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
在Vicsek结构的分形理论基础上进行了改进,提出了一种具有良好空间填充性和自相似特性的新型类Vicsek分形天线,并在接地板上引入缺陷地结构（Defected Ground Structure,DGS）来改善频率、抑制谐波,得到了可以运用在无线局域网（Wireles...在Vicsek结构的分形理论基础上进行了改进,提出了一种具有良好空间填充性和自相似特性的新型类Vicsek分形天线,并在接地板上引入缺陷地结构（Defected Ground Structure,DGS）来改善频率、抑制谐波,得到了可以运用在无线局域网（Wireless Local Area Networks,WLAN）、全球微波互联接入（Worldwide Interoperability For Microwave Access,WiMAX）以及C波段卫星通信的四个频段.天线的谐振频率分别为2.45GHz、3.46GHz、5.8GHz和7GHz,相应带宽为0.2GHz（2.37~2.57GHz）、0.49GHz（3.2~3.69GHz）、0.75GHz（5.52~6.27GHz）和0.56GHz（6.68~7.24GHz）,增益最高达到4.89dB.天线的小尺寸及全向性辐射特性表明该天线能很好地满足便携式多频段移动设备的要求.展开更多
Calibrating the super low frequency （SLF） magnetic antenna in magnetic free space or an outdoor environment is difficult and complicated due to the large size calibration instruments and lots of measurement times. A...Calibrating the super low frequency （SLF） magnetic antenna in magnetic free space or an outdoor environment is difficult and complicated due to the large size calibration instruments and lots of measurement times. Aiming to calibrate the SLF magnetic antenna simply and efficiently, a calibration system comprised of a multi-frequency source, an A.C constant-current source and a solenoid is proposed according to the characteristic of an SLF magnetic antenna. The static magnetic transfer coefficient of the designed solenoid is calibrated. The measurement of the frequency response characteristics suggests the transfer coefficient remains unchanged in the range of the SLF band and is unaffected by the magnetic antenna internally installed. The CORDIC algorithm implemented in an FPGA is realized to generate a linear evenly-spaced multi-frequency signal with equal energy at each frequency. An A.C constant weak current source circuit is designed in order to avoid the impact on the magnetic induction intensity of a calibration system affected by impedance variation when frequency changing, linearity and the precision of the source are measured. The frequency characteristic of a magnetic antenna calibrated by the proposed calibration system agrees with the theoretical result and the standard Glass ring calibration result. The calibration precision satisfies the experimental requirement.展开更多
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.
文摘在Vicsek结构的分形理论基础上进行了改进,提出了一种具有良好空间填充性和自相似特性的新型类Vicsek分形天线,并在接地板上引入缺陷地结构（Defected Ground Structure,DGS）来改善频率、抑制谐波,得到了可以运用在无线局域网（Wireless Local Area Networks,WLAN）、全球微波互联接入（Worldwide Interoperability For Microwave Access,WiMAX）以及C波段卫星通信的四个频段.天线的谐振频率分别为2.45GHz、3.46GHz、5.8GHz和7GHz,相应带宽为0.2GHz（2.37~2.57GHz）、0.49GHz（3.2~3.69GHz）、0.75GHz（5.52~6.27GHz）和0.56GHz（6.68~7.24GHz）,增益最高达到4.89dB.天线的小尺寸及全向性辐射特性表明该天线能很好地满足便携式多频段移动设备的要求.
基金supported by the Defense Pre-Research Foundation of China(No.51401020503)
文摘Calibrating the super low frequency （SLF） magnetic antenna in magnetic free space or an outdoor environment is difficult and complicated due to the large size calibration instruments and lots of measurement times. Aiming to calibrate the SLF magnetic antenna simply and efficiently, a calibration system comprised of a multi-frequency source, an A.C constant-current source and a solenoid is proposed according to the characteristic of an SLF magnetic antenna. The static magnetic transfer coefficient of the designed solenoid is calibrated. The measurement of the frequency response characteristics suggests the transfer coefficient remains unchanged in the range of the SLF band and is unaffected by the magnetic antenna internally installed. The CORDIC algorithm implemented in an FPGA is realized to generate a linear evenly-spaced multi-frequency signal with equal energy at each frequency. An A.C constant weak current source circuit is designed in order to avoid the impact on the magnetic induction intensity of a calibration system affected by impedance variation when frequency changing, linearity and the precision of the source are measured. The frequency characteristic of a magnetic antenna calibrated by the proposed calibration system agrees with the theoretical result and the standard Glass ring calibration result. The calibration precision satisfies the experimental requirement.
