Low-profile Spiral Antenna Research Articles

Design of High-Sensitivity Flexible Low-Profile Spiral Antenna Sensor for GIS Built-in PD Detection.

Spiral antenna sensors are commonly used in partial discharge (PD) ultra-high frequency (UHF) detection in gas-insulated switchgears (GISs). However, most of the existing UHF spiral antenna sensors are based on a rigid base and balun, such as FR-4. The safe built-in installation of antenna sensors requires the complex structural transformation of GISs. To solve this problem, a low-profile spiral antenna sensor is designed based on a polyimide (PI) flexible base, and its performance is optimized by improving the clearance ratio. The simulation and measurement results show that the profile height and diameter of the designed antenna sensor is 0.3 mm and 137 mm, which is 99.7% and 25.4% smaller than the traditional spiral antenna. Under a different bending radius, the antenna sensor can maintain VSWR ≤ 5 in 650 MHz~3 GHz, and its maximum gre is up to 6.1 dB. Finally, the PD detection performance of the antenna sensor is carried out on a real 220 kV GIS. The results show that, after being built in, the PD with a weak discharge magnitude of 4.5 pC can be effectively detected by the antenna sensor, and the antenna sensor has the ability to quantify the severity of PD. In addition, through the simulation, the antenna sensor has potential for the detection of micro water in GISs.

Low-Profile Wideband Spiral Antenna With a Circular HIS Reflector Composed of Homogenous Fan-Shaped Patch Elements

A low-profile spiral antenna backed by a circular high-impedance surface (HIS) reflector composed of homogeneous (CirHISRhomo) fan-shaped patch elements is investigated. The total antenna height from the bottom of the CirHISRhomo to the spiral antenna is very small: 0.09 wavelength at a lowest design frequency of 3 GHz. It is revealed that the CirHISRhomo contributes to a constant input impedance and a small axial ratio (AR) across the design frequency range of 3–10 GHz (the fractional bandwidth is approximately 108%). For comparison, the AR for the spiral antenna backed by a conventional perfect electric conducting reflector is also presented. The analysis results are verified by the measured results of the fabricated antenna.

Low-Profile Spiral Antenna Placed on an Extremely Thin Magnetodielectric Substrate

This letter presents a low-profile spiral antenna with an extremely thin magnetodielectric substrate (MagDS), which is backed by a conducting plane. A MagDS thickness of 0.1 mm (0.0001 λ at 300 MHz) provides a purely input resistance with an axial ratio of less than 3 dB across a wide frequency range. Using this thickness value, the radiation characteristics are analyzed. It is revealed that a VSWR of less than 2 and an axial ratio of less than 3 dB are obtained across a frequency range of 300–1000 MHz (fractional bandwidth: 108%). It should be emphasized that the total antenna height from the bottom conducting plane to the antenna top surface is very small: 0.061 λ at 300 MHz. Simulated results are confirmed by experimental work.

A novel textured ferrite ground plane for low-profile spiral antenna

This paper presents a novel textured ferrite ground plane for the metallic cavity used as a ground plane for spiral antennas. Impedance-matched ferrite is used at the outer rim of the ground plane, and a high impedance ferrite is employed in the inner section of the cavity. Simulations show that this textured ferrite ground plane improves the spiral performance at both low frequencies and high frequencies.

Effect of air-gap on axial ratio of low profile spiral antenna

A low-profile offset-fed spiral antenna over an artificial magnetic conductors (AMC) ground plane is studied in which the AMC ground plane has a two-layer structure with an air-gap present between the layers.The effect of such air gaps on the axial ratios of the antenna is investigated. The predicted numerical results are verified by testing a prototype sample of the proposed antenna showing a satisfactorily agreement between them. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2422–2423, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26248

Low Profile Spiral on a Thin Ferrite Ground Plane for 220–500 MHz Operation

A small size, low profile spiral antenna (2 thick and 14 in aperture) is described that is backed by a thin ferrite ground plane. The antenna is intended to cover Satellite (UHF TacSat earth to LEO: 243-318 MHz) and enhance Radio (PRC-148, PRC-117F, PSC-5D: 243-512 MHz) communications. We carry out a step-by-step design to achieve the challenging goals of RHCP gain >0 dBi at θ = 0°; Bandwidth 220-500 MHz; VSWR <;2:1; Low LHCP (cross-pol) gain (<; -10 dBi); Low profile (2) and desired aperture size 14. Ground plane ferrite treatment, inductive loading, resistive termination and impedance matching techniques are adopted to raise the gain between 200-300 MHz and achieve the stated goals. As the aperture size is about λ/3.5 at 220 MHz and only λ/30 in height, achieving 0 dBi (from 220-500 MHZ) is quite challenging. Measured and simulated data are presented in the last section leading to impressive conclusions about the capability of the magnetic material coating to overcome the perennial issue associated with the ground plane's negative effects.

The Broadband Spiral Antenna Design Based on Hybrid Backed-Cavity

Here, a hybrid backed-cavity with electromagnetic band-gap (EBG) structure and a perfect electronic conductor (PEC) is proposed for an Archimedean spiral antenna. This cavity makes the spiral antenna work operate over the 10:1 bandwidth and without the loss introduced by absorbing materials that are used conventionally to broadband spirals. Based on the artificial magnetic conductor (AMC) characteristic, an EBG is placed in the outer region of backed-cavity to improve the blind spot gain at low frequency. A PEC at the center of the structure is used to obtain high gain at high frequency. The antenna performances are improved significantly for of the low profile spiral antenna is improved significantly. A typical spiral antenna with a hybrid backed cavity is fabricated and studied experimentally. The experimental data are consistent with that of the simulation results.

The Numerical Simulation of the Broadband Spiral Antenna Design Based on Hybrid Backed-Cavity

In the paper, the hybrid backed-cavity with EBG (Electromagnetic Band-Gap) structure and PEC (Perfect Electronic Conductor) is proposed for Archimedean spiral antenna, which can make the spiral antenna work over the 10:1 bandwidth, without the loss introduced by absorbing materials. Based on the AMC characteristic (Artificial Magnetic Conductor), the EBG is placed in the outer region of backed-cavity to improve the blind spot gain in the low frequency. The PEC at the center of the structure is used to obtain high gain at high frequency. The better antenna performances are achieved in the low profile spiral antenna. A typical spiral antenna with hybrid backed cavity is numerically studied. The novel spiral antenna design with hybrid backed cavity is validated by simulated results.

Size Reduction of a Low-Profile Spiral Antenna Using Inductive and Dielectric Loading

This letter discusses a miniature low profile ultrawideband (UWB) spiral. The antenna is miniaturized using a combination of dielectric and inductive loading. In addition, a ferrite coated ground plane is adopted in place of the traditional metallic ground plane for profile reduction. Using full-wave simulations and measurements, it is shown that the miniaturized spiral can achieve similar performance to a traditional planar spiral twice its size.

Low profile spiral antenna with PBG substrate

A novel spiral antenna backed on photonic bandgap (PBG) material is presented. It consists of a spiral radiator, a PBG substrate and a feed network; and exhibits a wider frequency bandwidth, larger ratio of front-to-back radiation level, and higher gain than a traditional spiral antenna with /spl lambda//4 spaced ground plate.

Spiral antenna with coplanar strip line feed

A low-profile spiral antenna composed of a small number of turns is developed as a radiation element for circular polarisation. The spiral is fed without a balun circuit from a coplanar strip line located in the middle of two conducting planes. The upper plane has a circular aperture for the spiral to radiate. The spiral arm is optimised for 11.85 GHz. An array antenna consisting of four spirals is fabricated and the radiation characteristics are presented.