Search

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.

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 novel wideband omni-antenna with multi-functional units was proposed in this article. As example, an omni-antenna was studied composed of two half-wave antenna array. The balance of the feeding current to the array was realized by adjusting a l/4 choke at the antenna feeding structure. The VSWR of the designed antenna is below 2.0 in 4.0-5.5 GHz bandwidth, with relative bandwidth of 31% and gain larger than 3 dB. The antenna may find a wide range of application in fields such as communications.

The tapered line theory in circuit can be applied to the design of the special-shaped monopole antenna in order to obtain better electrical characteristics. So a novel Klopfenstein taper monopole antenna is proposed. The impedance matching characteristic of the Klopfenstein tapered line is the best, and the Klopfenstein taper monopole antenna is designed based on it. On this basis, the coplanar waveguide-fed planar Klopfenstein taper monopole antennas are designed. The simulation and measurement results prove that the Klopfenstein taper monopole antennas have small size and good performance. And the planar printed antenna can be convenient integrated with other radio frequency circuits. The idea to design antenna by using of tapered line theory directly can be used in practical operations.

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.

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.

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.

Exploding Magnetic Generator of Frequency (EMGF) is one kind of simple structure and miniaturized device for generation and radiation of electromagnetic pulse, and as one kind of modern weapon, the EMGF is paid more attention home and aboard. From the basic mathematics model of helical EMGF, this article discussed the generator operating principle, and mainly analyzed the influence of different inductance to generation when inductance coil coupling character and pitch changed, also with different resistance in the circuit. And finally some key technologies are discussed.

Two kinds of plasma monopole antennas are simulated and analyzed in this article. For different radius, reflection coefficient, radiation pattern and radiation efficiency of a cylindrical plasma monopole antenna are calculated respectively. According to actual situation, a conical plasma monopole antenna with different cone angle is simulated. Impedance and radiation characteristics of the plasma antenna are similar to the metal monopole antenna.

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.

Millimeter-wave imaging system is developing very quickly in airport security and aircraft navigation. Radiometer plays a key role in the millimeter-wave imaging system. The characteristic of full power radiometer and Dicke radiometer is compared. The key parts for a new direct-detection radiometer is designed and analyzed. The chips for LNA, detector and intergrator are chosen and simulated, which will meet the needs of the radiometer. The work can provide a good reference for the design of the radiometer for millimeter-wave imaging system.

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.

This paper proposes a novel multi-band semi-circle fractal antenna which develops from the multiple ring antenna. The antenna consists of nesting semi-circles with different radii. Simulated on the commercial software CST MICROWAVE STUDIOreg, the multi-band characteristic of the novel antenna can be controlled by modulating the radii of the nesting semi-circles and the nesting number. Summarized from the impact of these parameters, antenna with three passbands (900 MHz, 1.8 GHz, and 2.4 GHz) has been designed. In order to remove the infinite conductive ground, the antenna patch is placed on FR4 board and fed to get the printed antenna. The simulation results indicate that the antennas also have three pass bands with the same central frequencies with wide bandwidths. The antenna is manufactured and measured, the experiment results fit well with simulation. Thus, the multi-band semi-circle fractal antenna is a novel antenna with controllable frequency bands and promising application.

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.