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An improved double ridged horn antenna (DRHA) is proposed in this paper. By adding the dielectric lens at the aperture of the horn, radiation pattern distortion arising in the high frequency band of conventional DRHA is improved, which leads to higher radiation gain. Meanwhile, ridge slot loading contributes to better impedance matching characteristic, broadening the impedance bandwidth e-ciently. The improved antenna is fabricated and measured, with the measured results consist with the simulation perfectly, which proved the viability of the improvement.

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.

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.

The quasi-optics sub-system of Millimeter-wave focal plane arrays imaging system includes the design of system parameters, multi-beam design of focusing element and design of feed antenna. Design of focusing element decides the spatial resolution and the maximum field of view of the system. The design and arrangement of the feed antenna related to the overflow efficiency and the spatial sampling rate of the system. In this paper, fundamental mode Gaussian beam method is taken to design quasi-optics, and focusing lens antenna is designed with the principle of optical path difference of feed sources on optical axis. In this paper also proposed a new kind of dielectric rod antenna with new structure as the feed source to the lens. The simulation and measurement show that the multi-beam lens antenna has a better wide-angle scanning feather. The feed antenna has broader wave band, lower side lobe, lower mutual coupling, lower cross polarization, and the gain of it can be changed by changing its length but not the section area. It is easier to form a close feed array which can realize an effective exposure to the lens or the reflector antenna with less overflow loss.

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.

Effects of illumination on the object for millimeter wave imaging were investigated to improve the resolution. Relationship between apparent temperature of object and output voltage of the receiver was discussed, imaging results of passive millimeter wave system without illumination and system with illumination were simulated respectively, changes for object's apparent temperature and thermal sensitivity under illumination of artificial noise were analyzed. Results demonstrate that the temperature gradient for different pixels with different material is greater under illumination which can benefit the resolution of the image. Images with higher resolution can be obtained even without a low noise-figure receiver.

For the radiation characteristics investigation of antenna covered by a plasma sheath in wideband frequency, a ultra wideband planar reflector antenna is presented in this paper. The proposed antenna is composed of a circular disc dipole and a finite reflector plane. The working band width is from 5.1 GHz to 40 GHz. The plasma sheath media is simulated with layered medium given by drude dispersion model. The electron density in layered plasma model is presented following experimental data. According to the simulation results, return loss deteriorates seriously at low frequency, while deterioration is mitigated at high frequency. And the radiation patterns are mainly in opposition with the plasma sheath at high frequency due to the plasma sheath reflection. The theory analysis and simulation results are presented.

For radiation characteristics research on antenna coated with a plasma sheath, an axially slotted cylinder antenna is presented. The proposed antenna is composed of a narrow slot cut in the wall of a hollow circular cylinder. The working band width is about 200 MHz. The plasma sheath media was simulated with laminate medium given by drude dispersion model. The electron density in layered plasma model is presented following experimental data. According to the simulation results, return loss deteriorates seriously when thickness of plasma sheath is thickened. And the radiation patterns are mainly in opposition with the plasma sheath when thickness of plasma sheath is 25 mm due to the plasma sheath reflection. The theory analysis and simulation results are presented.

The focusing characteristics of ellipsoidal antenna in the millimeter-wave imaging system are analyzed in this paper, which is used for detecting objects hidden in people's body. And it is points out that the advantages of the ellipsoidal antenna having double focusing points, comparing to parabolic antenna in the condition of imaging in near-field. Through the analysis of axial focusing characteristics of even circular caliber antenna, some main parameters which influence axial focusing characteristics are obtained. Using statistics computational method and simulation of ellipsoidal conjugate imaging, the methods for designing ellipsoidal antenna, and the position of focusing spot and changing rule of radius in millimeter-wave imaging system are obtained.

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.

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.

Study of novel circular disc monopole ultrawide-band miniature antennas is presented in this paper. Based on the conventional circular disc monopole, two kinds of novel circular disc monopole ultrawide-band miniature antennas are proposed. The circular disc monopole is revolved or puckered. The improved antennas are not only favorable for satisfying ultrawide-band requirement but also advantageous in realizing the further miniaturization. Detailed analyses are conducted to determine the novel antennas' properties. And the return loss, current distributions, radiation patterns and gain of the antennas are discussed. The novel antenna proposed in this paper is suitable for the wireless, satellite and mobile communication systems with good prospects.

A novel ultra wideband planar reflector antenna is presented in this paper. The proposed antenna is composed of a circular disc dipole and a finite reflector plane. The impedance matching and bandwidth for the presented antenna are mainly affected by the diameter of the disc and feeding separation. The theory of ultra wideband planar reflector antenna is discussed and simulated. By properly choosing adequate dimension and adjusting feeding distance, impedance bandwidth of S11

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.

In this paper, the omnidirectional antenna which is conformal with cylinder is researched. The design methods of different kinds of cylindrical conformal antennas are described for different diameter of cylinder separately. The radiation characteristics of circle antenna array, circular microstrip antenna and a quarter-wavelength helical microstrip antenna are presented. The emulational results are given to illustrate that these antennas can radiate an omnidirectional pattern normal to the axis of the cylinder approximately. So these antennas have great practicability.

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 the research on a novel miniaturized printed log-periodic antenna with fractal tree structure for operation in a broadband of 0.4 GHz-2GHz. The antenna is designed and simulated with the application of CST MICROWAVE STUDIO®software based on the Finite Integral Method. The simulation results show that the antenna achieves the necessary lateral size reduction to 61% of the normal log-periodic antenna, while keeping its radiation characteristics nearly constant.

In this paper, a novel broadband slotted waveguide antenna is presented. A double-slot structure and a ridged waveguide are used. The structure of the double-slot is analyzed by means of the transmission line model. The analysis shows that the theoretical design is in good agreement with experimental results.

In this paper a four-cavity 60:1 frequency bandwidth (1-60 GHz) ultra-wideband nested coaxial waveguide feed with extended center conductors is designed and analyzed. The performance of the feed is presented and discussed in detail. The feed has less than -10 dB reflection loss over its operating frequency. The excitation of the coaxial cavities is accomplished by impressing a circularly polarized TE/sub 11/ coaxial waveguide mode. The correlated parameters are rigorously carried out by experimental measurement (1-8 GHz) and a finite element method (FEM) computer simulation study (8-60 GHz).

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.