits connected to the antenna and perform transient analyses. The computational cost of antenna analysis is reduced, being more computationally efficient than methods that involve full-wave simulation. This characteristic makes it an interesting approach for working with rectennas, or any application where the time constant of the circuit is much longer than the period of the incident wave.Originality/valueFor most antenna applications, the numerical stability of the circuit can be achieved using passive enforcement. However, depending on the phase response of the antenna, the impedance that represents its far-field characteristic may present a negative real part, in which case, passive enforcement will fail. In this paper, the problem of numerical instability is solved by introducing an offset resistance and a current-controlled voltage source to the model.

WIDEBAND PLANAR SPIRAL ANTENNA WITH PERIPHERAL FEEDING

The topology of a planar Archimedes spiral antenna with a small number of turns is presented. Its main feature is the peripheral feeding of the spiral, which does not violate the planarity of the structure. On the basis of numerical simulation, the main electrodynamic characteristics for several antenna designs, differing in the number of turns, including the constant and variable width of the tape of the spiral element, are obtained, compared and discussed. The results of the numerical analysis showed that the relative bandwidth defined by the VSWR at the antenna input and by the directivity, reach from 75 to 120 percent.

Diode Circuit-based Glass Plasma-Chemical Etching Capabilities

The paper discusses technological capabilities to improve a plasma-chemical etching (PCE) rate of the silicate glasses through a chromium mask in the equipment with a planar inductor located outside, which forms a high-frequency diode system. Suggests a case when the inductor in the form of a planar spiral antenna is above the work-piece.The PCE process stages were analytically studied and the limiting effects of each step that affect the etching rate and the quality of the treated surface were determined. The paper shows that for the type of equipment under consideration the stage of removing etch products from the work-piece is a quality-limiting factor for the PCE-exposed surface while the limiting factor for the etching rate is the stage of formation of chemically active particles (CAP) in plasma.The comparison of analytical results with the experimental data shows that in the considered case plasma of low density and high pressure is formed. The experimentation was aimed at studying the impact of the surface position under treatment and the working pressure in the chamber on the etching rate and the peculiarities of the etched surface formation. As a treated material, the blanks of the photomasks for integrated circuits made from Cr-covered silicate glass were considered. The electron beam lithography method was used to create a mask for the PCE process.It was experimentally found that when a treating surface of the work-piece in plasma is “downward” the etching depth is by 5-10% more than the etching depth of the “upward” surface. Another finding was that with raising gas flow the etching depth was twice increased as well.Optical-microscopic examinations of the etched surfaces of work-pieces have shown that there are areas with green or brown coating. Supposedly, this is due to the effect of the reverse deposition of the mask material as in the form of CrF3, CrF4 compounds that reinforce the need to look for a replacement of the chrome mask.The etching rates of 45-90 nm/min are obtained for the silicate glass, which is close in composition to the optical glass of K8 grade. This allows using the PCE in the equipment with a planar inductor located outside the chamber and realizing a high-frequency diode circuit to produce diffraction and hologram optical elements with a depth of the surface relief up to 400-500 nm.

Compact Circularly Polarized Archimedean Spiral Antenna for Ultrawideband Communication Applications

A novel compact circularly polarized Archimedean spiral antenna for ultrawideband (UWB) communication applications is presented. The basic structure is a two-arm planar Archimedean spiral antenna, which is fed by a tapered wideband balun. These two arms are extended on the profile and connected together at the end to elongate current path, while four lumped resistors are loaded on them to improve the reflection coefficient at low frequency. A circular reflector with cross slots that consists of one circular slot at the junction of two orthogonal rectangular slots are designed and optimized, which improves the performance of axial ratio (AR). The proposed antenna has a compact size of 36 × 36 × 20 mm3. The voltage standing-wave ratio is less than 2.5 in the frequency range of 1.9–8.5 GHz and the AR is less than 3 dB in the frequency range of 2–6 GHz. Both the simulation and measurement results are presented, demonstrating the UWB characteristics of the proposed antenna for wireless communication applications.