Gaosheng Li

The Time-Frequency Combination Measurement Method and its implementation for in-situ electronicmagnetic emission test

A Time-Frequency Combination Measurement Method is presented in this paper. The EMI signal is divided into two ways for signal processing in time and frequency domain respectively after analogue down conversion. The sampling and processing method in time domain is discussed. The function and the implementation of each module in measurement system are introduced. The in-situ test examples such as stationary EMI signal and non-stationary EMI signal are presented. The results show that the electronicmagnetic emission can be finished fast by time-frequency combination measurement, which has a good applicability.

A Broadband Helical Saline Water Liquid Antenna for Wearable Systems

ABSTRACT A broadband helical liquid antenna made of saline water is proposed. A transparent hollow support is employed to fabricate the antenna. The rotation structure is fabricated with a thin flexible tube. The saline water with a concentration of 3.5% can be injected into or be extracted out from the tube to change the quantity of the solution. Thus, the tunability of the radiation pattern could be realised by applying the fluidity of the liquid. The radiation feature of the liquid antenna is compared with that of a metal one, and fairly good agreement has been achieved. Furthermore, three statements of the radiation performance corresponding to the ratio of the diameter to the wavelength of the helical saline water antenna have been proposed. It has been found that the resonance frequency increases when the length of the feeding probe or the radius of the vertical part of the liquid decreases. The fractional bandwidth can reach over 20% with a total height of 185 mm at 1.80 GHz. The measured results indicate reasonable approximation to the simulated. The characteristics of the liquid antenna make it a good candidate for various wireless applications, especially the wearable systems.

An on-body watchband antenna for the applications of wearable systems

A wearable antenna based on the metal watchband is proposed. A prototype of a TISSOT® classic watch is used for the demonstration. The width of the strap has a slight impact on the radiation patterns. However, the variations of the feeding position would sharply influence the matching performance. A fractional bandwidth of 77.8% could be obtained when feeding to the side of the dial at 2.46 GHz, which falls into the ISM (Industrial, Scientific, and Medical) band. The main lobe is fairly wide in both E and H plane, which enables the strap antenna a good adaptation for the versatile gestures of the arm. The measured results show good agreement with that of the simulations, which indicates the antenna a potential choice for the applications of wearable systems.

An Echo Simulation Method for DBS Imaging That Considers Environmental Factors

DBS (Doppler Beam Sharpening) imaging for scene matching terminal guidance is investigated. An echo simulation method for DBS of missile-borne radar that considers environmental factors is presented. The transmission signals of missile-borne radar are studied first. Next, the method for the modeling of the echo signals is discussed with consideration of environmental influences including the objects on the ground, radome and seasonal variations, especially undulation of the ground. The status of the surface of the earth as well as internal elements of the radar will influence the precision of the height measurement, thereby indirectly influencing the image matching. Undulating terrain can also cause changes in the electromagnetic characteristics that lie in the translation of image points; in addition, there is a close relationship between the position offset and the altitude of the image area. The operation flow of DBS is provided together with the method of generating reference images. Finally, an optical image of an airport and the simulation results using echoes are presented for validation.

A Handbag Zipper Antenna for the Applications of Body-Centric Wireless Communications and Internet of Things

The idea of making use of the metal zipper on the handbag to serve as an off-body antenna is proposed, and the simulations together with measurements have been carried out. The feeding point can be located at the bottom of the zipper, and to be more specific, around one of the teeth. The excitation at certain tooth of the zipper would bring variations in the reflection coefficients as well as the radiation patterns. No matter the zipper is totally closed, quarterly opened, half opened, or is even totally opened, the antenna can operate with acceptable performance, though the common status of the handbag zipper is closed. Thus, it is to some extent reconfigurable, especially for radiation patterns. A fractional bandwidth of 4.92% at 2.44 GHz of the industrial, scientific, and medical band with a gain of about 5 dBi has been achieved. The impact of the human body has been evaluated. It is noticeable but affordable. The measured results indicate reasonable agreements to that of the simulations in both the matching performance and the radiation feature for the zipper antenna, which seems to be a promising candidate for body-centric wireless communications and the Internet of Things.

A Rapid Method for Measuring the Volume of a Large Cavity Using Averaged Absorption Cross Section

The rapid and accurate measurement of the volume of a large cavity is much in demand in practice, especially for a cavity of irregular shape. In this paper, a new method is proposed to measure the volume of a large cavity. This method is based on the measurement of the decay time constant of the cavity. A lossy object with a known averaged absorption cross section is used to aid the measurement. By measuring decay time constants of the cavity with and without the lossy object, the cavity volume can be extracted. It is found that only one antenna is required for the measurement and the whole measurement can be completed simply and rapidly. The method could be applied to both metallic and non-metallic cavities which makes the proposed method a very attractive alternative to existing methods.

A wideband annular cylindrical dielectric resonator antenna for X-band applications

The present work investigates a novel cylindrical dielectric resonator antenna (CDRA) excited by a coaxial feed monopole, which is mounted on a circular substrate with a deformed ground plane. A vertical electric monopole is placed in the center of the DR. The wideband characteristic is achieved by the deformed ground plane. The features of the proposed antenna meet the essential requirements of X-band communication applications.

Analysis of orbital angular momentum modes for low-frequency radio communications

The orbital angular momentum (OAM) has been utilized in the low-frequency wireless communication system tentatively. To analyze the characteristics of various OAM modes, the capacity differences are calculated by a novel update-QR decomposition method which can reduce the computational complexity significantly under the conditions of equal power allocation and optimal power allocation. Besides, in order to obtain the correlation of channel matrix, Sorenson similarity coefficient is introduced. Then, consider the actual receiving, the influence of various factors including the topological charge and working frequency on the optimal angles is presented. Finally, all the characteristics presented will be as useful guidance to future practical applications.

A tunable wideband liquid antenna

A tunable liquid antenna is designed and analyzed. The ability of adjustment is realized with the help of a thin post penetrating the solid dielectric and the liquid layers. The influence of the thickness and parameters of the substrate is investigated. The performance of different liquid materials including sea water, oil and distilled water is analyzed as well. The influence of the distribution of the liquid, the length of the probe, the feeding positions and other relevant factors are presented after that. The simulation results reveal that changing the distribution of the liquid as well as other relevant parameters can effectively bring forth the performance alternation, which indicates the validity and flexibility of the antenna.

Study of a hybrid antenna consists of solid and liquid materials

An antenna with both solid dielectric and liquid materials is designed and analyzed. The influence of the thickness and parameters of the substrate is investigated. The performance of different liquid materials including sea water, oil and distilled water is analyzed. The influence of the distribution of the liquid and other relevant factors are studied. The simulation results revealed the validity and flexibility of the combination of solid dielectric resonators and liquid ones.