The research of high-directive anisotropic magnetic metamaterial antenna loaded with frequency-selective surface

This paper uses a Computer Simulation Technology microwave studio to simulate the performance of a new highdirectivity anisotropic magnetic metamaterial antenna loaded with a frequency-selective surface. Frequency-selective surface with cross-dipole element has a great effect on the directivity, radiation pattern, and gain of such an antenna. The experimental results show that frequency-selective surface （FSS） significantly improve the radiation performance of anisotropic magnetic metamaterial antenna. For example, as a single anisotropic magnetic metamaterial antenna, half power beam width is 4 degrees in the H planes, and the gain of this antenna is 19.5dBi at 10CHz, achieving a 2.1 degree increment in half power beam width, and a 7.3 dB gain increment by loading with the FSS reflector. The simulating results are consistent with our experimental results.

Wireless contactless pressure measurement of an LC passive pressure sensor with a novel antenna for high-temperature applications

In this paper, a novel antenna is proposed for high-temperature testing, which can make the high-temperature pressure characteristics of a wireless passive ceramic pressure sensor demonstrated at up to a temperature of 600℃. The design parameters of the antenna are similar to those of the sensor, which will increase the coupling strength between the sensor and testing antenna. The antenna is fabricated in thick film integrated technology, and the properties of the alumina ceramic and silver ensure the feasibility of the antenna in high-temperature environments. The sensor, coupled with the ceramic antenna, is investigated using a high-temperature pressure testing platform. The experimental measurement results show that the pressure signal in a harsh environment can be detected by the frequency diversity of the sensor.

High-performance lens antenna using high refractive index metamaterials

In this paper, a high refractive index metamaterial （HRM）, whose element is composed of bilayer square patch （BSP） spaced by a dielectric plate, is proposed. By reducing the thickness of the dielectric plate and the gap between adjacent patches, the BSP can effectively enhance capacitive coupling and simultaneously suppress diamagnetic response, which significantly increases the refractive index of the proposed metamaterial. Furthermore, the high refractive index region is far away from the resonant region of the metamaterial, resulting in broadband. Based on these characteristics of BSP, a gradient refractive index （GRIN） lens with thin thickness （0.34/~0, where 2~0 is the wavelength at 5.75 GHz） is designed. By using this lens, we then design a circularly polarized horn antenna with high performance. The measurement results show that the 3-dB axial ratio bandwidth is 34.8% （4.75 GHz-6.75 GHz） and the antenna gain in this frequency range is increased by an average value of 3.4 dB. The proposed method opens up a new avenue to design high-performance antenna.

A Frequency Selective Surface Loaded UWB Antenna for High Gain Applications

This paper presents the design of wideband and high gainFrequency Selective Surface(FSS)loaded antenna for ultra-wideband(UWB)wireless applications requiring high-gain.The antenna consists of a monopole and an FSS reflector.Initially,a conventional rectangular monopole antenna is modified using slot and stub to achieve wide operational bandwidth and size reduction.This modified antenna shows 50%miniaturization compared to a primary rectangular monopole,having a wide impedance bandwidth of 3.6-11.8 GHz.Afterward,an FSS is constructed by the combination of circular and square ring structures.The FSS array consisting of 8×8-unit cells are integrated with the antenna as a reflector to enhance the performance of the proposed miniaturized UWB antenna.The loading of FSS results in an improvement of at least 4 dBi gain in the entire operational bandwidth.Moreover,the antenna’s bandwidth is also increased at the lower frequency band due to the presence of the FSS.A prototype of the antenna is fabricated and tested to verify the simulation results.The simulation and measurement results show that the antenna offers a wideband-10 dB impedance bandwidth ranging from 2.55-13GHz with a stable peak gain of 8.6 dBi and retains the radiation pattern stability.

Enhancement of terahertz coupling efficiency by improved antenna design in GaN/AlGaN high electron mobility transistor detectors

An optimized micro-gated terahertz detector with novel triple resonant antenna is presented.The novel resonant antenna operates at room temperature and shows more than a 700% increase in photocurrent response compared to the conventional bowtie antenna.In finite-difference-time-domain simulations,we found the performance of the self-mixing GaN/AlGaN high electron mobility transistor detector is mainly dependent on the parameters L gs（the gap between the gate and the source/drain antenna） and L w（the gap between the source and drain antenna）.With the improved triple resonant antenna,an optimized micrometer-sized AlGaN/GaN high electron mobility transistor detector can achieve a high responsivity of 9.45×102 V/W at a frequency of 903 GHz at room temperature.

Low-loss Cd-substituted Mg ferrites with matching impedance for high-frequency-range antennas

The effects of Cd^(2+) ions on the microstructure,magnetic properties,and dielectric properties of Bi_(2)O_(3)-added MgFe_(2)O_(4) ferrites(Cd_(x)Mg_(1-x)Fe_(2)O_(4),x=0.00,0.15,0.30 and 0.45)are obtained by adopting the solid-state reaction method at a low temperature(910℃).The objective is to achieve matching impedances,low magnetic and dielectric losses(tanδμand tanδε,respectively),and a relatively large miniaturization factor to reduce antenna size.Experimental results indicate that the cations occupying the tetrahedral(A)and octahedral(B)ion sites are redistributed,resulting in an enhanced super-exchange interaction between the two sublattices.As a result,improved magnetization,including the increase in saturation magnetization(41.74 emu/g)and decrease in coercivity(63.75 Oe),is realized.The real part of permeability(μ')also increases with increasing concentration of Cd^(2+) ions.When x is 0.15,matching impedances with equivalent μ'and ε'values are obtained over a long frequency range(1–150MHz).Moreover,the formation of a dense microstructure guarantees that losses occur at low orders of magnitude(tanδμ≈10−2 and tanδε≈10−3).Accordingly,these properties afford wide application perspectives for the proposed compounds in the high-frequency region,i.e.,from high-frequency to very-high-frequency bands.

Rectangular Microstrip Antenna with Air Cavity for High Gain and Improved Front to Back Ratio

A rectangular microstrip patch antenna using conventional Poly Tetra Fluride Ethelene (PTFE) substrate with air cavity is proposed and theoretically investigated. Considerably high gain along with improved front to back radiation isolation is demonstrated using such proposed antenna. The radiation performance of this new antenna has been compared to a conventional microstrip patch for some commonly used aspect ratios (width to length ratio). Compared to conventional microstrip antenna the proposed configuration shows more than 12% increment in peak gain and more than 10% increment in front to back radiation performance in each set of aspect ratio. The elucidation of such improvement in the radiation characteristics of the proposed antenna is also presented.

STUDY ON THE WIDE-BAND AND HIGH-GAIN MICROSTRIP ANTENNA ELEMENT

A novel three layers microstrip antenna element that has the advantages of wideband and high-gain is proposed. The eigenvalue equation and the frequency characteristic formulas of the input Voltage Stand Wave Ratio ( VSWR ) are obtained by using the spectral domain method and equivalent circuit method, respectively. With the aid of the numerical results, a C-band microstrip antenna element with bandwidth of 16% (VSWR【1.5) or 25% (VSWR【2) and gain of 10.2-11.3 dB is developed, which are much larger than the bandwidth of 5-6% and the gain of 6-7 dB of the common microstrip antenna element.

High-Power 30-Element Helical Antenna Array

A new radial-line helical array (RLHA) using dual-branch helical antennas has been designed for improving the power capacity of RLHAs. The helical element is cavity-backed to lower the mutual coupling and its power capacity is higher than the conventional ones. The components of the proposed array are discussed and the power capacity is obtained by simulation. Compared with the typical RLHAs, the proposed sub-array has not only higher power capacity but also uses fewer elements. Experimentally, the measured results of an array prototype indicate that high gain as well as circular polarization has been successfully achieved.

Doppler frequency offset estimation and diversity reception scheme of high-speed railway with multiple antennas on separated carriage

The challenges of severe Doppler effects in high-speed railway are considered. By building a cooperative antenna system; an algorithm of joint channel estimation and Doppler frequency offset （DFO） estimation is proposed based on Ricean channel model. First, a maximum likelihood estimation （MLE） algorithm for DFO is designed, show- ing that the Doppler estimation can be obtained by estimating moving velocity of the train and the path loss with the exploitation of pilots that are placed inside the frame. Then a joint detection algorithm for the receiver is proposed to exploit multi-antenna diversity gains. Last, the theoretical Crammer Rao bound （CRB） for joint channel estimation and DFO estimation is derived. The steady performance of the system is confirmed by numerical simulations. In particular, when the Ricean fading channel parameter equals 5 and the velocities of train are 100 m/s and 150 m/s, the estimation variances of DFO are very close to the theoretical results obtained by using CRB. Meanwhile, the corresponding sig- nal to noise ratio loss is less than 1.5 dB when the bit error rate is 10-5 for 16QAM signals.

STEERABLE ANTENNAS MOVEMENT COMPENSATION FOR HIGH ALTITUDE PLATFORM

High Altitude Platform(HAP) must compensate for relative motion with respect to the ground because of the stratosphere complexity,which is important to guarantee Quality of Service(QoS) in intended coverage area.With analysis on HAP movement models for predicting the geographical coverage in the cases of shift horizontally and vertically,yaw,roll and pitch,the mechanisms of steerable antennas movement compensation are investigated.The mechanism is applied to a scenario of 127 cell architecture,with a cell cluster size of four.By the simulation results of Carrier to Interference Ratio(CIR),the steerable antenna movement compensation mechanism decrease influence of HAP movement and guarantee effective coverage of the service area.

Design of MEMS C-Band Microstrip Antenna Array Based on High-Resistance Silicon for Intelligent Ammunition

In recent years, microstrip antennas have been more widely applied in satellite communications, mobile phones, unmanned aerial vehicle （UAV）, and weapons. A micro-electro-mechanical systems-based （MEMS-based） high-resistance silicon C-band microstrip antenna array has been designed for the intelligent ammunition. The center frequency is 4.5 GHz. A cavity has been designed in substrate to reduce the dielectric constant of silicon and high-resistance silicon has been used as the material of substrate to improve the gain of antenna. It is very easy to be manufactured by using MEMS technology because of the improved structure of the antenna. The results show that the gain of the antenna is 8 dB and voltage standing wave ratio （VSWR） is less than 2 by the analysis and simulation in high freauencv structure simulator （HFSS）.

Gain Enhancement of Dielectric Resonator Antenna Using Electromagnetic Bandgap Structure

High gain antennas are highly desirable for long-range wireless communication systems.In this paper,a compact,low profile,and high gain dielectric resonator antenna is proposed,fabricated,experimentally tested,and verified.The proposed antenna system has a cylindrical dielectric resonator antenna with a height of 9 mm and a radius of 6.35 mm as a radiating element.The proposed dielectric resonator antenna is sourced with a slot while the slot is excited with a rectangular microstrip transmission line.The microstrip transmission line is designed for a 50impedance to provide maximum power to the slot.As a result,the proposed antenna operates at 5.15 GHz with a 10-dB absolute bandwidth of 430 MHz(4.98–5.41 GHz).It is important to mention that the gain of the dielectric resonator antenna is enhanced by the introduction of an electromagnetic bandgap(EBG)structure.In fact,EBG units are placed below the antenna,which enhances the realized peak gain from 5.32 dBi to 8.36 dBi at 5.15 GHz.More specifically,a gain enhancement of 3.04 dB is observed with the introduction of the EBG array.This antenna has several good features such as high gain,compact size,large bandwidth,and lower losses which make it a suitable choice for long-range wireless communication systems.

Design and Analysis of Antipodal Vivaldi Antennas for Breast Cancer Detection

This paper presents the design and analysis of antipodal Vivaldi antennas(AVAs)for breast cancer detection.In order to enhance the antenna gain,different techniques such as using the uniform and non-uniform corrugation,expanding the dielectric substrate and adding the parasitic patch are applied to original AVA.The design procedure of two developed AVA structures i.e.,AVA with non-uniform corrugation and AVA with parasitic patch are presented.The proposed AVAs are designed on inexpensive FR4 substrate.The AVA with non-uniform corrugation has compact dimension of 50×50 mm2 or 0.28λL×0.28λL,whereλL is wavelength of the lowest operating frequency.The antenna can operate within the frequency range from 1.63 GHz to over 8 GHz.For the AVA with parasitic patch and uniform corrugation,the overall size of antenna is 50×86 mm2 or 0.24λL×0.41λL.It can operate within the frequency range from 1.4 GHz to over 8 GHz.The maximum gain for AVA with non-uniform corrugation and AVA with parasitic patch and uniform corrugation are 9.03 and 11.31 dBi,respectively.The corrugation profile and parasitic patch of the proposed antenna are optimized to achieve the desired properties for breast cancer detection.In addition,the proposed AVAs are measured with breast phantom to detect cancerous cell inside the breast and the performance in detecting cancerous cell are discussed.The measured result can confirm that the proposed AVAs can detect unwanted cell inside the breast while maintaining the compact size,simple structure and low complexity in design.

A Set of Space-Time Block Codes for the High-Rate Transmission Scheme with One Information Bit

In [1], the authors have proposed one high rate transmission scheme for Space-Time Block Codes (STBC) without additional system source such as power, bandwidth and time slot. To maintain the full rank property of the coding gain matrix, we propose a set of STBCs for 4 transmit antennas transmission to transmit one additional information bit achieving rate-9/8. Another orthogonal STBC code with rate-1 is proposed in this paper within the set. It shows by computer simulation results that by employing the set of STBCs, it achieves better bit error rate (BER) performance and?throughput than that of [1] with a valid BER improvement at the high SNR region above 20dB.

Mapping an on-chip terahertz antenna by a scanning near-field probe and a fixed field-effect transistor

In the terahertz（THz） regime,the active region for a solid-state detector usually needs to be implemented accurately in the near-field region of an on-chip antenna.Mapping of the near-field strength could allow for rapid verification and optimization of new antenna/detector designs.Here,we report a proof-of-concept experiment in which the field mapping is realized by a scanning metallic probe and a fixed AlGaN/GaN field-effect transistor.Experiment results agree well with the electromagnetic-wave simulations.The results also suggest a field-effect THz detector combined with a probe tip could serve as a high sensitivity THz near-field sensor.

基于CMOS的高响应度太赫兹探测器线阵

本文提出了一种基于CMOS 0.18μm工艺的改进型高响应度太赫兹探测器线阵,各探测像素单元由高增益片上天线、高耦合度差分自混频功率探测电路和集成电压放大器组成。其中,差分探测电路利用源极差分驱动场效应管的交叉耦合电容,将太赫兹差分信号耦合至场效应管的栅极与源极,增强场效应管沟道内自混频太赫兹信号的强度,实现高响应度。其次,该探测器配备高增益片上环形差分天线与集成电压放大器,可有效放大混频后的信号,进而提高系统信噪比,最终达到增强探测器响应度的目的。探测器1×3线阵系统充分利用CMOS工艺多层结构的特点,将电压放大器布置在天线地平面下方,提高了芯片面积的利用率,有效降低了制作成本,整个系统的面积为0.5 mm^(2)。测试结果表明,当场效应管的栅极偏置为0.42 V时,该探测系统对0.3 THz辐射信号的电压响应度(Rv)最大可达到43.8 kV/W,对应的最小噪声等效功率(NEP)为20.5 pW/Hz^(1/2)。动态测试结果显示该探测器可对不同材质的隔挡物进行区分。

偶极子对激发的宽带平面端射高增益天线

文中提出了一款单向辐射特性的微带缝隙结构双偶极子宽带天线。该天线由阶梯型缝隙结构、共面双偶极子和5组引向器构成。阶梯型缝隙结构用于改善阻抗匹配,拓展了天线的带宽;共面双偶极子改善了天线的辐射特性;引向器提高了天线的增益。仿真和实测表明,该天线的相对带宽为66.4%(5.78 GHz~11.53 GHz),带内前后比为15.7 dB~27.4 dB、增益为8.4 dBi~11.9 dBi,并且天线的交叉极化低、辐射方向图稳定。该天线的良好性能使其在无线通信和雷达领域的应用具有极强的吸引力。