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In this letter, a novel ultrawideband wire antenna with enhanced bandwidth is presented. The proposed antenna consists of a dipole structure, and each pole is formed by connecting four semicircular closed wires. A sphere crown and several rods are introduced to improve the impedance match during an ultrawide band. Experimental results show that the antenna achieves good impedance match from 0.45 to 28.4 GHz with the voltage standing wave ratio (VSWR) less than 2 while maintaining omnidirectional radiation pattern. The parameters that affect the impedance match of the antenna are also investigated. The proposed wire antenna is highly suitable for applications of wideband systems.

This paper presents a circular disc monopole antenna based on fractal geometry. The antenna is designed to be applied in UWB systems. So it is essential to ensure that the bandwidth of the antenna ranges from 3.1 GHz to 10.6 GHz, that is, IEEE 802.15.3a. However, the proposed antenna has achieved working in the required bandwidth. Compared to the antennas illustrated in most similar literatures, the proposed antenna has a much smaller size, which makes the antenna possible to be integrated with portable devices. Firstly, the antenna was designed through CST Microwave Studio. Then, the antenna was fabricated according to the simulated results. At last, the comparison between the simulated results and measured results was carried out which demonstrated good consistency.

A novel circular wide slot ultra wideband antenna fed by coplanar waveguide is proposed and designed. This antenna has the characteristics of miniaturization and planarity which is operated at 3GHz∼12GHz frequency band. The radiation pattern characteristic is improved by strip-line loaded in the circular wide slot. Results show that this antenna can realize ultra wideband impedance bandwidth characteristic, good radiation pattern bandwidth and gain flatness. Good agreement can be gotten between measurement and simulation results, and this antenna can satisfy ultra wideband communication system application.

Based on the conventional ultra-wide band (UWB) circular disk monopole antenna, a novel omni-directional dipole antenna is investigated both numerically and experimentally in this paper. The results demonstrate that the antenna can work well in the 1.75GHz∼40GHz frequency range. Compared with the conventional antenna, the proposed antenna has better omni-direction characteristics in H-plane radiation pattern and the main direction of the E-plane radiation pattern keeps stable. The proposed antenna provides the valuable reference for the future ultra-wide band omni-directional antenna design and shows great value in the fields of communication and radar system.

A new plasma monopole antenna is proposed in this paper. The cylindrical plasma antenna is fed by a metal ring. The impedance characteristics and radiation characteristics of the plasma antenna are calculated and analyzed. According to actual situation, a cylindrical plasma monopole antenna is designed and measured. The measurement results are similar to the calculation results.

The ultrawide-band antenna is one of the hot research areas. Based on the conventional ultrawide-band circular disk monopole antenna, a novel miniaturized ultrawide-band monopole antenna is presented in this paper. The simulation results demonstrate that the antenna can work well in the 2.3GHz∼24GHz frequency range. Compared with the conventional antenna, the novel antenna has better omnidirection in H-plane radiation pattern. It is proposed to be used in mobile communication and satellite communication with good prospects.

A novel planar composite triangle monopole ultrawideband antenna fed by microstrip is proposed in this paper. Radiating element of the antenna is a combination of three similar triangles from small to large, and the width of the microstrip change gradient. Simulation results from CST software demonstrate that the antenna has stable input impedance and stable patterns in the 3.1–10.6GHz, with H plane omni-directional radiation characteristic, which is suitable for short-range wireless ultra-wideband communications.

The log-periodical antenna (LPDA) is a kind of ultraw wide-band antennas. To achieve the purpose of miniaturization of the LPDA in radiate direction, this paper presents a novel structure log-periodically loaded with symmetrical meandering dipoles. The radiate direction is reduced to 46% of the conventional LDPA. The return loss is less than −10dB from 200MHz to 2GHz, according to the simulation results. A good directivity is also obtained that the gain ranges from 1.9dB to 7.2dB.

The feed part which uses gradually changing structure usually has wider impedance bandwidth. A kind of trapezoid dipole antenna that is similar to the parallel dual-feed is analyzed in the essay. Adopting the software of CST Microwave to simulate how the structure parameter of antenna influences impedance character, a type of dipole antenna working within 1.85∼3.75GHz is designed. The simulation results and experiments indicate that the antenna possesses wide impedance bandwidth. Meanwhile, the pattern is approximately omni-directional within the frequency band. So the antenna can be used in many fields, such as PCS, WLAN, WiMAX, and so on.

Based on the triangle fractal antenna, is proposed in this paper. This antenna consists of four nesting triangles with different vertex angle and height. The simulation of the antenna is performed by using CST MICROWAVE STUDIO® and the result shows that the center frequency of the pass band and the bandwidth can be controlled by modulating the height and angle of the nesting triangles and the nesting number. A multi-band with four bands (2.4GHz, 3.5GHz, 5.2GHz and 5.8GHz) has been designed, through simulation. The nesting fractal antenna is a multi-bands antenna with controllable frequency bands. And it also has a broad application prospects.

Dielectric rod antennas have a number of significant advantages over conventional waveguide, horn antennas, printed dipole or TSA when used as feed eltments in focal plane arrays (FPA). In this paper the principle of dielectric rod antenna is introduced and CST Microwave Studio is used to simulate the influence of antenna parameters, optimized dielectric rod antenna designed. The optimized dielectric rod antenna can raise the gain of the antenna by controlling the length of the antenna but not the cross-section, provide a broadband input matching, small side-lobe, coupling and cross polarization. The antenna is suitable for the arrangement of the array and and better edge illumination to realize better illumination effect to the lens.

Methods of designing quasi-optics are researched to improve the spatial resolution of the millimeter-wave imaging system. On the basis of characteristics comparison of different design methods and truncation effect considered, fundamental Gaussian beam method is used to design the quasi-optics. The relationship between waist radius and the gain of antenna is researched, and the lens as focusing element is designed together to meet the requirement of the system. Experimental results are given to illustrate the accuracy of the design method, and the reasons of the error are analyzed. The design process is easy to carry out while the result has good accuracy, so it is practical for designing the quasi-optics for millimeter wave imaging system.

A novel wide-band monopole antenna with parasitic elements is proposed in this paper. This antenna is made up of a monopole antenna and two parasitic elements. Simulation and experiment result approve that this novel antenna realize wide band without losing any other good characteristics. From 780 MHz to 1670 MHz, the return loss is less than -10 dB, and it has omnidirectional radiation pattern in horizon plane, stable gain. Base on scaled principle, this kind of antenna could be used in medium wave communications.

Ultra wide-band is one of the hottest issues in the current researches on antennas. The circular monopole antenna is a kind of ultra wide-band antennas with simple structure. Firstly a novel antenna was researched. Four circular disc monopoles were placed across each other. They were considered as the feedings, and the reflection plane was planar. It could achieve dual polarization characteristics. On this basis, further study was applied to two other novel antennas. The first was changing the planar reflector to parabolic one, and the purpose was to realize wide beam, high gain and directed radiation characteristic. The other was changing the circular disc shape, and the purpose was to realize wider lower frequency bandwidth. The novel antennas were theoretic analyzed, and the S- parameter and radiation patterns of the antennas were discussed by electromagnetism simulation software. The analytic results verify that the characteristic of the traditional monopole antenna is effective improved by the novel antennas. Dual-polarization, high gain, wide beam and directed radiation characteristics of the antenna are realized. The novel antennas are suitable for the satellite and mobile communication systems with good prospects.

Methods of quasi-optical subsystem is researched to improve the spatial resolution of the millimeter-wave imaging system. On the basis of characteristics comparison of different design methods, fundamental Gaussian beam method is introduced in detail and formulas are given. Relationship between waist radius and gain of feed antenna is researched. Effects of beam truncation are discussed and lens as the focusing element is designed as well. At last, the quasi-optical subsystem for millimeter-wave imaging systems is designed with fundamental Gaussian beam method. Design process is easy to carry out and all parameters are given by formulas. So the quasi-optical design is practical for millimeter-wave imaging system.

The principle of Quasi-Yagi antenna is introduced and the influences of different structure parameters. CST Microwave Studio is used to simulate and optimize the antenna. The influence of antenna parameters is researched and the antenna is manufactured. The simulation and measurement of the antenna show that 2.9-3.8 GHz band with the VSWR less than 2 is obtained, and gain is more than 6 dB in plusmn60deg of H plane, plusmn15deg of E plane. Wide beamwidth and high gain is obtained.

Study of a novel ultrawide-band antenna is presented in this paper. Firstly, the circular disc monopole is introduced simply. The radiator, ground plane and the feeder equipment of the antenna are placed on the same plate. The antenna has ultrawide-band property, and the special structure reduces the spatial volume. On this basis, a novel antenna is proposed. Four circular disc monopoles are placed across each other. The improved antenna is not only favorable for satisfying ultrawide-band return loss requirement but also advantageous in realizing the wide beams and good circular polarization performance within the beams. Analyses are conducted to determine the novel antennas' properties. The return loss, radiation patterns, axial ratio and gain of the antennas are discussed detailedly. The analytic results verify that the novel circular disc monopole ultrawide-band antenna has reliable ultrawide-band performance during realizing wide beam and circular polarization. The novel antenna proposed in this paper is suitable for the wireless, satellite and mobile communication systems with good prospects.

In this paper, the GPS (Global Position System) omnidirectional antenna array which is conformal with revolving cylinder is researched. The basic theory and design method of cylindrical conformal antenna array are described. The radiation characteristic of the antenna array is presented and it is simulated by the software Matlab. The theory and simulation results are given to illustrate that this antenna array can radiate an omnidirectional pattern normal to the axis of the cylinder approximately. So it has great practicability.

A novel broadband omnidirectional antenna is presented in this paper. The antenna is proposed for operating at mobile telephone bands. To achieve simple structure, the proposed antenna is composed of three monopoles in a plane. The impedance matching and bandwidth for the presented antenna are mainly affected by length and separation of the three monopoles. The theory of basic three monopoles antenna is discussed and simulated. By properly choosing the adequate dimension and adjusting the coupling distance, impedance bandwidth of S11< -10 dB is about 640 MHz, and relative bandwidth is greater than 60%. The antenna can get omnidirectional radiation pattern in the whole frequency band. And the main lobe 3 dB width is from 61deg to 72.6deg in the low frequency without side lobe. The highest gain is stable 4.7 dB. The theory analysis and simulation results are presented.

Wide band and miniaturization are both the hottest issues in the current researches on antennas. The circular monopole antenna is a kind of ultra-wideband antennas with simple feeding network. Detailed analyses are conducted to determinate the antenna's properties. The design method of the antenna is presented, and the influences on its impedance and radiation properties by varying the dimension parameters of the antenna are discussed. Through simulations and experiments, it is demonstrated that the antenna has a more than 10 times octave impedance bandwidth, good consistency of the horizon directivity diagram and the constant group delay. The results show that the circular monopole antenna has not only the ultra-wideband in frequency domain, but also the stable phase center, which makes the antenna suitable for the antennas in the time domain communication systems. Also, the antenna can easily cover the frequency range from 400 MHz to 4 GHz, which includes the usual bandwidth for RF devices such as RFID devices, GPS receivers, image transmission devices (all these RF devices are applied to various traffic control systems), so that the circular monopole antenna can be used as the antenna for the entire traffic control systems, which greatly reduces the complexity of the whole system

A triple-layer patch circularly polarized microstrip antenna is proposed for triple-frequency operation. It is shown that the antenna resonates at three different frequencies of 1.207GHz, 1.268GHz and 1.561GHz with adequate values of return loss and gain. The antenna is designed and simulated with the application of CST software based on the finite integral method. The simulation results and analyses are presented.

It was considered that the precondition of generating high frequency radiation was that the appended capacitor brought oscillating current signals in an explosive magnetic generator of frequency (EMGF). As a result, on the basis of equivalent circuit, by analyzing the energy losses, the variation of EMGF's current was studied, and the reason for the fish-shaped envelope of oscillating current was explained in this paper. Also, the principle of high frequency radiation was interpreted by studying the fish-shaped current energy spectrum. All the analyses were based on equivalent circuit and redounded to comprehend the operating principle of EMGF

In this paper, a circularly polarized microstrip patch antenna is proposed for triple-frequency operation. To achieve triple-frequency operation, the proposed antenna has three layers. The proposed antenna is designed and experimentally analyzed at three different frequencies. From the measured results, the resonator frequencies of this antenna are 1.207GHz, 1.268GHz and 1.561GHz, and the measured impedance bandwidths are 22MHz, 10MHz, and 40MHz for VSWR

Planar equiangular spiral antenna and Archimedean spiral antenna are two kinds of ultra-wideband circular polarized antennas, which are used in various applications. However, the lower frequencies of these antennas are limited by their dimensions. In order to minimize antenna's dimension, we designed an equiangular spiral-Archimedean spiral-integrated antenna. In the frequency spectra 400 MHz-2000 MHz, the measured return loss of the proposed UWB antenna is less than -10dB. This novel antenna's wide band characteristic, especially the characteristic in the lower frequency, is better than that of the planar equiangular spiral antenna in the same dimension.

This paper presents a circular monopole UWB antenna, which has an approximately 30 times octave bandwidth constant group delay, acceptable gain flatness and high efficiency, and introduces the primary antenna design. In this paper, the theoretical analysis, simulation by CST Microwave Studio and experiments are all conducted to further characterize the antenna in terms of the influences on its performance by varying the dimension parameters of the antenna. Also, via the experiments, this paper originally presents the idea of improving the impedance bandwidth by modifying the structure of feeding network.

A new 8mm-band sum-frequency upconvertor is described which consists of a double-ridge waveguide, a crossrod structure and varactors. The convertor operates over X, K. and Ka bands. The minimum conversion loss is 2.9 dB at a sum frequency of 35GHz, with bandwidth over 500 MHz. The maximum output power of the sum-frequency signal is 1.34mw; testing results show that the upconvertor converts the X-band signal to Ka-band linearly.