• Journal of Electrical Engineering and Technology
• /
• v.8 no.4
• /
• pp.856-862
• /
• 2013

A cavity-backed two-arm spiral antenna for partial discharge diagnosis is presented. The proposed antenna consists of a two-arm Archimedean spiral, a tapered microstrip balun as spiral antenna feed, and a ring-shaped absorber-loaded cavity. The Archimedean spiral antenna is designed for the operating frequency band of 0.3 GHz to 1.5 GHz and fed by the tapered microstrip balun. The cavity is utilized to transform the bidirectional beam into a unidirectional beam, thereby enhancing gain. The ring-shaped absorber is stacked in the cavity to reduce the reflected waves from the cavity wall. The proposed antenna is designed and simulated using CST Microwave Studio. A prototype of the proposed antenna is likewise fabricated and tested. The measured radiation patterns are directional to the positive z-axis, and the measured peak gain is 8.13 dBi at a frequency of 1.1 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.6
• /
• pp.627-634
• /
• 2010

In this paper, a novel voltage-controlled oscillator(VCO) using the complimentary bifilar archimedean spiral resonator(CBASR) is presented for reducing the phase noise characteristic. A CBASR has compact dimension, a sharp skirt characteristic in stopband, a low insertion loss in passband, and a large coupling coefficient value, which makes a high Q value and improve the phase noise of VCO. The proposed VCO has the oscillation frequency of 2.396~2.502 GHz in the tuning voltage of 0~5 V, the output power of 7.5 dBm and phase noise of -119.16~-120.2 dBc/㎐ at the offset frequency of 100 kHz in tuning range.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.24 no.1
• /
• pp.36-46
• /
• 2013

This paper proposes the design of broadband spiral antenna for a potable non-linear junction detector (NLJD) system. To realize the broadband antenna design, it was considered optimization of the number of spiral turns by iteration calculation. Ground plane with the Archimedean spiral slit to keep the same current distribution between radiating plane and ground is considered for circular polarization design. In order to realize high directivity and high gain of the proposed antenna, the cavity wall and the metal cap which is located on back of ground plane were also considered in design. Measurement results of return loss were agreed well with VSWR 2:1 at interested frequency band among 2.4 to 2.44 GHz, 4.84 to 4.92 GHz and 7.28 to 7.36 GHz. Measured axial ratio was observed 3 dB below and showed reasonable agreement with simulation results. Characteristics of the RHCP(Right Hand Circular Polarization) with the measured gain of 6.8 dBi above at interested frequency band were also observed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.21 no.3
• /
• pp.269-277
• /
• 2010

In this paper, the design of a 0.5~2 GHz cavity-backed spiral antenna is described. Combined arm pattern with a log spiral in the inner region and an Archimedean spiral in the outer region, a backing cavity, and a Marchand coaxial balun for feeding are designed. Termination resistors are used to improve antenna characteristics at the lower frequency of the operation frequency. VSWR, axial ratio, gain and HPBW(Half Power Beam Width) characteristics are simulated using CST's MWS. Finally, the validity of these approaches is verified by comparing the simulated results with the measured ones. Also, the measurement results are compared with the performance of a commercial spiral antenna.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.28 no.4
• /
• pp.251-260
• /
• 2017

This paper describes the design of a slit on ground plane to improve the axial ratio of the spiral antenna for the NLJD system application. A proposed slit shape located on the ground plane is changed to compare with the archimedean spiral slit shape of the antenna in reference [7]. In order to improve the axial ratio, the slit on the ground plane is divided by the uniform angle and the conductor of position where the current has the opposite direction each other is eliminated. Measured return loss, radiation pattern and gain show a good agreement with the computer simulation results. Even though the proposed slit structure on the ground plane was changed to compare with ones of reference [7], the characteristics such as return loss, radiation pattern and gain are not almost changed and only the axial ratio was remarkably improved at 4.88 GHz.

• Tunnel and Underground Space
• /
• v.30 no.4
• /
• pp.394-403
• /
• 2020

This technical note describes the calculation method of continuous constant linear velocity Archimedean spiral paths which are applied to the pin-on-disk abrasion test. Approximate constant linear velocity Archimedean spirals have unstable velocities in the very near region of the rotational origin. Thus, in this technical note, the offset distance from the rotational origin was given by using a hollow type rock sample to maintain the constant velocity during the test. Also, to connect the inward and outward spirals continuously, the information of start and end points were input on the next spiral path consecutively. Furthermore, the calculation program was developed to provide convenience for calculating constant linear velocity spirals according to the specimen dimension and abrasion test conditions.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.49 no.12
• /
• pp.89-94
• /
• 2012

In this paper, a UHF cavity-backed spiral antenna for partial discharge diagnosis is proposed. The proposed antenna consists of two-arm Archimedean spiral, a cavity, and a balun for feeding. The spiral antenna is designed for 0.3-1.5 GHz operating frequency. Two spiral arms of the proposed antenna are fed by a microstrip tapered-balun. In order to enhance the gain, the cavity is located in the back side of the spiral pattern. The proposed antenna is designed and simulated using CST Microwave Studio. The designed antenna is also fabricated and tested to validate performance. The measured radiation patterns are directional to the +z-axis and measured peak gain is 9.92 dBi.

• Tunnel and Underground Space
• /
• v.30 no.3
• /
• pp.181-192
• /
• 2020

Pin-on-disk test is a suggested abrasion testing method by ASTM (American Society for Testing and Materials). This briefly illustrated the Archimedean spiral motion of a pin type specimen on a disk. To apply this method to rock cutting tools, a constant linear velocity (CLV) is precisely maintained during the test. We defined the two velocity vectors (RPM and horizontal speed) which connected to the resultatnt velocity. We derived a differential equations for the two parameters under CLV condition. It was difficult to find a exact solution. Previous literatures had been reviewed, and an approximate solution was investigated. We mathematically simulated the result for a certain parameter, and examine the accuracy of the solution.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.19 no.10
• /
• pp.1166-1174
• /
• 2008

In this paper, design of a $2{\sim}18$ GHz wideband cavity-backed spiral antenna is investigated. Firstly, an arm pattern and a backing cavity of a cavity-backed spiral antenna are designed based on the design theory of an Archimedean spiral antenna as well as by using CST's MWS. VSWR, axial ratio, and HPBW(Half Power Beam Width) characteristics are considered in the simulation. Secondly, a Marchand coaxial balun is designed to meet the required VSWR within the frequency band of operation. Finally, the validity of these approaches is verified by comparing the simulated results with measured ones.

• Journal of electromagnetic engineering and science
• /
• v.13 no.3
• /
• pp.165-172
• /
• 2013

This paper describes a design for a spiral antenna with a conical wall to obtain the high gain. The gain and the axial ratio of the spiral antenna were improved by a new design that included a conical wall and an optimized Archimedean slit on the ground plane in a conventional antenna with a circular cavity wall and a 4.5-turn slit. A gain improvement of 9.5 dBi higher and a good axial ratio of 1.9 dB lower were measured by the added conical wall and the newly designed slit from the current distribution control on the ground plane, respectively. The measured return loss, gain and axial ratio of the proposed antenna showed a good agreement with the simulated results. The proposed antenna will be applied to a non-linear junction detector system.