Efforts to protect electric power systems from faults have commonly relied on the use of ultra-high frequency(UHF)antennas for detecting partial discharge(PD)as a common precursor to faults.However,the effectiveness o...Efforts to protect electric power systems from faults have commonly relied on the use of ultra-high frequency(UHF)antennas for detecting partial discharge(PD)as a common precursor to faults.However,the effectiveness of existing UHF antennas suffers from a number of challenges such as limited bandwidth,relatively large physical size,and low detection sensitivity.The present study addresses these issues by proposing a compact microstrip patch antenna with fixed dimensions of 100 mm×100 mm×1.6 mm.The results of computations yield an optimized antenna design consisting of 2nd-order Hilbert fractal units positioned within a four-layer serpentine arrangement with a fractal unit connection distance of 3.0 mm.Specifically,the optimized antenna design achieves a detection bandwidth for which the voltage standing wave ratio is less than 2 that is approximately 97.3%of the UHF frequency range(0.3–3 GHz).Finally,a prototype antenna is fabricated using standard printed circuit board technology,and the results of experiments demonstrate that the proposed antenna is capable of detecting PD signals at a distance of 8 m from the discharge source.展开更多
Fractal antennas are characterized by space filling and self-similarity properties which results in considerable size reduction and multiband operation as compared to conventional microstrip antenna. This paper outlin...Fractal antennas are characterized by space filling and self-similarity properties which results in considerable size reduction and multiband operation as compared to conventional microstrip antenna. This paper outlines a multiband antenna design based on fractal concepts. Fractal antennas show multiband behavior due to self-similarity in their structure. The plus shaped fractal antenna has been designed on a substrate of dielectric constant €r = 4.4 and thickness 1.6mm. The proposed antenna is characterized by a compact size and it is microstrip feed fractal patch of order 1/3. It is observed that the antenna is radiating at multiple resonant frequencies. The resonant frequency is reduced from 2.2 GHz to 900 MHz after I & II iterations respectively. Thus considerable size reduction of 81.77% & overall bandwidth of 12.92% are achieved. The proposed antenna is simulated using the method of moment based commercial software (IE3D) and it is found that simulated results are in good agreement with the experimental results.展开更多
A kind of novel multi-frequency monopole antenna with sector-nested fractal is proposed and designed, which is nested with a series of similar circular sector elements. By means of the trapeziform ground plane with th...A kind of novel multi-frequency monopole antenna with sector-nested fractal is proposed and designed, which is nested with a series of similar circular sector elements. By means of the trapeziform ground plane with the tapered CPW (coplanar waveguide) feeder in the middle, the antenna’s radiation performance is greatly improved. The antennas can synchronously operate in three frequencies, covering the working frequency bands of WLAN/WiMAX, 2.44 GHz/3.5 GHz/5.2 GHz - 5.8 GHz. The pattern and impedance measurements of antenna show a good performance over the WLAN/WiMAX band;it possesses a near omni-directional characteristic and good radiation efficiency. Moreover, the antenna is miniature and its design idea can be easily applied into other types of nested structure, the features of which make the proposed antenna have a promising application in other fields.展开更多
A new technique which is a combination of fractal antenna and array antenna is presented to design Plus Slotted Fractal Antenna Array (PSFAA) in this paper. PSFAA with corporate feed operates at 2.5 GHz frequency. PSF...A new technique which is a combination of fractal antenna and array antenna is presented to design Plus Slotted Fractal Antenna Array (PSFAA) in this paper. PSFAA with corporate feed operates at 2.5 GHz frequency. PSFAA is designed on FR4 substrate material with permittivity 4.4 and height 1.6 mm. PSFAA is designed up to 2nd iteration. High Frequency Structure Simulator (HFSS) software is used for simulation of PSFAA. The proposed antenna array operates at three bands with five frequencies 2.5 GHz, 4.1 GHz, 6.9 GHz, 7.4 GHz and 8.2 GHz. Simulated Return losses results of proposed PSFAA are -22.15 dB, -19.44 dB, -25.21 dB, -10 dB, -12.45 dB at above frequencies respectively. It has a gain of 9.22 dB at resonant frequency 2.5 GHz whereas conventional antenna array has a gain of 5.15 dB at resonant frequency 2.5 GHz. Return losses and gain of PSFAA also improved from conventional antenna array at various resonant frequencies.展开更多
An uncommon fractal construction method is applied in the microwave element design. A novel fractal defected ground structure (DGS) based on micro electro-mechanical system (MEMS) is proposed. The size of this nov...An uncommon fractal construction method is applied in the microwave element design. A novel fractal defected ground structure (DGS) based on micro electro-mechanical system (MEMS) is proposed. The size of this novel fractal DGS can achieve 86% size reduction compared with the conventional dumbbell type DGS. This novel fractal DGS is used in the miniaturization design of L-band microstrip antenna array. The simulation result shows that this novel fractal DGS can effectively reduce the mutual coupling between the antenna elements, so it is helpful to the miniaturization of microstrip array, namely the approximately same gain value can be achieved with the shorter distance between elements.展开更多
This paper describes the multiband behaviour as well as the response for dielectric loading of a pentagonal fractal patch antenna designed at frequency f = 2.45 GHz. The proposed antenna shape has been obtained by int...This paper describes the multiband behaviour as well as the response for dielectric loading of a pentagonal fractal patch antenna designed at frequency f = 2.45 GHz. The proposed antenna shape has been obtained by introducing slots in a pentagonal patch antenna up to second iteration. Detailed design steps and results of the designs are studied and investigated in this paper. Simulated and measured results reveal that the antenna will be operated at three different frequency bands—2.17 GHz, 3.56 GHz, and 7.93 GHz with acceptable performances (i.e. VSWR < 2). The measured results for the antennas are in good agreement with simulated results. The proposed antenna maintains good radiation pattern with gain. However dielectric loading increases its radiation efficiency at the cost of significant decrease in gain and directivity.展开更多
In this paper, a wideband Sierpinski carpet patterned cylindrical Dielectric Resonator Antenna (DRA) operating in the X-Band is proposed. This DRA is realized from low cost Teflon. An impedance bandwidth of 50% is obt...In this paper, a wideband Sierpinski carpet patterned cylindrical Dielectric Resonator Antenna (DRA) operating in the X-Band is proposed. This DRA is realized from low cost Teflon. An impedance bandwidth of 50% is obtained cove- ring the entire X-band with similar radiation pattern throughout the band. The average peak gain within the band is about 5.5 dBi.展开更多
A new ultawideband circular fractal antenna with notched-band characteristics is presented. A notched-band characteristic is achieved by employing a U-shape slot in 50 Ω feed lines. The ultra-wideband impedance match...A new ultawideband circular fractal antenna with notched-band characteristics is presented. A notched-band characteristic is achieved by employing a U-shape slot in 50 Ω feed lines. The ultra-wideband impedance matching and compact size have been obtained by using CPW-feed technique and the fractal concept. The measured result of proposed fractal antenna exhibits the ultra wideband characteristics from 3.0 to 18.0 GHz at VSWR 2:1 except notched-band frequency. The proposed antenna has been analyzed theoretically and experimentally with respect to design parameters. The measured radiation pattern of fractal antenna is nearly omnidirectional in azimuth plane throughout the operating frequency. This antenna is useful for UBW communication system.展开更多
Low profile antenna in communication is a new methodology. Fractal geometry is a methodology through which size reduction is achieved. A Self-similar fractal antenna using multicantor technique is proposed and experim...Low profile antenna in communication is a new methodology. Fractal geometry is a methodology through which size reduction is achieved. A Self-similar fractal antenna using multicantor technique is proposed and experimentally studied. Space-filling cantors and self-similarity properties of fractal geometry have been adopted in the proposed antenna to miniaturize the size of antenna. The antenna is designed in such a way to operate at MICS band (Medical Implant communication Service) for wireless telemedicine application. The prototype antenna exhibits wideband characteristics and provides a good agreement of return loss (S11). Experimental return loss has been compared with that which is obtained using method of moments. The objective of using self-similar concept in antenna makes it flexible in terms of controlling the resonance and bandwidth. In this paper, the Self-similar property of fractal geometry is examined by maintaining return loss (S11) more than –30 dB approximately in all the iterations (n) and the prototype antenna has return loss greater than –10 dB and exhibits wideband characteristics.展开更多
The RFID is a rapidly developing technology. It’s used in many applications such as logistics, ticketing, security, employee attendance record and others. Also, fractal technology is used in many areas, and recently ...The RFID is a rapidly developing technology. It’s used in many applications such as logistics, ticketing, security, employee attendance record and others. Also, fractal technology is used in many areas, and recently in antenna design because it allows making multi-band and wide-band antennas. In this paper, two tri-band fractal antennas are studied for the Radio Frequency Identification (RFID) applications using the Method of Moment (MoM). The first one is designed for the RFID readers and it operates at 3.85 GHZ, 5.80 GHZ and 8.12 GHZ. The second one is designed for the RFID Tags and it operates at 3.94 GHZ, 5.65 GHZ and 8.20 GHZ.展开更多
A kind of novel multiband antenna with square-nested fractal is proposed and designed, including printed monopole antenna and dipole antenna, which are nested with a series of similar square elements. The antennas can...A kind of novel multiband antenna with square-nested fractal is proposed and designed, including printed monopole antenna and dipole antenna, which are nested with a series of similar square elements. The antennas can synchronously operate in multiple frequencies, covering the four required frequencies, 24GHz/35GHz/52GHz/58GHz, for WLAN/WiMAX application. The antenna surface currents are simulated by CST MWS, a three-dimension full-wave electromagnetic simulator, and the multiband operating mechanism has been explained from analysis of the simulation results. Then the models of the two proposed antennas fed by coplanar waveguide (monopole antenna) and balanced microstripline (dipole antenna), respectively, have been obtained. Finally, prototypes of the two antennas have been manufactured and measured in anechoic chamber. The results well match the simulation results, which verifies the feasibility of design idea. Moreover, these antennas are miniature and the design idea can be easily applied into other types of nested structure, the features of which make the proposed antennas have promising application in multiband fields.展开更多
Anovel compact E shape High Impedance Surface(HIS) Electromagnetic Band-Gap(EBG) comprising Amended Minkowski Fractal Boundary(AMFB),Added Metal Strips(AMS),and metal plated via printed on a Rogers TMM 10i substrate i...Anovel compact E shape High Impedance Surface(HIS) Electromagnetic Band-Gap(EBG) comprising Amended Minkowski Fractal Boundary(AMFB),Added Metal Strips(AMS),and metal plated via printed on a Rogers TMM 10i substrate is presented.The first order AMFB and ABS are introduced for equivalent capacitance enhancement and miniaturization with effective space-filling characteristics.The dimension of lattice size is only The proposed structure exhibits a most compact characteristic about 35% size reduction as compared with conven-tional mushroom-like HIS-EBG,and better surface-wave decoupling of around 9 dB at the operating frequency band.Details of design parameters which affect the whole performance of certain band-gap are intensively investigated.A constructed prototype is potential candidate for antenna system per-formance enhancement.展开更多
Wireless communication industry is in rapid growth in the last years. Due to the huge progress in development of communication systems in the last decade development of wideband communication systems is continuous gro...Wireless communication industry is in rapid growth in the last years. Due to the huge progress in development of communication systems in the last decade development of wideband communication systems is continuous growth. However, development of wideband efficient antennas is one of the major challenges in development of wideband wireless communication systems. Low cost compact antennas are crucial in the development of communication systems. Printed notch antennas and miniaturization techniques are employed to develop efficient compact notch antennas. Fractal technology is used to improve the electrical performance and efficiency of notch antennas. Design tradeoffs, computed and measured results of wideband notch antennas with high efficiency are presented in this paper. All antennas are analyzed by using 3D full-wave software. The paper presents new compact Ultra-Wideband notch antenna 1 GHz to 6 GHz, a wideband notch antenna 2.1 GHz to 7.8 GHz and a 5.8 GHz to 18 GHz fractal notch antenna.展开更多
We applied the Koch snowflake fractal antenna in planning calibration of the Five-hundred-meter Aperture Spherical radio Telescope(FAST), hypothesizing second-order fractal primary reflectors can optimize the orientat...We applied the Koch snowflake fractal antenna in planning calibration of the Five-hundred-meter Aperture Spherical radio Telescope(FAST), hypothesizing second-order fractal primary reflectors can optimize the orientated sensitivity of the telescope. Meanwhile, on the grounds of NASA Science Working Group Report in 1984, we reexamine the strategy of Search for Extraterrestrial Intelligence(SETI).A mathematical analysis of the radar equation will be performed in the first section, aiming to make it convenient to design a receiver system that can detect activities of an extraterrestrial civilization, according to the observable region of the narrowband. Taking advantage of the inherent potential of FAST, we simulate the theoretical detection of a Kardashev Type I civilization by a snowflake-selected reflecting area(Drake et al.).展开更多
To investigate the partial discharge (PD) online monitoring of transformers by ultra-high-frequency (UHF) approaches,high-qualified UHF antennas are focused on as one key technique. The size of UHF sensor used for PD ...To investigate the partial discharge (PD) online monitoring of transformers by ultra-high-frequency (UHF) approaches,high-qualified UHF antennas are focused on as one key technique. The size of UHF sensor used for PD UHF online monitoring in transformer is excessively large,therefore,it is not convenient for internal installation of transformer. Two types of compact UHF antennas with small sizes,a Hilbert fractal antenna and a small loop antenna are presented. PD experiments of three typically artificial insulation defects are executed and both antennas are used for PD measurement. The spectra of power via frequency of detected PD signals are analyzed and compared. The experimental results show that the Hilbert fractal antenna and small loop antenna are qualified for PD online UHF monitoring.展开更多
文摘Efforts to protect electric power systems from faults have commonly relied on the use of ultra-high frequency(UHF)antennas for detecting partial discharge(PD)as a common precursor to faults.However,the effectiveness of existing UHF antennas suffers from a number of challenges such as limited bandwidth,relatively large physical size,and low detection sensitivity.The present study addresses these issues by proposing a compact microstrip patch antenna with fixed dimensions of 100 mm×100 mm×1.6 mm.The results of computations yield an optimized antenna design consisting of 2nd-order Hilbert fractal units positioned within a four-layer serpentine arrangement with a fractal unit connection distance of 3.0 mm.Specifically,the optimized antenna design achieves a detection bandwidth for which the voltage standing wave ratio is less than 2 that is approximately 97.3%of the UHF frequency range(0.3–3 GHz).Finally,a prototype antenna is fabricated using standard printed circuit board technology,and the results of experiments demonstrate that the proposed antenna is capable of detecting PD signals at a distance of 8 m from the discharge source.
文摘Fractal antennas are characterized by space filling and self-similarity properties which results in considerable size reduction and multiband operation as compared to conventional microstrip antenna. This paper outlines a multiband antenna design based on fractal concepts. Fractal antennas show multiband behavior due to self-similarity in their structure. The plus shaped fractal antenna has been designed on a substrate of dielectric constant €r = 4.4 and thickness 1.6mm. The proposed antenna is characterized by a compact size and it is microstrip feed fractal patch of order 1/3. It is observed that the antenna is radiating at multiple resonant frequencies. The resonant frequency is reduced from 2.2 GHz to 900 MHz after I & II iterations respectively. Thus considerable size reduction of 81.77% & overall bandwidth of 12.92% are achieved. The proposed antenna is simulated using the method of moment based commercial software (IE3D) and it is found that simulated results are in good agreement with the experimental results.
文摘A kind of novel multi-frequency monopole antenna with sector-nested fractal is proposed and designed, which is nested with a series of similar circular sector elements. By means of the trapeziform ground plane with the tapered CPW (coplanar waveguide) feeder in the middle, the antenna’s radiation performance is greatly improved. The antennas can synchronously operate in three frequencies, covering the working frequency bands of WLAN/WiMAX, 2.44 GHz/3.5 GHz/5.2 GHz - 5.8 GHz. The pattern and impedance measurements of antenna show a good performance over the WLAN/WiMAX band;it possesses a near omni-directional characteristic and good radiation efficiency. Moreover, the antenna is miniature and its design idea can be easily applied into other types of nested structure, the features of which make the proposed antenna have a promising application in other fields.
文摘A new technique which is a combination of fractal antenna and array antenna is presented to design Plus Slotted Fractal Antenna Array (PSFAA) in this paper. PSFAA with corporate feed operates at 2.5 GHz frequency. PSFAA is designed on FR4 substrate material with permittivity 4.4 and height 1.6 mm. PSFAA is designed up to 2nd iteration. High Frequency Structure Simulator (HFSS) software is used for simulation of PSFAA. The proposed antenna array operates at three bands with five frequencies 2.5 GHz, 4.1 GHz, 6.9 GHz, 7.4 GHz and 8.2 GHz. Simulated Return losses results of proposed PSFAA are -22.15 dB, -19.44 dB, -25.21 dB, -10 dB, -12.45 dB at above frequencies respectively. It has a gain of 9.22 dB at resonant frequency 2.5 GHz whereas conventional antenna array has a gain of 5.15 dB at resonant frequency 2.5 GHz. Return losses and gain of PSFAA also improved from conventional antenna array at various resonant frequencies.
基金supported by the 11th Five-Year Plan under Grant No. 11001030203
文摘An uncommon fractal construction method is applied in the microwave element design. A novel fractal defected ground structure (DGS) based on micro electro-mechanical system (MEMS) is proposed. The size of this novel fractal DGS can achieve 86% size reduction compared with the conventional dumbbell type DGS. This novel fractal DGS is used in the miniaturization design of L-band microstrip antenna array. The simulation result shows that this novel fractal DGS can effectively reduce the mutual coupling between the antenna elements, so it is helpful to the miniaturization of microstrip array, namely the approximately same gain value can be achieved with the shorter distance between elements.
文摘This paper describes the multiband behaviour as well as the response for dielectric loading of a pentagonal fractal patch antenna designed at frequency f = 2.45 GHz. The proposed antenna shape has been obtained by introducing slots in a pentagonal patch antenna up to second iteration. Detailed design steps and results of the designs are studied and investigated in this paper. Simulated and measured results reveal that the antenna will be operated at three different frequency bands—2.17 GHz, 3.56 GHz, and 7.93 GHz with acceptable performances (i.e. VSWR < 2). The measured results for the antennas are in good agreement with simulated results. The proposed antenna maintains good radiation pattern with gain. However dielectric loading increases its radiation efficiency at the cost of significant decrease in gain and directivity.
文摘In this paper, a wideband Sierpinski carpet patterned cylindrical Dielectric Resonator Antenna (DRA) operating in the X-Band is proposed. This DRA is realized from low cost Teflon. An impedance bandwidth of 50% is obtained cove- ring the entire X-band with similar radiation pattern throughout the band. The average peak gain within the band is about 5.5 dBi.
文摘A new ultawideband circular fractal antenna with notched-band characteristics is presented. A notched-band characteristic is achieved by employing a U-shape slot in 50 Ω feed lines. The ultra-wideband impedance matching and compact size have been obtained by using CPW-feed technique and the fractal concept. The measured result of proposed fractal antenna exhibits the ultra wideband characteristics from 3.0 to 18.0 GHz at VSWR 2:1 except notched-band frequency. The proposed antenna has been analyzed theoretically and experimentally with respect to design parameters. The measured radiation pattern of fractal antenna is nearly omnidirectional in azimuth plane throughout the operating frequency. This antenna is useful for UBW communication system.
文摘Low profile antenna in communication is a new methodology. Fractal geometry is a methodology through which size reduction is achieved. A Self-similar fractal antenna using multicantor technique is proposed and experimentally studied. Space-filling cantors and self-similarity properties of fractal geometry have been adopted in the proposed antenna to miniaturize the size of antenna. The antenna is designed in such a way to operate at MICS band (Medical Implant communication Service) for wireless telemedicine application. The prototype antenna exhibits wideband characteristics and provides a good agreement of return loss (S11). Experimental return loss has been compared with that which is obtained using method of moments. The objective of using self-similar concept in antenna makes it flexible in terms of controlling the resonance and bandwidth. In this paper, the Self-similar property of fractal geometry is examined by maintaining return loss (S11) more than –30 dB approximately in all the iterations (n) and the prototype antenna has return loss greater than –10 dB and exhibits wideband characteristics.
文摘The RFID is a rapidly developing technology. It’s used in many applications such as logistics, ticketing, security, employee attendance record and others. Also, fractal technology is used in many areas, and recently in antenna design because it allows making multi-band and wide-band antennas. In this paper, two tri-band fractal antennas are studied for the Radio Frequency Identification (RFID) applications using the Method of Moment (MoM). The first one is designed for the RFID readers and it operates at 3.85 GHZ, 5.80 GHZ and 8.12 GHZ. The second one is designed for the RFID Tags and it operates at 3.94 GHZ, 5.65 GHZ and 8.20 GHZ.
基金Sponsored by the Fundamental Research Funds for the Central Universities (Grant No. HIT. NSRIF. 2010096)the Heilongjiang Post-Doctorial Fi-nancial Assistance (Grant No. LBH-Z09187)
文摘A kind of novel multiband antenna with square-nested fractal is proposed and designed, including printed monopole antenna and dipole antenna, which are nested with a series of similar square elements. The antennas can synchronously operate in multiple frequencies, covering the four required frequencies, 24GHz/35GHz/52GHz/58GHz, for WLAN/WiMAX application. The antenna surface currents are simulated by CST MWS, a three-dimension full-wave electromagnetic simulator, and the multiband operating mechanism has been explained from analysis of the simulation results. Then the models of the two proposed antennas fed by coplanar waveguide (monopole antenna) and balanced microstripline (dipole antenna), respectively, have been obtained. Finally, prototypes of the two antennas have been manufactured and measured in anechoic chamber. The results well match the simulation results, which verifies the feasibility of design idea. Moreover, these antennas are miniature and the design idea can be easily applied into other types of nested structure, the features of which make the proposed antennas have promising application in multiband fields.
基金Supported by the 2010 Natural Science Foundation of Shanghai (No. 09ZR1430400)
文摘Anovel compact E shape High Impedance Surface(HIS) Electromagnetic Band-Gap(EBG) comprising Amended Minkowski Fractal Boundary(AMFB),Added Metal Strips(AMS),and metal plated via printed on a Rogers TMM 10i substrate is presented.The first order AMFB and ABS are introduced for equivalent capacitance enhancement and miniaturization with effective space-filling characteristics.The dimension of lattice size is only The proposed structure exhibits a most compact characteristic about 35% size reduction as compared with conven-tional mushroom-like HIS-EBG,and better surface-wave decoupling of around 9 dB at the operating frequency band.Details of design parameters which affect the whole performance of certain band-gap are intensively investigated.A constructed prototype is potential candidate for antenna system per-formance enhancement.
文摘Wireless communication industry is in rapid growth in the last years. Due to the huge progress in development of communication systems in the last decade development of wideband communication systems is continuous growth. However, development of wideband efficient antennas is one of the major challenges in development of wideband wireless communication systems. Low cost compact antennas are crucial in the development of communication systems. Printed notch antennas and miniaturization techniques are employed to develop efficient compact notch antennas. Fractal technology is used to improve the electrical performance and efficiency of notch antennas. Design tradeoffs, computed and measured results of wideband notch antennas with high efficiency are presented in this paper. All antennas are analyzed by using 3D full-wave software. The paper presents new compact Ultra-Wideband notch antenna 1 GHz to 6 GHz, a wideband notch antenna 2.1 GHz to 7.8 GHz and a 5.8 GHz to 18 GHz fractal notch antenna.
基金supported by the National Natural Science Foundation of China(Grant No.11929301)National Key R&D Program of China(2017YFA0402600)。
文摘We applied the Koch snowflake fractal antenna in planning calibration of the Five-hundred-meter Aperture Spherical radio Telescope(FAST), hypothesizing second-order fractal primary reflectors can optimize the orientated sensitivity of the telescope. Meanwhile, on the grounds of NASA Science Working Group Report in 1984, we reexamine the strategy of Search for Extraterrestrial Intelligence(SETI).A mathematical analysis of the radar equation will be performed in the first section, aiming to make it convenient to design a receiver system that can detect activities of an extraterrestrial civilization, according to the observable region of the narrowband. Taking advantage of the inherent potential of FAST, we simulate the theoretical detection of a Kardashev Type I civilization by a snowflake-selected reflecting area(Drake et al.).
基金Project Supported by New Century ExcellentTalents of the Ministry of Education (NCET-06-0763)the Foundation of the Key Project of the Science and Technology Depart ment inChongqing (CSTC2005AA6003)
文摘To investigate the partial discharge (PD) online monitoring of transformers by ultra-high-frequency (UHF) approaches,high-qualified UHF antennas are focused on as one key technique. The size of UHF sensor used for PD UHF online monitoring in transformer is excessively large,therefore,it is not convenient for internal installation of transformer. Two types of compact UHF antennas with small sizes,a Hilbert fractal antenna and a small loop antenna are presented. PD experiments of three typically artificial insulation defects are executed and both antennas are used for PD measurement. The spectra of power via frequency of detected PD signals are analyzed and compared. The experimental results show that the Hilbert fractal antenna and small loop antenna are qualified for PD online UHF monitoring.